The proportion of science to tests has increased markedly since the first scientific observations last July, with 16 GOT experiments among the 20 occurring since the beginning of September. Four of the five tracking stations now have compiled a fairly solid record of reliability.
Tracking passes no longer fail for unexplained reasons.
Occasional failures due to hardware faults or adverse weather conditions are being detected by tracking station personnel, who usually also provide the first notification of failures on the spacecraft, typically resulting from scheduling faults or mispointing of the data link antenna. The previous large constant delay offsets have been removed, and recent progress has aroused some hope of eliminating the delay instabilities currently exhibited by two of these stations at the level of a few hundred nanoseconds. These four tracking stations now are substantially more reliable, in terms of both recording quality and ancillary data, than many of the ground telescopes involved in the global ground arrays which have become nearly universal in VSOP observations. Occasional apparent anomalies will continue to be diagnosed using AIPS, just as is done with ground-based data. And as part of our continuing development of Space VLBI data analysis techniques, selected observations still will be carried through the entire process for test purposes.