Fleet GNSS Downlink

Measurement types

GNSS pseudorange · carrier phase

Delivered product

CCSDS OEM (operator ephemeris)

GNSS ephemeris downlinked from the fleet itself. This is the primary state for every OrbitGuard spacecraft; catalogue data covers only the secondary.

Range and angles constrain radial position well but leave along-track error to be inferred from arc length, so the covariance ellipsoid stays elongated along the velocity vector. A short fit span compounds this — there is not enough arc to separate drag from geometry.