ASCA weekly

[Fumiaki NAGASE <nagase@astro.isas.ac.jp>]

Dear ASCA users,

Please find below the ASCA schedule for the period of December 5-17.

[Report on the ASCA Attitude Control failure]

After the maneuver to SN1993J on October 24 at 2:10 (UT), we found that\
the pointing position was offset by about 1 degree. After the discovery of
the pointing position offset, we have investigated the cause of this 
malfunction and found that it was really happened after the maneuver to 
SGR 1915+105 on October 22 at 3:50 (UT) (KSC operation crew did not realized 
the offset at the time since no conspicuous source was expected in the field).
At present, we have resolved the cause of this offset maneuver. Fortunately 
it is not due to the degradation  of gyro, but  due to the onboard attitude 
control system. After a long distant maneuver of about 150 degrees, about 
0.3 degree error of pointing position occurred (this is normal from the 
current  accuracy of gyro rate counter) and unfortunately at the offset 
position of STT-B field there were a combination of stars with pattern 
same as the combination of tracking stars. During the Saturday (October 25) 
acquisitions of satellite, we caught the current position of ASCA and fixed 
the ASCA ACS to the normal mode. Regular operation of ASCA was started after 
the first  acquisition of ASCA on October 27 (Monday) after the observation 
of GRB920525.

Due to this malfunction of the ACS, four observations were not completed. 
They are,
 date	seq. No.	target		Pri.	Cat.	exp.	PI
 10/22	55040000	SGR1900+14	B	USJ	80 ks	K. Hurley
 10/24	55018010	SN1993J #2	B	JUS	50 ks	H. Inoue
 10/25	45023010	GRS1915+105	A	MUJ	20 ks	C. Robinson
 10/25	65016000	NGC 6876	C	JPN	40 ks	H. Matsumoto
The first three (priority-A and -B) targets are carried over to the next 
window in AO6. NGC 6876 (priority-C) is dropped out. All of the data 
collected during the offset pointings are immediately released public. 
You may find some serendipitous sources in these data.

Fumiaki Nagase

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A S C A     WEEKLY  OBSERVATION   PLAN
-----------------------------------------------------------------------------
December 5 - 17,  1997		ver-1   (97/10/28)
(ISAS contact scientist:  R. Fujimoto	(fujimoto@astro.isas.ac.jp)
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Date	MNV	Target 		Tag. 	Exp.	Observation	PI or 
	start	name  		Cat.	(ks)	Cat.  Pri./TC	 ( PPI/Co-PI)
-----------------------------------------------------------------------------
12/ 5	 4:50	C Hale-Bopp	CXB	30	MJU	2/Y	J. Watanabe
								/C Lisse
12/ 6	 3:30	Carina Dwarf	Gal.	50	JPN	2/n	N. Arimoto

12/ 7	16:10	NGC 4111 #1	Gal.	20	JUS	2/n	Y. Terashima

12/ 8	 4:50	A2667		CG	40	JPN	3/n	Y. Tanaka

12/ 9	 6:10	A133		CG	40	MUJ	2/n	C. Sarazin
								/K. Kikuchi
12/10	 9:20	RX J0134-42	AGN	50	ESJ	2/n	D. Grupe

12/11	18:50	IRAS 11598-0112	AGN	20	JPN	3/n	T. Yamada

12/12	11:10	MS 1244.2+7114	CG	40	JPN	3/n	A. Furuzawa

12/13	 7:50	Cl. Link Region	CG	40	JPN	3/n	H. Tomida

12/14	12:40	Mkn 205		AGN	40	JPN	2/n	F. Makino

12/15	 9:40	NGC 4111 #2	Gal.	20	JUS	2/n	Y. Terashima

12/15	22:10	MCG-2-58-22 #2	AGN	40	US	2/Y	K. Weaver
								
(12/17	 3:00	MNV to next target)
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(Note) Obs. Cat. JPN: Japan time, US: US time, JUS: Japan-US Collaboration, 
USJ: US-Japan Collaboration,  MJU: Merged Japan-US (PPI=Japan), 
MUJ: Merged US-Japan (PPI=US),  ESJ: ESA-Japan Program, 
MOT: Manager's observatory time (Calibration and maintenance)