NASA says that SpaceX’s proposal for a second-generation Starlink
constellation with 30,000 satellites could lead to a “significant increase”
in potential collisions in low Earth orbit and interfere with the agency’s
launches and scientific activities.
The
five-page letter
was submitted to the Federal Communications Commission Feb. 8 on NASA’s
behalf by the National Telecommunications and Information Administration,
along with a separate one-page letter from the National Science Foundation.
The letter was submitted to the FCC’s proceedings on SpaceX’s proposal for
its Starlink “Gen 2” system with approximately 30,000 satellites in LEO.
“With the increase in large constellation proposals to the FCC, NASA has
concerns with the potential for a significant increase in the frequency of
conjunction events and possible impacts to NASA’s science and human
spaceflight missions,” stated the letter, signed by Samantha Fonder, NASA’s
representative to the Commercial Space Transportation Interagency Group.
“NASA wants to ensure that the deployment of the Starlink Gen 2 system is
conducted prudently, in a manner that supports spaceflight safety and the
long-term sustainability of the space environment.”
The letter raised several issues about the proposed constellation, primarily
because it would increase the number of tracked objects in low Earth orbit
by more than a factor of five. “An increase of this magnitude into these
confined altitude bands inherently brings additional risk of
debris-generating collision events based on the number of objects alone,”
the agency stated. “NASA anticipates current and planned science missions,
as well as human space flight operations will see an increase in
conjunctions.”
NASA questioned whether the automated collision avoidance system SpaceX
developed for its current Starlink satellites will scale to the larger Gen 2
system. “NASA recommends SpaceX generate analysis demonstrating the
auto-maneuver capability is sufficiently scalable to the entire proposed
constellation size, including inter-constellation conjunctions, while
accounting for challenges in flying lower altitudes during greater solar
activity,” the letter stated.
NASA took issue with SpaceX’s claims there is “zero risk” of a Starlink
satellite colliding with a large spacecraft because of the Starlink
satellites’ maneuverability. “With the potential for multiple constellations
with thousands and tens of thousands of spacecraft, it is not recommended to
assume propulsion systems, ground detection systems, and software are 100%
reliable, or that manual operations (if any) are 100% error-free,” the
agency said.
Other constellations that also have autonomous collision avoidance
capabilities could cause problems if one of those satellites attempts to
avoid a Starlink satellite, triggering a series of maneuvers that could
increase, rather than decrease, the risk of a collision unless there are
“rules of the road” governing such interactions. NASA recommended SpaceX
perform a risk analysis of such events.
Beyond the risk of collisions with NASA and other satellites, the agency
said the Starlink Gen 2 system could interfere with science missions. Those
satellites will be in orbits below most NASA Earth science satellites and
could create reflections of sunlight that interfere with those satellites’
instruments. The Gen 2 constellation could double the number of Hubble Space
Telescope images that contain satellite streaks, currently 8% of all images.
The constellation would also risk interfering with ground-based astronomy,
in particular observations of near Earth objects as part of NASA’s planetary
defense program. With the Gen 2 system, the letter stated, “NASA estimates
that there would be a Starlink in every single asteroid survey image taken
for planetary defense against hazardous asteroid impacts, decreasing
asteroid survey effectiveness by rendering portions of images unusable.”
The Starlink constellation interferes with launches as well. NASA said about
20,000 Starlink satellites would be in orbits below the International Space
Station, complicating launches of cargo and crew missions. “NASA is also
concerned with an increasing unavailability of safe launch windows,
especially for missions requiring instantaneous or short launch windows,”
citing the upcoming Europa Clipper mission as one example.
NASA did not state in the letter it was opposed to an FCC license for
Starlink Gen 2, instead highlighting areas SpaceX needs to address. “NASA
appreciates SpaceX’s collaboration and partnership in addressing conjunction
concerns to date,” it stated. “The proposed increase in the number of
Starlink spacecraft on orbit will require expanded coordination and
communication between the two parties to ensure the continued safety of both
SpaceX and NASA assets.”
SpaceX did not immediately respond for a request for comment about the NASA
letter and its recommendations. The company infrequently responds to media
inquiries.
NASA added that it “has provided similar comments in response to other
proposed large constellations.” That includes a letter last year regarding a
planned constellation by AST SpaceMobile, where NASA raised concerns about
the risk of collisions posed by those satellites with very large antennas.
The company has since said it will reduce the size of those antennas.
Mark Dankberg, executive chairman of Viasat, discussed the letter with Jim
Bridenstine, former NASA administrator, during a “fireside chat” at the
SmallSat Symposium here Feb. 9.
Dankberg, a critic of Starlink but who did not mention SpaceX by name at the
event, outlined the various issues NASA raised in the letter, seeing them as
costs being imposed on the agency. “There are all of these costs that are
being externalized.”
Bridenstine, who serves on the board of directors of Viasat, agreed. “The
challenge that I had at NASA is becoming a lot bigger,” he said of past
concerns about space sustainability he raised during his time as agency
administrator.
He added that the constellation is just one of many proposed by companies
and countries. “This is true for every constellation that we’re going to see
coming up in the future in how it impacts NASA, which, of course, impacts
the American taxpayer,” he said. “This is a real challenge that I don’t
think is getting the attention that it needs as we move forward.”
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