A team of Chinese space engineers has accused SpaceX’s Starlink satellites of breaking the traffic rules of Earth’s lower orbit and warned that China will be giving the US an upper hand if it does not follow suit.The researchers said two of Starlink’s newest satellites, equipped with high-speed laser communication devices, came within 4.9km (3 miles) of each other on June 30. The commonly accepted – if unwritten – minimum distance to avoid collision is 10km (6.2 miles).In a study published by Chinese peer-reviewed journal Radio Engineering, the researchers said the unusually dense formation was no accident, but the result of a complex scheme by SpaceX to maximise the performance of its laser communications.
The recent reporting by SpaceX of the number of collision avoidance manoeuvres performed by Starlink has enabled an updated analysis & prediction... In a voluntary filing SpaceX indicated that each Starlink satellite has sufficient propellant to perform 5,000 propulsive manoeuvres over the satellite life, with 350 of those for collision avoidance. Depending on the model used, that level might be reached somewhere after 7,500-8,000 satellites have been launched. Quite important caveats apply here! The models used for prediction are based entirely on the extrapolation of simple trendlines (some where there is no real causation). As such, they assume that past behaviour is a perfect description of future behaviour, which is unlikely (e.g. if the launch cadence changes, if the Starlink 2nd generation satellites have different collision characteristics, or if the SSA data used for screening differs from the present-day SSA data, perhaps through the inclusion of smaller objects) The choice of model (i.e., linear, quadratic, cubic) is based not only on the fit but also on my expectations for the behaviour. Primarily, I expect the *cumulative* number of manoeuvres to increase non-linearly with time & number of Starlink satellites launched. As time goes on and SpaceX offers more data, I will update the models and predictions (and also test/validate the older predictions) keeping you informed. In the meantime, thanks for reading!
HE360 recently confirmed its deployment on January 24, 2023, of three satellites “at an orbital altitude of approximately 552 km (apogee) x 551 km (perigee).” Moreover, Rocket Lab disposed of the second and third stages of the Electron launch vehicle used for this injection in orbits of 329 km x 558 km and 549 km x 552 km, respectively.As of February 21, SpaceX had received 400 proximity alerts related to the three recently launchedHE360 satellites, resulting in 164 collision avoidance maneuvers. While HE360 does not publiclypost ephemeris and covariance data on Space-Track.org, SpaceX’s advanced collision avoidancesystem has operated successfully and continues to avoid the HE360 satellites.Rocket Lab left two stages of the launch vehicle that deployed the HE360 satellites in orbitsthat also affect SpaceX’s constellation. As of February 21, SpaceX had received 47 proximityalerts exceeding its safety threshold from the two stages, resulting in 35 collision avoidancemaneuvers. The SpaceX collision avoidance system is robust and can accommodate other systemsoperating in its approved orbital shells. Nonetheless, industry best practices and licensingrequirements call for both the launch provider and satellite owner/operator to coordinate prior tolaunch.SpaceX has raised these issues with both HE360 and Rocket Lab, and will continue to workwith them to minimize the risks of their future launches.
It's getting crowded in space. SpaceX is not happy three HawkEye360 satellites and two stages of the Electron were left in orbits next to Starlink satellites.QuoteHE360 recently confirmed its deployment on January 24, 2023, of three satellites “at an orbital altitude of approximately 552 km (apogee) x 551 km (perigee).” Moreover, Rocket Lab disposed of the second and third stages of the Electron launch vehicle used for this injection in orbits of 329 km x 558 km and 549 km x 552 km, respectively.As of February 21, SpaceX had received 400 proximity alerts related to the three recently launchedHE360 satellites, resulting in 164 collision avoidance maneuvers. While HE360 does not publiclypost ephemeris and covariance data on Space-Track.org, SpaceX’s advanced collision avoidancesystem has operated successfully and continues to avoid the HE360 satellites.Rocket Lab left two stages of the launch vehicle that deployed the HE360 satellites in orbitsthat also affect SpaceX’s constellation. As of February 21, SpaceX had received 47 proximityalerts exceeding its safety threshold from the two stages, resulting in 35 collision avoidancemaneuvers. The SpaceX collision avoidance system is robust and can accommodate other systemsoperating in its approved orbital shells. Nonetheless, industry best practices and licensingrequirements call for both the launch provider and satellite owner/operator to coordinate prior tolaunch.SpaceX has raised these issues with both HE360 and Rocket Lab, and will continue to workwith them to minimize the risks of their future launches.
SpaceX now nominally uses an even more conservative maneuver threshold twoorders of magnitude more sensitive than the industry standard. Specifically, SpaceX satellites willmaneuver when the probability of collision is greater than 1e-6 (1 in 1,000,000 chance of collision),as opposed to the industry standard of 1e-4 (1 in 10,000 chance of collision).
Using this very conservative threshold, along with even more conservative assumptions, SpaceX satellitesperformed 49,384 propulsive maneuvers over the reporting period, averaging approximately 27maneuvers per satellite, per year.
Using this very conservative threshold, along with even more conservative assumptions, SpaceX satellitesperformed 37,094 propulsive maneuvers over the reporting period.
Specifically, SpaceX satellites will maneuver when theprobability of collision is greater than 1e-5 (1 in 100,000 chance of collision), as opposed to theindustry standard of 1e-4 (1 in 10,000 chance of collision). Using this very conservative threshold,along with even more conservative triggers, SpaceX satellites performed 24,410 propulsivemaneuvers over the reporting period, averaging approximately 12 maneuvers per satellite, per year.
