Real-Time Orbit Determination

Real-Time Orbit Determination based on GPS Navigation Data

This package implements a sequential extended Kalman filter (EKF) to estimate the inertial state of a low Earth orbit satellite from GPS navigation solutions. The demonstration data set is GPS/MET on 1 October 1996. The dynamical model used for state prediction includes GGM03C gravity (tide-modified normalized Stokes coefficients when solid-Earth or ocean tides are on; otherwise the unnormalized Vnm/Wnm solid-harmonic field), optional IERS 2010 solid-Earth and FES2004 ocean tides, DE440 point-mass perturbations, conical solar radiation pressure, Knocke Earth radiation, NRLMSISE-00 drag, and IERS 2010 relativity.

The filter state is the 6-vector [r; v] in J2000/EME2000. Measurements are the three Earth-fixed GPS position components, rotated into the inertial frame at the observation epoch. Velocity from the GPS file is used only to initialize the first epoch and to print comparison statistics; it is not a Kalman measurement.

References:

• Montenbruck O., Gill E., Satellite Orbits: Models, Methods, and Applications, Springer, corrected 3rd printing, 2005 (RTOD example and the Vnm/Wnm force-model formulation).
• Tapley B., Ries J., Bettadpur S., et al., GGM02/GGM03 Earth gravity field, CSR.
• Petit G., Luzum B. (eds.), IERS Conventions (2010), IERS Technical Note 36 (solid Earth tides, ocean tides, pole tide, relativity).
• Picone J. M., Hedin A. E., Drob D. P., Aikin A. C., NRLMSISE-00 empirical atmosphere, JGR, 2002.
• Knocke P. C., Ries J. C., Tapley B. D., Earth Radiation Pressure Effects on Satellites, AIAA/AAS, 1988.
• Folkner W. M., et al., JPL planetary and lunar ephemerides DE440.
• https://celestrak.org/SpaceData/EOP-All.txt
• https://celestrak.org/SpaceData/SW-All.txt
• https://ssd.jpl.nasa.gov/planets/eph_export.html