Copernicus: Sentinel-3 — Global Sea/Land Monitoring Mission including Altimetry
The Sentinel-3 (S3) mission of ESA and the EC is one of the elements of the GMES (Global Monitoring for Environment and Security) program, which responds to the requirements for operational and near-real-time monitoring of ocean, land and ice surfaces over a period of 20 years. The topography element of this mission will serve primarily the marine operational users but will also allow the monitoring of sea ice and land ice, as well as inland water surfaces, using novel observation techniques.The Sentinel-3 mission is designed as a constellation of two identical polar orbiting satellites, separated by 180º, for the provision of long-term operational marine and land monitoring services. The operational character of this mission implies a high level of availability of the data products and fast delivery time, which have been important design drivers for the mission. 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14)
The Sentinel-3 program represents a series of operational spacecraft over the envisioned service period to guarantee access to an uninterrupted flow of robust global data products.
Table 1: Copernicus is the new name of the former GMES program 15)
The main observation objectives of the mission are summarized in the following list:
• Ocean and land color observation data, free from sun-glint, shall have a revisit time of 4 days (2 days goal) and a quality at least equivalent to that of Meris instrument on Envisat. The actual revisit obtained over ocean at the equator (worst case) is less than 3.8 days with a single satellite and drops below 1.9 days with 2 satellites, phased 180° on the same orbital plane.
• Ocean and land surface temperature shall be acquired with at least the level of quality of AATSR on Envisat, and shall have a maximum revisit time of 4 days with dual view (high accuracy) observations and 1 day with single view. Achieved performance is shown to be significantly better, even with a single satellite (dual view: 3.5 days max, 1.8 days average).
• Surface topography observations shall primarily cover the global ocean and provide sea surface height (SSH) and significant wave height (SWH) to an accuracy and precision at least equivalent to that of RA-2 on Envisat. Additionally, Sentinel-3 shall provide surface elevation measurements -in continuity to CryoSat-2 - over ice regions covered by the selected orbit, as well as measurements of in-land water surfaces (rivers and lakes).
In addition, Sentinel-3 will provide surface vegetation products derived from synergistic and co-located measurements of optical instruments, similar to those obtained from the Vegetation instrument on SPOT, and with complete Earth coverage in 1 to 2 days.
The EU Marine Core Service (MCS) and the Land Monitoring Core Service (LMCS), together with the ESA GMES Service Element (GSE), have been consolidating those services where continuity and success depends on operational data flowing from the Sentinels.
The operational character of the mission implies a high level of availability of the data products and fast delivery time, which have been important design drivers for the mission.
Figure 1: Artist's rendition of the deployed Sentinel-3 spacecraft (image credit: ESA/ATG medialab) 16)
Legend to Figure 1: Sentinel-3 is arguably the most comprehensive of all the Sentinel missions for Europe's Copernicus programme. Carrying a suite of state-of-the-art instruments, it provides systematic measurements of Earth's oceans, land, ice and atmosphere to monitor and understand large-scale global dynamics and provide critical information for ocean and weather forecasting.
The Sentinel-3 spacecraft is being built by TAS-F (Thales Alenia Space-France). A contract to this effect was signed on April 14, 2008. The spacecraft is 3-axis stabilized, with nominal pointing towards the local normal and yaw steering to compensate for the Earth rotation affecting the optical observations. The spacecraft has a launch mass of about 1150 kg, the height dimension is about 3.9 m. The overall power consumption is 1100 W. The design life is 7.5 years, with ~100 kg of hydrazine propellant for 12 years of operations, including deorbiting at the end.
AOCS (Attitude and Orbit Control Subsystem): The spacecraft is 3-axis stabilized based on the new generation of avionics for the TAS-F LEO (Low Earth Orbit) platform. The AOCS software of the GMES/Sentinel-3 project is of PROBA program heritage. NGC Aerospace Ltd (NGC) of Sherbrooke, (Québec), Canada was responsible for the design, implementation and validation of the autonomous GNC (Guidance, Navigation and Control) algorithms implemented as part of the AOCS software of PROBA-1, PROBA-2, and PROBA-V. 17)
Table 2: Overview of Sentinel-3 spacecraft parameters
Data handling architecture: The requirements for the Sentinel-3 data handling architecture call for: a) minimized development risks, b) system at minimum cost, c) operational system over 20 years. This has led to design architecture as robust as possible using a single SMU (Satellite Management Unit) computer as the platform controller, a single PDHU (Payload Data-Handling Unit) for mission data management, and to reuse existing qualified heritage. 18)
The payload accommodates 6 instruments, sources of mission data. The 3 high rate instruments provide mission data directly collected through the SpaceWire network, while the low rate instruments are acquired by the central computer for distribution through the SpaceWire network to the mass memory. The PDHU acquires and stores all mission data for latter multiplexing, formatting, encryption and encoding for download to the ground.
The payload architecture is built-up over a SpaceWire network (Figure 2) for direct collection of high rate SLSTR, OLCI and SRAL instruments and indirect collection of low rate MWR, GNSS and DORIS instrument data plus house-keeping data through the Mil-Std-1553 bus by the SMU, all data being acquired from SpaceWire links and managed by the PDHU.
The mission data budget is easily accommodated thanks to the SpaceWire performance. Each SpaceWire link being dedicated to point-to-point communication without interaction on the other links (no routing), the frequency is set according to the need plus a significant margin. The PDHU is able to handle the 4 SpaceWire sources at up to 100 Mbit/s.
All mission data sources (OLCI, SLSTR, SRAL and SMU) provide data through two cold redundant interfaces and harnesses. The PDHU, being critical as the central point of the mission data management, implements a full cross-strapping between nominal and redundant sources interfaces and its nominal and redundant sides.
The PDHU SpaceWire interfaces are performed thanks to a specific FPGA, the instrument's ones are based on the ESA Atmel SMCS-332, while the SMU interfaces are implemented by an EPICA ASIC circuit developed by Thales Alenia Space.
Figure 3: Schematic view of a full cross-strap redundancy within the PDHU (image credit: TAS-F, Ref. 18)
RF communications: The S-band is used for TT&C transmissions The S-band downlink rate is 123 kbit/s or 2 Mbit/s, the uplink data rate is 64 kbit/s. The X-band provide the payload data downlink at a rate of 520 Mbit/s. An onboard data storage capacity of 300 Gbit (EOL) is provided for payload data.
Four categories of data products will be delivered: ocean color, surface topography, surface temperature (land and sea) and land. The surface topography products will be delivered with three timeliness levels: NRT (Near-Real Time, 3 hours), STC (Standard Time Critical, 1-2 days) and NTC (Non-Time Critical, 1 month). Slower products allow more accurate processing and better quality. NRT products are ingested into numerical weather prediction and seastate prediction models for quick, short term forecasts. STC products are ingested into ocean models for accurate present state estimates and forecasts. NTC products are used in all high-precision climatological applications, such as sealevel estimates.
The resulting analysis and forecast products and predictions from ocean and atmosphere adding data from other missions and in situ observations, are the key products delivered to users. They provide a robust basis for downstream value-added products and specialized user services.
Introduction of new technology: A newly developed MEMS rate sensor (gyroscope), under the name of SiREUS, will be demonstrated on the AOCS of Sentinel-3. The gyros will be used for identifying satellite motion and also to place it into a preset attitude in association with optical sensors after its separation from the launcher, for Sun and Earth acquisition. Three of the devices will fly inside an integrated gyro unit, each measuring a different axis of motion, with a backup unit ensuring system redundancy. Each unit measures 11 cm x 11 cm x 7 cm, with an overall mass of 750 grams. 19)
The SiREUS device is of SiRRS-01 heritage, a single-axis rate sensor built by AIS (Atlantic Inertial Systems Ltd., UK), which is using a 'vibrating structure gyro', with a silicon ring fixed to a silicon structure and set vibrating by a small electric current. The SiRRS-01 MEMS gyro has been used in the automobile industry. These devices are embedded throughout modern cars: MEMS accelerometers trigger airbags, MEMS pressure sensors check tires and MEMS gyros help to prevent brakes locking and maintain traction during skids. - In a special project, ESA selected the silicon-based SiRRS-01 to have it modified for space use (and under the new name of SiREUS).
Figure 4: Photo of the MEMS rate sensor (image credit: ESA)
Figure 5: Alternate view of the Sentinel-3 spacecraft and the accommodation of the payload (image credit: ESA)
Figure 6: Photo of the Sentinel-3A spacecraft in the cleanroom of Thales Alenia Space in Cannes, France with the solar wings attached (image credit: ESA, A. Le Floc'h) 20)
Status of project development:
• April 13, 2018: The team of propulsion experts has spent two days carrying out the tricky task of fuelling the Copernicus Sentinel-3B satellite with 130 kg of hydrazine and pressurizing the tank for its life in orbit. 21) 22)
- Since hydrazine is extremely toxic, only specialists remained in the cleanroom for the duration. A doctor and security staff waited nearby with an ambulance and fire engine ready to respond to any problems.
- The satellite is scheduled for liftoff on 25 April from Russia's Plesetsk Cosmodrome at 17:57 GMT (19:57 CEST).
- In orbit it will join its identical twin, Sentinel-3A, which was launched in 2016. This pairing of satellites provides the best coverage and data delivery for Copernicus.
- Sentinel-3B is the seventh Sentinel satellite to be launched for Copernicus. Its launch will complete the constellation of the first set of Sentinel missions for Europe's Copernicus program.
Figure 7: Fuelling of the Sentinel-3B spacecraft (image credit: Thales Alenia Space)
• March 23, 2018: With the Sentinel-3B satellite now at the Plesetsk launch site in Russia and liftoff set for 25 April, engineers are steaming ahead with the task of getting Europe's next Copernicus satellite ready for its journey into orbit. 23)
- After arriving at the launch site on 18 March, the satellite has been taken out of its transport container and is being set up for testing. Kristof Gantois, ESA's Sentinel-3 engineering manager, said, "The satellite's journey from France was hampered slightly by the freezing winter weather here in Russia, but it's now safe in the milder cleanroom environment.
- Sentinel-3B will join its twin, Sentinel-3A, in orbit. The pairing of identical satellites provides the best coverage and data delivery for Europe's Copernicus program – the largest environmental monitoring program in the world.
Figure 8: Following its arrival at Russia's Plesetsk launch site, the Copernicus Sentinel-3B satellite has been removed from its transport container. The satellite will now be prepared for liftoff, scheduled for 25 April 2018. Its identical twin, Sentinel-3A, has been in orbit since February 2016. The two-satellite constellation offers optimum global coverage and data delivery. The mission has been designed to measure systematically Earth's oceans, land, ice and atmosphere to monitor and understand large-scale global dynamics. It will provide essential information in near-realtime for ocean and weather forecasting (image credit: ESA)
• February 2, 2018: After being put through its paces to make sure it is fit for life in orbit around Earth, the Copernicus Sentinel-3B satellite is ready to be packed up and shipped to Russia for liftoff. 24)
- Its twin, Sentinel-3A, has been in orbit since February 2016, systematically measuring our oceans, land, ice and atmosphere. The information feeds a range of practical applications and is used for monitoring and understanding large-scale global dynamics.
- The pairing of identical satellites provides the best coverage and data delivery for Europe's Copernicus program – the largest environmental monitoring program in the world.
- Sentinel-3B has spent the last year at Thales Alenia Space's premises in Cannes, France, being assembled and tested, and now it is fit and ready for its journey to the Plesetsk launch site in northern Russia.
- This included putting it in a vacuum chamber, exposing it to extreme temperatures, and we have also simulated the vibrations it will be subjected to during launch. - With liftoff expected to be confirmed for the end of April, the satellite will start its journey to Russia in March.
- Both Sentinel-3 satellites carry a suite of cutting-edge instruments to supply a new generation of data products, which are particularly useful for marine applications. For example, they monitor ocean-surface temperatures for ocean and weather forecasting services, aquatic biological productivity, ocean pollution and sea-level change. — Sentinel-3B also marks a milestone in Europe's Copernicus program.
- With the Sentinel-1 and Sentinel-2 pairs already in orbit monitoring our environment, the launch of Sentinel-3B means that three mission constellations will be complete. In addition, Sentinel-5P, a single-satellite mission to monitor air pollution, has been in orbit since October 2017.
- While the Sentinel-1 and Sentinel-2 satellites circle Earth 180° apart, the configuration for Sentinel-3 will be slightly different: the 140° separation will help to measure ocean features such as eddies as accurately as possible.
- Prior to this, however, they will fly just 223 km apart, which means that Sentinel-3B will be a mere 30 seconds behind Sentinel-3A.
- Flying in tandem like this for around four months is designed to understand any subtle differences between the two sets of instruments – measurements should be almost the same given their brief separation.
- ESA's ocean scientist, Craig Donlon, explains, "Our Sentinel-3 ocean climate record will eventually be derived from four satellites because we will be launching two further Sentinel-3s in the future.
- "We need to understand the small differences between each successive satellite instrument as these influence our ability to determine accurate climate trends. The Sentinel-3 tandem phase is a fantastic opportunity to do this and will provide results so that climate scientists can use all Sentinel-3 data with confidence."
• December 5, 2017: EUMETSAT has confirmed the readiness of its teams and the new version of its ground segment to support the launch and commissioning of the Copernicus Sentinel-3B satellite in a two-satellite configuration with Sentinel-3A. 25)
- The new version of the ground segment includes enhancements and upgrades necessary to exploit a dual Sentinel-3 system. Its acceptance follows a comprehensive campaign of verification and validation tests.
- During the commissioning of Sentinel-3B, the two Sentinel-3 satellites will fly in close formation, 30 seconds apart. In this phase, ESA will manage Sentinel-3B flight operations, and EUMETSAT will be progressively ramping up its flight control activity to prepare the hand-over, while continuing to perform flight operations of Sentinel-3A.
- The close formation flight will allow to compare thoroughly the measurements from all instruments aboard Sentinel-3A and –B, ensuring the best consistency between the products from the two satellites.
- The completion of commissioning will lead to a handover of the Sentinel-3B satellite from ESA to EUMETSAT once the latter has been moved to it final orbital position, at a 140º phasing from Sentinel-3A, to form the full Sentinel-3 constellation. The 140° phasing was chosen to optimize global coverage and ensure optimized sampling of ocean currents by the combined altimeters on board Sentinel-3A and -3B.
- Thus the Sentinel-3 constellation will also realize the best possible synergy with the cooperative Jason-3 high precision ocean altimeter mission, another Copernicus marine and climate mission exploited by EUMETSAT on behalf of the European Union.
- Under the Copernicus data policy, all Sentinel-3 marine data and products are available on a full, free and open basis to all users through EUMETSAT's Near Real Time dissemination channels EUMETCast, the Copernicus Online Data Access and EUMETview.
• June 1, 2017: While the Copernicus Sentinel-3A satellite is in orbit delivering a wealth of information about our home planet, engineers are putting its twin, Sentinel-3B satellite through a series of vigorous tests before it is shipped to the launch site next year. It is now in the thermal–vacuum chamber at Thales Alenia Space's facilities in Cannes, France. This huge chamber simulates the huge swings in temperature facing the satellite in space. Once this is over, the satellite will be put through other tests to prepare it for liftoff in the spring 2018. Both Sentinel-3 satellites carry the same suite of cutting-edge instruments to measure oceans, land, ice and atmosphere. 26)
Figure 9: Sentinel-3B being placed in the thermal/vacuum chamber in Cannes, France (image credit: Thales Alenia Space)
• January 14, 2016: Following the Christmas break, the Sentinel-3A satellite has been taken out of its storage container and woken up as the campaign to prepare it for launch resumes at the Russian Plesetsk Cosmodrome. Liftoff is set for 4 February. 27)
• Nov. 20, 2015: The Sentinel-3A spacecraft has left France bound for the Plesetsk launch site in Russia and launch in late December. An Antonov aircraft carries the precious cargo to Arkhangelsk in Russia after a stopover in Moscow to clear paperwork. 28)
• Oct. 15, 2015: Before the latest satellite for Copernicus is packed up and shipped to the Plesetsk Cosmodrome in Russia for launch at the end of the year, the media and specialists were given the chance to see this next-generation mission center-stage in the cleanroom. The event was hosted by Thales Alenia Space in Cannes, France, where engineers have spent the last few years building and testing Sentinel-3A. 29)
• In December 2014, the Sentinel-3A spacecraft is now fully integrated, hosting a package of different instruments to monitor Earth's oceans and land. After spending many months carefully piecing the satellite together, it is now being tested in preparation for launch towards the end of 2015. 30)
- Environmental tests will start in early 2015.
• In July 2014, the OLCI instrument was delivered and mounted onto the satellite.
Launch: The Sentinel-3A spacecraft was launched on February 16, 2016 (17.57 GMT) on a Rockot/Briz-KM vehicle of Eurockot Launch Services (a joint venture between Astrium, Bremen and the Khrunichev Space Center, Moscow). The launch site was the Plesetsk Cosmodrome in northern Russia. The satellite separated 79 minutes into the flight. 31) 32)
ESA awarded the contract to Eurockot Launch Services on Feb. 9, 2012. 33)
There are three spacecraft in this series: Sentinel-3A, -3B, and -3C. The second satellite is expected to be launched ~18 months after the first one.
Orbit: Frozen sun-synchronous orbit (14 +7/27 rev./day), mean altitude = 815 km, inclination = 98.6º, LTDN (Local Time on Descending Node) is at 10:00 hours. The revisit time is 27 days providing a global coverage of topography data at mesoscale.
With 1 satellite, the ground inter-track spacing at the equator is 2810 km after 1 day, 750 km after four days, and 104 km after 27 days.
For the altimetry mission, simulations show that this orbit provides an optimal compromise between spatial and temporal sampling for capturing mesoscale ocean structures, offering an improvement on SSH mapping error of up to 44% over Jason - due to improved spatial sampling (Figure )- and 8% over the Envisat 35-day orbit - due to better temporal sampling. After a complete cycle, the track spacing at the equator is approximately 100 km.
The Sentinel-3 mission poses the most demanding POD (Precise Orbit Determination) requirements, specially in the radial component, not only in post-processing on-ground, but also in real-time. This level of accuracy requires dual-frequency receivers. The main objective of the mission is the observation with a radar altimeter of sea surface topography and sea ice measurements (see columns 3, 4, 5 in Table 3).
Table 3: Error budget requirements in Sentinel-3 as a function of time wrt measurement 34)
The second satellite will be placed in the same orbit with an offset of 140º; this phasing improves interleave between S-3A and S-3B for better SRAL meso-scale sampling of 4-7 days. 37)
Commissioning will include a 4-5 month tandem flight. A tandem phase operation of the A/B pair with ~30 s separation in time between satellites on near identical ground-track for ~4-5 months will be flown during Phase E1.
Figure 10: Tandem phase operations overview (EUMETSAT, ESA, Ref. 37)
With two satellites flying simultaneously, the following coverage will be achieved (Ref. 11):
- Global Ocean color data is recorded with OLCI and SLSTR in less than 1.9 days at the equator, and in less than 1.4 days at latitudes higher than 30º, ignoring cloud effects.
- Global Land color data is recorded with OLCI and SLSTR in less than 1.1 days at the equator, and less than 0.9 days in latitudes higher than 30º.
- Global Surface temperature data is recorded in less than 0.9 days at the equator and in less than 0.8 days in latitudes higher than 30º.
- Continuous altimetry observations where global coverage is achieved after completion of the reference ground track of 27 days.
Status of the Sentinel-3 mission
• October 25, 2019: Wildfires have been making headlines again this month, with multiple fires burning in Lebanon and California, but these are just some of the many fires 2019 has seen. Fires in the Amazon sparked a global outcry this summer, but fires have also been blazing in the Arctic, France, Greece, Indonesia as well as many other areas in the world. 38)
Figure 11: Fires around the world. Global fires detected in August 2018 compared to August 2019. The Sentinel-3 World Fire Atlas recorded 79,000 wildfires in August 2019, compared to just over 16,000 fires during the same period in 2018 (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA on ONDA Copernicus DIAS)
- Data from the Sentinel-3 World Fire Atlas shows that there were almost five times as many wildfires in August 2019 compared to August 2018, but a detailed analysis reveals precisely where these fires have been occurring – most of which were in Asia.
- The Copernicus Sentinel-3 mission recorded 79,000 fires in August this year, compared to just over 16,000 fires detected during the same period last year. These figures were achieved by using data from the Sentinel-3 World Fire Atlas Prototype, which is also able to provide a breakdown of these fires per continent.
Figure 12: The trend of wildfires detected in 2019 are shown in red, while fires detected in 2018 can be seen in green. The Sentinel-3 World Fire Atlas shows 70,000 fires in August 2019, compared to just over 16,632 fires in August 2018 (image credit: ESA)
- The data reveals 49% of fires were detected in Asia, around 28% were detected in South America, 16% in Africa, and the remaining were recorded in North America, Europe and Oceania.
- Working like thermometers in the sky, the sensors on satellites measure thermal infrared radiation to take the temperature of Earth's land surfaces. This information is used to detect and monitor the heat emitted by the fires.
- Using its two dedicated fire channels, the Sentinel-3 World Fire Atlas uses a simplified operational version derived from Wooster et al. 2012 in order to identify all active fires at night.
- Data gathered are used to plot the number of fires occurring monthly. The number of input images from Copernicus Sentinel-3A satellite were around the same from one year to the other.
Figure 13: Out of the 79,000 wildfires detected in 2019, this pie chart shows the breakdown of the fires by continent. Around half of the fires were detected in Asia, 28% in South America, 16% in Africa and the remaining in Europe, Oceania and North America (image credit: ESA)
- Even if the atlas cannot pick up all fires due to satellite overpass constraints and cloud coverage, it is statistically representative from one month to the other and from one year to the other.
- ESA's Olivier Arino comments, "We have never seen an increase of wildfires of this kind since the ATSR World Fire Atlas was created in 1995."
- Quantifying and monitoring fires is important for the ongoing study of climate because they have a significant impact on global atmospheric emissions, with biomass burning contributing to the global budgets of greenhouse gases, like carbon dioxide.
- One of the biggest problems during and after fires is obtaining an overall view of the fires evolution and potential damage. With fires seen from space, Earth observation is also being used to detect and monitor the active spots over affected areas.
• October 18, 2019: The Korean Peninsula in East Asia can be seen in this image captured by the Copernicus Sentinel-3 mission. The peninsula is over 900 km long and is located between the Sea of Japan, also known as the East Sea, to the east and the Yellow Sea to the west. 39)
- The peninsula is divided into two countries – the Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea).
- North Korea is divided into nine provinces, with Pyongyang as the capital. Pyongyang, which can be seen in light grey in the upper left of the image, lies on the banks of the Taedong River and on a flat plain about 50 km inland from the Korea Bay.
- The capital of South Korea is Seoul, which is in the northwest of the country, slightly inland and around 50 km south of the North Korean border.
- As the image shows, the Korean peninsula is mostly mountainous and rocky, making less than 20% of the land suitable for farming.
- The Yellow Sea owes its name to the silt-laden waters from the Chinese rivers that empty into it. It is also one of the largest shallow areas of continental shelf in the world with an average depth of around 50 m.
- The waters off the coast of Korea are considered among the best in the world for fishing. The warm and cold currents attract a wide variety of species and the numerous islands, inlets and reefs provide excellent fishing grounds.
Figure 14: This image, which was captured on 21 May 2019 on Sentinel-3, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
• October 10, 2019: This enormous typhoon Hagibis, which is being compared to a Category 5 hurricane, can be seen in this image captured by the Copernicus Sentinel-3 mission on 10 October at 01:00 GMT (10:00 Japan Standard Time). The eye of the storm has a diameter of approximately 60 km. 40)
Figure 15: Typhoon Hagibis is headed towards Japan's main island of Honshu, where it is expected to make landfall over the weekend. Japan is bracing for potential damage from strong winds and torrential rain (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
• September 3, 2019: This Copernicus Sentinel-3 image features Hurricane Dorian as it pummels the Bahamas on 2 September 2019 at 15:16 GMT (11:16 EDT). This mighty storm has been parked over the northwest Bahamas for more than 24 hours unleashing a siege of devastation. Storm surges, wind and rain have claimed at least five lives and destroyed homes and infrastructure. 41)
- Dorian is reported to be one of the most powerful Atlantic hurricanes on record. Residents in Florida, US, are also starting to feel the effects of Dorian, though its path is difficult to predict as it creeps slowly over the Bahamas. However, the US National Hurricane Center expect life-threatening storm surges along Florida's east coast and along the coasts of Georgia and South Carolina. As the US authorities respond to the devastation, Europe's Copernicus Emergency Mapping Service has been activated to provide flood maps based on satellite data.
Figure 16: Copernicus Sentinel-3 image of Hurricane Dorian over the Bahamas on 2 September 2019 (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA)
• August 27, 2019: Thousands of fires have broken out in the Amazon rainforest. Satellite data show that there are almost four times as many fires this year compared to the same period last year. Apart from Brazil, parts of Peru, Bolivia, Paraguay and Argentina have also been affected. 42)
- While forest fires normally occur in Brazil's dry season, which runs from July to October, the unprecedented increase is reported to come from both legal and illegal deforestation which allows land to be used for agricultural purposes, rising global temperatures are also thought to be making the region more susceptible to fire.
- The Amazon basin is the world's largest tropical rainforest, spanning four countries and is home to millions of plants and animals. It produces around 20% of the world's oxygen – hence the region being called ‘the lungs of the world' – and is crucial for helping to regulate global warming as the forests absorb millions of tonnes of carbon emissions every year.
- Using Copernicus Sentinel-3 data, as part of the Sentinel-3 World Fires Atlas, almost 4000 fires were detected from 1 August to 24 August 2019, while last year there were far fewer during the same period, just 1110 fires.
- "By processing 249 images for August 2018 and 275 images for August 2019, we are able to see the incredible number of fires burning in the Amazon. This was achieved by the World Fire Atlas night time algorithm, in order to avoid any possible false alarms with the daytime algorithm," says ESA's Olivier Arino.
- Plumes of smoke have spread across the Amazon region. Strong winds have blown smoke to São Paulo – more than 2500 km away— causing a black out in the city. According to the Copernicus Atmosphere Monitoring System (CAMS), smoke has travelled as far as the Atlantic coast.
- CAMS also reports that the fires have released 228 megatons of carbon dioxide into the atmosphere, as well as copious amounts of carbon monoxide. The fires also threaten the lives of many indigenous people.
- The Copernicus Emergency Mapping Service was activated to help respond to the fire. The service uses satellite observations to help civil protection authorities and, in cases of disaster, the international humanitarian community to help to respond to emergencies.
Figure 17: Number of wildfires in the Amazon. Using Copernicus Sentinel-3 data, as part of the Sentinel-3 World Fires Atlas, 3951 fires were detected at night from 1 August to 24 August 2019, compared to 1110 fires detected in 2018 during the same period (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA on ONDA Copernicus DIAS)
Figure 18: Wildfires in Brazil from Copernicus Sentinel-3. An unprecedented amount of fires have broken out in Brazil's Amazon rainforest. In this image, captured on 21 August 2019, the fires and plumes of smoke can clearly be seen (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
- The severity of the fires has reached the highest political levels. Deemed an international crisis, the G7 nations who met in France yesterday, have offered a 20 million euro emergency funding to assist Brazil and its neighboring countries to put out the fires, according to French President Emmanuel Macron.
- Josef Aschbacher, ESA's Director of Earth Observation Programs, said, "As we continue to face the ongoing climate crisis, satellites are essential in monitoring wildfires in remote areas, especially for a key component of the Earth system such as the Amazon."
Figure 19: Wildfires on the border between Bolivia, Paraguay and Brazil from Copernicus Sentinel-2. This false-color animation captured by the Copernicus Sentinel-2 mission shows the fires breaking out on the border between Bolivia, Paraguay and Brazil. The animation contains three separate images from 8, 18 and 23 August 2019. On the 23 August, the smoke from the fire is visible in blue, while clouds can be seen in white. The orange areas show the burned land (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA; CC BY-SA 3.0 IGO)
• July 30, 2019: Hundreds of wildfires have broken out in Siberia, some of which can be seen in this image captured from space on 28 July 2019. Almost three million hectares of land are estimated to have been affected, according to Russia's Federal Forestry Agency. 43)
Figure 20: This Copernicus Sentinel-3 image shows a number of fires, producing plumes of smoke. The smoke has carried air pollution into the Kemerovo, Tomsk, Novosibirsk, and Altai regions (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
- An unprecedented amount of wildfires have been raging in various regions of the Arctic, including Greenland and Alaska in the US. They have been caused by record-breaking temperatures and lightning, fuelled by strong winds.
- Wildfires release harmful pollutants and toxic gases into the atmosphere. According to the WMO (World Meteorological Organization), fires in the Arctic released around 50 megatons of carbon dioxide in June alone – equivalent to Sweden's total annual emissions.
• July 25, 2019: An extreme heatwave has hit Europe once again this week, following extreme weather in June. High temperatures are expected to peak today, reaching as high as 39—40°C, with Netherlands, Belgium and Germany recording their highest ever temperatures. Paris reached a sweltering 41°C, breaking its previous record in 1947. 44)
Figure 21: This animation of two images shows the land surface temperature from today 25 July, compared to data recorded during the previous heatwave on 26 June 2019 (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
- The map has been generated using the Copernicus Sentinel-3's SLSTR (Sea and Land Surface Temperature Radiometer). Whereas weather forecasts use predicted air temperatures, the satellite measures the real amount of energy radiating from Earth – therefore this map better represents the real temperature of the land surface. Clouds are visible in white in the image, while the light blue represent snow-covered areas.
- The heatwave in June broke several records for many countries, with France reaching over 45°C for the first time. Germany, Hungary, Poland, Austria, Czech Republic, Slovakia also reached peak temperatures.
- In many countries, red heat warnings have been issued, including Italy, Spain and France and civilians are advised to avoid travelling and stay hydrated.
• June 27, 2019: With some places expecting to be hit with air temperatures of over 40°C in the next days, much of Europe is in the grip of a heatwave – and one that is setting record highs for June. According to meteorologists this current bout of sweltering weather is down to hot air being drawn from north Africa. 45)
- Countries worst hit by this unusual June weather include Spain, France, Germany, Italy and Poland. In many places heat warnings have been issued and cities such as Paris have connected fountains and sprinklers to hydrants to help give people some relief. Wildfires in Catalonia, said to be the worst in two decades, have already ripped across 5000 hectares of land and are being blamed on the heat and strong winds.
Figure 22: This map shows the temperature of the land on 26 June. It has been generated using information from the Copernicus Sentinel-3's SLSTR (Sea and Land Surface Temperature Radiometer), which measures energy radiating from Earth's surface in nine spectral bands – the map therefore represents temperature of the land surface, not air temperature which is normally used in forecasts. The white areas in the image are where cloud obscured readings of land temperature and the light blue patches are snow-covered areas (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
• June 24, 2019: An unexpected and powerful eruption started at Raikoke volcano in the Kuril Islands on 21 June 2019. 46)
- The Kuril Islands are an island chain, located in the Pacific Ocean between northern Japan (i.e. Hokkaido) and the Kamchatka Peninsula. The Kuril Islands are claimed by Russia.
Figure 23: This image, which was captured on 22 June, shows the brown ash plumes rising high above the dense clouds – drifting eastwards over the North Pacific Ocean (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
- According to the Volcanic Ash Advisories Center (VAAC) Tokyo, the thick ash plumes rose to approximately 13 km above sea level. Weather officials warned aircraft flying over the area to be careful of any volcanic ash following the eruption.
- The majority of the plume is now drifting over the Bering Sea. Raikoke is a circular stratovolcano located on an inhabited island. Its last eruption was in 1924.
• May 29, 2019: Most of us probably wouldn't think of describing snow in terms of its grain size. However, grain size is fundamental to the amount of sunlight that snow reflects back into space – its albedo. With both snow and albedo part of the climate system, scientists are applying a novel analytical theory to Copernicus Sentinel-3 data and shedding new light on Greenland's changing albedo. 47)
Figure 24: Greenland snow grain and albedo. A sequence of snow grain size and albedo from the Copernicus Sentinel-3 satellites' OLCI (Ocean Land and Color Instruments). The animation illustrates a view through clear skies to the surface of the Greenland ice sheet where warming causes snow grain growth and reduced albedo. The darkest albedo areas are where snow melt gives way to bare glacier ice that melts even faster than snow cover, highlighting the fact that snow and ice are sensitive responders to weather and climate (image credit: GEUS–J. Box/ESA)
- The amount of sunlight absorbed or reflected by Earth's surface drives our climate and weather. About one-third of the sunlight that hits Earth is reflected back into space and the other two-thirds is absorbed by the land, oceans and atmosphere. This ratio is governed by the reflectivity, or albedo, of the surface that the sunlight hits.
- Surfaces with lighter colors reflect more sunlight than darker surfaces. An everyday example of this is the difference we feel on a hot sunny day when wearing black clothes compared to wearing white. Earth is affected in the same way.
- So hypothetically, if the planet were completely covered in ice, it would reflect over 80% of incident sunlight back into space. On the other hand, if it were covered by dark green forest, it would only reflect about 10%.
- The albedo of Earth's surface varies naturally according to the changing colors of the season, but long-term trends in changing snow and ice cover, as well as changing vegetation cover and air pollution, are having an impact on the overall balance of Earth's albedo – and, hence, on how much heat it absorbs.
- The Global Climate Observing System lists both albedo and snow as essential climate variables, which when measured and studied over time are used to understand, monitor and predict climate change.
- Ice and snow are often cited as the first causalities of climate change, and are measured and monitored from space in a variety of ways. However, while ice and snow may be present, the melting process affects its albedo.
- Snow grain size is a fundamental property of snow and is directly proportional to its surface area. Fresh dry snow tends to have a small grain size (under 0.5 mm in diameter), but as it melts the grain size grows and the larger grains reflect less sunlight.
- Thanks to Alex Kokhanovsky from Vitrociset who, along with several authors, published an elegant analytical theory, scientists have a fast new way of retrieving snow grain size from satellite images.
- Scientists from the Geological Survey of Denmark and Greenland (GEUS) in Copenhagen are coupling this theory with data from the Copernicus Sentinel-3 satellites' Ocean Land and Color Instruments – as the animation above shows.
- Jason Box, from GEUS, explains, "One way of measuring the albedo of snow is to monitor how the surface color changes because of pollution such as from wildfire soot. But this doesn't give us the whole story. Remarkably, this exciting new theory allows us to retrieve snow grain size from satellite optical images.
- "Through ESA's Earth Observation Science for Society program, we have been able to demonstrate this over Greenland. We have found that pulses of warm air cause dark blemishes far inland on the ice sheet, contributing to increased climate sensitivity."
- In fact, the Copernicus Sentinel-3 satellite constellation can now take the relay in maintaining the climate record on snow albedo, which was first provided by the AVHRR (Advanced Very High Resolution Radiometer) instruments on the US NOAA and Europe's MetOp satellites, and then the MODIS (Moderate Resolution Imaging Spectroradiometer) on the US Terra and Aqua satellites.
- In the future, the method will be extended and applied to areas with more complex terrain than Greenland. Furthermore, grain size data is now on the horizon for being used operationally to improve weather, hydrological and hazards forecasts, in service to society.
Figure 25: Grainy nature of snow. Most of us probably wouldn't think of describing snow in terms of its grain size. However, grain size is fundamental to the amount of sunlight that snow reflects back into space, its albedo (image credit: H. C. Steen Larsen)
Figure 26: Polluted snow and ice on Greenland. Dark and colored impurities resurface from melting snow and lie atop water-saturated glacier ice on Greenland. Much of the colored material is biological in origin (image credit: GEUS–J. Box)
• May 02, 2019: This Copernicus Sentinel-3 image, captured just yesterday on 1 May 2019, shows Cyclone Fani. Brewed in the Bay of Bengal and heading westwards, the cyclone is expected to make landfall on India's east coast on Friday 3 May. 48)
Figure 27: With wind speeds of up to 200 km per hour, heavy rainfall and flooding have been forecast along the Odisha coast, and has led to the evacuation of around 800 000 people from the nearby low-lying areas. In the image, the width of the storm is estimated to be around 700-800 km. Once Cyclone Fani makes landfall, it is expected to move north-east, hitting Bangladesh and Bhutan on Saturday 4 May (image credit: ESA, the image contains modified Copernicus Sentinel data (2019), processed by ESA, CC BY-SA 3.0 IGO)
- On the island's east coast, bright turquoise colors in the Pacific Ocean suggest the presence of sediment being carried into the ocean by river discharge as well as algal blooms.
- Algal blooms occur when there is a rapid increase in the number of algae in water, and are usually a result of slow water circulation and high water temperatures, they can be toxic and potentially dangerous to both fish and humans.
- The emerald green color of the coastal Lake Ellesmere (Te Waihora), below the circular peninsula jutting out, is most likely because of a high concentration of chlorophyll. This brackish lake is home to over 150 species of birds and more than 40 species of fish thanks to the influx of both freshwater and marine species migrating in and out of the lake.
- Across the Cook Strait, nestling on the southern tip of the North Island, the image shows a body of water called Lake Wairarapa. It is yellow-ochre in color owing to high concentrations of sediment. This shallow lake, which is surrounded by wetlands and farms, drains into the smaller Lake Onoke, further south.
- Tongariro National Park, in the center of the North Island, is a UNESCO World Heritage Site owing to its natural and cultural significance. The park has three active volcanoes. At 2797 m high, the snow-covered Ruapehu – a majestic stratovolcano – is the most visible in the image. The area's rugged terrain and jagged rocks made it the ideal location for filming the Lord of the Rings trilogy.
- On the far west, the snow-capped cone of Mount Taranaki is in the middle of Egmont National Park. The mountain is surrounded by dark-colored dense forest that is in contrast to the unprotected pasture outside of the park's circular boundary. It is considered one of the most symmetrical volcano cones in the world.
Figure 28: This true color image of New Zealand, captured on 22 August 2018 with Sentinel-3A, shows the snow-covered Southern Alps stretching 500 km across the west coast of the South Island. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• March 06, 2019: A new study of the Sentinel-3 mission shows its great potential for precision elevation data observations of the Antarctic ice sheet proving a valuable addition to monitoring efforts in the region, according to work published this week in The Cryosphere. The study, led by researchers from the new joint Lancaster University (UK)-CEH Centre of Excellence in Environmental Data Science (CEEDS), alongside ESA (European Space Agency) and industry partners, shows the potential of Sentinel-3 — one of the EU Copernicus satellite missions — to contribute towards long-term ice sheet monitoring programs. 50) 51)
- The scientists also found that Sentinel-3 could detect areas where the ice surface was rapidly lowering, thereby establishing the satellite's credentials as a new platform which can help to monitor Antarctica's contribution to sea level rise.
- Determining how well Sentinel-3 functions over ice sheets is particularly important given that CryoSat-2, ESA's dedicated polar mission, is already operating well beyond its planned lifetime.
- CryoSat-2 was designed to fly in a unique orbit, to maximize coverage of coastal areas of the ice sheet, and to map the regions close to the North and South Poles that were beyond the reach of previous satellites.
- Although Sentinel-3 — which has to balance many applications — cannot match this coverage, it still holds potential as a valuable long-term monitoring platform for decades to come.
- Dr Mal McMillan, lead author and co-Director of CEEDS, said: "Although the Sentinel-3 altimeter was primarily designed to monitor the oceans, we wanted to test how well it works over ice, and to see whether it is able to detect signs of glaciological change. Through the support offered by ESA's Scientific Exploitation of Operational Missions element, we have been able to study the performance of the Sentinel-3 mission for several years now, and we are pleased to be able to publish these results."
- He added: "From what we can see here, with just two years' worth of data, Sentinel-3 is going to be a very useful tool for surveying the Antarctic ice sheet."
- Sentinel-3 uses a radar technique called Delay-Doppler altimetry [use of SRAL (SAR Radar Altimeter) instrument] to make high resolution measurements of the height of the ice sheet.
- Where the ice is relatively flat, Sentinel-3 could map its height to within 10 cm of measurements taken by aircraft, as part of NASA's Operation Icebridge campaign.
- Dr McMillan explained: "This level of accuracy means that we can also use Sentinel-3 to track important features on the ice surface, like the imprint of active subglacial lakes draining and refilling beneath several kilometers of ice."
- Using radar satellites like Sentinel-3 over ice nonetheless has its challenges. For example, measurements over Antarctica's steeper, craggy coastal areas were less accurate because of how the rough landscape affects the radar signal.
- Future research into Sentinel-3's performance, as well as further improvements to data processing, will help take these effects into account. In the meantime, Sentinel-3 has already shown its value as a new tool for detecting ice sheet change.
- Co-author Jérôme Benveniste of the European Space Agency summarized: "We are delighted with the early promise shown by Sentinel-3 for ice sheet monitoring, and are increasingly confident that it will be a long-term asset to climate science."
Figure 29: Sentinel-3, a workhorse mission for Copernicus. Following its launch in February 2016 and subsequent commissioning phase, the Copernicus Sentinel-3A satellite has been systematically measuring our oceans, land, ice and atmosphere. The information feeds a range of practical applications and is used for monitoring and understanding large-scale global dynamics. Sentinel-3A will soon be joined in orbit by its identical twin, Sentinel-3B. Both satellites carry a suite of cutting-edge instruments to supply a new generation of data products, which are particularly useful for marine applications. For example, they monitor ocean-surface temperatures for ocean and weather forecasting services, aquatic biological productivity, ocean pollution and sea-level change. The mission also delivers unique and timely information about changing land cover, vegetation, urban heat islands, and for tracking wildfires. With the two satellites in orbit, global coverage and data delivery will be optimized (video credit: ESA, published 6 March 2019)
• March 01, 2019: The Alps extend 1200 km through eight different countries: France, Monaco, Italy, Switzerland, Liechtenstein, Germany, Austria and Slovenia. This mountain range, which is inhabited by some 20 million people, covers an area of approximately 200,000 km2. 52)
- The Copernicus Sentinel-3A satellite takes us over the high, snow-studded Alps under clear skies (Figure 30). Patches of snow are visible on the island of Corsica, to the left of mainland Italy, Croatia, to the right, and at the bottom of the Apennines in central Italy. Most of Italy's rivers find their source in the Apennines, including the Tiber and the Arno.
- The Adriatic Sea to the east of Italy is visible in turquoise, particularly the coastal area surrounding the Gargano National Park, jutting out. This light-green color of the sea along the coast is likely to be caused by sediment carried into the sea by river discharge.
- Directly to the right of the Alps, the image shows a pale-green Lake Neusiedl straddling the Austrian-Hungarian border. Neusiedl, meaning ‘swamp' in Hungarian, is the largest endorheic lake in central Europe, meaning water flows into but not out of the lake, hence its size and level frequently fluctuates. It is a popular area for windsurfing, sailing and spotting the woolly Mangalica pig.
- To the right, the freshwater Lake Balaton is visible, it is the largest lake in central Europe. It stretches for over 75 km in the southern foothills of Hungary. Its striking emerald-green color is probably due to the presence of algae that grow in the shallow waters.
Figure 30: Captured on 16 February 2019 with Sentinel-3A, this true-color image shows little clouds, particularly over the Alps and the surrounding flatter lands in southern France. There is an interesting contrast between this and the haze hanging over the Po valley in Italy, directly south of the Alps. The haze is most likely to be a mix of both fog and smog, trapped at the base of the Alps owing to both its topography and atmospheric conditions. This image is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• December 6, 2018: From 12 December 2018, Sentinel-3B OLCI Level-1 Products will be available at Near Real Time (NRT) and Non Time Critical (NTC) timeliness. These data are the first Sentinel-3B OLCI data to be released after the successful completion of the Sentinel-3B commissioning phase. 53)
- The Sentinel-3 Product Notice for OLCI Level 1 provides information on the OLCI current processing baseline, product quality, known limitations, and product availability status. It is relevant for both Sentinel-3A and Sentinel-3B OLCI products.
- To receive Sentinel-3B UNS (User Notification Service) alerts by email, make sure you update your UNS subscriptions via our Earth Observation Portal (EOP).
Figure 31: Sentinel-3B OLCI L2 algal pigment concentration (image credit: EUMETSAT)
• December 3, 2018: From 6 December 2018, Sentinel-3B STM Level-1 and Marine Level-2 Products will be available at Near Real Time (NRT), Short Time Critical (STC) and Non Time Critical (NTC) timeliness. 54)
- These data are the first Sentinel-3B STM (Surface Topography Mission) data products to be released after the successful completion of the Sentinel-3B commissioning phase.
- The Sentinel-3 Product Notices for STM Level-1 and for Level-2 Marine provide information on the SRAL/MWR current processing baseline, product quality, known limitations, and product availability status. They are relevant for both Sentinel-3A and Sentinel-3B STM data products.
Figure 32: Example of the Sentinel 3A and B SRAL Significant Wave Height product (image credit: EUMETSAT)
• November 23, 2018: The Copernicus Sentinel-3A satellite takes us over the Gulf. Also known as the Arabian Gulf and the Persian Gulf, this marginal sea of the Indian Ocean is just under 1000 km long and covers an area of around 250,000 km2 (Figure 33) . It is bordered by eight nations shown counter-clockwise from the top of the image – Iran, Iraq, Kuwait, Saudi Arabia, Bahrain, Qatar, United Arab Emirates and Oman. 55)
- Most of these countries are shown in a warm shade of orange in the lower part of the image. The variations in color in this area represent the different surface types and compositions. Some areas are purely sand, whilst others are a mixture of rocks and sand, or salt mineral deposits. Sand dunes are prevalent in the central area, depicting one of the largest and driest sand deserts in the world – the Rubh al Khali or the Empty Quarter.
- The satellite image shows in particular the significance of the Strait of Hormuz, the narrowest passage in the Gulf, a strait between the Persian Gulf and the Gulf of Oman. It provides the only sea passage from the Persian Gulf to the open ocean and is one of the world's most strategically important choke points. On the north coast lies Iran, and on the south coast the United Arab Emirates and Musandam, an exclave of Oman. At its narrowest, the strait has a width of 21 nautical miles (39 km). - About 20% of the world's petroleum (about 35% of the petroleum traded by sea) passes through the strait, making it a highly important strategic location for international trade.
- To reduce the risk of collision, ships moving through the Strait follow a Traffic Separation Scheme (TSS): inbound ships use one lane, outbound ships another, each lane being two miles wide. The lanes are separated by a two-mile-wide "median". To traverse the Strait, ships pass through the territorial waters of Iran and Oman under the transit passage provisions of the United Nations Convention on the Law of the Sea. The Strait of Hormuz is of vital importance of these waterways – not only economically, but also politically.
Figure 33: This image of Sentinel-3A, which was captured on 30 September 2018, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• November 9, 2018: The Copernicus Sentinel-3 mission takes us over Madagascar. This huge island nation, located off the east coast of Africa and seen in the left of the image, has a population of around 25 million. More than half of the country's inhabitants are aged under 25. The island is also home to rare flora and fauna, having developed its own ecosystems and wildlife since splitting from the African continent some 160 million years ago. 56)
- Preserving its impressive biodiversity is an ongoing challenge for the country. With an area of almost 600,000 km2, Madagascar is the fourth largest island in the world. Some of the world's most extensive coral reef systems, huge mangrove areas, and a vast array of birds, lemurs, and many other species can be found here. Deforestation poses a serious threat to the island's habitats, with illegal wildlife trade representing a further challenge.
- In this true-color image from Copernicus Sentinel-3's (OLCI (Ocean and Land Color Instrument), we can see sediment in the water along the coast. The island appears in green on the east coast, where the prevailing trade winds bring clouds and up to 3.5 m of rain per year to the low-lying coast.
- The central and western highlands and coast appear in brown and are much dryer, especially between May to October. The volcanic mountainous area of Ankaratra can be found in the central highlands. In the north of the island, the highest peak of Maromokotro stands almost 2900 m above sea level.
- The Mozambique Channel, which separates Madagascar from the continent, is an important shipping route for east Africa and home to significant tuna reserves. Efforts are underway to ensure that sustainability is considered in local development. Identifying and protecting critical habitats, such as migratory corridors, is part of this work.
- Sentinel-3 is a two-satellite mission to supply the coverage and data delivery needed for Europe's Copernicus environmental monitoring program. It provides critical information for a range of applications from marine observation to large-area vegetation monitoring.
Figure 34: Sentinel-3 captured this image on 7 August 2018. The image is also featured in the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• October 5, 2018: The Copernicus Sentinel-3 satellite takes us over eastern US. Spanning a huge area, including the states of Ohio, Maryland, West Virginia and Delaware, a number of major cities can be seen in this true-color image. The megacity of New York is visible in the top right. A megacity is defined by the United Nations as a city with a population of over ten million. According to the latest estimates there will be 43 megacities across the globe by 2030. 57) The image of Figure 35 is also featured on the Earth from Space video program
- Further down the coast, the US capital of Washington, D.C. can be seen in the upper-central part of the image. Washington, D.C. is a territory, not a state. The first part of the capital's name is in honor of the first president of the US, George Washington, and D.C. stands for District of Columbia, derived from Christopher Columbus.
- The brown color, that dominates the central part of the image, represents mountainous areas and forests, running through West Virginia and beyond. Known as the Mountain State, this is the only state completely within the Appalachian Mountain region. At around 460 m, its average elevation is higher than any other state east of the Mississippi River.
- To the north of West Virginia, Pennsylvania, which takes its name from a combination of Latin words, meaning ‘Penn's woods', stretches up towards New York. Half of this state is covered by forests, including the Allegheny National Forest, which can be seen in the top-center of the image.
Figure 35: This true-color image from Sentinel-3's OLCI (Ocean and Land Color Instrument), captured on 1 May 2018, shows sediment being carried into the North Atlantic Ocean along the coast. Sediment and potentially algae can also be seen in Lake Erie in the top left. This lake is the fourth-largest of the five Great Lakes of North America. It has a surface area of over 25,000 km2. Around five million tons of a type of rock salt called halite is mined from beneath the lake every year. The state of Ohio is also known for its fertile soil, coal, and natural gas reserves (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• September 7, 2018: The Copernicus Sentinel-3A satellite takes us over the North Sea, revealing a significant algae bloom covering most of the southern part. One of Europe's most productive fisheries, the North Sea covers an area of 570, 000 km2 and is linked to the Atlantic by one of the world's busiest shipping regions – the English Channel. 58)
- The image of Figure 36 covers a large section of Scandinavia, including Norway, the south of Sweden, and Denmark, stretching down to Germany and the Netherlands in the bottom right. On the left of the image we can see the east coast of Scotland and the Northern Isles, comprising two archipelagos – Orkney and Shetland. This image is also featured on the Earth from Space video program. 59)
- Harmful algal blooms caused by excessive growth of marine algae have occurred in the North Sea and the English Channel area in recent years, with satellite data being used to track their growth and spread. These data can then be used to help develop alert systems to mitigate against damaging impacts for tourism and fishing industries.
- Harmful blooms, which pose a threat to various forms of water life, are thought to carry an annual cost of over 900 million euros to these industries in the EU.
- Helping to map algal blooms and providing critical information for marine operations are just some of the ways that the two-satellite Sentinel-3 is used for Europe's Copernicus environmental monitoring program. Since 2016, Sentinel-3A has been measuring our oceans, land, ice and atmosphere to monitor and understand large-scale global dynamics. In April 2018, it was joined by its twin satellite Sentinel-3B.
Figure 36: This true-color image taken using Sentinel-3's OLCI (Ocean and Land Color Instrument) shows a significant algae bloom. The image was captured on 27 May 2017 (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• August 24, 2018: The Copernicus Sentinel-3A satellite took the temperature at the top of Hurricane Lane as it headed towards Hawaii's Big Island on 22 August 2018. Lane weakened to a Category 3 storm on 23 August, just before it hit Hawaii. Still a powerful storm, it has brought torrential rain to the Big Island. The island is still reeling from months of devastating lava flows from the Kilauea volcano and is now coping with heavy rain and flooding. The brightness temperature of the clouds at the top of the storm, some 12–15 km above the ocean, range from about –80°C near the eye of the storm to about 15°C at the edges (Figure 37). 60)
- Hurricanes are one of the forces of nature that can be tracked only by satellites, providing up-to-date imagery so that authorities know when to take precautionary measures. Satellites deliver information on a storm's extent, wind speed and path, and on key features such as cloud thickness, temperature, and water and ice content. Sentinel-3's Sea and Land Surface Temperature Radiometer measures energy radiating from Earth's surface in nine spectral bands.
Figure 37: The Copernicus Sentinel-3 mission takes the temperature of Hurricane Lane on 22 August as it headed for Hawaii (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• July 2018: Full coverage and revisit performance are achieved with both Sentinel-3A and Sentinel-3B in orbit. In order to guarantee long-term continuity of the Sentinel-3 mission, additional satellites (Sentinel-3C and Sentinel-3D) are under development as replacements to the initial satellite pair (S-3A and S-3B). In this way the series of Sentinel-3 satellites will ensure global, frequent and near-realtime ocean, ice and land monitoring, with the provision of observation data in routine, long term (up to 20 years of operations) and continuous fashion, with a consistent quality and a high level of reliability and availability. 61)
Table 4: Sentinel-3 mission activities
Figure 38: Schematic overview of planned Sentinel-3A and Sentinel-3B tandem mission activities identifying key elements (image credit: ESA, Ref. 61)
• July 20, 2018: With Europe in the grip of a heatwave and little rain, the scorched ground and dry vegetation is succumbing to fire. Fires have now broken out as far as the Arctic Circle, in Sweden. This animation shows images from the Copernicus Sentinel-2 (Figure 40) and Sentinel-3 (Figure 39) missions. Sentinel-2 carries a high-resolution MSI (Multispectral Imager) and Sentinel-3 carries a suite of instruments including an OLCI (Ocean and Land Color Instrument). The missions offer complementary views of Earth to help monitor environmental change and events such as these fires. 62)
- The fires have led to the authorities evacuating some villages and appealing for help from other countries, and concerns that the current record temperatures and drought are linked to climate change.
- There are said to be around 50 fires now burning in the country. Through July there have been three times as many fires as there were last year.
- Jonas Olsson from the Swedish Meteorological and Hydrological Institute is reported to have said, "It's very, very dry in most of Sweden. The flows in the rivers and lakes are exceptionally low, except in the very northern part of the country. We have water shortages. Rainfall has only been around a seventh of the normal amount, the lowest since record-keeping began in the late 19th century."
- While the focus is clearly on trying to extinguish these fires, the Copernicus Sentinel missions offer an eye in the sky to identify where fires have broken out. This is especially valuable in areas that are sparsely populated.
Figure 39: The wider view, which stretches from the west coast of Norway to central Sweden, was captured by Sentinel-3 on 17 July 2018. Here, smoke can be seen billowing from several fires (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA)
Figure 40: The closer view was captured on the same day (17 July) by Sentinel-2. Here, flames and smoke from two of the fires can be seen clearly, along with smoke from other fires in the vicinity (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA)
• July 13, 2018: The Copernicus Sentinel-3A satellite takes us over Shanghai, China. One of the most populous cities in the world and home to over 24 million people, the city is visible in the lower right of the image just above the Yangtze River mouth. As a significant global financial center it is also the site of the world's busiest container ports because of its strategic location on the Yangtze River delta. 63)
- The Taihu Lake is shown in green in the lower right part of the image. In 2007, an algal bloom on the lake caused major problems with water supplies in the neighboring city of Wuxi. Such algal blooms may well be linked to the discharge of phosphates found in fertilizers used in industry and agriculture into the water.
- Steps have been taken to limit the use of such fertilizers in a bid to reduce algal blooms, which can significantly alter the ecology of the environment below the surface and pose a threat to various forms of water life.
Figure 41: This true color image taken using Sentinel-3A's OLCI (Ocean and Land Color Instrument) shows the huge amount of sediment carried into the ocean along the coast. The image covers an area of over 1200 km side length, showing Beijing at the center-top, the salt flats close to the Mongolian border in the top left, and North Korea, with its capital, Pyongyang, just visible in the top right of the image. A large number of urban settlements represented as grey flecks are interspersed with agricultural fields, dominating the central part of the image (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• June 19,2018: The key to monitoring Earth's changing environment and to guaranteeing a consistent stream of satellite data to improve our daily lives is to take the same measurements over the course of decades. But how do you know that measurements from successive satellites, even though identical in build, are like for like? The answer, for the Copernicus Sentinel-3 mission, is to engage in some nifty orbital flying. 64)
- Sentinel-3 is a two-satellite mission to supply the coverage and data delivery needed for Europe's Copernicus environmental monitoring program.
- Launched in 2016, Sentinel-3A has been measuring our oceans, land, ice and atmosphere to monitor and understand large-scale global dynamics and to provide critical information for marine operations, and more.
- Its twin, Sentinel-3B, was launched in April 2018 and is having its instruments calibrated and being commissioned for service. Once Sentinel-3B is operational, the two satellites will orbit Earth 140° apart.
- Now, however, the satellites have been positioned much closer together, flying a mere 30 seconds apart. Travelling at 7.4 km/s, the separation equates to a distance of 223 km. - The reason for this is to see how their instruments compare.
- Even though the two Sentinel-3 satellites are identical, each carrying a radar altimeter, a radiometer and an imaging spectrometer, there's a chance that their instruments could behave slightly differently. It is important that any differences are carefully accounted for otherwise the information they deliver could be misinterpreted as changes happening on Earth's surface.
- Given the satellites' current brief separation, their measurements should be virtually the same. This tandem phase is also important for the future Sentinel-3 satellites.
- ESA's ocean scientist, Craig Donlon, explains, "Our Sentinel-3 ocean climate record will eventually be derived from four satellites because we will be launching two further Sentinel-3s in the future. We need to understand the small differences between each successive satellite instrument as these influence our ability to determine accurate climate trends. The four-month Sentinel-3 tandem phase is a fantastic opportunity to do this and will provide results so that climate scientists can use all Sentinel-3 data with confidence."
- ESA's Sentinel-3 project manager, Bruno Berruti, said, "Following liftoff and the usual checks, the operations team has been expertly flying Sentinel-3B so that it gradually flies closer to Sentinel-3A. We recently reached the magic separation of 30 seconds and I am happy to say that we are now officially in the tandem phase. This will last around four months, after which the two satellites will be gently moved apart until they reach their operational separation of 140°. This is different to the other Sentinel missions, but for our mission it is better to measure ocean features such as eddies as accurately as possible."
- ESA's Sentinel-3 mission manager, Susanne Mecklenburg, added, "So far, we are really happy with the results of the tandem phase. Measurements from the satellites' instrument packages seem to be very much aligned, but we will be analyzing the results very carefully over the next months to make sure we account for any minor differences."
Figure 42: Sentinel-3 tandem mission comparison (image credit: ESA, the images contain modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• June 8, 2018: For World Oceans Day, the Copernicus Sentinel-3A satellite takes us over the Atlantic Ocean and the Republic of Cabo Verde. Several of the small islands that make up the archipelago of Cabo Verde can be seen peeking out from beneath the clouds (Figure 43). These 10 volcanic islands, with a total area of about 4000 km 2, lie in the Atlantic Ocean about 570 km off the west coast of Senegal and Mauritania, which frame the image on the right. 65) 66)
- The most striking thing about this image, however, is the dust and sand being carried by the wind towards Cabo Verde from Africa. The sand comes mainly from the Sahara and Sahel region. Owing to Cabo Verde's position and the trade winds, these storms are not uncommon and can disrupt air traffic.
- However, this sand also fertilizes the ocean with nutrients and promotes the growth of phytoplankton, which are microscopic plants that sustain the marine food web. The iron in the dust is particularly important. Without iron mammals cannot make haemoglobin to transport oxygen around the bloodstream and plants cannot make chlorophyll to photosynthesize. Research has shown that around 80% of iron in samples of water taken across the North Atlantic originates from the Sahara. It can be assumed, therefore, that life in the deep ocean depends on this delivery of fertilizer from one of the world's most parched regions.
- World Oceans Day takes place on 8 June each year and celebrates the ocean, its importance in all our lives, and how we can protect it.
- Historically, the name "Cape Verde" has been used in English for the archipelago and, since independence in 1975, for the country. In 2013, the Cape Verdean government determined that the Portuguese designation Cabo Verde would henceforth be used for official purposes, such as at the United Nations, even in English contexts. Cape Verde is a member of the African Union.
Figure 43: The Sentinel-3A satellite captured this image on 30 May 2018 (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• June 5, 2018: Launched on 25 April 2018, Sentinel-3B has already delivered some impressive first images from its ocean and land color instrument, from its altimeter and from the optical channels of its radiometer. With the radiometer's thermal-infrared channels now turned on, the satellite completes its set of firsts with an image that depicts thermal signatures over southern Italy, the Mediterranean Sea and Sicily – with the hotspot of Mount Etna clearly visible. This image shows the ‘brightness temperature', which corresponds to radiation emitted from the surface. Further processing is needed to turn this into an actual temperature map. The land surface is shown in red–orange colors, corresponding to a brightness temperature range of 296–320K. The blue colors over the ocean correspond to a range of 290–295K. The dark blue–black areas correspond to clouds, which are opaque to thermal-infrared radiation and so prevent a view of the ocean or land surface. 67)
- Mount Etna, Europe's largest and most active volcano in Europe, appears much hotter than the surrounding land. In a state of almost continuous unrest, the volcano is currently classified as having ‘minor activity'.
- Over the oceans, the Sentinel-3 radiometer is important for providing SST (Sea Surface Temperature) measurements for oceanographic and weather forecasting centers. Over land, the instrument can be used, in particular, to monitor urban heat islands and wildfires.
- Sentinel-3B joins its identical twin, Sentinel-3A, in orbit. This pairing of satellites increases coverage and data delivery for the European Union's Copernicus environment program.
Figure 44: The infrared channels of Sentinel-3B's radiometer have been turned on and reveal the hotspot of Mount Etna in Sicily (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• May 11, 2018: Sentinel-3B has also delivered first data from its altimeter, SRAL (SAR Radar Altimeter), – which means that all of the instruments are working well. 68)
Figure 45: The altimeter has measured the height of Lake Van in east Turkey, close to the boarder of Iran. This brackish lake is the largest body of water in Turkey. The image shows two tracks, about 7 km apart, across the lake: one from the Sentinel-3A satellite on 26 April 2018 and one from Sentinel-3B on 9 May. They measure the lake to be 1647 m above sea level and clearly show the transition from land to water (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA)
- Sentinel-3B will not be fully commissioned for service for another five months or so, but even at this early stage in its life in orbit, these data compare well with those of its fully-operational twin, Sentinel-3A. The altimeter is particularly important for measuring changes in sea level, but as this example shows, the instrument also contributes to monitoring the height of lake water through the Copernicus Global Land Service. It is also used to measure the height of ice.
• May 11, 2018: The high-precision sea level anomaly measurements from SRAL (Synthetic Aperture Radar Altimeter) on Sentinel-3B enhance the Copernicus altimeter constellation of Sentinel-3A and Jason-3, along with Jason-2. 69)
Figure 46: The altimeter measurements, all acquired on 8 May 2018 over the Atlantic Ocean and the north American coastline, clearly match well at crossing points and the map of sea level anomalies produced by the Copernicus Marine Environment Monitoring Service (CMEMS), image credit: EUMETSAT, CMENS
- Pierre Yves Le Traon, Scientific Director at Mercator Ocean, which operates the Copernicus Marine Environment Monitoring Service (CMEMS), said receiving data from altimeters on two Sentinel-3 satellites will bring benefits to marine safety and industries.
- "The joint use of Sentinel-3A and Sentinel-3B high precision altimeters will improve capabilities of CMEMS to forecast waves and ocean currents at fine scale," Le Traon said. "This is highly needed for the applications we service, such as marine safety, maritime transport and offshore operations."
• May 10, 2018: The SLSTR (Sea and Land Surface Temperature Radiometer) is particularly sophisticated, measuring energy radiating from Earth's surface in nine spectral bands, including visible and infrared. It also includes dedicated channels for measuring fires. This early image came from its optical channels. 70)
- SLSTR measures the energy radiating from the Earth's surface in nine spectral bands, including visible and infrared. The thermal channels will be switched on once the instrument has completed outgassing water vapor, and the infrared channels have been cooled to the operating temperatures. 71)
- Sentinel-3B is currently flying in tandem with its twin, Sentinel-A, which was launched in 2016, so that their observations can be cross calibrated. The spacecraft are part of a series of Sentinel satellites under the umbrella of the EU's Copernicus program, which takes a continuous "health check" of our planet.
Figure 47: The SLSTR instrument on Sentinel-3B captured this image on 9 May 2018. It shows a low pressure system over the UK and Ireland, France, the Bay of Biscay, Spain and part of north Africa. Vegetation appears in red (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by EUMETSAT)
• May 9, 2018: Less than two weeks after it was launched, the Copernicus Sentinel-3B satellite has delivered its first images of Earth. Exceeding expectations, this first set of images include the sunset over Antarctica, sea ice in the Arctic and a view of northern Europe. 72)
- The very first image, captured on 7 May at 10:33 GMT , shows the transition between day and night over the Weddell Sea in Antarctica. The satellite also captured swirls of sea ice off Greenland on the same day. Another in this first set of images offers a rare cloud-free view of northern Europe. They were taken by OLCI (Ocean and Land Color Instrument) on Sentinel-3B.
Figure 48: The first image of OLCI on Sentinel-3B was captured on 7 May 2018 (10:33 GMT). The image shows the sunset over the Weddell Sea off the coast of Antarctica. While the line between day and night is clearly visible, bright streaks glint on the clouds from the sunset. OLCI, features 21 distinct bands, a resolution of 300 m and a swath width of 1270 km. The instrument can be used to monitor aquatic biological productivity and marine pollution, and over land it can be used to monitor the health of vegetation (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by EUMETSAT, CC BY-SA 3.0 IGO)
Figure 49: One of the Copernicus Sentinel-3B's first images of OLCI features Greenland. Captured on 7 May 2018 at 13:20 GMT, the image shows sea ice swirled into eddies caused by the wind and ocean currents (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by EUMETSAT, CC BY-SA 3.0 IGO)
- Josef Aschbacher, ESA's Director of Earth Observation Programs, said, "The launch of Sentinel-3B completed the first batch of Sentinels that we are delivering for Copernicus. We finished the launch and early orbit phase in a record time and we are now getting on with the task of commissioning the satellite for service. These first images from the ocean and land color instrument already show how the satellite is set to play its role in providing a stream of high-quality environmental data to improve lives, boost the economy and protect our world."
- Over oceans, OLCI measures the temperature, color and height of the sea surface as well as the thickness of sea ice. These measurements are used, for example, to monitor changes in Earth's climate and for more hands-on applications such as for monitoring marine pollution. Over land, this innovative mission monitors wildfires, maps the way land is used, checks vegetation health and measures the height of rivers and lakes.
Figure 50: This OLCI image of cloud-free Northern Europe on Sentinel-3B was captured on 8 May 2018 at 09:33 GMT. Features over land and water can been seen clearly such as different types of land cover, snow and also a plume of phytoplankton in the North Sea (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by EUMETSAT, CC BY-SA 3.0 IGO)
• April 27, 2018: This mosaic of cloud-free images from the Copernicus Sentinel-3A satellite spans the entire continent of Europe, and more. The view stretches from Iceland in the northwest across to Scandinavia and Russia in the northeast, and from the northern tips of Norway and Finland to as far south as Algeria, Libya and Egypt. 73)
- While the satellite's OLCI (Ocean and Land Color Instrument) depicts the green of summer in many parts of Europe, the dryness that summer brings, particularly to the south, can also be seen in parts of Spain, Italy and Turkey, for example.
- This week, aerospace fans have had their eyes firmly set on the ILA Berlin Air Show in Germany. Berlin lies in the center of the image (Figure 51). Here, participants have been learning about new space technologies as well as being treated to latest results from satellite missions such as ESA's Gaia, which has been used to chart the position, brightness and motion of more than a billion stars. With the second Sentinel-3 satellite, Sentinel-3B, lifting off from Russia this week, the focus has also been this latest Copernicus mission.
- Like Gaia maps stars thousands of light-years away to understand the Universe, the Sentinel-3 mission observes our home planet to understand large-scale environmental dynamics. Based on a constellation of two identical satellites, the Sentinel-3 mission carries a suite of instruments to measure our oceans, land and ice.
- Over land, this innovative mission is being used to map the way land is used, provide indices of vegetation, monitor wildfires and measure the height of rivers and lakes. Over oceans it measures the temperature, color and height of the sea surface as well as the thickness of sea ice.
Figure 51: The image, which is made up of scenes captured between 1 March 2017 and 30 July 2017, is also featured on the Earth from Space video program (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by Sinergise/ESA)
• April 26, 2018: With the launch of Sentinel-3B, the first set of Sentinels for Copernicus is now in orbit delivering an almost mind-boggling amount of data. While this wealth of information advances environmental monitoring, it also opens up huge business opportunities. To help bring these data to market, ESA and SAP have joined forces to create the World Space Alliance. SAP (Systems, Applications & Products in Data Processing) is a German-based (HQs in Walldorf) European multinational software corporation that makes enterprise software to manage business operations and customer relations. 74)
- ESA and SAP first teamed up two years ago to close the gap between traditional Earth observation and the digitalized business world. Building on this fruitful partnership, the two organizations today signed another agreement to strengthen the use of digital technologies and Earth observation data for a range of business sectors.
- Josef Aschbacher, Director of Earth Observation Programs at ESA, said, "Data from the Sentinels are, of course, open and freely available to everybody, but through our partnership with SAP we are working on making data products that businesses can easily tap into."
- The World Space Alliance will be powered by the SAP Cloud Platform. In turn, ESA also benefits from the platform's big-data handling and dissemination capabilities. The data it uses will come primarily from the Copernicus Sentinel missions, but also from other satellite missions that contribute to Copernicus.
- The agreement was signed at the ILA Berlin Air Show on 26 April 2018, this new agreement paves the way to strengthen the use of digital technologies and Earth observation data for a range of business sectors.
• April 26, 2018: ESA's mission control team keeping a close watch on the launch and progress of Sentinel-3B as it joined its identical twin, Sentinel-3A, to complete a constellation that will provide global monitoring of Earth's oceans, land, ice and atmosphere for Europe's Copernicus environmental monitoring program. 75)
- Europe's Copernicus program now has three complete two-satellite constellations in orbit plus an additional single satellite, Sentinel-5P, a mission to monitor air pollution.
- At the end of the commissioning phase, encompassing the first five months in orbit to test the functionality of the satellite, ESA will hand over operations of the satellite to EUMETSAT. ESA and EUMETSAT manage the mission jointly with ESA producing land products and EUMETSAT marine products for application through the Copernicus services.
Table 5: About the Tandem Phase of the Sentinel-3 mission (Craig Donlon, the Mission Scientist for the Copernicus Sentinel-3 and Sentinel-6 Satellites at ESA) 76)
- In two years since its launch, the Sentinel-3A satellite has delivered over 500 Terabytes of data about the Earth's oceans, land, ice and atmosphere. Its free and open data has allowed us to improve our understanding of large-scale global dynamics beyond expectations. Now, after two years of a solo journey, the Sentinel-3A finally has a twin – Sentinel-3B (Ref. 76).
• April 25, 2018: Just 92 minutes after liftoff, Sentinel-3B sent its first signals to the Kiruna station in Sweden. Data links were quickly established by teams at ESA's operations center in Darmstadt, Germany, allowing them to assume control of the satellite (Ref. 35).
- During the three-day launch and the early orbit phase, controllers will check that all the satellite's systems are working and begin calibrating the instruments to commission the satellite. The mission is expected to begin routine operations after five months.
- "This is the seventh launch of a Sentinel satellite in the last four years. It is a clear demonstration of what European cooperation can achieve and it is another piece to operating the largest Earth observation program in the world, together with our partners from the European Commission and EUMETSAT," said ESA Director General Jan Wörner.
- With this launch, the first set of Sentinel missions for the European Union's Copernicus environmental monitoring network are in orbit, carrying a range of technologies to monitor Earth's land, oceans and atmosphere.
- ESA's Director of Earth Observation Programs, Josef Aschbacher, said, "With Sentinel-3B, Europe has put the first constellation of Sentinel missions into orbit – this is no small job and has required strong support by all involved. It allows us to get a very detailed picture of our planet on a daily basis and provides crucial information for policy makers. "It also offers lots of opportunities for commercial companies to develop new innovative services. And, the free and open data policy allows every citizen to have updates for their own use. When we designed such a satellite constellation 20 years ago not everyone was convinced Europe could do that. I am glad to see this has become reality and that it is now a large European success story."
• April 13, 2018: EUMETSAT collects and disseminates data from three instruments carried by the Sentinel-3 satellites. They are: OLCI (Ocean and Land Color Instrument), SLSTR (Sea and Land Surface Temperature Radiometer), and SRAL (Synthetic Aperture Radar Altimeter). The SRAL instrument has been designed to deliver accurate measurements of sea surface height, significant wave height and surface wind speeds over the world's oceans. 77)
- Sea level rise is an important indicator of climate change. Globally, the sea level has been rising by an average of just over 3mm per year for the past 20 years. However, the rise is not uniform – it varies considerably around the world. Additionally, the rate of sea level rise is increasing by about 1mm per year each decade. This suggests that by the end of the century the sea level could have risen by as much as 65cm more than current projections.
- EUMETSAT Project Scientist and Altimetry Expert Remko Scharroo said the SRAL measures an array of important data in addition to sea level. "Sea surface height data from the satellite's altimeter have significantly improved our capability to analyze and forecast ocean currents," Scharroo said. "This is essential for the applications we serve such as marine safety, ship routing and predicting the fate of marine pollution events. Another set of data maps significant wave height, which again is important information needed for ship safety. Finally, the SRAL also provides accurate topography measurements over sea ice, ice sheets, rivers and lakes."
- The successful launch of Sentinel-3B at the end of April will represent the full deployment of the Sentinel-3 mission. Sentinel-3A was launched in February 2016 and has been delivering observations for two years. The two satellites are needed to provide the full set of measurements required by users.
- This includes for use in ocean meteorology, which is all about capturing significant wave height, wind speed and sea level measurements. Altimetry ensures the monitoring of ocean currents and eddies which carry a lot of energy throughout the ocean and interact with the atmosphere, thereby influencing the weather.
- An important example is the forecasting of hurricanes. Altimeters can help derive the latent heat in oceans. "You might argue that the SLSTR instrument does the same thing, that it measures heat in the ocean," Scharroo said. "But these are two different types of measurements entirely. "While sea surface temperature covers the total top layer of the ocean, it does not tell you much about the structure below. For this, you need altimeter measurements. Water expands when it's hot. The more heat penetrate the depth of the oceans, the higher the sea level rises and that will give you vital information about the column of water underneath. In short, the SLSTR provides information about the surface but not about the column of water underneath or the latent heat."
- Scharroo said both measurements were valid and important. "There is no competition between the instruments, believe me," he said. "It is in synergy that they work best."
Figure 52: Typical measurements of the instruments SRAL and SLSTR (image credit: EUMETSAT)
• April 9, 2018: EUMETSAT operates the Sentinel-3 satellites on behalf of the EU and delivers the marine mission. 78)
- Ocean Color data can be used for a wide variety of purposes. They can help to track and forecast harmful algal blooms, which can endanger humans, marine or freshwater life and aquaculture. These data also support the monitoring of coastal water quality, by tracking eutrophication, nuisance blooms, sedimentation and erosion.
- Ocean color data are also of a truly global importance as they help monitor climate change: ocean color is one of the so-called Essential Climate Variables (ECV) listed by the WMO (World Meteorological Organization) that help detect changes in biological activity in the ocean's surface layer.
- Ewa Kwiatkowska, EUMETSAT Remote Sensing Scientist explains: "Phytoplankton take up carbon dioxide (CO2) during photosynthesis, making the ocean the most important carbon sink. Alternatively, ocean color data can be used to monitor the annual global uptake of CO2 by phytoplankton on a global scale."
- Observations of ocean color support many industries, including fisheries and aquaculture, because of the phytoplankton role at the base of the aquatic food chain. They also support studies of the Earth system, for instance through monitoring El Niño/La Niña events and their impacts on ocean living ecosystems.
- She added: "Ocean color data can aid reporting obligations of the European Union's legislation within Marine Strategy Framework Directive and Water Framework Directive, the goal of which is to achieve or maintain Good Environmental Status of the seas by the year 2020."
- To ensure a steady flow of these vital data, two Sentinels are a must as Kwiatkowska explains. "Harmful outbreaks of algal bloom, require constant and consistent monitoring and forecasting from the OLCI instrument. With a cloud cover and gaps in coverage between successive orbits, there could be a discontinuity in the observations – with possibly detrimental effects.
- She continued "Also, there is a need to time phytoplankton blooms for ecosystem forecasts and to detect trends in eutrophication, where water body gets over-enriched with an excess amount of nutrients. This process induces growth of plants and algae and due to the biomass load, may result in oxygen depletion of the water body."
Figure 53: A typical OLCI ocean color image of Sentinel-3A (image credit: NASA Earth Observatory, image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response)
• April 6, 2018: The Copernicus Sentinel-3A satellite takes us over southern Siberia and the world's largest freshwater lake: Lake Baikal. Imaged on 14 March 2017, this deep lake is covered by ice. The entire lake is typically covered between January and May and in some places the ice can be more than 2 m thick. 79) 80)
- Holding around 23 000 km3 of water, Lake Baikal is the largest freshwater lake by volume in the world. It contains about 20% of the world's fresh surface water, which is more than all of the North American Great Lakes put together. Baikal water is extraordinarily clean, transparent and saturated with oxygen. The high transparency is thanks to numerous aquatic organisms purifying the water and making it similar to distilled water.
- At 25 million years, this remarkable lake is also the oldest in the world. It is known as the Galapagos of Russia because its age and isolation have produced rich and unusual water wildlife, which is of exceptional value to evolutionary science. Occasionally, new species are discovered and it has been estimated that we know of only 70–80% of all the species inhabiting the lake. For these reasons, in 1996 it was listed as a UNESCO World Heritage Site. The lake is surrounded by mountain-taiga landscapes, which are also protected to preserve their natural state.
Figure 54: This false-color image was acquired on 14 March 2018 with Sentinel-3A (image credit: ESA, this image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• March 9, 2018: The Copernicus Sentinel-3A satellite carries a suite of state-of-the art sensors that deliver a wealth of information to monitor our changing world, but this image was captured with its OLCI (Ocean and Land Color Instrument) . With a swath-width of 1270 km, this instrument delivers images that can span several countries, as we see here. 81)
- From east to west, the image features the islands of Corsica and Sardinia in the Mediterranean Sea, Italy and across the Adriatic Sea to Croatia, Bosnia and Herzegovina, Serbia, and to the western edges of Romania. To the north and partly obscured by clouds, lie Germany, Switzerland, Austria and the Alps.
- South of the Alps, haze hovers over Italy's Po Valley. Following the Po River to the east, the sediment it carries can be seen entering the Adriatic Sea. In fact, sediments line most of the eastern coast of Italy, giving it a greenish blue frame, while the western coast is mostly sediment-free.
- As the colors in this image suggest, the camera can be used to monitor ocean ecosystems and vegetation on land – all of which will bring significant benefits to society through more informed decision-making.
- Sentinel-3A will soon be joined in orbit by its twin Sentinel-3B, which is scheduled for liftoff from Russia on 25 April. The pairing of identical satellites provides the best coverage and data delivery for Europe's Copernicus program – the largest environmental monitoring program in the world.
Figure 55: This image was captured by Sentinel-3A on 28 September 2016 (image credit: ESA, the image contains modified Copernicus Sentinel data (2016), processed by ESA, CC BY-SA 3.0 IGO)
• February 28, 2018: Italy is usually associated with relatively warm weather, but this week it, too, has fallen victim to the cold snap nicknamed the Beast from the East. 82)
- Freezing temperatures carried on winds from Siberia have brought snow to much of Europe, causing widespread disruption. As this image captured on 27 February by the Copernicus Sentinel-3A satellite shows, Italy in southern Europe was not spared. Temperatures in Rome (bottom right of the image) are normally between 6°C and 14°C, but this week it has been down to –5°C during the night, and it is the first time the city has seen snowfall in six years. Naples also had its heaviest snowfall in decades.
Figure 56: Sentinel-3A image of northern Italy, acquired on 27 Feb. 2018, showing in partucular the snow-capped Apennine mountain range (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• February 9, 2018: The Copernicus Sentinel-3A satellite takes us over the Atlantic Ocean close to Spain and Portugal where the sky not only features clouds but also crisscross tracks from maritime vessels. 83)
- The familiar condensation trails – or contrails – we see in the sky usually come from aircraft, so it might seem strange that ships can also occasionally leave their mark in the sky. This rarely seen maritime twist on aircraft contrails was captured by Sentinel-3A on 16 January 2018. Known as ship tracks, these narrow cloud streaks form when water vapor condenses around small particles that ships emit in their exhaust fumes. They typically form when low-lying stratus and cumulus clouds are present and when the air surrounding the ship is calm.
- Like aircraft contrails, ship tracks may also play a role in our climate by reducing the amount of sunlight that reaches Earth's surface or conversely by trapping the Sun's radiation in our atmosphere – but this remains an uncertain aspect of climate science.
- The Copernicus Sentinel-3A satellite carries a suite of sensors including OLCI (Ocean and Land Color Instrument), which was used to capture this image of Figure 57.
Figure 57: Sentinel-3A image of the Atlantic Ocean off the coast of Portugal and Spain, captured on 16 January 2018, showing ship track contrails in the clouds. Although the Strait of Gibraltar is a busy shipping lane, with numerous ships travelling in and out of the Mediterranean Sea, there are no ship tracks visible here in the image. Most tracks are several hundred of kilometers off shore (image credit: ESA, the image contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO)
• January 11, 2018: Wave information is crucial for people working at sea, to be able to navigate and operate safely. A new product based on satellite altimeter data detailing ‘Significant Wave Height' now enables this. 84)
- High waves are not only dangerous but can threaten delicate procedures at sea, so wave information is paramount for operating safely and efficiently. For instance, in oil and gas offshore platform operations, historic data and forecasts of wave heights are vital for the safety of personnel, equipment and the environment.
- Marine renewable energy operations and site studies require similar information on waves and ship routing can also be improved by such forecasts.
- In physical oceanography, the SWH (Significant Wave Height) is defined traditionally as the mean wave height (trough to crest) of the highest third of the waves. This mathematical definition of ocean wave height is intended to express the height that would be estimated by a trained observer, capturing the most significant waves over the water surface.
- Satellite wave measurements come from two main sources: altimetry and SAR (Synthetic Aperture Radar). The SWH can be obtained through altimetry and directional and spectral information with SAR.
- CMEMS (Copernicus Marine Environment Monitoring Service) released the first realtime global wave product based on satellite data, broadening its offer—previously based on numerical wave forecast models. Released in the summer of 2017, this new product from satellite altimeter data contains the Significant Wave Height from Jason-3 and from the Copernicus Sentinel-3A satellite altimeter data, provided within three hours after data acquisition.
- It provides quality-filtered and inter-calibrated along-track high-resolution SWH (one measurement every 0.7 km, or every second). These measurements contribute to global ocean coverage along the satellite ground tracks with 0.7 km resolution.
- Such satellite wave products represent actual measurements of the waves, covering the entire Earth, regularly and homogeneously over several years. They often offer a better portrayal of extreme events, which numerical models tend to under estimate.
- In-situ wave data, typically provided by buoys, are similarly very helpful but in many open-water areas such moored buoys are not available, mainly due to the technical difficulty and cost of installing and maintaining them in deep ocean, far from the coast (Figure 58).
Figure 58: In-situ wave data, typically provided by buoys, are very helpful to validate satellite wave products but in many areas of open water such buoys are not available, because of the difficulty and costliness of installation and maintenance (image credit: INSITU TAC /CMEMS)
- Sentinel-3A's wave data are also assimilated into numerical realtime wave models to provide wave forecasts with better accuracy. For example, assimilation into the CMEMS global wave forecast model has a strong impact in the north-west of the Pacific Ocean related to the typhoon season and in the Gulf of Mexico after Hurricane Harvey (Figure 59).
- Dr Romain Husson, responsible for wave products at CLS for CMEMS, says, "In the first quarter of 2018, CMEMS will also deliver wave products derived from Sentinel-1A and -1B's SAR instruments. With respect to altimetry, SAR has the unique ability to measure the wave period and direction on top of the SWH and is particularly well suited for long waves, sometimes also referred to as swell."
Figure 59: Sentinel-3A wave data assimilation in the CMEMS global wave forecast model has a strong impact in the north-west of the Pacific Ocean related to the typhoon season and in the Gulf of Mexico after Hurricane Harvey. Analysis increment (in meters) of SWH after 1-day of assimilation of Sentinel-3A wave data in the CMEMS Global Wave Model MFWAM (starting date on 29 August, 2017 at 06:00 UTC to 30 August, 2017 at 0:00 UTC), image credit: ESA, the image contains Copernicus Sentinel data (2017)/ processed by Météo France/CMEMS
• December 22, 2017: EUMETSAT has released a series of videos that provide training on how to access, download and manipulate Sentinel-3 marine data from its Copernicus Online Data Access (CODA) platform. - A set of three Copernicus Sentinel-3 marine user handbooks has also been published. They will enable end users to become familiar with the main features of products based on data coming from instruments onboard Sentinel-3. 85)
• December 21, 2017: Monitoring large, remote bodies of water is logistically challenging, time consuming and expensive. Responding quickly to events that pose a risk to human health has been almost impossible, given the size of some lakes and seas. An innovative satellite data service is now able to change things around. 86)
- Based on satellite remote-sensing data, CyanoLakes RealTime is an online monitoring and mapping service, designed by leading specialist scientists at CyanoLakes (Pty) Ltd. It significantly improves water and health authorities' ability to monitor, respond to and manage cyanobacteria, algal blooms and water weeds in both fresh and salt waters.
- Cyanobacteria blooms pose a serious health threat to humans and animals and are increasingly common due to pollution and a warming climate. Eutrophication can devastate natural ecosystems and increases the cost of water treatment.
- In October 2014, Mark Matthews won the Copernicus Masters Ideas Challenge for applications using satellites. He developed an algorithm able to distinguish between cyanobacteria and algae, which was recognized as a breakthrough in research and innovation, and also solved many of the challenges associated with using satellite data for routine monitoring applications.
- With his new algorithm, Dr. Matthews envisaged an online information service providing daily warnings on the health risks from cyanobacteria blooms. This would allow water and health authorities an unprecedented ability to monitor in near-real time for cyanobacteria and algal blooms, ultimately protecting the general public from this kind of pollution.
Figure 60: Products from Sentinel-3 and MERIS: The products from the maximum peak height algorithm include cyanobacteria, floating cyanobacteria also known as scum, and floating aquatic vegetation (image credit: the image contains MERIS imagery modified by CyanoLakes Pty Ltd.)
- In 2015, after being awarded with a research grant by the Water Research Commission, CyanoLakes (Pty) Ltd began working on a prototype for South Africa.
- The South African Department of Water and Sanitation became the first user of the prototype, using the information to fill gaps in their monitoring database and for reporting.
Figure 61: Cyanobacteria risk level map: The cyanobacteria risk level map of the CyanoLakes RealTime prototype service for 102 water bodies in South Africa (image credit: CyanoLakes (Pty) Ltd.)
- In January 2017, following the public release of data from the Copernicus Sentinel-3 satellite, the prototype started to be used in near realtime operations, enabling a variety of solutions for many fields.
- These applications included filling information gaps in data-poor regions for water scientists and engineers, improving the safety of water sport events, providing aquaculture operators with warnings of harmful algal blooms to reduce economic losses, and wide-scale monitoring and mapping of cyanobacteria blooms and eutrophication for water and health authorities.
Figure 62: Near real-time monitoring of chlorophyll-a: The CyanoLakes RealTime detailed viewer showing chlorophyll-a concentrations for the Vaal Dam, South Africa, on 08 October 2017 (image credit: the image contains modified Copernicus Sentinel data (2017), processed by CyanoLakes Pty Ltd.)
- The OLCI (Ocean and Land Color Instrument) on Sentinel-3A is currently the only sensor in space with the necessary spectral bands, radiometric sensitivity, spatial resolution and coverage for near realtime services related to the detection of cyanobacteria.
- Using the prototype service, the Department of Water and Sanitation was able to monitor the massive outbreak of the invasive water hyacinth at Hartbeespoort dam, which occurred during 2016–17.
- Dr Matthews said, "Sentinel-3 is the backbone of the CyanoLakes RealTime service, given its unique instrument characteristics. Without it, we could not provide our service to the market. We are excited about the launch of Sentinel-3B in 2018 because it will allow us to provide an even better service, with daily updates to clients anywhere around the globe."
Figure 63: Near real-time monitoring of water hyacinth: The CyanoLakes RealTime detailed viewer is showing water hyacinth (magenta) at Hartbeespoort Dam, South Africa, on 11 October 2017 (image credit: the image contains modified Copernicus Sentinel data (2017), processed by CyanoLakes Pty Ltd.)
• November 3, 2017: From the fourth most populous city to the rugged Outback, the Sentinel-3A satellite gives us a wide-ranging view over Australia's southwestern corner. This perspective from space clearly illustrates human's influence on our environment: the agricultural landscape that dominates in the lower-left is suddenly interrupted by the more densely vegetated national parks and forests.
- The city of Perth is located on the coast along the left edge of the image (Figure 64). About 150 km north of Perth sits ESA's tracking station at New Norcia, where a 35 m diameter radio dish communicates with deep-space missions such as Rosetta and Mars Express.
- Moving further inland, grasslands give way to the deserts of Australia's vast and remote interior – known as the Outback – with a landscape dominated by red soil and sparse vegetation. Several large salt lakes are visible across the image in white, including the appropriately named Lake Disappointment by explorer Frank Hann in search of fresh water (top of image).
- Clouds over the ocean obstruct our view of the southern coast, but the lack of cloud cover over the interior desert pronounces the dry climate, which is a consequence of global wind patterns.
- Sentinel-3 offers a ‘bigger picture' for Europe's Copernicus program by systematically monitoring Earth's oceans, land, ice and atmosphere to understand large-scale global dynamics.
- While the satellite mission carries a suite of cutting-edge instruments, this image, also featured on the Earth from Space video program, was captured on 9 April 2017 by the satellite's OLCI (Ocean and Land Color Instrument), which helps to monitor ocean ecosystems, supports crop management and agriculture, and provides estimates of atmospheric aerosol and clouds.
Figure 64: Sentinel-3A image of western Australia, acquired on 9 April 2017 with OLCI (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• October 12, 2017: The Copernicus Sentinel-3A satellite captured this image on 11 October 2017 (Figure 65), when Hurricane Ophelia was about 1300 km southwest of the Azores islands and some 2000 km off the African coast. 87)
- Originally classified as a tropical storm, it has been upgraded to a hurricane. The US National Hurricane Center said that Ophelia could become even stronger in the next days.
Figure 65: The image was acquired at 12:45 GMT on 11 Oct. 2017 by the satellite's OLCI instrument (image credit: the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• On 28 August, 2017, EUMETSAT's near-real-time dissemination service went to the next level when EUMETSAT's CODA (Copernicus Online Data Access) service, became operationally available to users via the new single-sign on option. 88)
- It ensures that CODA users can access both Copernicus and data from EUMETSAT's Earth observation portal with one username and password.
- In combination with EUMETCast - a flexible multicasting service delivering the unified data streams from Copernicus and EUMETSAT's own missions, as well as EUMETview - an interactive visualization service especially for satellite imagery, EUMETSAT's data services provide solutions for a variety of different needs:
a) Sourcing Copernicus Data with CODA: EUMETSAT's CODA service is a rolling archive featuring a month's worth of Sentinel-3 data through an uncomplicated web interface as well as a scripting service, which allows users to automate bulk data downloads (within certain parameters).
After an extensive pilot phase, the CODA service is now fully available to users. CODA is particularly relevant for the ocean and remote sensing scientists, but its benefits reach beyond the scientific community. Developers in the public and private sector, be it for products or information services, can use CODA to develop innovative applications.
Hayley Evers King (Plymouth Marine Laboratory) summarizes her experience: "CODA is ideal for our daily business. It allows us to investigate specific areas and locate data for a particular region anywhere on the globe. This is, for example, useful when spotting algae blooms. The handling is particularly easy and follows a streamlined, user-friendly process. CODA allows us to select data without needing much experience. This is immensely helpful."
b) Data dissemination via EUMETCast: The vast majority of marine data from the Copernicus-3A satellite, operated by EUMETSAT on behalf of the European Union, are now available on EUMETCast. With this milestone, EUMETSAT's flexible multicasting service now delivers unified data streams to Copernicus users integrating observations from Copernicus and its own missions. This new marine data stream, involving products from Sentinel-3A, Jason-3, Metop and Meteosat creates a broad range of opportunities for the downstream development of applications, services and – ultimately – added value in Europe.
For Hayley Evers King (Plymouth Marine Laboratory) EUMETCast is important because "... it allows us to routinely and quickly access large amounts of data. We use it together with CODA and EUMETview; having these various sources of data access will increase the number of users for Copernicus data."
• August 25, 2017: The Copernicus Sentinel-3A satellite saw the temperature at the top of Hurricane Harvey on 25 August 2017 at 04:06 GMT as the storm approached the US state of Texas. The brightness temperature of the clouds at the top of the storm, some 12–15 km above the ocean, range from about –80°C near the eye of the storm to about 20°C at the edges. 89)
- Hurricanes are one of the forces of nature that can be tracked only by satellites, providing up-to-date imagery so that authorities know when to take precautionary measures. Satellites deliver information on a storm's extent, wind speed and path, and on key features such as cloud thickness, temperature, and water and ice content.
Figure 66: SLSTR (Sea and Land Surface Temperature Radiometer) image of Hurricane Harvey, acquired on 25 Aug. 2017 at 04:06 GMT, approaching the coast of Texas (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• August 11, 2017: Southern Europe is in the grip of a relentless heatwave, fuelling wildfires and water shortages. Information from the Copernicus Sentinel-3A satellite has been used to map the sweltering heat across the region. 90)
- The map of Figure 67 shows that on 7 August 2017, temperatures of the land surface rose above 40°C – not an usual occurrence over the last weeks. Much of Italy, including Rome, Naples, Florence, Sardinia and Sicily has been suffering these highs. With numerous towns and cities on the ministry of health's maximum heat alert, the Italians have aptly dubbed the heatwave ‘Lucifer'. Extreme temperatures have also been recorded in Spain and Portugal, the Balkans and Greece.
- As well as wildfires and water shortages, the heat has also led to some tourist attractions being closed, ill health and even some fatalities, and the drought is also threatening crops.
- The map uses data from the satellite's SLSTR (Sea and Land Surface Temperature Radiometer), which measures energy radiating from Earth's surface in nine spectral bands – the map therefore represents temperature of the land surface, not air temperature which is normally used in forecasts. The white areas in the image are where cloud obscured readings of land temperature.
Figure 67: Southern Europe is in the grip of a heatwave, fuelling wildfires and water shortages. Information from the Copernicus Sentinel-3A satellite has been used to map the sweltering heat across the region (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• July 6, 2017: With the Copernicus Sentinel-3A satellite fully fledged and its data freely available, the task of monitoring and understanding our changing planet has been made that much easier. Seeing the effect spring has on our plant life is just one of its many uses. — Launched in February 2016 and carrying a suite of instruments, Sentinel-3 is the most complex of all the Sentinel missions. 91)
- As the workhorse mission for Europe's environmental monitoring Copernicus program, it measures Earth's oceans, land, ice and atmosphere systematically so that large-scale global changes can be monitored and understood. While Sentinel-3 offers this ‘big picture', it can also be used to monitor smaller-scale environmental issues such as urban heat islands.
- Sentinel-3 is well on the way to being at the heart of operational oceanography, but it also provides unique and timely information about changing land cover and vegetation health.
- For instance, the animation of Figure 68 uses information from the satellite's ocean and land color instrument to measure changing amounts of chlorophyll in plants. Here we clearly see the progress of spring greening in the northern hemisphere, for example.
Figure 68: The Copernicus Sentinel-3A's ocean and land color instrument can ‘see' chlorophyll in vegetation. The animation shows how chlorophyll, which is essential in photosynthesis, around the world changed between 1 April and 27 May 2017. While tropical rainforests can be seen to maintain a high degree of chlorophyll, the animation clearly shows the progress of spring greening in the northern hemisphere. This is particularly evident in the eastern part of the USA. It also captures the progress of agricultural planting for summer crops across China where planting normally takes place between March and May. Here various stages of growth are captured. The chlorophyll index ranges from 1 to 6.5 (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by University of Southampton–J. Dash/Brockman Consult (S3-MPC))
- Since its initial commissioning, when the satellite and instruments were meticulously fine-tuned, Sentinel-3A has been in a ‘ramp up' phase. - This means that over the last year, while the satellite was being prepared for its life as a fully operational mission, only ‘direct instrument' data were available. Another step in the processing chain is needed to translate them into more tangible information for users worldwide.
- This milestone has now been passed so that the best quality data possible are now freely available from the satellite's ocean and land color instrument and from the sea and land surface temperature sensor, which measures energy radiating from Earth's surface.
- This level of data from its other instrument – a radar altimeter, which measures the height of the sea surface, rivers, lakes and land – have been available since last December.
- ESA's Sentinel-3 mission manager, Susanne Mecklenburg, explained, "Sentinel-3 is an extremely complex mission, and I'm very proud to say that it's delivering on its promise.
Figure 69: Feeling the heat: Sentinel-3's Sea and Land Surface Temperature Radiometer includes dedicated channels for measuring fires. This will help to map carbon emissions from burnt biomass and to assess damage and estimate recovery of burnt areas. Information to help manage forest fires will be available using Sentinel-3 measurements combined with meteorological forecasting data. In addition, forests can be monitored systematically to assess risk and develop efficient plans to prevent forest fires (image credit: ESA/ATG medialab)
- "We have been working closely with our colleagues at Eumetsat to make sure it is ready to deliver top-quality data. This is important because while Eumetsat operates the satellite, both organizations manage the mission together.
- "ESA is responsible for the land data products and Eumetsat for the marine products – all of which are made available for the Copernicus services and other users. Measurements made by the satellite's color instrument over land now offer users key information to monitor the health of our vegetation, which is essential for agricultural practices, and to help plan resources. This also complements other missions such as the Copernicus Sentinel-2 and Proba-V. Together, they will be a powerful tool to map our changing lands."
- Sentinel-3 shows how Earth's surface temperature changes, which is also important for weather forecasting and for monitoring climate change. Over land, measurements can be used for urban planning, for example.
- Later in the year, data products will also be available for monitoring fires.
Figure 70: Sentinel-3A senses Earth's heat: Information from Sentinel-3A's radiometer, which measures radiation emitted from Earth's surface, reveal how the temperature of Earth's land changes between July and November 2016. Measurements are in kelvin (image credit: ESA, the image contains modified Copernicus Sentinel data (2016), processed by UK National Center for Earth Observation/University of Leicester)
• June 23, 2017: Sentinel-3 gives us a nearly cloud-free view of France and the surrounding countries (Figure 71). Much of the landscape is covered with agricultural features. In fact, farmers manage nearly half of Europe's land area. While agriculture brings benefits for economy and food security, it puts the environment under pressure. Satellites can help to map and monitor land use, and the information they provide can be used to improve agricultural practices. 92)
- On the right side of the image we can see the snow-covered Alps, while the Pyrenees mountains are visible near the bottom.
- To the west of the Alps a green area of mountains and plateaus is visible, called the Massif Central. The region has more than 400 volcanoes, considered by scientists to be extinct.
- On the right side of the image, the light brown area flanked by dark areas is the Rhine River forming part of France's border with Germany. The dark area to the east is the Black Forest, while the dark area to the west are the Vosges Mountains.
- Just above the center of the image, we can see Paris – the site of ESA's headquarters as well as the Paris Air & Space Show taking place this week.
Figure 71: This image of France was captured by the Copernicus Sentinel-3A satellite's OLCI (Ocean and Land Color Instrument) on 7 April 2017. OLCI monitors ocean ecosystems, supports crop management and agriculture, and provides estimates of atmospheric aerosol and clouds – all of which bring significant benefits through more informed decision-making (image credit: ESA, this image contains modified Copernicus Sentinel data (2017), processed by ESA, CC BY-SA 3.0 IGO)
• April 27, 2017: The Copernicus Sentinel-3A satellite brings us over the Bering Sea, north of the Alaska Peninsula, on 26 March. Seasonal sea ice dominates the upper part of the image. Ice plays an important role in the sea's ecosystem. Growing algae attach to the bottom of the ice; when the ice melts in the spring, it leaves behind a layer of nutrient-rich freshwater on which the algae thrive. Organisms higher up the food chain then eat the algae. 93)
- In the top-right corner of Figure 72, we can see part of Alaska's mainland blanketed with snow, as well as Nunivak Island appearing like a massive piece of floating ice. At the center of the image are the islands of Saint Paul and Saint George – part of the Pribilof Islands. An estimated two million seabirds nest on these islands annually.
- The swirling clouds on the right side of the image are the result of a meteorological phenomenon known as a von Kármán vortex street. As wind-driven clouds pass over the Unimak Island on the right edge of the image, they flow around the high volcanoes to form the large spinning eddies that can clearly be seen in the image.
Figure 72: A Sentinel-3A image of the Bering Sea, acquired on March 26, 2017 (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA , CC BY-SA 3.0 IGO)
• March 10, 2017: A Sentinel-3 image in the Russian Far East and of the Kamchatka Peninsula is provided , located between the Pacific Ocean to the east and the Sea of Okhotsk to the west, where clouds blend with the ice and snow beneath from the bird's-eye view (Figure 73). One of the fascinating features is the pattern of floating sea ice, appearing in light blue. Along the left, one can see cracks in the ice covering the water. In the middle/right, small pieces of fragmented ice, driven by wind and currents, create the swirls of blue along the coast of the Kamchatka Peninsula. 94)
- Kamchatka, a 1250 km long peninsula with an area of 270, 000 km2, has a landscape covered with volcanoes due to its location along the highly active Pacific ‘Ring of Fire'. There are about 160 volcanoes on the peninsula, 29 of which are still active. The central mountain range running down the spine of the peninsula, is visible in the image, while the eastern range is mostly covered by clouds. Between them lies the central valley, appearing somewhat brown from the lack of snow cover.
- It is no surprise that the area is often referred to as the ‘land of fire and ice'. Owing to minimal development, the peninsula is known for its abundance of large brown bears. Other common animals include foxes, wolves, reindeer and wolverines.
Figure 73: The OLCI (Ocean and Land Color Instrument) on Sentinel-3A image of the Kamchatka Peninsula (on the right side) was acquired on Feb. 15, 2017 (image credit: ESA, the image contains modified Copernicus Sentinel data (2017), processed by ESA)
• December 13, 2016: Launched in February 2016 with a suite of cutting-edge instruments, Sentinel-3A is arguably the most comprehensive of all the Copernicus Sentinel missions. Since then, the satellite has been thoroughly tested and fine-tuned. This led to the release of its first Earth color data in October and first radiometer data last month. Now, the public also have access to data from its radar altimeter. 95)
- Sentinel-3A's topography package will bring a step change in satellite altimetry, measuring the height of the sea surface, waves and surface wind speed over the oceans. It also provides accurate topography measurements over sea ice, ice sheets, rivers, lakes and land. Over the oceans, the radar altimeter contributes information for forecasting, which is essential for safe maritime operations, for example. Monitoring sea-level change and diminishing Arctic ice is also important for monitoring the effects brought about by climate change.
- As the image of Antarctica shows (Figure 74), the radar altimeter is also important for measuring changes in the height of land ice. The data may seem relatively sparse at the moment, but this is because they only show a few days' readings. Accurately measuring changes in the height of the huge ice sheets that blanket Antarctica and Greenland is important for climate research and understanding sea-level change.
- ESA's CryoSat mission currently measures changes in ice height and paved the way for Sentinel-3's radar altimeter. Importantly, Sentinel-3's radar altimeter is the first to provide 100% coverage over all of Earth's surfaces in ‘synthetic aperture radar' mode. For accuracy, Sentinel-3's topography package also includes a microwave radiometer that is used to correct measurements from the radar altimeter affected by water vapor in the atmosphere.
- While changes in ice height may be relatively slow, the radar altimeter will also be used to measure changes that can be more abrupt, such as the height of water in lakes and rivers.
- The Sentinel-3 mission is managed jointly by ESA and EUMETSAT. The day-to-day operations of the Sentinel-3A satellite are carried out by EUMETSAT. ESA, as the developer of the mission, continues to monitor its health and performance. ESA is responsible for the land data products and EUMETSAT for the marine products – all of which are made available for application through Copernicus services.
Figure 74: The SRAL (SAR Radar Altimeter) of the Sentinel-3A spacecraft measured the height of the Antarctic ice sheet (image credit: ESA, the image contains modified Copernicus Sentinel data (2015), processed by UCL–MSSL)
• November 17, 2016: Following the release of Sentinel-3A's first Earth color data, the public now have access to data from the satellite's radiometer, which measures energy radiating from Earth's surface in nine spectral bands. Arguably the most comprehensive of all the Copernicus Sentinel missions, Sentinel-3A carries a suite of state-of-the-art instruments to systematically measure Earth's oceans, land, ice and atmosphere. 96)
- Since it was launched in February 2016, the satellite has been thoroughly tested and fine-tuned. This led to the release of first-level data from its OLCI (Ocean and Land Color Instrument) in October and now data from the SLSTR (Sea and Land Surface Temperature Radiometer) are also available.
- Information from the radiometer will be used to create global maps of SST (Sea Surface Temperature) for ocean and weather forecasting. Over land, the instrument will be used, for example, to detect heat stress, which is useful for improving agricultural practices and monitoring urban heat islands. As cities continue to expand, understanding how heat islands develop is important for planners and developers.
- Importantly, the radiometer has dedicated channels for measuring fires. This will help to assess damage and estimate recovery of burned areas.
- Further processing is needed to turn this kind of data (Figure 75) into actual ocean- and land-surface temperature maps. These next-stage data will start to be released in early 2017. Nevertheless, differences between the land, coasts and sea can be seen clearly in this brightness temperature image. — Data from the satellite's radar altimeter will be made available in December.
- While the day-to-day operations of the Sentinel-3A satellite are carried out by EUMETSAT, the mission is managed jointly by ESA and EUMETSAT. ESA is responsible for the land data products and EUMETSAT for the marine products – all of which are made available for application through Copernicus services.
Figure 75: The image, which stretches from northern France and Belgium to Italy and western Greece, is an example of first-level data from the radiometer. It shows ‘brightness temperature', which corresponds to radiation emitted from the surface (image credit: ESA, the image contains modified Copernicus Sentinel data (2015), processed by ESA)
• October 20, 2016: Today, the Copernicus Sentinel-3A satellite has taken another step towards being fully ‘operational' as the first data from its OLCI (Ocean and Land Color Instrument) are made available to monitor the health of our planet. Following its launch in February, the satellite and instruments have been thoroughly tested and fine-tuned – leading to this important milestone. - Carrying a suite of instruments, Sentinel-3A is arguably the most complex of all the Copernicus Sentinels. 97) 98)
- It has been designed to measure Earth's oceans, land, ice and atmosphere to monitor large-scale global dynamics and to provide critical near-realtime information for numerous ocean, land and weather applications.
- The Sentinel-3 validation team, a group of expert users, has been receiving sample products since May. Their feedback is essential to both ESA and EUMETSAT to ensure the data are of the highest quality, as is needed for the myriad of operational applications that the mission will serve.
- At the ‘end of commissioning' review in July, it was noted that a couple of points had to be addressed before the first data were officially released to the public.
- Susanne Mecklenburg, ESA's Sentinel-3 mission manager, said, "It is imperative that these first-level data are the best quality possible so we are being extremely careful. It is now very gratifying to see data from the satellite's Ocean and Land Color Instrument being released to users worldwide. "Data from the other two instruments – the SLSTR (Sea and Land Surface Temperature Radiometer) and SRAL (SAR Radar Altimeter) – will be made available in November and December, respectively."
- Offering new eyes on Earth, the OLCI (Ocean and Land Color Instrument) will monitor the global oceans, and inland waters, including phytoplankton, water quality, harmful algal blooms, sediment transport in coastal areas, El Niño and La Niña events, and climate change. It will also support observations of vegetation and crop conditions, as well as provide estimates of atmospheric aerosol and clouds – all of which bring significant benefits to society through more informed decision-making.
- While the operations of the Sentinel-3A satellite are carried out by EUMETSAT, the mission is managed jointly by ESA and EUMETSAT. ESA is responsible for the land data products and EUMETSAT for the marine products – all of which are made available for application through Copernicus services.
- Hilary Wilson, EUMETSAT's Sentinel-3 project manager, said, "The release of Sentinel-3A's first operational data is the culmination of a lot of hard work by ESA, EUMETSAT and the expert user teams. It represents an important milestone for the Copernicus Marine Environment Monitoring Service and also for the wider marine monitoring community. Routine operations of the satellite have been proceeding smoothly since EUMETSAT took over this responsibility in July and we are now focusing on bringing the remaining marine products to this community."
Figure 76: These two images, taken on 13 June 2016 and 22 August by Sentinel-3A's OLCI (Ocean and Land Color Instrument), show differences in ice cover in northeast Greenland. Differences in sea ice off the coast are clear to see. (image credit: ESA, the image contains modified Copernicus Sentinel data (2016), processed by ESA). 99)
• October 2016: Commissioning phase results of the Sentinel-2A Optical Payloads. 100)
Table 6: Optical CalVal activities of the Sentinel-3A spacecraft launch on Feb. 16, 2016 from Plesetsk/Russia Cosmodrome
With the successful launch of Sentinel-3A, a new era for the Copernicus Services has started offering data over oceans and lands with unprecedented coverage. Together with Sentinel-3B, its twin satellite scheduled for launch in 2017, and later on with the launch/replacement of the Sentinel-3C and D units, a 20-year period of continuous observations is guaranteed. Among the five instruments embarked, the OLCI and SLSTR optical payload ensure the continuity of the ENVISAT mission with very much improved performance. During the calibration validation (CalVal) phase functional, performance, product verification and validation were performed confirming the overall excellent performance of the optical payload.
Figure 77: This image of Europe was taken by Sentinel-3A's OLCI on 16 October 2016. The framed part of the image shows, for example, how its 1270 km-wide swath captures an area stretching from Spain to Italy. The ‘zoom in', depicted in Figure 78, shows the French landscape in detail and changes in water color off the south coast. The OLCI features 21 distinct bands in the 400–1020 µm spectral region tuned to specific ocean color, vegetation and atmospheric correction measurement requirements. As well as its wide swath, it has a spatial resolution of 300 m for all measurements, overlapping the satellite's SLSTR (Sea and Land Surface Temperature Radiometer) swath (image credit: ESA, the image contains modified Copernicus Sentinel data (2016), processed by ESA)
Figure 78: Zoom in image from Figure 77. The islands of Corsica and Sardinia can be seen in the west with coast of Tuscany and the island of Elba to the northeast. The waters along the east coast of Corsica and along the Italian coast are colored by discharge from the land following recent heavy rainfall (image credit: ESA, the image contains modified Copernicus Sentinel data (2016) processed by EUMETSAT) 101)
• September 30, 2016: The SLSTR (Sea and Land Surface Temperature Radiometer) visible channels onboard Sentinel-3A were turned on from 2nd March 2016 and the infrared channels on the 23rd March 2016. The first level 1 (L1b) data was released to expert and validation users on the 14th June 2016, with the level 2 (L2) data similarly released on the 21st June 2016. A successful commissioning review was held on the 12th July 2016, following this EUMETSAT resumed operations of the Sentinel-3A satellite. EUMETSAT processes Sentinel-3 marine data and products at its Sentinel-3 Marine Center, for real time delivery to end-users. 102)
- SST (Sea Surface Temperature) from SLSTR provides increased global coverage than AATSR due to an increased swath width (up to 1400 km) for both nadir only and dual (740 km) view scans. An example of the daily SST global coverage from Sentinel-3A for one day is shown in Figure 79.
Figure 79: Global map of Sentinel-3A SLSTR Sea Surface Temperature (day and night-time) for 17th September 2016 (image credit: EUMETSAT, ESA)