HALCA onboard VLBI observing system performance Original Research Article

The space VLBI satellite HALCA was launched on February 12, 1997. It is the first Radio astronomy satellite. We report the performance of onboard radio astronomy system. Typical system noise temperatures are 70K and 90K at L and C band respectively. For K band, the apparent system noise temperature is 400 K. It is caused by the attenuation between the main antenna and the K band LNA. Bandpass characteristics of each observing band are almost the same as the ground test. The phase stability of local oscillators are around 5 degrees r.m.s. at C band. And the total gain of the receiving system and the bit distribution of high rate samplers are checked. Basically the in-orbit performance of the VLBI observing system matches the pre-launch ground test results.