Minimize Starlink

Starlink Satellite Constellation of SpaceX

Spacecraft     Launch    Light Pollution     References

Starlink is a satellite constellation development project underway by SpaceX, to develop a low-cost, high-performance satellite bus and requisite customer ground transceivers to implement a new spaceborne Internet communication system.

SpaceX has said it will offer speeds of up to 1 Gbit/s, with latencies between 25 ms and 35 ms. Those latencies would make SpaceX's service comparable to cable and fiber, while existing satellite broadband services have latencies of 600 ms or more, according to FCC measurements.

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Figure 1: Starlink constellation logo (image credit: SpaceX)

Some background: In November 2016, SpaceX filed an application with the FCC (Federal Communications Commission) for a license to operate a constellation of 4425 non-geostationary satellites (NGS) in orbits ranging from 1100 and 1300 km. However, when they issued their regulatory filings in 2017, the plan called for the deployment of nearly 12,000 satellites in Low Earth Orbit (LEO). 1)

However, competition from other satellite internet providers forced SpaceX to expedite their plans. By the Fall of 2018, the company announced a new plan to deploy their first batch of 1600 satellites to a lower altitude at 550 km. The development team also introduced a simplified design so that the first batch would be ready to go no later than the June of 2019.

Rather than broadcasting in two bands ("Ku" and "Ka"), the simplified design of the first batch will broadcast only in the "Ku" band. At present, SpaceX hopes to launch 2200 satellites in the next five years, which will act as a sort of prototype while the company develops an improved design for full-scale production.

Eventually, this will result in a constellation that offers the kinds of performance outlined in the company's original plan. This presents numerous challenges, not the least of which is the fact that they will need to conduct launches every month for the next five years, averaging 44 satellites per launch.

Second, there's the matter of attrition, as satellites will begin to deorbit after a few years and SpaceX will need to replace them regularly in order to maintain its constellation. In fact, Hugh Lewis – the UK Space Agency's representative on the Inter-Agency Space Debris Coordination Committee – recently stated that in order to maintain a constellation of just 4425 satellites, SpaceX will have to launch that many every five years.

However, SpaceX intends to use this to their advantage by gradually replacing inactive satellites with ones that offer superior performance. In this way, the constellation will gradually be upgraded with the addition of heavier satellites that are capable of transmitting more information, and which are placed in longer-lasting, higher orbits.

SpaceX will also need a lot of production space if they are going to meet even the more modestly-sized constellation of 4425. While the company has commenced converting one of their Starlink buildings into a prototype production facility that will assemble the first few dozen satellites, this is merely a fraction of what they will need in the long run.

Starlink is also going to be seeing competition in the coming years thanks to companies like OneWeb and Telesat, which plans to create smaller constellations that will offer service by 2021. Tech giants like Amazon and Samsung have also announced plans to deploy their own constellations, which would consist of 3,236 to 4600 broadband satellites, respectively.


Spacecraft

Designed and built upon the heritage of Dragon, each spacecraft is equipped with a Startracker navigation system that allows SpaceX to point the satellites with precision. Importantly, Starlink satellites are capable of tracking on-orbit debris and autonomously avoiding collision. Additionally, 95 percent of all components of this design will quickly burn in Earth's atmosphere at the end of each satellite's lifecycle—exceeding all current safety standards—with future iterative designs moving to complete disintegration. This mission will push the operational capabilities of the satellites to the limit. SpaceX expects to encounter issues along the way, but the lessons learned here are key to developing an affordable and reliable broadband service in the future (Ref. 16).

Some spacecraft parameters: 2)

• Flat-panel design with multiple high-throughput antennas and a single solar array

• Spacecraft mass: 227 kg

• Hall-effect thrusters using krypton as the reaction mass, for position adjustment on orbit, altitude maintenance and deorbit

• Star tracker navigation system for precision pointing

• Able to use Department of Defense provided debris data to autonomously avoid collision 3)

• 95 percent of "all components of this design will quickly burn in Earth's atmosphere at the end of each satellite's lifecycle"

The 60 Starlink V1.0 satellites, launched on 11 November 2019, have the additional following characteristics:

• 100% of "all components of this design will quickly burn in Earth's atmosphere at the end of each satellite's lifecycle."

• Ka-band added

• Spacecraft mass of 260 kg

• Albedo reduced.

The satellites are stacked for launch without the need for a dispenser. As a propulsion system for orbit adjustment and maintenance as well as deorbiting, they use krypton-fueled Hall thrusters. The startracker navigation system is based on the heritage of Dragon. The satellites are designed autonomously avoid collisions based on uplinked tracking data. At the end of life, the Starlink satellites are to be actively deorbited, leading to reentry.

Orbit: Circular orbit with an altitude of 550 km. The Starlink spacecraft constellation will be spread into 24 orbital planes with an inclination of 53º.

 


 

Development status of the Starlink constellation

• March 23, 2020: SpaceX has secured the approval of the Federal Communications Commission (FCC) to deploy up to a million ground antennas for its Starlink satellite constellation project. Previously, the company's founder Elon Musk referred to the antenna as "a UFO on a stick." 4)

- SpaceX recently came from the successful launch of its sixth batch of Starlink satellites. It is part of the company's impressive project to deliver high-speed internet from space.

- Recently, the company was able to secure a key government license to begin rolling out another important feature of its Starlink project. According to federal documents filed by the company, the FCC has given SpaceX approval release about a million antennas that are designed to work with the Starlink satellites.

- According to the company, the antennas are designed to connect users to SpaceX's network of satellites. Measuring at about 19 inches across, Musk noted that the antennas look like small UFOs. The SpaceX founder also said these devices are very easy to install and use.

- "It looks like a UFO on a stick," he said according to CNBC. "It's very important that you don't need a specialist to install. The goal is for ... just two instructions and they can be done in either order: Point at sky, plug in."

- SpaceX's first batch of Starlink satellites was official deployed in May last year. Since then, the company has been regularly carrying out launches for new batches of satellites. Currently, there around 360 Starlink units operating in low-Earth orbit. The launch for the next batch of satellites is scheduled to take place next month.

- Originally, SpaceX planned to deploy a total of 12,000 satellites for its Starlink project. However, documents filed by the company last year revealed that SpaceX was planning to launch an additional 30,000 satellites. Once completed, the entire project could be comprised of about 42,000 satellites.

- As noted by the company, the massive satellite constellation will enable telecommunication companies to provide internet services to customers residing in remote and hard-to-reach regions in different parts of the globe.

- "With performance that far surpasses that of traditional satellite internet, and a global network unbounded by ground infrastructure limitations, Starlink will deliver high-speed broadband internet to locations where access has been unreliable, expensive, or completely unavailable," SpaceX explained in a statement.

• January 17, 2020: SpaceX plans to launch its next group of Starlink broadband satellites aboard a Falcon 9 rocket as soon as Tuesday, Jan. 21, from Cape Canaveral, two days after the company is scheduled to launch a modified Falcon 9 booster from a separate facility at the Florida spaceport to test the Crew Dragon spaceship's emergency escape system. 5)

- SpaceX's ability to achieve back-to-back launch schedule hinges on several factors, including an expected test-firing in the coming days of the Falcon 9 booster slated to fly on the next Starlink launch.

- The Starlink mission — SpaceX's fourth launch dedicated to the broadband network — was previously scheduled for Monday, Jan. 20. But sources said Friday the launch was pushed back to Jan. 21.

• January 8, 2020: SpaceX says it's committed to working with the astronomy community to address the brightness of its Starlink satellites, but some astronomers remain concerned about the deleterious effect that system and other megaconstellations will have on their field. 6)

- One of the 60 satellites in the latest Starlink launch Jan. 6 featured an experimental coating intended to reduce its brightness. SpaceX said it will see in the coming weeks how well those coatings work, as well as study any effects they have on the performance of the satellite itself, before deciding how to move forward.

- "Our level of brightness and visibility was a surprise to us," said Patricia Cooper, vice president of satellite government affairs for SpaceX, during a Jan. 8 special session on the topic of megaconstellation effects on astronomy during the 235th Meeting of the American Astronomical Society (AAS) in Honolulu. SpaceX President Gwynne Shotwell also said last month that SpaceX was surprised by the brightness of the satellites.

- Cooper said that brightness is affected by several issues. The Starlink satellites initially appear bright when released in a lower parking orbit, and the configuration of each satellites' single large solar array when raising its orbit can also influence its brightness. Once in a final operating orbit of 550 kilometers, the spacecraft brightness decreases to a visual magnitude of about five, making them visible to the naked eye only in darker night skies.

- One challenge, she said, is the unique design of the satellite made it difficult to determine exactly what causes the spacecraft to reflect so much light. "It turns out, we think, that surfaces that scatter light, or reflect light diffusely, are also significant contributors," she said. That led to the testing of surfaces on the experimental satellite, nicknamed "DarkSat" by some, to reduce that reflectivity.

- While DarkSat is now in orbit, it will take some time to see how effective it is. Patrick Seitzer, an astronomer at the University of Michigan who is studying the effect of satellite constellations on optical astronomy, said at a later press conference that the satellite likely won't reach its operational orbit until late February. "Then serious measurements can begin," he said.

- Cooper said that SpaceX would work quickly to reduce the brightness of its satellites, but didn't give a specific timetable or state if other experimental satellites are in the works. In the meantime, the company will continue to launch the original design of Starlink satellites that are designed to be operational for five years, a plan that some astronomers at the meeting criticized.

- "We don't know yet if these mitigations are useful and effective," she said. "We tend to work very quickly. We tend to test, learn and iterate."

- SpaceX has been meeting with a committee of the AAS to discuss the astronomy community's concerns about Starlink and to examine ways to mitigate them. That work has included a half-dozen teleconferences and an in-person meeting during this AAS conference, said Jeff Hall, director of Lowell Observatory and chair of the AAS committee.

- "We have not had to cajole SpaceX in any way. They've been very receptive and very proactive," he said. Those discussions, he said, initially focused on SpaceX's Starlink deployment plans, but more recently have been more just "keeping in touch" as SpaceX prepared to launch its experimental DarkSat.

- Hall added that it was premature to discuss regulations regarding satellite brightness. "Regulation of the Wild West up there is necessary, but that is going to take a great deal of time to implement," he said, while the problem posed by Starlink and other constellations is a near-term issue that needs to be addressed now.

- Hall added that it was premature to discuss regulations regarding satellite brightness. "Regulation of the Wild West up there is necessary, but that is going to take a great deal of time to implement," he said, while the problem posed by Starlink and other constellations is a near-term issue that needs to be addressed now.

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Figure 2: SpaceX says it's committed to reducing the brightness of its Starlink satellites, but while it works on that the company will continue to launch unmodified satellites (image credit: SpaceX)

- Hall and other astronomers said that, like SpaceX, they were surprised by how bright the Starlink satellites appeared. "What surprised everyone — the astronomy community and SpaceX — was how bright their satellites are," Seitzer said. "We knew these tens of thousands of megaconstellations were coming, but based on the sizes and shapes of things currently in orbit, I thought they'd be maybe eighth or ninth magnitude. We were not expecting second or third magnitude."

- Both astronomers and SpaceX said they hope, as an initial step to get the Starlink satellites dim enough to not be visible to the naked eye even in the darkest skies. The next step will be to figure out what else can be done to mitigate their effects on major observatories, specifically the Vera Rubin Observatory (formerly Large Synoptic Survey Telescope) under construction in Chile. Astronomers said that wide-field telescope was particularly threatened by Starlink and other megaconstellation satellites.

- Hall said his AAS committee plans to start discussions with OneWeb later this month, shortly before the company begins full-scale deployment of its constellation. Six OneWeb demonstration satellites are currently in orbit, at altitudes higher than SpaceX. Seitzer said the satellites, at about eighth magnitude, are too dim to be seen by the naked eye, but pose in some cases greater concerns to professional astronomers than Starlink satellites because, at their altitudes, they may be visible all night during the summer, rather than just around sunset and sunrise.

- With SpaceX seeking to deploy up to 1,500 Starlink satellites in 2020 alone, and with OneWeb and other constellations under development, astronomers warned this was a major issue to them. "The issue of megaconstellations and astronomy is a serious issue," Seitzer said. "We have a very short time to deal with this issue."

• October 16, 2019: SpaceX wants spectrum access for nearly four times as many satellites as originally planned for its high-speed internet constellation, the company and a UN agency confirmed on 16 October. 7)

- On October 7, the US FCC (Federal Communications Commission) sent the Geneva-based ITU (International Telecommunication Union) 20 filings with each one asking permission for 1,500 satellites, the ITU's Alexandre Vallet, chief of space services department, told AFP (Agence France Presse).

- A SpaceX request for 12,000 satellites had already been approved. This new lot would add 30,000 to the network called Starlink.

- The ITU manages radio spectrum frequencies and satellite orbits around the world. The 20 new filings mentioned by the ITU official can be seen on its website.

- A SpaceX spokeswoman did not directly confirm that number but said the company "is taking steps to responsibly scale Starlink's total network capacity and data density to meet the growth in users' anticipated needs."

- The idea behind Starlink is that the network of mini-satellites will allow fast response time between user and internet provider.

- The grid created by all these satellites will be such that several of them will be in direct sight from any point on Earth.

- SpaceX launched the first 60 satellites in May and says the constellation will be operational for Canada and the northern US next year.

- It says it will take 24 launches for the rest of the world to be covered.

- To put things into context, there are currently 2,100 active satellites orbiting our planet, out of 23,000 objects recorded. These can be rocket stages, inactive satellites, space junk and other things.

- The prospect of adding another 42,000 satellites to the skies is causing worries for two reasons.

- On one hand, astronomers fear these satellites will get in the way of telescope observations made from Earth.

- When a first group of satellites was launched, many astronomers reported seeing a string of bright lights. SpaceX says it is trying to make the base of the satellites black.

- The second problem is crowding of LEO (Low Earth Orbit), which is up to altitudes of 2,000 km.

- SpaceX has said that three of the first 60 satellites it placed in orbit were out of service a month after being deployed. The company says it has ways of "deorbiting" faulty satellites and keeping them from colliding with other satellites.

- But an incident last month showed these procedures are not yet fully effective.

- ESA (European Space Agency) had to modify the trajectory of its Aeolus satellite to avoid collision with a Starlink orbiter. This is a routine maneuver. However, ESA tried to contact SpaceX and got no answer because the latter did not see the message.

• May 11, 2019: SpaceX CEO Elon Musk has published the first official photo of the company's near-final Starlink design and confirmed that Falcon 9 will launch a staggering 60 satellites into orbit. 8)

- Known internally as Starlink v0.9, this mission will not be the first launch of operational satellites, but it will be the first internal SpaceX mission with a dedicated Falcon 9 launch. Additionally, the payload will be the heaviest yet launched by SpaceX, signifying an extraordinarily ambitious first step towards realizing the company's ~12,000-satellite Starlink megaconstellation.

- Put simply, SpaceX's Starlink v0.9 launch is extremely unique for several reasons. Aside from the unprecedented step of launching 60 spacecraft weighing ~13,000 kg on a developmental mission, both the form factor of each satellite and the style of dispenser/payload adapter has never been seen before. SpaceX appears to have settled on a square dispenser with four separate quadrants for satellites. The satellites themselves look truly bizarre – it's actually difficult to discern where one spacecraft stops and the next begins.

- Nevertheless, it appears that each Starlink satellite is a relatively thin rectangle, possibly with a squared top and bottom. It's also possible that they are all around rectangular and that the dispenser instead has two main sections. Either way, the very fact that the Starlink v0.9 payload can scarcely be parsed into recognizable satellites is thrilling. Aside from the rise of smallsats and cubesats, satellite design and engineering has been relatively stagnant for decades, particularly with respect to form factors and structural layouts. Most modern satellites are simply squarish boxes with electronics inside and payloads bolted on the outside.

- Despite using the same exact Falcon fairing that has been standard for years, SpaceX has managed to cram 60 spacecraft – each weighing around 227 kg into just the bottom two-thirds of the fairing, leaving a considerable amount of unused volume for future expansion.

- According to President and COO Gwynne Shotwell, Starlink v0.9 satellites are extremely close to SpaceX's true final design. However, they are still considered by SpaceX to be a "test batch" of satellites and do not have the optical (laser) interlinks that will be a critical part of Starlink's unique constellation design.

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Figure 3: The second phase of Starlink testing – 60 advanced satellites – stacked in a single fairing (image credit: SpaceX)

• April 30, 2019: The FCC has granted a request by SpaceX to begin launching spacecraft for the company's Starlink broadband network to a lower orbit than originally planned, overruling protests by competitors and clearing a major regulatory hurdle before the launch of the first batch of Internet satellites from Cape Canaveral in May. 9)

- The regulatory commission approved SpaceX's proposal Friday to fly more than 1,500 of its Starlink satellites at an altitude of 550 km, instead of the 1,150 km orbit originally planned.

- "This approval underscores the FCC's confidence in SpaceX's plans to deploy its next-generation satellite constellation and connect people around the world with reliable and affordable broadband service," said Gwynne Shotwell, SpaceX's president and chief operating officer. "Starlink production is well underway, and the first group of satellites have already arrived at the launch site for processing."

• April 8, 2019: SpaceX has announced a launch target of May 2019 for the first batch of operational Starlink satellites in a sign that the proposed internet satellite constellation has reached a major milestone, effectively transitioning from pure research and development to serious manufacturing. 10)

- R&D will continue as SpaceX Starlink engineers work to implement the true final design of the first several hundred or thousand spacecraft, but a significant amount of the team's work will now be centered on producing as many Starlink satellites as possible, as quickly as possible. With anywhere from 4400 to nearly 12,000 satellites needed to complete the three major proposed phases of Starlink, SpaceX will have to build and launch a minimum of ~2200 satellites in the next five years, averaging 37 high-performance, low-cost spacecraft built and launched every month for the next 60 months.

- Despite the major challenges ahead of SpaceX, things seem to be going quite smoothly with the current mix of manufacturing and development. As previously reported on Teslarati, SpaceX CEO Elon Musk forced the Starlink group through a painful reorganization in the summer of 2018, challenging the remaining leaders and their team to launch the first batch of operational Starlink satellites no later than June 2019. As a consequence, a sort of compromise had to be reached where one additional group of quasi-prototype satellites would be launched before settling on a truly final design for serious mass-production.

- According to SpaceX filings with the FCC, the first group of operational satellites – potentially anywhere from 75 to 1000 or more – will rely on just one band ("Ku") for communications instead of the nominal two ("Ku" and "Ka"), a change that SpaceX says will significantly simplify the first spacecraft. By simplifying them, SpaceX believes it can expedite Starlink's initial deployment without losing a great deal of performance or interfering with constellations from competitors like OneWeb.

• On 16 November 2018, the US Federal Communications Commission (FCC) announced it had authorized SpaceX to launch 7,518 satellites, adding to 4,425 satellites it has already approved. 11)

- None of the satellites has launched yet. SpaceX has six years to put half in orbit, and nine years to complete the satellite network, according to FCC rules.

• On 1 April 2018, SpaceX received US approval to launch 4,425 LEO (Low Earth Orbit) satellites, a key milestone in its plan to offer broadband with high speeds and low latency around the world. 12) 13)

- The FCC (Federal Communications Commission) issued an order approving SpaceX's application with some conditions. SpaceX intends to start launching operational satellites as early as 2019, with the goal of reaching the full capacity of 4,425 satellites in 2024. The FCC approval just requires SpaceX to launch 50 percent of the satellites by March 2024, and all of them by March 2027.

- "Grant of this application will enable SpaceX to bring high-speed, reliable, and affordable broadband service to consumers in the United States and around the world, including areas underserved or currently unserved by existing networks," the FCC order said.

- SpaceX's network (known as "Starlink") will need separate approval from the ITU (International Telecommunication Union). The FCC said its approval is conditioned on "SpaceX receiving a favorable or 'qualified favorable' rating of its EPFD (Equivalent Power Flux-Density) limits demonstration by the ITU prior to initiation of service." SpaceX will also have to follow other ITU rules.

• February 22, 2018: SpaceX has launched with the debuting of an upgraded payload fairing for the Falcon 9 rocket during Spain's PAZ satellite lofting from Vandenberg Air Force Base. The launch carried the first two demonstration satellites for SpaceX's own satellite internet constellation. The launch occurred at an instantaneous launch opportunity at 06:17 Pacific Time (14:17 UTC) on 22 February 2018. 14)

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Figure 4: SpaceX's first two Starlink prototype satellites are pictured here before their inaugural launch, showing off a thoroughly utilitarian bus and several advanced components. They were launched as secondary payloads with the Spanish radar observation satellite (PAZ) on a Falcon 9 rocket from Vandenberg Air Force Base, California. SpaceX called these two prototype Starlink satellites, Tintin-A and Tintin-B (image credit: SpaceX)


Launch 1: The first flight of SpaceX's Starlink satellite constellation launched on 24 May ,2019 (02:30 UTC) with the twice-flown Falcon-9 rocket from SLC-40 (Space Launch Complex-40) at Cape Canaveral Air Force Station, Florida. The Falcon vehicle contained a payload of 60 minisatellites, each with a mass of 227 kg. 15) 16)

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Figure 5: Image of the first launch of SpaceX's Starlink satellite constellation on 24 May 2019 at 2:30 UTC (image credit: Satnews Daily)

Today's launch is a major step towards the final goal of launching and operating 12,000 satellites in orbit to beam internet to the ground by the 2020s, reaching those who are not yet connected, with reliable and affordable broadband internet services. It's estimated that 4 billion people in the world remain unconnected to the internet.

Eight minutes after the launch, the first stage of the rocket successfully landed on the drone ship Of Course I Still Love You (OCISLY) in the Atlantic Ocean. This was the third flight for the first stage booster, having flown on the Telstar 18 VANTAGE mission in September 2018, and the Iridium-8 mission in January 2019.

With a flat-panel design featuring multiple high-throughput antennas and a single solar array, each Starlink satellite has a mass of ~227 kg, this is SpaceX's heaviest launch to date at about 13,620 kg, thus allowing SpaceX to maximize mass production and take full advantage of Falcon- 9's launch capabilities. To adjust position on orbit, maintain intended altitude, and deorbit, Starlink satellites feature Hall thrusters powered by krypton.

An hour later, the Falcon-9 rocket began to release the satellites at an altitude of 450 km. The satellites then had to separate and use their thrusters to take up their positions in a relatively low orbit of 550 km. 17)

"Successful deployment of 60 Starlink satellites confirmed!", the company said on its official Twitter account.

 

Launch 2: Sixty upgraded satellites for SpaceX's Starlink broadband network (Starlink V1.0-L1) rocketed into orbit on Monday,11 November 2019 (14:56 UTC) from Florida's Space Coast (SLC-40), debuting performance enhancements and notching new firsts in SpaceX's list of rocket reuse accomplishments. 18)

- SpaceX's second batch of Starlink satellites joined 60 previous broadband-beaming spacecraft in orbit after deployment from a Falcon 9 rocket, adding to a network that may eventually include thousands of satellites broadcasting high-speed Internet signals from space.

- The 70 m Falcon 9 climbed away from Cape Canaveral's Complex 40 launch pad at 9:56 a.m. EST (14:56 GMT), turned toward the northeast and soared through scattered clouds on a gorgeous Veterans Day morning.

- The Falcon 9's first stage shut down and detached from the rocket's second stage around two-and-a-half minutes into the flight. Moments later, the Falcon 9's second stage lit its single Merlin powerplant to propel itself into orbit with the Starlink payloads, then the rocket's nose cone opened and fell away, revealing the Starlink satellites after transiting through the thick, lower layers of the atmosphere.

- The first stage booster returned to a propulsive landing on SpaceX's drone ship "Of Course I Still Love You" holding position around 250 miles downrange from Cape Canaveral in the Atlantic Ocean, roughly due east of Charleston, South Carolina. The rocket completed its fourth mission, following three previous launches and landings — two last year, and one in February that helped loft into space an Indonesian communications satellite and the Israeli Beresheet moon lander.

- This launch was the first time SpaceX flew a Falcon 9 booster on a fourth mission. It also marked another first for SpaceX, which demonstrated its capability to reuse a payload fairing recovered from a previous launch.

- The bulbous payload shroud protects satellites during the first few minutes of flight, then drops away from the rocket in two halves. The fairing halves flown on 11 November originally launched on a Falcon Heavy mission April 11, then parachuted into the Atlantic Ocean, where SpaceX teams pulled them from the sea for inspections, refurbishment and reuse.

- Pursuing the prime objective of Monday's mission, the Falcon 9's second stage engine switched off about nine minutes after launch, and the rocket coasted over Europe and the Middle East before reigniting its engine at around 10:41 a.m. EST (15:41 GMT) to circularize its orbit. The Falcon 9 aimed for an altitude of around 174 miles (280 km) for deployment of the Starlink satellites, and a member of SpaceX's launch team confirmed the rocket achieved an on-target orbit.

- The Falcon 9 sent commands at 10:56 a.m. EST (15:46 GMT) to release retention pins holding the Starlink satellites to the launcher, and live video from a camera on-board the rocket showed the 60 flat-panel spacecraft receding in the blackness of space.

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Figure 6: Sixty Starlink satellites separated from the Falcon 9 rocket about one hour after launch Monday. The spacecraft deployed in one piece, then will disperse over the coming hours and days (image credit: SpaceX)

- The satellites, monitored at the SpaceX Control Center facility in Redmond, Washington, are designed to gradually disperse over the coming hours and days. Ion thrusters fed by krypton fuel will maneuver the satellites into their orbits at an altitude of 550 km with an inclination of 53º.

- SpaceX says 1,440 of the satellites are needed to provide Internet service over the "populated world," a service level the company says could be achieved after 24 launches.

- The Starlink network could offer service for northern parts of the United States and Canada after six launches, according to SpaceX.

- SpaceX could launch thousands more Starlink satellites if merited by market demand. The Federal Communications Commission has authorized SpaceX to operate nearly 12,000 Starlink satellites broadcasting in Ku-band, Ka-band and V-band frequencies, with groups of spacecraft positioned at different altitudes and in various planes in low Earth orbit.

- The Starlink network is rapidly becoming a core business area for SpaceX, which is competing with companies like OneWeb and Amazon's Project Kuiper to deploy fleets of thousands of small satellites in low Earth orbit to beam broadband Internet signals from space to users around the world.

- Developers of the so-called "mega-constellations" in low Earth orbit say their networks offer key advantages over traditional satellite Internet architectures, which relay on satellites in higher orbits, where radio transmissions — even traveling at the speed of light — take longer to reach.

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Figure 7: Artist's illustration of the distribution of satellites in SpaceX's Starlink network (image credit: SpaceX)

- "Since the most recent launch of Starlink satellites in May, SpaceX has increased spectrum capacity for the end user through upgrades in design that maximize the use of both Ka- and Ku-bands," SpaceX wrote in a press kit for Monday's launch. "Additionally, components of each satellite are 100% demisable and will quickly burn up in Earth's atmosphere at the end of their life cycle — a measure that exceeds all current safety standards."

- SpaceX said the new Starlink spacecraft design can provide a 400 percent increase in data throughout per satellite, and each satellite carries double the number of steerable phased array broadband beams than on earlier Starlink platforms.

- The first 60 Starlink satellites, which launched May 23, carried only Ku-band antennas. At the time, SpaceX said 95 percent of the materials in each of the first 60 satellites would burn up in the atmosphere after their missions were complete.

- Gwynne Shotwell, SpaceX's president and chief operating officer, said last month that the company plans to begin launching Starlink spacecraft equipped with inter-satellite laser crosslinks some time mid-to-late next year.

- Three of the 60 satellites launched in May have stopped communicating with ground controllers, but SpaceX officials say they are pleased with the overall performance of the initial block of Starlink spacecraft.

- The U.S. Air Force is testing Internet connections between aircraft and SpaceX's Starlink satellites to evaluate the network's suitability for future military use, and Elon Musk, SpaceX's founder and CEO, said he sent a tweet last month through a Starlink satellite.

- "We still have ways to go from tweets to 4K cat videos, but we are on our way," joked Lauren Lyons, a SpaceX engineer who hosted the company's webcast of Monday's launch.

 

Launch 3: On 7 January 2020 (02:19 UTC), SpaceX launched its third batch of 60 Starlink minisatellites (Starlink V1.0-L2) into orbit on a Falcon-9 Block 5 vehicle from Cape Canaveral SLC-40. 19)

- The launch of 60 more spacecraft for the Starlink project, which SpaceX sees as a core business area in the coming years, makes the company the operator of the largest fleet of commercial satellites, surpassing the previous mark set by Planet, an operator of Earth-imaging nanosatellites.

- SpaceX wants to begin limited Internet service through the Starlink network later this year, then expand to global service to beam Internet signals to consumers in far-flung locales outside the reach of terrestrial wired broadband connections. Users on airplanes, ships and the U.S. military could also be Starlink customers.

- Blazing a similar trail to two previous Starlink satellite launches last year, a SpaceX Falcon 9 rocket lifted off from pad 40 at Cape Canaveral at 9:19:21 p.m. EST Monday (02:19:21 GMT on 7 January) and turned on a northeasterly heading over the Atlantic Ocean.

- Nine kerosene-fueled Merlin 1D engines on the base of the first stage powered the rocket off the launch pad with 1.7 million pounds of thrust.

- After two-and-a-half minutes, the nine main engines shut down and the first stage separated to begin descent maneuvers toward a landing on SpaceX's drone ship "Of Course I Still Love You" in the Atlantic Ocean.

- The first stage — flying for the fourth time on Monday night's mission — nailed its landing on the drone ship, marking the 48th time SpaceX has successfully landed a Falcon booster since the company's first rocket recovery in 2015. An attempt to catch one half of the Falcon 9's clamshell-like payload fairing in a net fastened to an ocean-going vessel was unsuccessful, SpaceX said.

- The Falcon 9's second stage ignited its Merlin engine two times to place the 60 Starlink satellites into an orbit with a target altitude of 180 miles (290 kilometers) and an inclination of 53 degrees to the equator. SpaceX confirmed the Falcon 9 injected the payloads close to the planned orbit.

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Figure 8: SpaceX's Falcon 9 rocket streaks downrange to the northeast from Cape Canaveral Monday night with 60 Starlink satellites for the company's planned global Internet network (image credit: SpaceX)

 

Launch 4: On January 29, 2020, SpaceX launched a Falcon 9 rocket carrying it's third batch of 60 Starlink satellites. The launch was at 9:06 a.m EST (14:06 GMT) Wednesday from Cape Canaveral Air Force Station, Fla. Two-and-a-half minutes after liftoff, the rocket's first stage shut down its engines and dropped away from the Falcon 9's second stage. Seconds later, the upper stage's single Merlin engine — modified with an enlarged nozzle for better performance in space — ignited to accelerate the 60 Starlink satellites into orbit. 20)

The Falcon 9 jettisoned its clamshell-like payload fairing nearly three-and-a-half minutes into the mission.

Flying tail first, the rocket's first stage booster reignited three of its nine engines to guide it toward SpaceX's drone ship "Of Course I Still Love You" positioned around 630 km northeast of Cape Canaveral. A final landing burn using the center engine slowed the booster for a controlled vertical touchdown on the football field-sized barge, marking the 49th time SpaceX has recovered one of its rockets intact.

The booster flown Wednesday was making its third trip to space, following successful launches and landings in March 2019 and June 2019 on flights carrying SpaceX's Crew Dragon spacecraft and Canada's Radarsat Constellation Mission. With Wednesday's mission, the booster has launched from all three of SpaceX's active launch pads in Florida and California.

SpaceX said the rocket did its job placing the satellites into the proper orbit, and live video from the Falcon 9's second stage showed the 60 flat-panel satellites separating from the launch vehicle as it flew south of Australia about one hour after liftoff from Cape Canaveral.

The spacecraft were expected to extend their power-generating solar panels, and krypton ion thrusters on each satellite will begin raising their orbits to an altitude of around 550 km, where SpaceX intends to operate its first 1,584 Starlink platforms to provide worldwide Internet service.

The Starlink satellites, built at a SpaceX facility in Redmond, Washington, filled the volume of the Falcon 9's payload fairing. Each satellite has a mass of 260 kg, and the Starlink spacecraft stacked together form the heaviest payload SpaceX has ever launched.

With Wednesday's launch, SpaceX has deployed 240 Starlink satellites on four dedicated missions since last May. That makes SpaceX the owner of the world's largest fleet of commercial satellites.

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Figure 9: A view of the 60 Starlink satellites stacked before Wednesday's launch (image credit: SpaceX)

SpaceX says 24 launches are needed to provide global broadband service through the Starlink service. But the company could provide an interim level of service over parts of the Earth later this year, once SpaceX has launched around 720 satellites on 12 Falcon 9 flights.

 

Launch 5: On February 17, 2020 (15:06 GMT), 60 more satellites for SpaceX's Starlink broadband network launched Monday on a Falcon 9 rocket from Cape Canaveral, bringing the total number of Starlink platforms deployed in orbit since last May to 300. 21)

Two-and-a-half minutes into the mission, the Falcon 9's first stage booster shut down its engines and separated, allowing a single Merlin engine on the launcher's second stage to fire into orbit.

Seconds later, the Falcon 9's payload shroud jettisoned as the rocket soared into space, revealing the launcher's more than 15.6-metric ton payload package, comprised of 60 flat-panel signal relay nodes for SpaceX's Starlink network.

While the second stage accelerated into orbit, the first stage of the Falcon 9 descended back through the atmosphere and attempted landing on SpaceX's football field-sized drone ship "Of Course I Still Love You" holding position nearly 630 km northeast of Cape Canaveral.

But the rocket missed the drone ship and appeared to make a soft landing in the water nearby, according to streaming video from the offshore vessel. The missed landing marked the first time a first stage booster on a Falcon 9 rocket has missed a landing attempt on a SpaceX drone ship since 2016.

The Falcon rocket used on Monday's mission was a veteran of three previous launches and landings. It's not likely to be reused after landing in sea water.

Two other SpaceX vessels were positioned in the Atlantic Ocean to try to catch the two halves of the Falcon 9's payload shroud. SpaceX did not announce the results of the fairing recovery attempt, but a company employee said engineers are still experimenting with catching the aerodynamic shroud using fast-moving ships fitted with giant nets. Previous catch attempts have been hit or miss.

Around the same time as the first stage reached the ocean, a SpaceX launch controller announced that the Falcon 9 upper stage had arrived in orbit and was poised to release the 60 Starlink satellites, the mission's primary objective.

After firing thrusters to enter a controlled spin, the upper stage released retention rods holding the Starlink satellites to the rocket. That allowed the spacecraft to fly away from the Falcon 9 as the vehicles soared over the North Atlantic Ocean.

One change introduced Monday different from past Starlink missions was the release of the Starlink payloads into an elliptical transfer orbit, instead of a circular orbit.

"We are executing a direct inject of the Starlink satellites into an elliptical orbit," said Jessica Anderson, a manufacturing engineer at SpaceX. "In prior Starlink missions, we deployed the satellites into a 290-kilometer circular orbit, which required two burns of the Merlin vacuum engine on the second stage.

"Keep in mind the stack of 60 Starlink satellites combined is one of the heaviest payloads we fly, so putting them directly into this orbit requires more vehicle performance and makes recovery more challenging," she said. "Going forward, and starting with today, we will deploy the satellites shortly after the first burn of the second stage, putting the Starlink satellites into an elliptical orbit.

"Once checkouts are complete, the satellites will then use their on-board ion thrusters to move into their intended orbits at an operational altitude of 550 km."

According to preflight predictions, the Starlink craft on Monday were programmed for deployment in an elliptical, or egg-shaped, orbit ranging between 212 and 386 kilometers in altitude, with an inclination of 53º to the equator.

As a result of the orbit change, the Falcon 9's second stage remained in orbit after release the Starlink satellites Monday. It is expected to passively re-enter the atmosphere in the coming months, instead of performing a controlled de-orbit burn, as the stage did after previous Starlink launches.

Like SpaceX's previous Starlink launches, the satellites deployed in a tight cluster. SpaceX ground teams will activate krypton ion thrusters and other systems on the satellites to maneuver them into a higher orbit, targeting an altitude of 341 miles (578 km) for operational service broadcasting signals in Ku-band.

The first phase of SpaceX's Starlink program, which aims to beam consumer broadband to customers around the world, will include 1,584 of the flat-panel satellites — including spares — in orbit 578 km above Earth.

SpaceX has approval from the Federal Communications Commission to operate nearly 12,000 Starlink satellites in Ku-band, Ka-band and V-band frequencies, with groups of spacecraft flying at different altitudes with various orbital inclinations.

 

Launch 6: SpaceX launched their 6th Starlink mission of 60 satellites on March 18, 2020 (12:16 UTC). The company's Falcon 9 launch vehicle lifted off from Launch Complex 39A (LC-39A) at NASA's Kennedy Space Center in Florida. 22) 23)

Falcon 9's first stage previously supported the Iridium-7 NEXT mission in July of 2018, the SAOCOM 1A mission in October of 2018, the Nusantara Satu mission in February of 2019, and the second launch of Starlink in November of 2019. Falcon 9's fairing previously supported the first launch of Starlink in May 2019.

he Starlink satellites deployed in an elliptical orbit approximately 15 minutes after liftoff. Prior to orbit raise, SpaceX engineers conducted data reviews to ensure all Starlink satellites are operating as intended. Once the checkouts are complete, the satellites will then use their onboard ion thrusters to move into their intended orbits and an operational altitude of 550 km.

An attempt to land the Falcon 9's first stage in the Atlantic Ocean on SpaceX's drone ship "Of Course I Still Love You" was unsuccessful.

And despite the loss of one of its nine engines, SpaceX CEO Elon Musk said they were still able to deliver the 60 Starlink satellites on board the Falcon 9, which went exactly as planned. That's due in part to the redundancy built into the design of the Falcon 9 launch vehicle, which uses nine Merlin engines working together.

 

Launch 7: On 22 April 2020 (19:30: 30 UTC), SpaceX launched 60 more Starlink satellites from Launch Complex 39A (LC-39A) at NASA's Kennedy Space Center in Florida. 24)

Two-and-a-half minutes after liftoff, the Falcon 9's first stage booster shut down and separated to begin a controlled descent back into the atmosphere. The rocket's single-engine upper stage ignited seconds later, and the Falcon 9 released its clamshell-like payload fairing more than three minutes into the mission.

Flying into space for the fourth time, the reusable first stage nailed a pinpoint landing on SpaceX's drone ship in the Atlantic Ocean east of Charleston, South Carolina. Two recovery ships were stationed in the Atlantic to retrieve the rocket's two-piece payload shroud, which was also recycled from a previous flight.

The Falcon 9 rocket released retention rods holding the Starlink satellites to the upper stage around 15 minutes after launch. Video from camera on the rocket showed the 60 flat-panel satellites — each with mass of about a quarter-ton — receding into space over the North Atlantic Ocean.

The satellites were each expected to extend their power-generating solar panel wing go through an activation sequence. Krypton ion thrusters on the spacecraft will boost them from their preliminary elliptical transfer orbit to an operational altitude of 550 km over the coming weeks and months.

With this launch, SpaceX has delivered 422 Starlink satellites to space, including two prototypes that are now being deorbited. Since last May, SpaceX has orbited 420 Starlink spacecraft. Three of those relay stations are no longer in orbit, according to publicly-available U.S. military tracking data.

 

Launch 8: On June 4 2020 (01:25 UTC, or at 9:25 pm EDT on June 3), SpaceX launched the eighth batch of Starlink communication satellites on a flight-proven Falcon 9 rocket from Cape Canaveral's Space Launch Complex 40 (LC-40). The successful launch boosted the number of Starlink satellites circling the Earth to 480, by far the greatest number of any communications network. 25)

- At about 2 minutes, 45 seconds after launch, the nine main engines of the rocket's first stage shut off, and that stage re-entered the Earth's atmosphere for recovery off Florida on the SpaceX barge named Just Read the Instructions. - The first stage landed mostly inside a bull's-eye on the flat deck.

- The second stage carried the satellites into orbit successfully, SpaceX engineers said. Video showed the Starlink cluster deploying roughly 15 minutes after liftoff.

- The size of the Starlink constellation already is large enough for "minor" Internet coverage around the world, according to SpaceX founder Elon Musk's statements to the press before the first Starlink launch in 2019.

- But SpaceX hasn't released more information about the network's operation or its intended customers.

- Starlink aims to provide next-generation broadband Internet service to the globe, outpacing that offered by such players as Iridium or Intelsat. SpaceX said in 2019 it aimed to launch 1,600 satellites in the first phase.

- At that point, the satellites would transmit data to each other via laser pulses through the vacuum of space — a far faster method than even fiber optic cables on Earth.

- Starlink, which the company said could cost $10 billion to develop and launch, has boosted the value of SpaceX and its recent rounds of investment, according to stock analysts and SpaceX's filings with the Securities and Exchange Commission.

- SpaceX raised $567 million, according to the commission documents filed in the last few months.

- "We are modeling for $10 billion to $15 billion from 2020-2025 for Starlink, with the potential for more from ground terminals, 30,000 additional satellites and replacement of satellites" and other SpaceX endeavors, according to a recent note from analysts at Morgan Stanley.

- Starlink also would owe some of its speed to its much lower orbit than previous communication satellite networks — 340 miles (550 km) up.

- By comparison, Iridium satellites are about 485 miles (780 km ) up. The Kármán line that defines space is 62 miles high, and the International Space Station is more than 250 miles (400 km) high.

- On this mission, SpaceX was to launch the first Starlink satellite with a visor to block sunlight from hitting the brightest spots of the spacecraft. Musk announced April 27 that the sunshade, which he called a VisorSat, would be included in the next Starlink launch.

- VisorSat is designed to prevent the satellites from reflecting sunlight back to the Earth, which can interrupt astronomy observations.

- This was the second Starlink launch during restrictions on access to the Air Force station due to the coronavirus pandemic. The launch also came on the heels of Saturday's (31 May) successful SpaceX launch of the first flight of NASA astronauts from U.S. soil since 2011.

- The first-stage booster for this launch previously flew four times, including the launch of an Iridium satellite in January 2019, and two separate Starlink missions in May 2019 and January 2020.

 

Launch9: On June 13, 2020 (9:21 UTC), SpaceX successfully launched their ninth Starlink mission, carrying 58 Starlink satellites and three of Planet's SkySat Earth Observation microsatellites (110 kg each) from the Cape Canaveral Air Force Station in Florida — this mission marked SpaceX's first SmallSat Rideshare Program launch. 26)

- SpaceX deployed the SkySat satellites first, about 13 minutes after liftoff, followed by the Starlink satellites about 39 minutes after liftoff.

- The mission used a Falcon 9 booster that flew two cargo missions to the International Space Station for NASA, the last being CRS-20 in March. The rocket featured a previously flown payload fairing, with one half recovered from the Jcsat-18/Kacific-1 satellite mission in December, and the other from SpaceX's third Starlink mission, which took place in January.

- SpaceX recovered the rocket's first-stage for a third time, landing the booster on the drone ship "Of Course I Still Love You" in the Atlantic Ocean.

- SpaceX Lead Manufacturing Engineer Jessie Anderson said the launch contract covering Planet's three SkySat satellites was signed six months ago. Planet's Saturday launch, and a second Starlink rideshare scheduled for July will complete the operator's constellation of 21 SkySats, a fleet that complements Planet's larger constellation of Dove CubeSats.

- Once all 21 SkySats are in orbit, Planet says it will be able to image locations an average of seven times a day, with some locations seeing up to 12 revisits a day, at 50-centimeter resolution. Planet's CubeSats collect imagery in 3-5 meter resolution.

- Another Earth-observation company, BlackSky, said in a recent interview that it has two satellites scheduled to launch June 24 on a Starlink rideshare mission. Barring schedule slips, that would be three Starlink launches in June, which would be the highest number of Starlink launches conducted in a month.

- SpaceX was targeting two Starlink launches a month throughout 2020, but has averaged one Starlink launch a month so far. The company has launched 540 Starlink satellites to date, counting two prototypes, out of a planned system comprising several thousand.

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Figure 10: Three of Planet's SkySat Earth-imaging microsatellites are mounted on top of 58 SpaceX Starlink Internet satellites for launch on 13 June 2020 (image credit: Planet / SpaceX)



 

Light pollution problem from large satellite constellations for astronomy

• May 15, 2020: Every two weeks, late in the evening, people are able to see a swarm of strikingly bright points of light crossing the night sky. An array of images and spectacular videos of such sightings circulate on social media. Word soon gets around that these glowing strings of light are not, in fact, an alien fleet. Rather, they are the Starlink satellites from SpaceX, the US space company run by Elon Musk, streaking across the night sky in 'trains'. 27)

- This visual spectacle and the ambitious project behind it, which is on an enormous scale, are fascinating. Felix Huber and Manfred Gaida explain the background to the project in an interview. They talk about the impact that these strings of light have on astronomy and space, and answer the questions that people sent to DLR when it put out a call on social media.

- Felix Huber is Director of DLR Space Operations and Astronaut Training. This is the central institution for spaceflight operations in Germany. Manfred Gaida is an astronomer and researcher at the DLR Space Administration and an expert on satellite-based space research and optical astronomy.

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Figure 11: Eye-catching newcomers to the sky (image credit: Giancarlo Foto4U CC-BY 2.0)

• April 27, 2020: SpaceX Chief Executive Elon Musk said April 27 that he hopes to test a new way to reduce the brightness of the company's Starlink satellites on the next launch for the broadband megaconstellation. 28)

- In a briefing to a committee working on the next astrophysics decadal survey, Musk said the experimental "VisorSat," along with a new approach for orienting Starlink satellites as they raise their orbits, should address concerns raised by astronomers that the Starlink constellation could interfere with their observations.

- "Our objectives, generally, are to make the satellites invisible to the naked eye within a week, and to minimize the impact on astronomy, especially so that we do not saturate observatory detectors and inhibit discoveries," Musk said.

- SpaceX first attempted to address the brightness problem with an experimental "DarkSat" included in a batch of Starlink satellites launched in January. The satellite used what the company described as experimental darkening treatments over reflective surfaces, like its antennas, in an effort to reduce the amount of sunlight it reflects and thus make it darker.

- While DarkSat has shown some promise, appearing about one magnitude darker than untreated Starlink satellites, the company is moving in a different direction. "We found an option that is even better than that, which is basically to give the satellites shades," he said.

- Musk and others at SpaceX have previously discussed a sunshade that they compared to a patio umbrella that would deploy from a satellite, keeping the antennas in shadow. Musk, at the committee meeting, described a concept called VisorSat that would deploy panels, like sun visors mounted on a car windshield, to block the sun.

- "We have a radio-transparent foam that will deploy nearly upon the satellite being released, and it blocks the sun from reaching the antennas," he said. "They're sun visors, essentially: they flip out and block the sun and prevent reflections." He predicted that the visors would have a "massive effect" on the brightness of the satellites.

- SpaceX is planning test VisorSat on the company's next Starlink launch. "It's a bit of a challenge, but that's our goal," he said. He didn't say how many satellites would be equipped with visors, or when the launch was scheduled. SpaceX has been performing Starlink launches at the rate of at least one a month so far this year, most recently April 22.

- A second effort involves the brightness of the satellites as they raise their orbits after launch. Musk said the satellites appear bright because of the orientation of the solar panels, which are aligned differently during orbit raising than once at their operational orbit.

- As soon as this week, Musk said SpaceX will try an "orientation roll" to change the alignment of the solar panels relative to the Earth, reducing the amount of sunlight they reflect to the ground. "Early indications are this will have a significant effect on the brightness during orbit raise," he said. "The satellites will be significantly less visible from the ground."

- The measures SpaceX has taken have come after months of discussions with astronomers, who have been worried about the effects a full constellation of Starlink satellites — about 12,000 according to current plans, with proposals for up to 30,000 more — would have on astronomy. The situation was of particular concern to those operating telescopes with wide fields of view, like the Vera Rubin Observatory under construction in Chile, where Starlink satellites would be visible in a large fraction of images taken each night.

- In a separate presentation to the committee earlier in the day, Tony Tyson, chief scientist for the Rubin Observatory, said the concern was that the brightness of unmodified Starlink satellites would cause "nonlinear crosstalk," or severe image artifacts, in the observatory's camera. "We would be left with all of these fake trails, fake galaxies, etc., in our data, damaging the science," he said.

- SpaceX has already made progress darkening the satellites, with newer satellites about one magnitude darker than the original "v0.9" satellites launched in May 2019 even without the darkening treatments used on DarkSat. If the satellites can be made about a factor of two darker than DarkSat, Tyson said a technique to correct for the nonlinear crosstalk can work, although it is computer intensive and won't correct for the original streak left in the images by passing satellites.

- The new approaches won't address the issue of brightness of existing Starlink satellites, but Musk said their lifetime is limited. He estimated the initial generation of satellites will be deorbited in about three to four years to make way for improved satellites. "We'll just have far greater throughput capability with version two" of the Starlink satellites, he said.

- While the focus of the committee presentation and subsequent discussion, which lasted for more than an hour, was on Starlink, there was some talk about the role SpaceX could play in supporting space-based astronomy, which is not affected by Starlink or other megaconstellations.

- "I'm very excited about the future of space-based telescopes that could be very large," he said. He mentioned Starship, the company's next-generation large reusable launch system, which will begin regular flights "I think within a couple of years," he promised. "It allows for space telescopes to be transported to orbit at probably an order of magnitude lower cost than in the past."

- "I'm pretty interested in trying to figure out how to help launch and possibly build a big observatory in space," he said, offering to meet with astronomers to discuss mission concepts. "Like a planet imager or something like that."

• March 19, 2020: SpaceX, the largest commercial satellite constellation operator in the world, has ambitious plans of installing 12,000 satellites in low-orbit over a span of several years, as part of its Starlink project to provide low-cost broadband internet service. 29)

A well-known astronomer and satellite tracker has voiced concerns that efforts to scan the skies for potentially dangerous near-Earth asteroids might be in jeopardy due to ambitious plans by SpaceX to deploy over 12,000 satellites in low-Earth orbit over the next several years.

The study "The Low Earth Orbit Satellite Population and Impacts of the SpaceX Starlink" by Jonathan McDowell from the Harvard-Smithsonian Center for Astrophysics analyses the impact that the broadband service mega-constellation could have on different observatories. 30)

The research, still awaiting peer review and accepted for pre-print publication in Astrophysical Journal Letters, states:

"Astronomers - and casual viewers of the night sky - must expect a future in which the low Earth orbit population includes tens of thousands of relatively large satellites."

The researcher has modelled how many satellites in a constellation of 12,000 that the FCC has already approved for SpaceX would be lit up by the Sun and above the horizon from three different latitudes on Earth.

"We see that several hundred satellites are above the horizon at all times of night; during winter twilight, and all summer night long, most of them are illuminated," writes McDowell.

Since Elon Musk's SpaceX began launching batches of satellites in 2019, astronomers have been voicing concerns that the expanding number of huge satellite constellations, driven by Starlink's target plan of installing up to 42,000 satellites in low orbit could wreak havoc on scientific observations of space.

Both skywatchers and astronomers were shocked by the bright lights of the satellites that were obstructing the view for major telescopes and potentially corrupting between 30 to 40 percent of astronomical images.

Satellites from companies other than SpaceX, such as OneWeb pose a similar problem, as many observatories with particularly wide fields of view, like the Vera C. Rubin Observatory currently under construction in Chile, are likely to be impacted.

According to a recent study from the European Southern Observatory (ESO), satellite mega-constellations are projected as "severely" affecting between 30 and 50 percent of observations taken by the Rubin Observatory.

"However, there appear to be other science projects which may be more severely affected... For example, searches for near-Earth asteroids include observations taken in twilight, a time when the satellites are illuminated year-round," writes McDowell.

The astronomer has recently been expounding the importance of continued, unhampered observation of asteroids that may pose a danger to the Earth due to the close proximity in which they move.

When it comes to detection of near-Earth objects travelling close to the Sun, researchers typically search for them after sunset, when Starlink's satellites illuminate the sky.

While urging additional regulation, which he claimed might help solve the issue, he stressed measures being proposed at the moment are not effective.

There has been no official comment from SpaceX.

Previously, to allay concerns, SpaceX CEO Elon Musk stated the company would work with astronomers to develop solutions to mitigate any impact on scientific observation. In response to the criticism, Elon Musk tweeted in May 2019 that the amount of light the satellites have been sending down toward Earth would be studied and measures to mitigate the effects would be taken by modifying them to be less reflective.

"Agreed, sent a note to Starlink team last week specifically regarding albedo reduction. We'll get a better sense of value of this when satellites have raised orbits and arrays are tracking to Sun."

Meanwhile, the company continues to launch new batches of satellites, as a Falcon 9 rocket is geared up to carry 60 more satellites to space on 18 March.

SpaceX has plans to have over 1,500 satellites in space by the end of the year, with the long-term plan for the mega-constellation aiming at 42,000 satellites that would beam high-speed internet to every corner of the globe.

• March 5, 2020: Astronomers have recently raised concerns about the impact of satellite mega-constellations on scientific research. To better understand the effect these constellations could have on astronomical observations, ESO commissioned a scientific study of their impact, focusing on observations with ESO telescopes in the visible and infrared but also considering other observatories. The study, which considers a total of 18 representative satellite constellations under development by SpaceX, Amazon, OneWeb and others, together amounting to over 26 thousand satellites [1], has now been accepted for publication in Astronomy & Astrophysics. 31) 32)
Note [1]: Many of the parameters characterizing satellite constellations, including the total number of satellites, are changing on a frequent basis. The study assumes 26,000 constellation satellites in total will be orbiting the Earth, but this number could be higher.

The study finds that large telescopes like ESO's Very Large Telescope (VLT) and ESO's upcoming Extremely Large Telescope (ELT) will be "moderately affected" by the constellations under development. The effect is more pronounced for long exposures (of about 1000 s), up to 3% of which could be ruined during twilight, the time between dawn and sunrise and between sunset and dusk. Shorter exposures would be less impacted, with fewer than 0.5% of observations of this type affected. Observations conducted at other times during the night would also be less affected, as the satellites would be in the shadow of the Earth and therefore not illuminated. Depending on the science case, the impacts could be lessened by making changes to the operating schedules of ESO telescopes, though these changes come at a cost [2]. On the industry side, an effective step to mitigate impacts would be to darken the satellites.
Note [2]: Examples of mitigation measures include: computing the position of the satellites to avoid observing where one will pass; closing the telescope shutter at the precise moment when a satellite crosses the field of view; and constraining observations to areas of the sky that are in Earth's shadow, where satellites are not illuminated by the sun. These methods, however, are not suitable for all science cases.

The study also finds that the greatest impact could be on wide-field surveys, in particular those done with large telescopes. For example, up to 30% to 50% of exposures with the US National Science Foundation's Vera C. Rubin Observatory (not an ESO facility) would be "severely affected", depending on the time of year, the time of night, and the simplifying assumptions of the study. Mitigation techniques that could be applied on ESO telescopes would not work for this observatory although other strategies are being actively explored. Further studies are required to fully understand the scientific implications of this loss of observational data and complexities in their analysis. Wide-field survey telescopes like the Rubin Observatory can scan large parts of the sky quickly, making them crucial to spot short-lived phenomena like supernovae or potentially dangerous asteroids. Because of their unique capability to generate very large data sets and to find observation targets for many other observatories, astronomy communities and funding agencies in Europe and elsewhere have ranked wide-field survey telescopes as a top priority for future developments in astronomy.

Professional and amateur astronomers alike have also raised concerns about how satellite mega-constellations could impact the pristine views of the night sky. The study shows that about 1600 satellites from the constellations will be above the horizon of an observatory at mid-latitude, most of which will be low in the sky — within 30 degrees of the horizon. Above this — the part of the sky where most astronomical observations take place — there will be about 250 constellation satellites at any given time. While they are all illuminated by the Sun at sunset and sunrise, more and more get into the shadow of the Earth toward the middle of the night. The ESO study assumes a brightness for all of these satellites. With this assumption, up to about 100 satellites could be bright enough to be visible with the naked eye during twilight hours, about 10 of which would be higher than 30 degrees of elevation. All these numbers plummet as the night gets darker and the satellites fall into the shadow of the Earth. Overall, these new satellite constellations would about double the number of satellites visible in the night sky to the naked eye above 30 degrees [3].
Note [3]: It is estimated that about 34,000 objects greater than 10 cm in size are currently orbiting the Earth. Of these, about 5500 are satellites, including about 2300 functional ones. The remainder are space debris, including rocket upper stages and satellite launch adapters. About 2000 of these objects are above the horizon at any given place at any one time. During twilight hours, about 5–10 of them are illuminated by the Sun and bright enough to be seen with the naked eye.

These numbers do not include the trains of satellites visible immediately after launch. Whilst spectacular and bright, they are short lived and visible only briefly after sunset or before sunrise, and — at any given time — only from a very limited area on Earth.

The ESO study uses simplifications and assumptions to obtain conservative estimates of the effects, which may be smaller in reality than calculated in the paper. More sophisticated modelling will be necessary to more precisely quantify the actual impacts. While the focus is on ESO telescopes, the results apply to similar non-ESO telescopes that also operate in the visible and infrared, with similar instrumentation and science cases.

Satellite constellations will also have an impact on radio, millimeter and submillimeter observatories, including the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX). This impact will be considered in further studies.

ESO, together with other observatories, the International Astronomical Union (IAU), the American Astronomical Society (AAS), the UK Royal Astronomical Society (RAS), and other societies, is taking measures to raise the awareness of this issue in global fora such as the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) and the European Committee on Radio Astronomy Frequencies (CRAF). This is being done while exploring with the space companies practical solutions that can safeguard the large-scale investments made in cutting-edge ground-based astronomy facilities. ESO supports the development of regulatory frameworks that will ultimately ensure the harmonious coexistence of highly promising technological advancements in low Earth orbit with the conditions that enable humankind to continue its observation and understanding of the Universe.

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Figure 12: This annotated image shows the night sky at ESO's Paranal Observatory around twilight, about 90 minutes before sunrise. The blue lines mark degrees of elevation above the horizon. A new ESO study looking into the impact of satellite constellations on astronomical observations shows that up to about 100 satellites could be bright enough to be visible with the naked eye during twilight hours (magnitude 5–6 or brighter). The vast majority of these, their locations marked with small green circles in the image, would be low in the sky, below about 30 degrees elevation, and/or would be rather faint. Only a few satellites, their locations marked in red, would be above 30 degrees of the horizon — the part of the sky where most astronomical observations take place — and be relatively bright (magnitude of about 3–4). For comparison, Polaris, the North Star, has a magnitude of 2, which is 2.5 times brighter than an object of magnitude 3. The number of visible satellites plummets towards the middle of the night when more satellites fall into the shadow of the Earth, represented by the dark area on the left of the image. Satellites within the Earth's shadow are invisible. (image credit: ESO/Y. Beletsky/L. Calçada)

• June 14, 2019: SpaceX's ambitious Starlink project could eventually launch more than 10,000 satellites into orbit and rewrite the future of the internet. But Elon Musk's company SpaceX has been taking heat from the astronomical community after an initial launch in late May released the first 60 satellites. The satellites with a mass of 227 kg were clearly visible in Earth's night sky, inspiring concern that they could increase light pollution, interfere with radio signals, and contribute to the growing issue of space debris. 33)

This week, the American Astronomical Society, the International Astronomical Union, the British Royal Astronomical Society, and the International Dark-Sky Association (IDA) all issued statements expressing concern about Starlink's potential to damage astronomical research by leaving bright streaks through images.

"The Starlink affair has raised the attention of the astronomy community in a way that I've not seen during my couple of decades in it," says John Barentine, director of public policy at the IDA, which lobbies against light pollution. "I hope that this moment is the wake-up call that is needed to prompt a new discussion in the international community about the nature of outer space, especially near the Earth, in a commercial context."

Musk had repeatedly assured people on Twitter that his satellites wouldn't be visible at night, so the light caught some people by surprise. However, the satellites' initial brightness is intended to wane as they climb higher into their permanent orbits.

"The observability of the Starlink satellites is dramatically reduced as they raise orbit to greater distance and orient themselves with the phased array antennas toward Earth and their solar arrays behind the body of the satellite," a spokesperson for SpaceX said in an email.

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Figure 13: Telescopes at Lowell Observatory in Arizona captured this image of galaxies on May 25, their images marred by the reflected light from more than 25 Starlink satellites as they passed overhead (image credit: Victoria Girgis/Lowell Observatory)

But Barentine and other astronomers aren't so sure, especially given that this is only the beginning for Starlink. Plus, many other companies — including Amazon, Boeing, OneWeb, Telesat, LeoSat, and even Facebook — are planning other so-called "mega-constellations" for connecting the masses online.

"There are billions of people around the world who lack access to broadband internet," a spokesperson for Amazon's Project Kuiper said in an email. "Our vision is to provide low-latency, high-speed broadband connectivity to many of these unserved and underserved communities around the world .... Many of our satellite and mission design decisions are, and will continue to be, driven by our goals of ensuring space safety and taking into account concerns about light pollution."

But there are already 22,000 artificial objects currently in orbit. And as the microlaunch space race kicks into high gear, that number is destined to double. Communications satellites aren't the only things headed up, either. One group even proposed launching orbiting billboards that would shine ads back down to Earth. And an artist recently launched the "Humanity Star" – a purely artistic light beacon.

"Space is already crowded, and roughly doubling the number of objects in low- and near-Earth orbit will only add to the visual pollution of the night sky," Barentine says. "Being in a dark place and seeing one satellite fly over every few minutes is one thing. But seeing literally dozens of them at any given time for hours every night is another story entirely."

Part of the reason this problem stands to get worse, according to astrophysicist Laura Forczyk, is "there is no regulatory body in the United States that directs companies as to the kind of light pollution or the brightness of satellites. This is a fairly new topic and as always the government regulations are behind technology."

But Forczyk, owner of the space consulting firm Astralytical, also says that changing the night skies isn't the same thing as losing the night sky — and it's a little too early to know what the total impact is going to be. After all, the Starlink satellites still haven't reached their final orbit. "We're very reactive when it comes to these kinds of things," she says, but emphasizes miscommunication from both sides.

Whether the problem stands to worsen or not, most experts see the growth of these mega-constellations as inevitable.

"I don't think we're going to be able to create political will to stop the satellites because there is so much commercial potential and politicians tend to respond to economics," says Phil Metzger, a planetary scientist at the University of Central Florida and a former NASA physicist. However, he says future designs of satellites can ensure they'll cause less interference with on-the-ground astronomy.

"We can change the surface of the spacecraft so it is more absorptive and less reflective or we can even make it more transparent," Metzger says. "We do have the ability to make electrical conductors completely transparent so we don't need metal. You could have glass with transparent conductors in the glass ... I think we'll probably be doing all of these things in the future."

 

• January 9, 2020: The aerospace company SpaceX launched 60 of its Starlink broadband Internet satellites into orbit on 6 January 2020 — including one, called DarkSat, that is partially painted black. The probe is testing one strategy to reduce the brightness of satellite ‘megaconstellations', which scientists fear could interfere with astronomical observations. 34)

Various companies plan to launch thousands of Internet satellites in the coming years; SpaceX, of Hawthorne, California, aims to launch 24 batches of Starlinks this year. By the mid-2020s, thousands to tens of thousands of new satellites could be soaring overhead. Bright streaks caused by light reflecting off them could degrade astronomical images.

"I was complaining to my wife that I can't sleep very well these days because of this," says Tony Tyson, a physicist at the University of California, Davis, and chief scientist of the Vera C. Rubin Observatory, a major US telescope under construction in Chile. (It was renamed this week from the Large Synoptic Survey Telescope to honor the late Rubin, who discovered evidence for the existence of dark matter.)

Astronomers discussed the potential impacts of the satellites on various telescopes, and what could be done about them, on 8 January at a meeting of the American Astronomical Society in Honolulu, Hawaii. "2020 is the window to figure out what makes a difference in reducing the impact," says Jeffrey Hall, director of Lowell Observatory in Flagstaff, Arizona, and chair of the society's committee on light pollution.

"SpaceX is absolutely committed to finding a way forward so our Starlink project doesn't impede the value of the research you all are undertaking," Patricia Cooper, SpaceX's vice-president for satellite government affairs, told a session at the astronomy meeting.

Star light, star bright: Three batches of Starlinks have been launched, for a total of about 180 satellites so far. They are most obvious in the night sky immediately after launch, before they boost their orbits to higher altitudes where they are farther away and appear dimmer. It's not yet clear how significant a problem Starlinks will be for astronomy; scientists have complained about trails in their images since the first launch, but if the company ultimately moves to paint most of the Starlinks black, the impact could be substantially reduced.

Many astronomers panicked in June, soon after SpaceX launched the first batch of 60 Starlinks and telescopes began photographing their trails. Their brightness came as a surprise, says Patrick Seitzer, an astronomer at the University of Michigan in Ann Arbor. "The new megaconstellations coming online have the potential to be brighter than 99% of everything else in Earth orbit, and that's where the concern comes from," he says.

Several factors contribute to their puzzling brightness, astronomers reported at the meeting. SpaceX says the position of the solar panels might have something to do with it: at lower elevations, before the orbit boost, the satellites' panels are positioned like an open book to reduce drag. That temporary orientation could make them reflect more sunlight. The speed at which a satellite moves across a telescope's field of view is also important — the slower it moves, the more brightness accumulates per pixel of imagery.

There are no regulations that control how bright or dim a satellite needs to be, notes Ralph Gaume, director of the astronomical-sciences division of the US National Science Foundation in Alexandria, Virginia.

Twilight zone: Calculations suggest the Starlink trails will interfere with astronomy most significantly during the hours surrounding twilight and dawn. That's a particular problem for observations that need to be made during twilight, such as searches for some near-Earth asteroids. And on short summer nights, the satellite trails could be visible all night long.

The Rubin Observatory is particularly vulnerable because it will scan huge amounts of the sky very frequently. When it begins operating in 2022, it will photograph the entire night sky every three days, for ten years.

Tyson's team is working on possible software fixes for the anticipated satellite trails, such as ways to electronically erase trails and other glitches they induce in astronomical images. But "we're still left with all the complexity of having all these things removed and all these systematic errors", Tyson says.

If telescope operators know precisely where each satellite will appear and at what time, they can swivel the telescope to point at a different part of the sky that does not have a satellite in it, says Tyson. That's feasible if there are 1,000 satellites, but not if there are tens of thousands, because the telescope loses so much time maneuvering that "it's hopeless", he says.

That leaves darkening as a leading option. With DarkSat, SpaceX engineers painted surfaces on the satellite that scatter light or reflect light diffusely, says Cooper. That could make them faint enough to be invisible to anyone looking up at a typical night sky — but almost certainly still visible to most astronomical research telescopes.

"It's still going to be very much a part of astronomers' lives," says Jonathan McDowell, an astronomer at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts. "Just not a part of everyone's lives."



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34) Alexandra Witze, "SpaceX tests black satellite to reduce ‘megaconstellation' threat to astronomy — Latest launch includes ‘DarkSat' prototype to reduce reflection from fleets of broadband Internet satellites," Nature Astronomy News, 9 January 2020, URL: https://www.nature.com/articles/d41586-020-00041-4
 


The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net)

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