Mission Status
-- by H. Inoue and F. Nagase, ISASAlmost one and a half years have passed since the launch of ASCA. All the instruments on board ASCA are functioning normally, except that one gyroscope among five has degraded. Since three gyros are necessary for the attitude control, one of two spare gyros is now used instead of the degraded gyro and the attitude control is being performed as well as before. The ASCA operations performed so far are summarized in Table 1.
Table 1. ASCA Operation Status
Launch of ASTRO-D 1993 Feb. 20 Initial operation & instrument turn on 1993 Feb. 21 - Mar. 20 Instrument calibration 1993 Mar. 22 - Apr. 18 PV phase observations 1993 Apr. 19 - Oct. 14 PV to GO1 transient period 1993 Oct. 15 - Dec. 14 GO-1 observations 1993 Dec. 15 - 1994 May 14 GO-2 observations 1994 May 15 - Nov. 30 AO-3 period 1994 Dec 1- 1995 Nov. 30 (proposal due date: 1994 Aug. 30)
During the performance verification (PV) phase, ASCA observed 157 targets of various astronomical classes which had been selected beforehand by the ASCA team. The guest observer (GO) phase in which general observers can participate in ASCA, based on peer-reviewed proposals, began in 1993 October.
Data in the PV phase will be moved to the archival database after 18 months from the observation, on a monthly basis.
Mainly based on the observations in the PV phase, 20 papers have been published and about 40 papers have been submitted to the refereed journals.
Observations for the GO-1 phase were finished by carrying over a few priority A and B targets and most priority C targets. Occasionally, we had troubles with operations at KSC (Kagoshima Space Center) and in data acquisition at the DSN down-link, which caused insufficient observations for several targets. For a few such observations in the early GO-1 phase, we have readily installed supplemental observations. For others, we will install supplemental observations during the GO-2 phase.
At present, the observations of the GO-2 phase targets are progressing along the released long-term timeline, a few days behind schedule. Most of the priority C targets accepted in AO-2 are out of the present timeline and they will be carried over to the next phase (for US targets) or will be deleted in the next phase (for targets of Japan time).
TOO (Target of Opportunity Observation) observations with ASCA are performed according to the following principles agreed by the Japan-US Scientific Working Group:
- Only very important targets will be accepted as TOO observations. TOO observations are approved by the ASCA manager and are performed under his responsibility.
- TOO observations are performed in the Japan time category. The ASCA manager will designate a principal investigator for individual targets among the Japanese ASCA operation team.
- Japanese Co-Is are arranged by the PI and the manager among the members of Japanese ASCA operation team.
- The ASCA manager is also able to invite one or a few foreign investigators who have contributed to the TOO observation.
During GO-1 period, we performed four TOO observations. The PI, Co-Is and invited Co-Is are listed below:
Table.2. TOO observations during GO-1 period
Obs. Date Target Exp. PI & Japanese Invited Comments (ksec) Co-Is Co-Is --------------------------------------------------------------------------------------------------------- 93 Oct. 24 SN1993J 40 Inoue None 1st paper Kohmura submitted & TBD 2nd in preparat. 93 Nov. 10 GRS 1009-45 20 Tanaka None paper TBD in preparation 94 Feb. 28 PSR 1259-63 10 Nagase M. Tavani TBD 94 May 4 SN1994I 40 Itoh R. Petre TBD W. Lewin ------------------------------------------------------------------------------------------------------------
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