FCC's Satellite Collision-Risk Approach Raising Concerns; Dish Appeals SpaceX OK
A new FCC approach on how it calculates satellite constellation collision risks, used in its partial approval of SpaceX's second-generation constellation, is raising some space expert concerns, especially since it's seen as a possible harbinger of how the FCC might look at collision risk for future constellations. Viasat petitioned the commission to clarify aspects of that SpaceX authorization granted in November (see 2212010052). The agency and SpaceX didn't comment.
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That authorization also faces another challenge in federal court. In its notice of appeal posted Thursday in U.S. Court of Appeals for the D.C. Circuit (docket 23-1001), Dish Network said the order wrongly ignores "unrebutted expert studies ... showing that SpaceX’s Gen2 system would significantly exceed the applicable power limits adopted by the FCC for the 12 GHz band, and thus would risk causing unacceptable interference" with its direct broadcast satellite service. It said the FCC also violated the Administrative Procedure Act by not letting Dish access underlying data behind SpaceX claims its system would fall within ITU power limits. Dish asked the court to vacate the authorization order. International Dark-Sky Association is also appealing the order (see 2301030014).
As a condition of the authorization, the FCC said setting a cap of 100 "object years" -- the number of years each failed satellite remains in orbit, added up across all the satellites -- "is appropriate in the context of a planned deployment that is at a scale not previously undertaken and also untested." If the object years reach 100, SpaceX would have to pause further launches. It said the 100 object years approach, suggested by LeoLabs, is "a useful benchmark, if triggered, for pausing deployment and reassessing spacecraft reliability."
The 100 object years approach wasn't meant to be an actual suggestion of how the FCC should calculate collision risk, but an illustration meant to get the agency thinking about different approaches, Darren McKnight, LeoLabs senior technical fellow, told us. He said he hoped to see the agency actually use as an approach "object kilogram years" -- a calculation using the total objects in space and their total mass and how long they will be in space. "The good news is, [the FCC] listened" to him, McKnight said: "The bad news is, they listened" to the wrong suggestion. Optimally, the commission should initiate a rulemaking about using an object kilogram years metric for all constellations and get comment on that idea and related issues such as thresholds, he said.
The FCC in its second-generation authorization acknowledges its object-years provision is untested, emailed Secure World Foundation Director-Private Sector Programs Ian Christensen. It doesn't appear to be an overall policy change but a requirement for the second-gen Starlinks specifically, he said. Christensen said it's reasonable to expect the commission might apply it or something similar to other constellation operators in the future.
The FCC doesn't lay out a clear methodology for calculating object years, Viasat said last week in its International Bureau petition for clarification of the SpaceX order. Absent clarification, the collision risk condition on the second-gen authorization could be read in a way that "ignores decades of Commission policy and precedent based on the tenet that realized collision risk varies depending on the design of a satellite and its orbit," Viasat said. It said the agency has been inconsistent in its SpaceX orders, setting one collision risk threshold in one order and then in the second-gen authorization seemingly allowing SpaceX levels of collision risk "that are orders of magnitude beyond." The condition on satellite failures could be read in a way that treats every failed satellite as if it presents the same level of collision risk and ignores years of FCC policy recognizing collision risks depends on the design and orbit of a satellite, said Viasat. It said the agency should clarify the collision risk condition by requiring SpaceX to use NASA’s Debris Assessment Software to calculate the collision risk of any non-maneuverable satellite in orbit and add the resulting values across all non-maneuverable satellites in orbit to calculate a cumulative total.
Seeking clarification on the relationship between the object-years approach and the FCC's existing requirement about how they demonstrate probability of collision makes sense, Christensen said.
Viasat in its petition also seeks clarification about interference limits applying to all second-gen user links across the Ka and Ku bands, not just the 19.7-20.2 GHz and 12.2-12.7 GHz band segments.