Kinematic Orbit Determination

Kinematic Orbit Determination (KOD) for the Swarm-A LEO satellite

This package performs kinematic orbit determination (KOD) for the Swarm-A LEO satellite from dual-frequency GPS observations. At each selected epoch, an independent weighted least-squares solution estimates ECEF position and receiver clock bias. Dual-frequency ionosphere-free (IF) code is first Hatch-smoothed with carrier phase on the 1 Hz arc, then thinned for OD. GPS satellite states come from IGS/MGEX precise orbits/clocks (COD0MGXFIN SP3).

The Swarm Level-1b precise orbit product (SW_OPER_SP3ACOM) is used only for final epoch-by-epoch comparison against the kinematic solution. It is never passed into the estimator and is never used as an OD input or initial state.

Typical accuracy for the reference test case is about 1.8 m 3D RMS versus the Swarm L47 SP3 reference orbit (121 epochs at ~30 s spacing over the first hour).

References:

1. RTKLIB source: preceph.c (pephpos, peph2pos), rtkcmn.c (geodist, satazel).
2. Hatch R. (1982); recent LEO kinematic SPP with code-carrier smoothing (e.g. EGU26-6051).
3. Montenbruck O., Gill E.; Satellite Orbits: Models, Methods, and Applications; Springer, Heidelberg (2005).
4. SP3-c format specification; RINEX 3.x observation format.
5. ESA Swarm Level-1b GPS and precise orbit products; CODE MGEX final orbits (COD0MGXFIN).