- Introduction
- History
- Operational Orbit Determination
- Satellite Laser Ranging Data
- Altimeter Data
- Results
- Estimating the Radial Orbit Error
- Conclusions
- References
ERS-1 Operational Orbit Determination
by Remko Scharroo
Excerpt from:
E. Wisse, M. C. Naeije, and R. Scharroo
Processing of ERS-1 and TOPEX/Poseidon Altimeter Measurements
BCRS report 93-11
Netherlands Remote Sensing Board, The Netherlands, ISBN 90-5411-092-9,
December 1993
Delft University of Technology
Department of Aerospace Engineering
Section Space Research and Technology
Kluyverweg 1, 2629 HS Delft, The Netherlands
Abstract
Since December 1991, Delft University of Technology's Section Space Research and Technology is computing ERS-1 orbits on an operational basis. The orbits (based on global quick-look SLR data only) are delivered twice-weekly to NOAA to be incorporated in the NOAA ERS-1 IGDRs. After a startup period using the GEM-T2 gravity model, these orbits are generated with the JGM-2 gravity model, providing an unprecedented orbit accuracy. Until today, the DUT ERS-1 orbits have found wide approval from many users and have been used by institutes throughout Europe and the United States (e.g., CNES, ESOC, MSSL, NASA, and NOAA). Results of orbit comparisons and orbit error determinations have been presented at various congresses and symposia [Scharroo et al., 1993a; Scharroo et al., 1993b; Scharroo et al., 1993c; Scharroo et al., 1994].This Chapter addresses various aspects of the computation of ERS-1 orbits on an operational basis, of the effects of gravity model errors, and of methods to assess the orbit accuracy, based on SLR residuals, altimeter height residuals, crossover height differences, and orbital overlaps. Also, the use of altimeter height measurements and dual-satellite crossovers as additional tracking data are investigated.
The results are based on altimeter data extracted from the most recent OPR02 (version 3.0) ``ocean product'' for Cycle 9 of the ERS-1 Multi-disciplinary Phase. In addition, the DUT orbits are compared with the ``best accurate precise orbit'' (generated by D-PAF) provided on this data product.
These analyses consistently indicate a radial orbit error below 13 cm for the DUT orbits and almost 14 cm for the D-PAF orbits.
Note that these results are badly outdated. More precise orbits are currently being generated with the JGM-3 gravity model. Their radial precision is of the order of 8 cm. Similar results are being obtained by ESOC and D-PAF.
Contents
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