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F. Nagase, H. Inoue (ISAS), ASCA Team
Japanese X-ray astronomy satellite ASCA has transfered to a Safe-Hold mode around 22:00- 23:00 (UT) on July 15, 2000. This transfer of ASCA attitude control was due to a large geomagnetic storm that was excited by a large solar flare occured on July 14 at 10:00. During the geomagnetic storm, atmospheric density has increased drastically even at the altitude of 440 km, in which ASCA is currently orbitting. Hence, external torque due to air drag became so strong as to perturb ASCA attitude control, thus ASCA transfered to a Safe-Hold mode.
Moreover during the Safe-Hold mode operation, further air drag unfortunately forced the solar paddle to turn its face away from the sun. This reduced power supply from solar cell, thus resulting over-discharge of battery.
Thus, regular observations became impossible since July 15. Currently, the efforts to recover ASCA to the regular operation mode have been continued. Although the first step toward recovery is to charge-up the battery, we are not successful yet at the time of submitting this abstract. We will report the details of the event and current status of ASCA. We will aslo highlight the results made with ASCA over the past 7.5 years.