DETERMINATION OF POSITION OF JUPITER FROM VERY-LONG BASE-LINE INTERFEROMETRY OBSERVATIONS OF ULYSSES

Very-long baseline interferometry (VLBI) observations of the Ulysses s pacecraft near its encounter with Jupiter on 1992 February 8 were made to determine the angular position of Jupiter with respect to well kno wn extragalactic radio sources. Spacecraft range and Doppler data were used to determine the position of the spacecraft with respect to Jupi ter. Thirty-one VLBI observations of the spacecraft were made within 3 0 days of Ulysses closest approach to Jupiter, using the California-Sp ain and California-Australia baselines of NASA's Deep Space Network. W hen combined, these data determine the position of Jupiter at the time of encounter with an accuracy of 0.003 '' in right ascension and 0.00 5 '' in declination. In addition, the Earth-Jupiter distance was deter mined with 20 m accuracy. (C) 1996 American Astronomical Society.