FCC lets SpaceX cut satellite altitude to improve Starlink speed and latency
SpaceX today was granted permission to use a lower orbit for Starlink satellites, as regulators agreed with SpaceX that the change will improve broadband speed and latency while making it easier to minimize orbital debris. In granting SpaceX's request, the Federal Communications Commission dismissed opposition from Viasat, Hughes, Dish Network, OneWeb, the Amazon subsidiary known as Kuiper, and other satellite companies that claimed the change would cause too much interference with other systems.
In 2018, SpaceX received FCC approval to launch 4,425 broadband satellites at orbits of 1,110 km to 1,325 km. An FCC order in 2019 gave SpaceX permission to use a lower altitude for over 1,500 of those satellites. Today's FCC order granting SpaceX's additional license-change request lowers the altitude for 2,814 of the satellites, letting them orbit in the 540-570 km range. Today's FCC order will also let SpaceX use a lower elevation angle for antennas on user terminals and gateway Earth stations.
"Based on our review, we agree with SpaceX that the modification will improve the experience for users of the SpaceX service, including in often-underserved polar regions," the FCC order said. "We conclude that the lower elevation angle of its earth station antennas and lower altitude of its satellites enables a better user experience by improving speeds and latency."
The FCC order also said, "a number of the satellites being deployed pursuant to this modification are satellites orbiting at high inclinations, which are uniquely able to provide improved service to higher latitude regions." As for the license change's impact on orbital debris, the FCC said that "deployment to a lower altitude guarantees removal of satellites from orbit within a relatively short period of time, and consequently has beneficial effects with respect to orbital debris mitigation."
The FCC previously allowed SpaceX to operate 1,584 of the satellites at an altitude of 550 km, via an approval in April 2019.
Many satellites at different altitudes
The number of Starlink satellites from the first batch approved in March 2018 has since been reduced from 4,425 to 4,408, and all of those are now approved for orbits between 540 and 570 km. SpaceX separately was granted permission in November 2018 to launch another 7,518 satellites at even lower altitudes of 335 km to 346 km. The space company is also seeking permission for 30,000 more satellites at altitudes ranging from 328 km to 614 km.
Besides what we've already mentioned, today's FCC order gives SpaceX "authority to conduct launch and early orbit phase (LEOP) operations and payload testing during orbit-raising and deorbit of its satellites."
"Our action will allow SpaceX to implement safety-focused changes to the deployment of its satellite constellation to deliver broadband service throughout the United States, including to those who live in areas underserved or unserved by terrestrial systems," the FCC said.
Rejecting opposition’s interference claims
The FCC order said that SpaceX's license change "does not create significant interference problems," rejecting allegations made by Dish Network and other companies.
The FCC denied "petitions to deny or defer" SpaceX's request filed by Viasat, SES Americom and O3B Limited, Kepler Communications, and Kuiper Systems. Other satellite companies such as Hughes and OneWeb had filed comments challenging SpaceX's claims and requesting that the FCC impose new conditions on SpaceX. The FCC also denied Viasat's petition to reconsider the commission's earlier decision to let SpaceX use the 540-570 km altitudes for ten satellites.
Opponents of SpaceX argued that the license change "will increase the number of in-line interference events because of its proposed lower elevation angles and doubling of the number of satellites communicating with each gateway earth station simultaneously" and that "SpaceX's redesigned antennas and wider beam footprints would worsen the interference environment and eliminate earth station separation as an interference mitigation technique," the FCC said.
The FCC agreed that the license change "would result in new interference to other NGSO [non-geostationary satellite orbit] systems in certain areas where previously interference did not exist," but the agency concluded that the license would not create "any significant interference problems."
The FCC explained further:
Specifically, after analyzing the technical arguments in the record, we conclude that the lower altitude of the satellites will in fact result in fewer satellites in view, and therefore will result in fewer in-line interference events with respect to other NGSO operators, even if the number of active satellites in view of a particular earth station is increased. We observe that by lowering the earth station elevation angle, more of the sky is visible from the perspective of the earth station, and as a result more satellites may be visible. However, when the satellite altitude is lowered, the satellites will need to be closer to the earth station in order to be within view, and therefore lowering the altitude of the satellites helps to offset the fact that additional satellites may be visible due to the lower elevation angles, in turn offsetting the potential increase in inline interference events. We also conclude that the reduced satellite PFD [power flux-density] at the satellites enabled by operating the satellites at lower altitudes will help to offset the potential for increased interference.
SpaceX already has over 1,300 satellites in orbit while it provides Starlink service in beta for $99 a month plus $499 upfront for equipment. SpaceX has been advertising beta-service speeds of 50Mbps to 150Mbps, with latency of 20 ms to 40 ms. CEO Elon Musk said in February that speeds will hit 300Mbps later this year and that the service will become available to "most of Earth" by the end of 2021.
SpaceX was tentatively granted $885.51 million over 10 years in rural-broadband funding, but the company is facing opposition from other ISPs, and the FCC hasn't made a final decision on the funding. SpaceX also has a pending application to be designated as an Eligible Telecommunications Carrier as part of plans to offer phone service and discounted telecom service to people with low incomes.
Update: Viasat contacted Ars with a statement, saying it is "pleased the commission confirmed that Starlink satellites must be reliable and safe, and also recognized the need to assess the cumulative (aggregate) collision risk presented by the entire Starlink constellation." Viasat claimed that the FCC failed to use "a science-based approach" in its order.
Amazon also provided a statement, saying, "This is a positive outcome that places clear conditions on SpaceX, including requirements that it remain below 580 km and accept additional interference resulting from its redesign."
The interference-related "condition means that if the [Starlink] redesign creates interference with other systems (including Kuiper), the burden is on SpaceX to either alter its operations or accept the impact on its service," an Amazon spokesperson told Ars.
While SpaceX only asked for orbits between 540 and 570 km, Amazon told Ars that it requested the hard limit of 580 km because "SpaceX satellites have an orbital tolerance of +/- 30 km." Amazon plans to use orbits as low as 590 km in its Kuiper constellation.
"These conditions address our primary concerns regarding space safety and interference, and we appreciate the commission's work to maintain a safe and competitive environment in low-earth orbit," Amazon said.