ROSAT S/C Status 1995-10-02 ... 1998-04-25

Compiled by Jakob Englhauser
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Contents

   980429 Safe mode continued due to XRT startracker failure
   980425 Safe mode due to high battery temperatures
   980415 (Short) Hangup of XRT startracker camera STC-1
   980218 Reactivation of the PSPC
   980121 HRI High Voltage reduced
   980120 Annual spacecraft clock reset
   980119 Telemetry Loss
   980114 Battery Reconditioning III
   971208 New Setting of the HRI High Voltage
   971127 DPS Hang-Up
   971111 Battery Reconditioning II
   971103 Hangup of XRT startracker camera STC-1
   971027 FI safe mode
   970920 Safe mode due to sun cone violation
   970901 Solar Eclipse
   970714 Telemetry Problems
   970530 Battery Reconditioning I
   970506 HRI high voltage changes
   970416 Hangup of XRT startracker camera STC-1
   970117 Spacecraft clock reset
   970110 Synchronisation problems
   970105 Acquisition problems
   961231 New year
   961219 RAM safe mode
   961202 Synchronisation problems
   961128 Hangup of XRT startracker camera STC-1
   961029 Failure of ZDE2
   951220 Hangup of XRT startracker camera STC-1
   951202 RAM safe mode
   951002 Hangup of XRT startracker camera STC-1

1998-04-29 ? to ???
"Safe mode continued due to startracker failure"
Data loss: > 75 days Description: Due to a complete failure of the remaining XRT startracker no recovery from the safemode triggered by too high battery temperatures was possible. The startracker showed several hang-ups during the previous safemode. Repeatedly switching off and on - the usual method to bring the startracker back to normal operations - did not work this time. Currently a new operation mode using the WFC startracker camera is being tested. See protocol for a log of events.
Source of information: GSOC; DASA; MPE / 980428-...
1998-04-25 21:15:34 UTC to 1998-04-29 ?
"Safe mode due to high battery temperature"
Data loss: ~ 4 days Description: On 1998-04-25, 21:15:34 UTC the satellite was intentionally put into safe mode since there was an indication that the battery temperature was by far too high. Status: 1998-04-29: Battery temperatures are back to normal values. No safemode recovery possible due to startracker failure. Source of information: GSOC/ATOR; MPE / 980428, 980429, 980430; ...
1998-04-15 02:37 UTC to 1998-04-15 03:38 UTC
"Hangup of XRT startracker camera STC-1"
Data loss: 3600 s Description: See 951220. Action: STC-1 was restarted at 03:37 UTC (during a Weilheim contact). Source of information: GSOC / H. Wallner / 980420 AMCS Summary Protocol for ROSAT Day 2918
1998-02-18 20:50:15 UTC to 1998-02-22 20:19:00 UTC
"Reactivation of the PSPC"
Data affected: 24 hours Description: "After a hibernation phase of one year the PSPC was reactivated on Feb 18, 1998. The main objective of this effort was the observation of a lunar occultation of Sco X-1, due to its brightness the only forbidden source for ROSAT. In addition, a few other targets of opportunity including SN 1987A were observed in order to take full advantage of the remaining PSPC gas. According to quicklook data, the quality of the PSPC data was as good as observed last year. On Feb 22, 1998, 21:00 UT the nominal HRI timeline was resumed. HRI observations from the guaranteed program which were cancelled due to the short PSPC intermezzo will be rescheduled in the second half of AO8." (cf. ROSAT NEWS No. 59) Sequence of Events: UTC yyyy-mm-dd hh:mm event -------------------------------------------------------------------------- 1998-02-18 20:50:15 WHM2 detector change to PSPCB 1998-02-22 20:19:00 WHM2 detector change to HRI -------------------------------------------------------------------------- Source of information: MPE / 980223 GSOC / ROSAT Summary Report 1998-Feb
1998-01-20 10:41 UTC to 1998-01-21 08:53 UTC
"HRI High Voltage reduced"
Data affected: 24 hours Description: High voltage step 13 was used for one day after the spacecraft clock time reset. Sequence of Events: UTC yyyy-mm-dd hh:mm event -------------------------------------------------------------------------- 1998-01-20 10:41 WHM3 HRI HV reduced to step 13 1998-01-21 08:53 WHM3 HRI HV set back to step 14 -------------------------------------------------------------------------- Source of information: MPE / U.Briel / 980121
1998-01-20, ??:40:48.411 h UTC
"Annual spacecraft clock reset"
Data loss: 1.5 hours (1 orbit) Description: As always at the beginning of a new year, the spacecraft clock counter was reset in order to avoid its overflow. Sequence of Events: UTC yyyy-mm-dd hh:mm event -------------------------------------------------------------------------- 1998-01-20 09:00 WHM1 upload timeline up to start of WHM3 to spacecraft ? 1998-01-20 10:39 WHM3 HRI HV off; spacecraft clock reset ? 1998-01-20 12:20 WHM4 upload timeline starting at end of WHM4; HRI HV ON -------------------------------------------------------------------------- Source of information: GSOC / W. Bartel / 980107, 980114
1998-01-19, 17:41 UTC to 18:27 UTC
"Telemetry loss"
Data loss: 46 min Description: Part of the telemetry was lost. Source of information: GSOC / H. Wallner / 980128
1998-01-14 08:15 UTC to 1998-01-17 13:35 UTC
"Battery Reconditioning III"
Data loss: none Description: A third reconditioning of the ROSAT battery has been performed in order to improve its overall behaviour (see also 970530 and 971111). Again, during this battery reconditioning no intentional AMCS safemode was necessary, therefore no observing slots were lost. Targets were observed even if their sun-satellite-target angles were beyond the range 80 to 100 degrees. Sequence of Events: UTC yyyy-mm-dd hh:mm event ---------------------------------------------------------------- 1998-01-14 08:13 WHM1 TEST SASD (microswitches open) 1998-01-14 08:15 WHM1 reconditioning start 1998-01-17 07:21 end of discharge 1998-01-17 07:25 start of battery recharging 1998-01-17 13:35 end of battery recharging 1998-01-20 16:30 end of full sun orbit phase ---------------------------------------------------------------- Source of information: GSOC / W. Bartel / 980107, 980114, 980119; ROSAT Summary Report 1998-Jan
1997-12-08 06:56:40 UTC
"New Setting of the HRI High Voltage"
Description: The HRI HV has been increased from step 13 to step 14. Source of information: MPE / 971208
1997-11-27 12:41:26 UTC to 1997-11-28 03:36:02 UTC
"DPS Hang-Up"
Data loss: 15 hours Description: The CPU of the on-board data handling system crashed. Action: None. Source of information: GSOC / Fleming / 971201; ROSAT Summary Report 1997-Nov
1997-11-11 20:31 UTC to 1997-11-15 02:00:?? UTC
"Battery Reconditioning II"
Data loss: none Description: Another reconditioning of the ROSAT battery has been performed in order to improve its overall behaviour (see also 970530). Action: All targets with sun-satellite-target angles beyond the range 80 to 100 degrees had to be replaced. During this battery reconditioning no intentional AMCS safemode was necessary, therefore no observing slots were lost. Sequence of Events: UTC yyyy-mm-dd hh:mm event ---------------------------------------------------------------- 1997-11-11 20:28 test SASD (microswitches open) -> ok 1997-11-11 20:31 WPS1 reconditioning (discharging) start 1997-11-14 19:38 reconditioning (discharging) end 1997-11-14 22:38 start of battery recharging 1997-11-15 02:04 end of battery recharging; battery reconnected to S/C bus power DNEL safemode re-enabled ---------------------------------------------------------------- Source of information: GSOC / W. Bartel / 971107, 971114; ROSAT Summary Report 1997-Nov
1997-11-03 03:33:02 UTC to 1997-11-03 11:48:43 UTC
"Hangup of XRT startracker camera STC-1"
Data loss: 32000 s Description: See 951220. Action: STC-1 had to be restarted during the first Weilheim contact after the STC-1 failure. Source of information: GSOC / H. Wallner / 971105 AMCS Summary Protocol for ROSAT Day 2753
1997-10-27 ..:.. UTC to 1997-10-27 ..:.. UTC
"FI safe mode"
Data loss: several hours Description: The FI went into safe mode due to an erroneous AMCS safe mode signal. Recovery of the FI was done during the first possible Weilheim contact after the safe mode. Actions: None Source of information: MPE / S. M"uller / 971103
1997-09-20 11:40 UTC to 1997-09-23 14:30 UTC
"Safe mode due to sun cone violation"
No usable data for 69 hours Description: The AMCD relied on the erroneous (but stable) values supplied by the startracker camera (STC-1) after a hangup of STC-1 (similar to 961219). Drift rates were derived from the only star indicated by STC-1 to be zero. This erroneous information was used with highest priority for the AMCS. A strong gravity gradient, however, caused a shift of the pointing direction beyond the sun cone, which triggered a safe mode. Sequence of events: Sat, 1997-09-20, 11:40 UTC - STC 1 hangup Sat, 1997-09-20, 11:55 UTC - AMCS safe mode triggered (recognized on RODAY 2709 during WPS 1) Sun, 1997-09-21, 04:53 UTC - STC 1 off / on (during WHM 1) Sun, 1997-09-21, 06:33 UTC - start of recovery Sun, 1997-09-21, 10:15 UTC - AMCS back on timeline Mon, 1997-09-22, 16:15 UTC - HRI switched on again (out of focus) Tue, 1997-09-23, 08:00 UTC - HRI back in focus; mode recognition doesn't work; data can probably be recovered Tue, 1997-09-23, 14:30 UTC - HRI is working nominally again Actions: Further investigated by GSOC. Source of information: GSOC / U. Feucht / 970923 MPE / S. M"uller / 970923 GSOC / ROSAT Daily Report (ROSAT Days 2707-2718) GSOC / AMCS Summary Protocol (ROSAT Days 2705-2716)
1997-09-01 23:00 UTC
"Solar Eclipse"
One slot for ROR 702927 had to be replaced by ROR 601010 in order to avoid a forbidden slew during the solar eclipse on 1997-09-01. No problems were noticed during the eclipse. Source of information: GSOC / J. Weisner; H. Wallner / 970903
1997-07-14
"Telemetry Problems"
Data loss: about 6 hours (from 1997-07-14 04:02:27 UTC to 1997-07-14 09:54:47 UTC) Source of information: GSOC / K. Vrana / 970718
1997-05-30 19:45:00 UTC to 1997-06-03 09:00:00 UTC
"Battery Reconditioning I"
Data loss: 36.5 hours During the initial phase of the battery reconditioning the satellite was put into safemode. Sequence of Events: UTC yyyy-mm-dd hh:mm event ---------------------------------------------------------------- 1997-05-30 19:45 safemode start 1997-05-30 20:15 test microswitches -> ok 1997-05-30 20:18 reconditioning (discharging) start 1997-06-01 03:52 recovery from AMCS safemode 1997-06-01 09:10 recovery from FI safemode safemode end 1997-06-02 19:30 reconditioning end start battery recharging 1997-06-03 01:50 end battery recharging 1997-06-03 09:00 power DNEL safemode re-enabled ---------------------------------------------------------------- Description: (see ROSAT News 54) From May 30 to June 3, 1997, a reconditioning of the ROSAT battery was performed: after disconnecting it from the spacecraft main and charge bus, the battery was completely discharged over a period of 72 hours, and then recharged within 5 hours. At the beginning of this operation ROSAT had to be put into safemode (May 30, 1997, 19:45 UT to June 1, 1997, 9:15 UT); after that, a reduced observing programme (sun angle of targets within 80 and 100 degrees) was executed until June 3, 1997, 20:00 UT. According to the specifications of the manufacturer, the nominal battery lifetime is about 35000 charge/discharge cycles, if no reconditioning is performed. Until now, the ROSAT battery has undergone more than 37000 such cycles. During the past few months the end of the nominal battery lifetime was indicated by individual cell voltages reaching values only a few hundreths of a volt above the threshold where all non-essential load (including the focal instruments!) is disconnected from the spacecraft power supply. A prerequisite for the battery reconditioning is a sufficiently long period of full sun orbits, since there is no backup battery available on ROSAT. Such periods occur about twice per year, the period starting on May 30 being the best opportunity in 1997. It is expected that the reconditioning will significantly improve the quality of the battery for at least one year. Source of information: GSOC / W. Bartel, M. Steinhoff / 970530-970603
1997-03-03 14:30:00 UTC to 1997-05-06 12:40:00 UTC
The HRI high voltage was set to step 12 (initial value) from 1997-03-03 14:30:00 UTC to 1997-05-06 12:40:00 UTC. It was set back to step 13 on 1997-05-06 12:40:00 UTC. For further reference, see URL http://hea-www.harvard.edu/rosat/rsdc_www/hri_status.html and ROSAT News 54. Source of information: MPE / U. Briel / 970506 SAO / D. Harris / 970508
1997-04-16 00:45:00 UTC to 1997-04-16 05:00:00 UTC
"Hangup of XRT startracker camera STC-1"
Data loss: 15300 s / 4 slots Description: (not yet available) See 951220. Action: STC-1 had to be switched off and on twice by the operator. Source of information: GSOC / U. Feucht / 970416
1997-01-17, 01:40:48.411 h UTC
"Spacecraft clock reset"
Description: As always at the beginning of a new year, the spacecraft clock counter was reset in order to avoid its overflow.
1997-01-10 ???
"Failure of ZDE1"
(not yet fully described) Data loss: approximately 18 hours Description: A similar problem as on 1996-12-02 was detected (data were no longer transmitted from the FI; "Realtime Sync Error" was displayed at DPS). ? Consequently, the satellite went into safe mode. The problem seems to be related to synchronisation problems, and not to problems with the ZDE; therefore ZDE2 probably works as well as ZDE1. Actions: Software had to be uploaded. HRI was brought into focus again. (The HRI is automatically moved out of focus, if the AMCS doesn't get attitude information correctly, as this was the case during this event; as a by-product, this proved that the detector carrousel is still working!) Since the problem doesn't seem to be related to ZDE, Dornier has to investigate the problem. Source of information: MPE / HWG / 960113
1997-01-05 10:44:43 UTC to 1997-01-05 19:28:26 UTC
"Acquisition problems"
Data loss: 31000 s Description: The acquisition of ROR 600932 failed due to a missing "EB End command". Actions: No further action required Source of information: GSOC / ATOR / 970107 GSOC / AMCS Summary Protocol
1996-12-31 23:40:25 UTC to 1997-01-01 22:11:52 UTC
"New year"
Data loss: 81000 s Description: The onground software (at GSOC) didn't treat the change to the new year correctly. As a result, all commands in the time tag buffer were executed immediately until no commands were left. After that ROSAT took a "New Year's Break" (pointing to the last target before the problem occured). Similar problems were encountered also in earlier years. Actions: None. Source of information: GSOC / ATOR / 970107 GSOC / Feucht / 970108
1996-12-19 03:28:12 UTC to 1996-12-19 14:28:17 UTC
"Safe mode"
Data loss: 40000 s Description: For the first time a startracker camera (STC-1) hangup during an ongoing observation occured. The AMCD, however, still relied on the erroneous (but stable) values supplied by STC-1, since 'steady' was signalled by STC-1. Therefore the AMCS tried to reacquire the target while using the erroneous STC-1 information. During this procedure the sun angle constraint was violated. After about 1min ROSAT went into safe mode. The safe mode was triggered by the 3V presence threshold of CSS3 (5s delay counter); the usual 7.7V presence threshold of CSS3 (300s delay counter) did not react since STC-1 signalled reliable values. The CSS3 voltage dropped from 7.7V to 3V in about 1min, therefore the safe mode was triggered after 1min plus 5s. Actions: Investigated by GSOC and DSS. Source of information: GSOC / ATOR / 970107 GSOC / Feucht / 970108; 970127
1996-12-02 15:00:00 UTC to 1996-12-03 20:00:00 UTC
"Synchronisation Problems"
Data loss: approx 100 000 s Description: On 1996-12-02, 15h data were no longer transmitted from the FI; "Realtime Sync Error" was displayed at DPS. Actions: The HRI High voltage was switched off. On 1996-12-02, 15h: ZDE2 was switched off and on again, and tested; result: ZDE2 ok. ZDE2 was switched off again, and ZDE1 was switched on and tested; result: ZDE1 ok. Due to a few problems with ZDE2 during the past few months it was decided to use ZDE1 from now on; ZDE1 hadn't be used for several years, but now seems to be more reliable than ZDE2. Source of information: MPE / HWG / 961209
1996-11-28 00:00:00 UTC to 1996-11-28 20:20:48 UTC
"Hangup of XRT startracker camera STC-1"
Data loss: 73000 s Description: See 951220. Action: Restart of STC-1 during WHM-3. Source of information: GSOC / ROSAT Summary Report, 20-Dec-96
1996-10-29 04:00:00 UTC to 1996-10-29 14:00:00 UTC
"Failure of ZDE2"
Data loss: approx 100 000 s Description: Unknown. On 1996-12-02, 04:00: ZDE2 transmits RESET frames; (no housekeeping data) ZDE2 does not react to commands; however, HRI experiment data are ok Actions: On 1996-12-02, 10h: Both ZDE1 and ZDE2 were tested; result: both ZDE1 and ZDE2 are ok On 1996-12-02, 14:00 : ZDE2 running nominally again (all housekeeping values ok again) Source of information: MPE / HWG / 961029
1995-12-20 10:16:37 UTC to 1995-12-21 04:21:44 UTC
"Hangup of XRT startracker camera STC-1"
Description: Startracker 1 (ST1) failed at the end of a Weilheim contact period. ST1 was recovered after 18 hours, at the beginning of the next Weilheim contact period (had to be done manually). No attitude information is available for the time during failure of ST1; data are lost. The same problem occured during 5 occasions in November 1995 and during 5 occasions in December 1995. Source of information: GSOC / Uwe Feucht / 960103
1995-12-02 00:45:10 UTC to 1995-12-02 11:48:02 UTC
"Safe Mode"
Data loss: No data during safe mode. Source of information: J. Schmitt / M.Kürster / GSOC
1995-10-02 16:05 UTC to 1995-10-03 02:58 UTC
"Hangup of XRT startracker camera STC-1"
Data loss: XRT data were lost. Source of information: H. Wallner/GSOC

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