Reduced-Dynamic Orbit Determination

Reduced-Dynamic Orbit Determination for LEO satellites that carry a dual-frequency GPS receiver

This package implements reduced-dynamic orbit determination (RDOD) for low Earth orbit (LEO) satellites that carry a dual-frequency GPS receiver. The estimator combines ionosphere-free carrier-phase observations with a high-fidelity force model within an extended Kalman filter (EKF), augmented with empirical accelerations in the along-track/cross-track/radial (ACR) frame. A Rauch-Tung-Striebel (RTS) backward smoother is applied over the processed arc.

The reference test case is Swarm-A on 10 May 2024. CODE final GPS products provide the GNSS satellite orbits, clocks, and observable-specific biases. The ESA Swarm Level-1b GPS RINEX and star-tracker attitude are used as LEO inputs. The official Swarm SP3 precise orbit is used only for final comparison and is never ingested by the filter.

References:

1. Montenbruck, O., Gill, E., Satellite Orbits: Models, Methods, and Applications. Springer, 2005.
2. IERS Conventions (2010).
3. Teunissen, P.J.G. — LAMBDA.
4. Siemes et al. — Swarm non-gravitational force modeling / macromodel.
5. ESA Swarm Level 1b Product Definition / Processor Algorithms.
6. CODE MGEX final products — SP3, CLK, OSB, OBX.
7. ITSG GROOPS — LEO receiver antenna PCV products.