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J.D. Romney (NRAO)
NRAO recently began a NASA-sponsored pilot project to investigate the suitability of VLBA snapshot observations for enhancing spacecraft navigation. High-precision angular position measurements obtained by imaging the spacecraft downlink transmitter are expected to provide strong additional constraints on orbit determination. Since current solutions are derived primarily from range data, the addition of fairly frequent, straightforwardly obtainable measurements of the orthogonal angular coordinates should be powerfully synergistic. Angular position measurements would be performed using standard VLBA phase-referencing techniques to correct for atmospheric effects, with a goal of 1 nano-radian precision in an individual measurement. It is expected that each such measurement could be completed in about ten minutes, so that several snapshots daily could be interleaved expeditiously with ongoing astronomical VLBA observations.
The central thread of the feasibility study, to be performed in collaboration between NRAO and JPL, will evaluate the enhancement that can be achieved in orbit determination by the incorporation of high precision angular positions. As part of this study, the required interval between observations, sensitivity, density of phase-reference sources, and impact of atmospheric and meteorological conditions, will all be estimated. Other aspects of the NRAO portion of the study involve evaluation and design of the necessary enhancements to several areas of the VLBA's instrumentation and operational procedures.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.