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ASCA Guest Observer Facility

Mission Status

-- by H. Inoue and F. Nagase, ISAS

Almost 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

94 May  4	SN1994I		40	Itoh		R. Petre
					TBD		W. Lewin

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