NASA has formally commented (PDF) on a request by a US company to build a megaconstellation of satellites at an altitude of 720km above the Earth’s surface, citing concerns about collisions. This appears to be the first time that NASA has publicly commented on such an application for market access, which is pending before the Federal Communications Commission.
“NASA submits this letter during the public comment period for the purpose of providing a better understanding of NASA’s concerns with respect to its assets on-orbit, to further mitigate the risks of collisions for the mutual benefit of all involved,” wrote Samantha Fonder, an engineer for the space agency.
At issue are plans put forth by AST & Science, which intends to build a constellation of more than 240 large satellites, essentially deploying “cell towers” in space to provide 4G and possibly 5G broadband connection directly to cell phones on Earth. The company, based in Midland, Texas, calls its constellation “SpaceMobile” and has raised an estimated $120 million.
The space agency felt compelled to comment on AST’s proposal for several reasons. Most notably, the proposed altitude for the SpaceMobile constellation lies near the “A-Train,” a group of 10 Earth-science monitoring satellites operated by NASA and the US Geological Survey, as well as partners in France and Japan. “Historical experience with the A-Train constellation has shown that this particular region of space tends to produce a large number of conjunctions between space objects,” the NASA letter states.
They’re big, too
The satellites are also very large. In order to provide service, AST plans to build spacecraft with large phased array antennae—900 square meters. According to NASA, in planning for potential conjunctions with other satellites and debris in this orbit, this would require proscribing a “hard-body radius” of 30 meters, or as much as 10 times larger than other satellites.
Maneuvering around the proposed SpaceMobile constellation would be extraordinarily taxing, NASA said. “For the completed constellation of 243 satellites, one can expect 1,500 mitigation actions per year and perhaps 15,000 planning activities,” the space agency stated. “This would equate to four maneuvers and 40 active planning activities on any given day.”
Finally, the space agency is concerned because AST has never built a satellite remotely close in size to the 1-ton or larger vehicles that will populate its constellation. Given this lack of experience, it is expected that 10 percent or more of the satellites may fail, making them unable to maneuver to avoid collisions. NASA found the risk of a catastrophic collision to be “unacceptably high.”
NASA submitted its comment on October 30, and the comment period closed Monday. Most of the other comments on the AST application were supportive.
In response to a query from Ars about NASA’s submission, AST said it would work with NASA to ameliorate its concerns. “We have reviewed NASA’s letter and are confident that we can work with them to