8. Operation of Satellite in Orbit

ASTRO-D was launched on February 20, 1993, into a roughly circular orbit at 520-620 km altitude. The new satellite was named ASCA, "Advanced Satellite for Cosmology and Astrophysics." One reason for the new name was that the satellite in orbit looks like a migratory bird soaring into deep space--the Japanese letters of "asuka" means "a flying bird." Another reason was that the satellite's launch marked an important step toward the full maturing of Japan's space science--just as Japan's Buddhist culture bloomed in the "Asuka" era that heralded the dawn of Japan.

The key elements of ASCA have been successfully activated in orbit. Performance verifications and test observations continued until October 1993 and guest observations started after then. In the performance verification observations, about 150 targets were scheduled to be observed and most of them have been done so far. The variety of the targets are as follows;

In the guest observation phase, observing time on ASCA is open to competitive proposals. The available observing time, after reserving about 5% for recalibrations and readjustments of the instruments or spacecraft subsystems,will be apportioned as follows:

The opportunity for the first round guest observations was announced and about 200 proposals were submitted to ISAS and 250 to NASA respectively. From these proposals, about 165 proposals (after merging those for the same targets) and 215 targets (Japan 119; US 38; Japan-US 57) were selected. The numbers of targets for various source categories are summarized as;

ASCA operations are managed mainly by Japanese scientists, including graduate students, of the ASCA team at ISAS. The institutions and the numbers of the members of the ASCA team are shown in the Table and the system diagram of the ASCA operation is shown in the Figure. The team schedules observations, directs the satellite, collects the data, and monitors the health of the spacecraft and its payload. Direct contact between the satellite and the ground stations is currently made for 10 of the 15 orbits per day on the average, 5 from ISAS Kagoshima Space Center and about 5 from NASA Deep Space Network Stations (DSN) in Madrid, Canberra, and Goldstone. All the data from ASCA are, together with satellite attitude and orbital information, stored at ISAS and will be distributed to Japanese investigators. The data are also sent to the US ASCA Guest Observer Facility at the Goddard Space Flight Center and will be distributed to US guest observers.