Meteorology - Geostationary
Measurement Types
The monitoring of weather from space is an incredibly valuable tool in predicting future weather events and patterns, both for daily use and for planning disaster relief efforts in the face of extreme weather. One of the most major developments in space-based weather monitoring has been the deployment of geostationary satellites. By matching their orbits to the rotation of the Earth, these satellites maintain a constant relative position over the Earth’s surface, enabling them to capture ‘stationary’ images of the planet. This allows weather patterns to be observed without changing perspectives, which polar-orbiting satellites experience. 1) 2) 3)
While advantageous, the geostationary orbit faces limitations and challenges. To reach this orbit, a satellite must match its orbital velocity to the Earth's rotation, which is achieved at an altitude of 35,786 km—a distance that spans nearly three times Earth's diameter. Such a distance reduces the resolution available to sensors imaging the Earth, compared to those in low Earth orbit. Additionally, geostationary orbits can only be achieved at the equator, leading to a limited view of the polar regions. However, due to their distance from the Earth, each satellite can view an entire hemisphere of the planet. These ‘full Earth disks’ provide coverage of all locations in view, regardless of country or remoteness. As a result, places with less developed weather forecasting technologies can still receive adequate disaster information, such as the tracks of hurricanes or other severe weather storms. These images are also captured with a high frequency and, because they are fixed in orbit relative to the ground, information can be readily collected and transmitted between ground stations and the satellites.
The first geostationary satellite was launched in 1966, and they have now become a quintessential part of modern weather forecasting. These early satellites were ‘spin-stabilised’, which meant that they would only view the Earth for 10% of each rotation. Newer satellites, such as those in the GOES (Geostationary Operational Environmental Satellites) series, are three-axis stabilised, and so are always pointed directly at the Earth. When a geostationary satellite is replaced, the predecessor needs to be moved out of the way. This is done by either reducing its altitude, where its speed becomes faster relative to the Earth’s rotation and it moves East, or by increasing its altitude, where its speed becomes slower relative to the Earth’s rotation and it moves West. It is common for geostationary satellites to be moved to ‘graveyard orbits’ at higher altitudes. 1)
Example Products
Full Disc Images
The images provided by modern geostationary satellites are ‘full disc’, meaning they cover the whole of the part of the Earth which is facing them (Figure 1). Having this stationary basemap allows the movement of particulates in the atmosphere to be observed over time, such as clouds, sand, or smog. They also permit weather observations in all parts of the Earth, as advocated for in the Early Warnings For All Initiative. Technological developments have drastically improved the image quality that geostationary satellites offer. 4) 5)
Target Area Images
While geostationary satellites can image the full Earth disc or, some are tasked to focus in on a target area in response to meteorological conditions, like the Himawari satellites which observe two fixed areas over Japan. For example, if a cyclone develops over the Pacific Ocean, Himawari-8 can target the cyclone’s location to take more frequent scans of the area than a full-Earth disc-viewing satellite would (Figure 2, 3). 6)
WeatherFAX
WeatherFAX is derived from radiofax, a technology in the 1920s developed to transmit monochromatic images with radio transmissions. The tool’s analogue mode allows weather information to be transmitted to remote areas of the ocean in support of sailing vessels. WeatherFAX is most effective in remote areas, as built-up areas introduce radio interference that affects signal transmission. Much of the satellite imagery and weather information used in WeatherFAX is derived from geostationary meteorological satellites (Figure 4). 7) 8) 9) 12)
Lightning Sensing
Lightning sensing is a capability to which geostationary meteorology is uniquely suited, as continuous observation provides a crucial element of timely warnings and forecasting. Space-based lightning sensing, particularly with regards to geostationary meteorology, tends to focus on the time, location, brightness, size, and duration of lightning strikes, however electric current, magnetic field and radiation can also be measured from orbit. Satellite-based lightning sensing typically uses an optical detection method, detecting brief bursts of visible light between cloud to cloud, cloud to ground, and intracloud lightning. An example of this is the Geostationary Lightning Mapper (GLM), a staring charge coupled device (CCD) array imager carried by the Geostationary Operational Environmental Satellite 16 (GOES-16) mission, also known as GOES-R. 13) 14)
Read more about space-based lightning sensors here.
Related Missions
GOES-R (Geostationary Operational Environmental Satellite-R)
Launched November 2016, GOES-R is a geostationary weather monitoring satellite operated by NOAA and NASA. It has a minimum operational life of 14 years and carries six instruments for monitoring the Earth’s surface, weather patterns, atmosphere, and space weather events such as solar flares. 14)
METEOSAT Second Generation
METEOSAT is a series of climate and forecasting missions developed by ESA and EUMETSAT. The METEOSAT Second Generation satellites began launching from August 2002, with spacecraft housing two primary instruments, the Spinning Enhanced Visible and Infra-red Imager (SEVIRI) and the Geostationary Earth Radiation Budget (GERB), which monitor widespread aspects of Earth’s climate and weather. 15)
MTG (METEOSAT Third Generation)
MTG was designed to enhance current imager capabilities of the METEOSAT constellation, including a new infrared sounding capability and real time lightning imaging for the early detection of severe storms. The first MTG satellite was launched in December 2022, with five more satellites planned to follow. 16)
Fengyun-2 and 4
Operated by NSMC (National Satellite Meteorological Centre) of CMA (China Meteorological Administration), Fengyun is the geostationary meteorological satellite series of China built by SAST (Shanghai Academy of Spaceflight Technology). The odd-numbered spacecraft in the constellation (e.g., FY-1, FY-3) designate polar orbiting satellites, while the even-numbered (e.g., FY-2, FY-4) designate the geostationary satellites. The first in the FY-2 series (FY-2A) was launched June 1997, while the first of the FY-4 series, FY-4A, was launched December 2016. 17) 18)
INSAT-3 (Indian National Satellite-3)
The INSAT-3 constellation of the Indian Space Research Organisation (ISRO) is a series of multipurpose geostationary satellites with applications in weather forecasting, meteorology, communications, disaster monitoring, and Satellite Aided Search and Rescue (SAS&R). The mission began with INSAT-3B launching in 2000, followed by 3C (2002), 3A (2003), 3D (2013), 3DR (2016), and 3DS (2024).
Launched in April 2003, INSAT-3A is a multipurpose geostationary spacecraft with state-of-the-art communication technology operated by ISRO (Indian Space Research Organisation). The satellite serves applications in communications, television broadcasting, meteorology, and Satellite Aided Search and Rescue (SAS&R). 19) 20)
Read more: INSAT-3A | INST-3D and 3DS | INSAT-3DR
GMS (Geostationary Meteorological Satellite)
Administered in partnership by JMA (Japan Meteorological Agency) as the operator and JAXA (Japanese Aerospace Exploration Agency) as the spacecraft and launch service provider, GMS is Japan’s first national satellite program for weather and environmental observations. It was launched 14 July 1977 and is also known by the name of Himawari (Sunflower). 21)
Himawari-8 and 9
Identical satellites owned and operated by JMA (Japanese Meteorological Agency), Himawari-8 and 9 aimed to provide typhoon, rainstorm, and weather forecasting for East Asia, Japan, and the West Pacific region. They were launched October 2014 and November 2016, respectively, carrying the AHI (Advanced Himawari Imager) and SEDA (Space Environment Data Acquisition Monitor) instruments. 22)
MTSAT (Multi-Functional Transport Satellites)
MTSAT is a geostationary dual-function satellite program operated by JMA, procured by JCAB (Japan Civil Aviation Bureau), and funded by the Japanese MLIT (Ministry of Land, Infrastructure and Transport). It includes an aeronautical mission to assist air navigation and a meteorological mission to provide imagery over the Asia-Pacific region. 23) 24)
References
1) “Weather Satellites,” NOAA, September 2023, URL:https://www.noaa.gov/jetstream/weather-satellites
2) “Types of Orbits,” ESA, March 2020, URL:https://www.esa.int/Enabling_Support/Space_Transportation/Types_of_orbits
3) “Geostationary Satellite,” ScienceDirect, URL:https://www.sciencedirect.com/topics/earth-and-planetary-sciences/geostationary-satellite
4) “New Weather Satellite Reveals Spectacular Images of Earth,” ESA, May 2023, URL:https://www.esa.int/Applications/Observing_the_Earth/Meteorological_missions/meteosat_third_generation/New_weather_satellite_reveals_spectacular_images_of_Earth
5) “WMO and the Early Warnings for All Initiative,” WMO, 2024, URL:https://wmo.int/site/wmo-and-early-warnings-all-initiative
6) “Imager (AHI),” Himawari User’s Guide, Meteorological Satellite Center of JMA, URL:https://www.data.jma.go.jp/mscweb/en/himawari89/space_segment/spsg_ahi.html
7) “WHEATHERFAX,” RCOM, URL:https://www.rcom.nl/weatherfax/
8) “Radiofax Hardware Companies,” NOAA National Weather Service, URL:https://www.weather.gov/marine/rfax_hardware
9) “Marine Weather Broadcasts from the USCG,” NWS (National Weather Service), NOAA, URL:https://www.weather.gov/marine/uscg_broadcasts
10) “Marine Radiofax Charts,” NWS, NOAA, URL:https://www.weather.gov/marine/radiofax_charts
11) “Receiving Weather Fax and Weather Satellite Images With Your Macintosh,” Black Cat Systems, URL:https://www.blackcatsystems.com/software/multimode/fax.html
12) “OPC’s Radiofacsimile Charts User’s Guide,” OPC (Ocean Prediction Center), NOAA, URL:https://ocean.weather.gov/UsersGuide/UGprint.php
13) “Lightning Sensors”, eoPortal, ESA, May 2024, URL: https://www.eoportal.org/other-space-activities/lightning-sensors
14) “GOES-R (Geostationary Operational Environmental Satellite-R),” EoPortal, ESA, May 2012, URL:https://www.eoportal.org/satellite-missions/goes-r
15) “Meteosat Second Generation,” eoPortal, ESA, June 2012, URL:https://www.eoportal.org/satellite-missions/meteosat-second-generation
16) “MTG (Meteosat Third Generation),” eoPortal, ESA, April 2023, URL:https://www.eoportal.org/satellite-missions/meteosat-third-generation
17) “FY-2 (FengYun-2),” eoPortal, ESA, May 2012, URL:https://www.eoportal.org/satellite-missions/fy-2
18) “FY-4 (FengYun-4),” eoPortal, ESA, August 2016, URL:https://www.eoportal.org/satellite-missions/fy-4
19) “INSAT-3A (Indian National Satellite-3) Series,” eoPortal, ESA, June 2012, URL:https://www.eoportal.org/satellite-missions/insat-3
20) “INSAT-3D (Indian National Satellite – 3D),” eoPortal, ESA, July 2013, URL:https://www.eoportal.org/satellite-missions/insat-3d
21) “GMS (Geostationary Meteorological Satellite),” eoPortal, ESA, May 2012, URL:https://www.eoportal.org/satellite-missions/gms
22) “Himawari-8 and 9,” eoPortal, ESA, February 2014, URL:https://www.eoportal.org/satellite-missions/himawari-8-9
23) “MTSAT (Multifunction Transport Satellite),” eoPortal, ESA, June 2012, URL:https://www.eoportal.org/satellite-missions/mtsat
24) “About Environmental Satellites,” Bureau of Meteorology, Australian Government, URL:http://www.bom.gov.au/australia/satellite/about_satellites.shtml