The goal for Jason-1 orbit determination is to achieve an orbit accuracy at least as good as that of TOPEX/POSEIDON. It should be possible to merge the altimeter products from Jason-1 with the long history of data from TOPEX/POSEIDON without introducing any artificial signals from the orbits. The orbit verification activities will be directed towards assuring consistency between the two missions, as well as attempting to further reduce the radial orbit error to the 1 cm level.
The TOPEX/POSEIDON (T/P) mission has contributed significantly to our understanding of the large scale variability of sea surface height as well as global mean sea level, and Jason-1 is expected to continue this valuable time series of altimetric data.
To attain this remarkable level of orbit accuracy for a low-Earth altimeter satellite, a decade-long gravity model improvement effort was initiated, which resulted in the Joint Gravity Model (JGM)-1 [Nerem et al., 1994]. This model, along with other model and tracking system improvements, resulted in a prelaunch radial orbit accuracy on the order of 6 cm. Postlaunch adjustment of the gravity model resulted in JGM-2 [Nerem et al., 1994], which reduced the errors to the 3-4 cm level [Tapley et al, 1994].
At present, one of the principal limitations to further improving the orbit accuracy is the problem of modeling the complex surface forces acting on the spacecraft [Ries et al, 1993]. The improved design of the GPS processor on Jason-1 may provide the opportunity for further enhancements to the orbit accuracy. The enhanced GPS receiver on Jason-1 has the potential to allow a more refined parameterization of the force model errors, which is a requirement for orbits at the 1-cm level.
The goal for Jason-1 orbit determination is to provide orbits which are equally as accurate as T/P.
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Jason-1 precision orbit verification