Important Events during the ASCA mission

This document lists important events in the history of ASCA. This list may be helpful in judging the data quality of specific observations, or point out the need for a special step in data reduction and analyis.

Please also refer to ASCA Operation News for operation news from ISAS.

Important Events in the history of ASCA

(updated on April 23rd, 2001)

Note: 93/02/20 denotes February 20th, 1993

General:

93/02/20: Launch
93/02/21-93/03/20: Initial operation
93/03/22-93/04/18: Instrument calibration
93/04/19-93/10/14: Performance verification phase
93/10/15-93/12/14: PV to AO1 transition phase
93/12/15-94/05/14: AO1 phase
94/05/15-94/11/14: AO2 phase
94/11/15-95/12/10: AO3 phase
95/12/10-96/11/30: AO4 phase
96/12/01-97/12/19: AO5 phase
97/12/20-99/01/03: AO6 phase
99/01/04-00/02/12: AO7 phase
00/02/13-00/07/15: Long-look observations ("AO8")
01/03/02: Reentry

Data loss:

Please refer to the ASCA data loss report.

Operation/Attitude:

93/04/03 04:15 - 93/04/05 05:55 : Unexpected safe-hold mode (=no observations).
93/04/09 16:30 - 93/04/14 02:32 : Unexpected safe-hold mode (=no observations).
93/09/06 - 93/09/07: KSC shut-down by typhoons and the antenna repaire.
93/09/07 23:00 - 93/09/10 22:17 : Unexpected safe-hold mode (=no observations).
93/10/31 07:54 - 93/11/03 04:50 : Attitude troubles.
93/11/04 : Change of nominal pointing directions
93/11/17 23:34 - 93/11/20 12:20 : attitude mulfunction, no data
93/11/24 - 93/11/26 : command sender broken, no observations
93/11/27 - 93/11/28 : Unexpected safe-hold mode (=no observations).
93/11/29 - 93/12/07 : Gyro change from S1 --> S2, Gyro on-board ACS parameter adjustment
94/07/06 19:20 - 94/07/08 00:10 : KSC groud station system trouble, wrong pointings.
94/08/13 - 94/08/14: KSC was hit by a typhoon, no operations
94/09/05 17:22 - 94/09/06 11:38 : Command trouble, wrong pointing.
94/11/07 - 94/11/11 05:50 : Unexpected safe-hold mode (=no observations).
96/05/07 - 96/05/11 : ACS re-configuration (switch from S2 rto Z.
96/08/14 : Typhoon - no operations.
97/06/27 : Typhoon - no operations. Continued the observation of A1885, and deferred the IC1481 observation.
97/08/13 : Her X-1 observation was scheduled to begin at 13:00, however due to a mis-commanding, ASCA maneuvered instead to IC4329A. Her X-1 observation started at 16:22.
97/09/15 : Typhoon - no operations. AGP 267.3-27.4 not observed, observations before (X1658-298) and after (OAO 1657-415) also slightly affected.
97/10/22 - 97/10/25 : Attitude error after long maneuver - observations of SGR1900+14, SN1993J no2, GRS1915+105, and NGC 6876 were affected
00/03/22 : Safe-hold
00/04/08 : Safe-hold
00/07/15: : Safe-hold mode due to a geomagnetic strom; end of scientific observations.

SIS:

93/03/26: SIS-1 door open
93/03/29: SIS-0 door open
93/04/15: Split threshold set to 40 ADU

(earlier data were taken with split th.=20 ADU)
93/07/09 : S0C2 and C3 temporary area masking start, when the angular distance between SIS fov and the closest edge of the bright Earth is less than 25 degree.

Mask region
S0 C2 : H-address 6-200, V-address 2-150
S0 C3 : H-address 316-425, V-address 2-112
93/09/15 - 94/02/08 23:10 : Corruption of the on-board dark frame boundary setting in S1C0.
From 93/11/30 07:30 : Bright mode grade 6 events are sent to ground (up to this time, events with grades 0, 1, 2, 3, 4 and 5 are sent to ground).
From 94/07/11: Change of lower level discriminators

0.48 keV for 4CCD BRIGHT bit-M and 2CCD FAINT bit-M and
0.41 keV for 4CCD FAINT bit-H.
From 94 December: Change of lower level discriminator

0.55 keV for 2CCD FAINT bit-M
From 95/12/23: SIS event threshold set to 0.40 keV

Previously, event threshold was 100 ADU, or 0.3 - 0.4 keV depending on chips.
99/05/25: SIS1, Chip2 mulfunction

This chip (not a standard chip) developed a defect between 1999 May 14 and 25, and is no longer usable for observation.

GIS:

93/05/28: Spread Discriminater ON:: Note: Spread Discriminator OFF periods (sequences):
* ALL the observations up to 1993 May 28 (80015000, Hydra A).
* 40007000, 1993 June 11-12, Cyg X-3,
* 60038000, 1993 June 12-13, NGC 253
* 20000000, 1993 June 13-14, 30 Dor (but a part of this observation was carried out with S_DSCR=ON).

93/11/05 - 11/09: CPU2 trouble: 93/11/05 15:30 - 23:00 : no GIS2 data
93/11/06 - 93/11/09: GIS2 is connected to CPU3

94/02/10 - 94/04/08: GIS3 bit assignment trouble

In the standard mode in which PHA channel number is supposed to be 1024 (0-1023ch), PHA values are quantized to 5, 13, 21, ,, 1021 (consequently, the PHA channel is 128 ch). In the timing observations in which number of the timing bits is 9 or 10, the lowest 1 or 2 bits, respectively, are lost. Please refer to Fixing the GIS3 Bit Problem, to see how to analyze GIS3 data taken during this perold.
94/11/02: CPU3 Error

The error occured during observations of Cygnuls Loop (#2 and #3) and SS433 (#5). GIS3 position determination will be affected by this error.
96/01/13-96/01/15: CPU Error

The error occured during the observation of RD J13434+0001. On-board Spread-Discriminator is not available due to this error.
96/03/20: CPU2 Position determination Error
96/04/05-96/04/07: CPU2 Error

GIS2 data was not available during this period. GIS3 was all right.
97/06/17: CPU3 2-bit Error, PH data and RT data lost

The problem happened between the Pass 2 and Pass 3 (19:00-19:40), and was corrected at Pass 3 (970617-14-44).
97/09/01-97/09/02: CPU2 Error

CPU-2 for the GIS misbehaved at about 05:50 UT; Switched GIS-2 to CPU-3 at about Sep 2 04:00, fully recovered at around 09:10 on Sep 2. Affected a part of PKS 420-01 observation, all of AK Her observation, and a part of Galactic Ridge 10 no1 observation.
98/06/08: CPU3 Error

The problem discovered at Pass 1, recovered at Pass 3.
98/08/19: CPU2 Error, PH data lost

The problem discovered at Pass 1, recovered at Pass 3.
98/11/16 16:30 - 98/11/18 17:40: GIS HV off

GIS HV was turned off during the peak of the Leonid shower, hence there are no GIS data on NGC 7252.
98/12/07: CPU3 2-bit Error

The error in the address 6BED was found at the pass 981207-14-43. GIS observation data should not be affected.
99/01/25: CPU2 3-bit Error

Error in the address 58F2. The error happned between 1999/1/23 23:01:01 and 1/25 15:45:00 (pass1), and corrected at 1/25 19:07(pass 3). A part of the GIS2 data was lost.
99/02/18: CPU2 2-bit Error

Address 7751 was affected, but no effects on the observation data.
99/05/31: CPU3 3-bit Error

Address DA5C was affected, but no effects on the observation.
99/08/03: CPU2 Memory Error

Address 2AC8 was affected, but observations will not be affected.
99/08/10: CPU3 Memory Error

The on-board position determination program is affected. Event X-position determination could be wrong.
99/11/17 4:30 - 99/11/19 2:00: GIS HV off

GIS HV was turned off during the peak of the Leonid shower, hence there are no GIS data on LBQS 2212-1759.

This file was last modified on Tuesday, 09-Jul-2024 11:13:45 EDT
Curator: Michael Arida (SP Sys); arida@milkyway.gsfc.nasa.gov
HEASARC Guest Observer Facility

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This file was last modified on Tuesday, 09-Jul-2024 11:13:45 EDT