Citation
Abstract
The pointing accuracy needed to support Magellan’s Svnthetic Aperture Radar mapping of Venus places stringent requirements on navigation accuracy. This need is met with a combination of two-way Doppler and narrowband A Very Long Baseline Interferometer (A VLBI) data, which are capable of determining the spacecraft's orbit to the required level, typically about one-kilometer position uncertainty. Differenced Doppler (two-way Doppler minus three-way Doppler) is also capable of meeting mission navigation requirements, and serves as a backup to narrowband AVLBHI. The Magellan Project specifies that the turn-around time for processing narrowband AVLBI data must be 12 hours or less, a very difficult requirement to meet operationally. In this article, the use of phase-delay data, taken from a Connected-Element Interferometer (CEI) with a 21-km baseline, for Magellan orbit determination was investigated to determine if navigation performance comparable with narrowband AVLBI and differenced Doppler could be achieved. CEI possesses an operational advantage over AVLBI data in that the observables are constructed in near-real time, thus greatly reducing the turn-around time needed to process the data, relative to the off-line system used to generate AVLBI observables. Unfortunately, the results indicate that CEI data are much less powerful than narrowband AVLEI and differenced Doppler for orbiter navigation, although there was some inarginal Improvement over the navigation performance obtained when only twoway Doppler data were used.
Details
- Volume
- 42-100
- Published
- February 15, 1990
- Pages
- 48–54
- File Size
- 320.0 KB