Near real-time astrometry for spacecraft navigation with the VLBA: A demonstration with the Mars Reconnaissance Orbiter and Odyssey

摘要

We present a demonstration of near real-time spacecraft astrometry with theVLBA. We detect the X-band downlink signal from Mars Reconnaissance Orbiter andOdyssey with the VLBA and transmit the data over the internet for correlationat the VLBA correlator in near real-time. Quasars near Mars in the plane of thesky are used as position references. In the demonstration we were able toobtain initial position measurements within about 15 minutes of the start ofthe observation. The measured positions differ from the projected ephemeridesby a few milliarcseconds, and the repeatability of the measurement is betterthan 0.3 milliarcseconds as determined from measurements from multiple scans.We demonstrate that robust and repeatable offsets are obtained even whenremoving half of the antennas. These observations demonstrate the feasibilityof astrometry with the VLBA with a low latency and sub-milliarcsecondrepeatability.