[perihelions]

Also—how accurately do those satellites track their own position? Unlike the high-orbit GNSS constellations, LEO satellites would bounce around a bit from orbit to orbit, as they're relatively close to the earth and sensitive to uneven distributions of mass. I don't know the exact magnitudes, but I understand they're large by GNSS standards.

[generuso]

Starlink satellites use on-board GPS receivers for extremely accurate (centimeter level) measurements of their position. The orbits which SpaceX reports to the world (for collision avoidance) are based on these measurements.