Arc lengths
The POE, or Precise Orbit Ephemeris, is calculated using different arc lengths depending on the mission:
- 10-day arcs for Jason-1 and Spot satellites,
- 7-day arcs for Envisat.
The delay is usually 2 to 4 week from the beginning of the arc in order to take into account the latest environmental data in the solution.
Processed data
The POE orbit is obtained using all the tracking techniques available for a given satellite:
- Doris only for Spot 2,4,5,
- Doris+ SLR for Envisat,
- Doris+SLR+ GPS for Jason-1.
Processing configuration
Measurement models include ITRF2000 coordinates for SLR and DORIS and JPL's solution at IGS for GPS ephemeris and clocks. Station coordinates are corrected for displacements induced by solid earth tides and ocean loading.
- For Doris measurements a frequency and a troposphere bias per pass are estimated.
- For SLR, a bias per pass is also estimated for a few low quality stations in the network.
Dynamic models for all the satellites follow the GDR-B standards:
- EIGEN-CG03C for the static gravity field,
- solid earth tides from IERS2003 conventions,
- FES2004 for the ocean tides and the Haurwitz/Cowley model for the atmospheric tides.
Solid Earth pole tide is also included as from the IERS 2003 conventions. Atmospheric drag uses DTM94 model for Spot and Jason-1, while MSIS86 is used for Envisat. Solar radiation pressure is calculated using satellite specific macromodels.
Finally, the dynamic parameterization also differs for different missions, as it depends on the amount of the available tracking data.
- For Jason, the amplitude of 1/rev empirical forces is adjusted every 12 hours in the along-track and cross-track directions, while the drag coefficient is estimated once every 3 revolutions.
- Spot 2,4,5 and Envisat use 24 hours intervals for the 1/rev empiricals and 6 hours intervals for the drag coefficient.
Detailed standards of the CNES/SOD POD configuration for the DORIS satellites
Summary of the GDRB and GDRC configurations applied to Jason and Envisat CNES/SOD POD
