ROSAT S/C Status 1998-04-25 ... 1998-08-30

Compiled by Jakob Englhauser
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Introduction



Sat 1998-04-25 (DoY 115)

  21:15:34  ....  satellite put into safemode due to high battery temperatures
                  (S00)

   (no record of events)


Thu 1998-06-25 (DoY 176)

  23:30     ....  start of AMCS recovery


Fri 1998-06-26 (DoY 177)

? 11:18     ....  HRI moved into focus; switched on
? 23:20     ....  AMCS safemode due to begin of full sun orbits (S01)




Mon 1998-06-29 (DoY 180)

  19:45   ?       recovery from AMCS safemode

  10:50   ?       HRI moved into focus; switched on

  21:14   ?       period of WFC reset cycle increased (from 30 to 60 s)
  21:23:34        first valid long-duration (2154 s) pointing
                    after more than 2 months


Sat 1998-07-04 (DoY 185)

  05:00   ?       AMCS safemode due to end of full sun orbits
                    (or due to slew and belt?) (S02)



Mon 1998-07-06 (DoY 187)


  17:08           recovery from AMCS safemode

     No valid pointings.


Tue 1998-07-07 (DoY 188)

  06:42           AMCS safemode (during slew and belt) (S03)




Thu 1998-07-09 (DoY 190)

  16:45           recovery from AMCS safemode

  01:31:52        AMCS safemode (shortly before slew) (S04)
                     no CSS3 presence after ROSAT night at 01:30:30
                       (target at sun angle of 90-14.6 deg)
                     -> start of safemode delay counter
                  unclear:
                     reset of safemode delay counter at 77 s
                     safemode triggered already after another 5 s



  16:35     WHM1  recovery from AMCS safemode; new parameters:
                    increase period of WFC STC reset cycle
                       from 60 to 120 s
  18:14     WHM2  AMCS back on timeline
  19:54     WHM3  HRI back in focus

     in between:  3 targets at rim of sun cone (-14.2/-13.3/-14.1 deg)
                  3 long slews (171.7/136.6/136.6 deg)

  23:05           AMCS safemode (during slew and belt) (S05)




Sat 1998-07-11 (DoY 192)

  16:30     WHM2  recovery from AMCS safemode
                    increase WFC STC reset cycle from 120 to 240 s
                    increase upper threshold for magnetometer updates
                       from 10 deg to 20 deg
                    increase time delay before safemode
                       from 300 s to (?) 600 s
  18:10     WHM3  AMCS back on timeline
  23:10     WHM6  HRI back in focus


Sun 1998-07-12 (DoY 193)

  12:33           AMCS safemode (during slew and belt) (S06)
                    ROSAT night ended ad 12:24:30



 ?16:20     WHM2  recovery from AMCS safemode
                     parameters unchanged

                  ? slew to timeline not successful (ATOR)
                      (timeline commanding problem?)
                  NRTA 'earth limb' signal never disappeared
                  HRI was not brought into focus
  22:57:40  WHM6  AMCS safemode (shortly before ROSAT night) (S07)

     Explanation of this safemode:
        Safemode was commanded by the operator due to
        unsafe status of recovery.



     Suspicion: There seems to be an S-gyro problem.


Mon 1998-07-13 (DoY 194)

  14:30     WHM1  recovery from AMCS safemode
                    - WFC STC reset cycle at 240 s
                    - upper threshold for magnetometer updates at 20 deg
                    - time delay before safemode at (?) 480 s
                    - S-gyro no longer in AMCS control loop
                    - [wobble is no longer available anyway]


Tue 1998-07-14 (DoY 195)

  01:03           AMCS safemode (during slew and belt) (S08)



    New strategy: test of AMCS during long (many orbits) pointings


Wed 1998-07-15 (DoY 196)

  14:20 ?   WHM1  recovery from AMCS safemode
                  ? - WFC STC reset cycle at 240 s
                  ? - upper threshold for magnetometer updates at 20 deg
                  ? - time delay before safemode at (?) 480 s
                  ? - S-gyro no longer in AMCS control loop
                  ? slew to timeline not successful (ATOR/Fleming)
                      (timeline commanding problem?)

  18:30:54        again safemode (during slew) (S09)
                     sun presence in CSS2, ie. solar panels not lit by the sun!





Fri 1998-07-17 (DoY 198)

  15:40     WHM2  recovery from AMCS safemode
                    - WFC STC reset cycle at 150 s
                    - lower threshold for magnetometer updates at  3.8 deg
                    - upper threshold for magnetometer updates at 15   deg
                    - time delay before safemode at 600 s
                    - S-gyro no longer in AMCS control loop
                  step 1 successfully performed
  17:20     WHM3  step 2 successfully performed
  19:00     WHM4  HRI back in focus
  19:47           AMCS identifies guide stars for periods up to
                    600 s (continuously)


Sat 1998-07-18 (DoY 199)

  07:00     WHM2  again in safemode (S10)
                    10 min after ROSAT night; during belt




  No more recoveries due to safemode S09 which caused sun presence
  in CSS2 (on the backside of the solar panels!).

  Reason for S09 was clarified on Thu 1998-07-23, therefore recoveries
  could be resumed.


Fri 1998-07-24 (DoY 205)

  Target (close to CVZ):

703991 H  8 2675  1 2 4 US EDELSON    IRAS 13224166  0  0 201.3 -38.4  10.3  13.4

  ??:??     ????  recovery


Sat 1998-07-25 (DoY 206)

  02:56:07        safemode triggered (S11)



  ??:??     ????  recovery


Sun 1998-07-26 (DoY 207)

  01:12:59  ????  again safemode (S12)



  ??:??     ????  recovery; safemode after a few hours (S13)


  No significant improvement during these recoveries; recoveries stopped.


Tue 1998-07-28 (DoY 209)

  11:00           probable communication bug in case of one of the
                  WFC telemetry modes (low speed mode)
                  was discovered (by the WFC team)

  12:30     WHM3  recovery from AMCS safemode started (step 1)
                   - WFC STC reset cycle at 150 s
                   - lower threshold for magnetometer updates at  3.8 deg
                   - upper threshold for magnetometer updates at 15   deg
                   - time delay before safemode at 600 s
                   - S-gyro in AMCS control loop
                   - WFC low speed telemetry mode prohibited
  14:10     WHM4  target commanded; several periods of steady state
  15:50     WHM5  satellite again in safemode (S14)




Wed 1998-07-29 (DoY 210)

     Communication bug could not be verified; original
     location of STC data in low speed mode seems to
     be correct; new strategy:
     force WFC into low speed mode (by command and
       by not switching on WFC HV)
     don't perform step 3 of the recovery (the slew to
       a timeline target); rather stay on the arbitrary
       target the satellite was looking to after
       switching to degraded mode.
     don't recover HRI (the satellite is pointing to an
       arbitrary target anyway).

  12:25     WHM3 ?recovery from AMCS safemode started (step 1)
                    - force WFC into low speed telemetry mode
                    - other parameters unchanged (?)
  14:05     WHM4 ?step 2: command catalogue for target of step 1
                    (R.A.=39.1148 deg, Dec.=-1.6348 deg)
  15:45     WHM5 ?again in safemode? (S15)


Thu 1998-07-30 (DoY 211)

  Suspicion: safemode could have been caused by a WFC-SEU
  -> try next recovery

  12:15     WHM3  recovery from AMCS safemode started (step 1)
                    - force WFC into low speed telemetry mode
                    - SEU fixed
                    - other parameters unchanged (?)
  13:55     WHM4  step 2: command catalogue for target of step 1
  14:10           slew to (arbitrary) target
                    (R.A.=39.1148 deg, Dec.=-1.6348 deg) of the day before
                    (not requested by MPE)
  15:35     WHM5  no further timeline commanded (on request by MPE)
                    satellite again in safemode (S16)

  Further recoveries stopped since there were cases when ROSAT
  pointed to targets only 20 deg off the sun (though during the 
  ROSAT night).

  Ongoing detailed analysis of the 'communication' problems.


Thu 1998-08-06 (DoY 218)

  Obviously the WFC STC data are sometimes mis-interpreted by the AMCS.

  GSOC will now test whether this is the only reason for the frequent
  safemodes during the past few weeks.

  Starting with the next recovery, the WFC STC will be disconnected 
  from the AMCS. In the past no safemodes were encountered in this
  configuration (also true for simulations at GSOC during the past 
  few days).


  06:17:45  WHM1  step 1 of recovery
                    - completely reinitialize WFC 
                    - (arbitrary) pointing direction: 
                         R.A. = 58.763 deg, Dec. = -36.181 deg
  07:56:15  WHM2  step 2 (planned): command catalogue for target of step 1
                    (even if it will not be used since there is no source
                     of stars).

  Actually: sun in CSS2 (i.e. on the backside of the satellite)!
  Chance coincidence (eg singularity in magnetic field model)? (S17)

  Since there is no real danger for the satellite (instruments are saved),
  another recovery is planned for WHM3.


  09:36:15  WHM3  step 1 of recovery -> successful

                  all further steps skipped:
                    - no slew to timeline targets
                    - HRI (and WFC?) remains off


Fri 1998-08-07 (DoY 219)

  ROSAT remained in degraded mode during the last night.

  However, the experts are concerned about the CSS2 event from the day
  before.


  Next steps:

  09:28:15  WHM3  slew to LMC (R.A. = 82.5 deg; Dec = -69.5 deg);
                    focal instruments still in safe position.
  11:07:45  WHM4  slew worked; still on target


  Continue till Monday, and see whether satellite remains in degraded mode.


Mon 1998-08-10 (DoY 222)

  05:44:15  WHM2  still not in safemode

  07:23:45  WHM3  HRI in focus; switch on
                    - perform LMC raster survey by PI CHU
                      -> useful scientific data

  12:23:30  WHM6  no longer enforce WFC telemetry high speed mode
                    (not required as long as WFC STC is not in
                     control loop of AMCS)


Tue 1998-08-11 (DoY 223)

  Diffuse emission from LMC causes excessive
  'measured dark charge out of limits' error messages.

  This target is obviously not suited to perform STC tests;
  therefore slew to a new target :

      - northern target
      - visible during Weilheim
      - visible mainly during ROSAT day
      - sufficiently enough guide stars
      - close (but not too close) to CVZ

  05:36:00  WHM2  still not in safemode

  07:15:45  WHM3  no FI data (!)
                    probably due to an FI sync problem;
                    to be fixed in WHM5

  08:55:45  WHM4  slew to northern target:
                    R.A.=250.0 deg, Dec = +50.0 deg

  10:35:15  WHM5  send FI timeline (esp. BELTMID commands)
                    in order to fix problem detected in WHM 3

  12:15:45  WHM6  ? time correlation
                    FI still out of sync

  16:59     DSN   change STCW search and track mode windows
                    FI in sync again


Wed 1998-08-12 (DoY 224)

  07:07:45  WHM3  still not in safemode

  - Actual pointing checked by GSOC, using magnetometer and sun sensor: ok
  - No longer track data starting at uplink of patch during DSN 
      of previous day.

  10:27:00  WHM5  change STCW search and track mode windows
                    by corrected command (swap of data words LSB and MSB):
                    track mode frames were received immediately afterwards.

  12:08:15  WHM6  change STCW status frame interval to 0 (default: 8)
                    (A_STATUS_FR_INT=0)
                  dump data for the period WHM4 to WHM5

  16:50     DSN   dump STCW memory starting at 9564x
                    (12 bytes = 6 words; MEMBLK command)


Thu 1998-08-13 (DoY 225)

  05:19:45  WHM2  still not in safemode

  STCW data of last night look very clean:
    - nearly continuously in trackmode,
        even at closest approach (5.5 deg) to the Earth horizon 
        (exception: directly after ROSAT night)

  06:59:30  WHM3  include STCW into AMCS control loop:
                    - AMCS source flag points to STCW
                    - disable WFC telemetry low speed mode
                    - enable STCW resets by AMCS

  No problems, but no star identification during WHM 3

  08:39:15  WHM4  slew to WFC Meaty calibration source
                    (R.A.=247.266 deg, Dec = +78.074 deg)
                    - STCW control NOT disabled during slew
                    - WFC resets disabled

  10:18:45  WHM5  dump of data
                    investigate STCW data and AMCS behaviour for
                    reliability during slew and Earth block

  Discrepancy between CSS3 (17 deg off) and actual quaternion (11 deg off);
  not acquired.


  18:25:06        safemode triggered (S18)
                    reason: suncone violation after ROSAT night


Fri 1998-08-14 (DoY 226)

? 03:32:45  WHM1  recovery from safemode, step 1

  08:31:15  WHM4  slew to TZ CrB:
                    - R.A. = 243.67 deg, Dec = +33.86 deg
                    - 10 cts/s during RASS (PSPC)
                    - 19 deg offset from CVZ center at 12:00:00
                    - 89.94 deg sun offset at 12:00:00
                    - sufficiently enough guide stars within STCW FOV
                        (13 brighter than 6.0 mag)
                    - no diffuse emission (?)
                  STCW resets enabled (formerly: every 250s; now: every 60s)

  10:10:45  WHM5  dump data
                  moved HRI into focus; switched on
                  lower threshold for magnetometer updates lowered
                    from 3.8 deg to 2 deg

                  Target was partially acquired during WHM5,
                    and the X-ray source (TZ CrB) was clearly visible on the
                    quick-look screen.

  16:30     DSN   back in safemode (S19)


Sat 1998-08-15 (DoY 227)

  03:24:15  WHM1  uplink star catalogue again, but take into account
                    the reduced STCW FOV (remove guide stars at the
                    rim of the FOV)

  06:43:15  WHM3  pointed to North ecliptic pole
                    (this recovery didn't work correctly)

  08:23:00  WHM4  another try for a recovery - the first one didn't work
                  - HRI moved into focus, and switched on

  10:02:30  WHM5  slew to TZ CrB (like the day before)
                  - use revised star catalogue
                  - HRI NOT in focus (intentionally)


Sun 1998-08-16 (DoY 228)

  06:35:15  WHM3  no safemode


Mon 1998-08-17 (DoY 229)

  06:35:15  WHM3  back in safemode (S20)

     No recovery was performed due to computer problems on ground.


Tue 1998-08-18 (DoY 230)

  02:59:15  WHM2  recovery / step 1

  04:39:00  WHM3  recovery / step 2
                  - NO STCW control during ROSAT nights
                      (should avoid further safemode)
                  - change AMCS feedback constants (more damping)
                      current setting:
                        Sun:   0.25
                        STCW:  0.25   (previously 1.0)
                       [STCX:  0.70 ]

     Consequently, permanent acquisition during the Weilheim contacts
     was observed (!).

  07:58:15  WHM5  move HRI into focus; switch on

     Several transient periods (of the order of 10 seconds)
     were observed as soon as the HRI had benn moved into focus.

  09:38:45  WHM6  slew to TZ CrB (like end of last week)
                  - use revised star catalogue

     Target was continuously acquired until slew started.

     Is the change of the AMCS feedback constant the key for
     stable AMCS operations ?!

  14:22     DSN   WFC Low Speed Telemetry Mode no longer disabled.

     X-ray target was clearly visible on the HRI screen.
     Nearly continuously acquired (one exception).


Wed 1998-08-19 (DoY 231)

     No problems occurred so far.

  01:13:00  WHM1  STCW again in AMCS control loop during ROSAT nights

  02:51:00  WHM2  Acquisition at the end of the contact
                    (after start of ROSAT daylight?)

  04:30:45  WHM3  Continuous acquisition 
                    (contact begins shortly after ROSAT night)

  07:50:00  WHM4  Steady at the beginning, but not at the end of 
                    the contact

     The current target lies within the continuous viewing zone.
     Now the behaviour of the AMCS shall be tested under worse conditions.
     In the last WHM contact of this period a slew to MKN 1073
     will be performed, which gets bright and dark Earth blocks within
     each orbit of the satellite.
!
!  iror  d ao iprp t# p t cc  PI         target    tr ts td   ra     dec    sun
! 703998 H  8 2677  5 3 0 US HECKMAN    MKN 1073   30 14  0  48.756 42.036 -14.9
!
  09:31:00  WHM6  Slew to MKN 1073
                  - sequence of MPL events:
                      visible / bright Earth / dark Earth / night
                  - target visible during Weilheim
                  - bright guide stars (of magnitudes 2, 2, and 4)

  12:45     DSN   MKN 1073 was continuously acquired
  14:15     DSN   MKN 1073 was again continuously acquired


Thu 1998-08-20 (DoY 232)

  04:22:45  WHM3  MKN 1073 was acquired at the end of the contact
                    (after ROSAT night)

     No problems occurred so far, and recent data seem to be ok:

       - return to timeline, thereby testing the AMCS behaviour 
            during slews
       - fine tuning of AMCS parameters.


  06:02:30  WHM4  return to timeline

  07:41:45  WHM5  on target direction (Earth block during contact)

  12:25     DSN   back in safemode (!) (S21)

  13:50     DSN   ?


Fri 1998-08-21 (DoY 233)

     There seems to be a problem with slews and/or ROSAT nights.
     Therefore a few long-duration pointings will be scheduled for
     the weekend, in order to minimize the risk of a safemode
     (reduced observing program).
     In the meantime the data will be investigated for the
     slew problem.

  04:14:30  WHM3  step 1 of recovery
              (WHM1/2 were not available for recovery due to ROSAT night)

  05:54:15  WHM4  step 2 of recovery

  07:33:45  WHM5  - HRI in focus; switched on
                  - slew to ROR 704045 (shortly after WHM5):
                  !--------------------------------------------------------------------------
                  !  iror  d ao iprp t# p t cc  PI         target    tr ts td    ra     dec  
                  ! 704045 H  8 7330  1 2 0 UK MERRIFIELD 4C34.16    90 17  0  60.229  34.719
                  !--------------------------------------------------------------------------

  12:16     DSN   again in safemode :( (S22)


Sat 1998-08-22 (DoY 234)

  04:06:15  WHM3  step 1 of recovery
              (WHM1/2 were not available for recovery due to ROSAT night)

  05:46:00  WHM4  step 2 of recovery
                  - slew to ROR 704045 (shortly after WHM4 ?)

  07:25:30  WHM5  - HRI in focus; switched on

                  - upper limit for CSS3 updates of actual quaternions
                      increased to 18 deg (previously: 10 deg);
                      this could avoid safemodes like on days 218,
                      when the actual quaternions were no longer updated
                      by the CSS3 values (more than 10 deg off the reference)

                  - in order to avoid safemodes:
                      disabled STCW during ROSAT nights

     No acquisition was observed during WHM5, probably due to
     bright Earth horizon: the HRI count rate decreased from
     200 cts/s to 5 cts/s during the contact

  19:10     DSN   Satellite was commanded into safemode as soon as the
                  safemode data of the previous day had been analyzed:
                    CSS2 (on the back of the solar arrays) suddenly
                    showed sun presence in the middle of a ROSAT day.
                  (S23)

Sun 1998-08-23 (DoY 235)

     Safemode continued.

Mon 1998-08-24 (DoY 236)

     Safemode continued.


Tue 1998-08-25 (DoY 237)

     The safemode of DoY 233 can be explained by continuous
     (wrong) updates of the actual quaternion by the magentometer
     (every two minutes). No correction by sun sensor information
     was possible as soon as these updates led to an offset of
     more than 10 deg.
     The threshold for sun sensor updates has now been changed to
     18 deg; therefore safemodes of this kind should no longer occur.

     Today a recovery will be performed; the focal instruments
     will remain in the safe position for security reasons.

  03:42:00  WHM3  step 1 of recovery (to degraded mode)

  05:21:15  WHM4  step 2 of recovery
                  - don't move HRI into focus
                  - upper limit for CSS3 updates of actual quaternions
                      increased to 18 deg (previously: 10 deg);
                      this could avoid safemodes like on days 218 and 233,
                      when the actual quaternions were no longer updated
                      by the CSS3 values (more than 10 deg off the reference)
                  - slew to ROR 202805 (?shortly after WHM4)
                  !--------------------------------------------------------------------------
                  !  iror  d ao iprp t# p t cc  PI         target    tr ts td   ra      dec
                  ! 202805 H  8 9134  1 2 1 WG GUENTHER   V 773 TAU  10  0  0  63.600  28.189
                  !--------------------------------------------------------------------------

  07:01:30  WHM5  target was continuously acquired

     The HRI will be moved into the focus, if the satellite is still 
     not in safemode during the following DSN contact.
     The geometric situation for observing the current target
     should be sufficiently stable if no safemode has occured
     during the past three orbits, and there should be no risk 
     for the FI.

  11:50      WPS  move HRI into focus; switched on

     The satellite was steady during this contact, except for the
     period during and shortly after the HRI was moved into focus
     (caused by the carroussell motor momentum?).
     The X-ray source was clearly detected on the quicklook screen.

  15:20      AGO  

     Steady at the beginning of this contact, but no X-ray data (SAA);
     transient at the end of the contact (Earth block).


Wed 1998-08-26 (DoY 238)

  Safemode of DoY 233:

     The continuous updates from the magnetometer were caused by a 
     large attitude error (wrong by 60 deg around the sun direction),
     starting at the very beginning of the recovery.
     STCW stars and magnetometer information are in good agreement
     all the time; the magnetometer seems to be ok.
     What was then the reason of this large error?

     Lateron, magnetometer updates were allowed at some point 
     due to projection effects during certain parts of the orbit
     (update range: 2 deg to 20 deg).


  01:59:54   WHM3  safemode triggered (S24)
                     (CSS3 lost presence shortly after the end of the
                        ROSAT night)

  05:13:00   WHM5  step 1 of recovery
  06:53:45   WHM6  steps 2 and 3 of recovery
                    - slew to 202805 (shortly after the end of WHM6)
                    - HRI wasn't moved into focus

  11:40      WPS   - HRI moved into focus; switched on
                   - slew from 202805 to 704045 (completed during contact)
                   - never steady during the contact
                   - probably bright Earth block
                       (at least according to the X-ray infromation)

  15:10      AGO   again in safemode (S25)


Thu 1998-08-27 (DoY 239)

     The second safemode of DoY 238 (the day before) is obviously due to 
     an error in the actual attitude: WFC stars are tracked during the 
     nominal Earth block. The safemode was triggered when CSS2 got sun 
     presence during the ROSAT day (similar to the safemode of DoY 233).


  05:05:00   WHM5  step 2 of recovery                                          M
                     - uplink catalogue and actual quaternion of
                       arbitrary target pointed to after the recovery

  06:46:30   WHM6  recovery stopped:                                           H
                     - NO slew to 202805
                     - DON'T move HRI into focus

     A cross check of the attitude information revealed again a large 
     offset between actual and reference quaternion.

  11:38      WPS   again in safemode (as expected ...) (S26)

     A few of the safemodes in the past (characteristics: safemode was
     triggered before the safemode delay counter reached the maximum value
     of 300 or 600 seconds, and there was no sun in CSS2) can be
     avoided by setting the allowed time difference between the presence
     signals of CSS1 and CSS3 to 3 seconds (previously 4 seconds);
     starting at 5 seconds the counter is decremented (LK & EB).

     Safemode S24 (DoY 237; the one after 21 hours of good acquisition)
     would not have been triggered if this value had been set (!).


     In future CSS1 updates should be allowed for angle offsets
     of at least 50 deg (now: 20 deg); the sun sensor characteristics
     is still monoton (although not linear) at these large values (LK & EB).

     This change could avoid safemodes which are caused by exceeding
     the safemode delay threshold (600 s) after ROSAT nights,
     since now the sun sensor would be allowed to update the
     attitude information even in cases when the offsets are quite large
     (eg if there is a large nutation due to wrongly estimated
      velocities during the ROSAT nights).


  17:30      AGO   - new value for the maximum time difference between
                       the presence signals of CSS1 and CSS3 (3 seconds
                       instead of 4 seconds).
                   - new update range for CSS1: 2 to 50 deg
                       (previously: 2 to 20 deg)


Fri 1998-08-28 (DoY 240)
                                                                               
     Try another (careful) recovery.                                           

  03:17:15   WHM4  step 1 of recovery                                          T
                    - Several quaternion updates were observed after
                        commanding the true attitude as reference
                        and actual quaternion
                    - new value for the maximum time difference between
                        the presence signals of CSS1 and CSS3 has been
                        verified.

     The actual attitude was verified by a different method between
     the two contacts (ok).

  04:56:45   WHM5  step 2 of recovery (command catalogue of reference stars)   H
                    - Towards the end of the contact several 'steady' periods
                      were observed.
                    - Slew to 202805 after the end of WHM5
                    - HRI was not yet moved into focus

  11:20      WPS   since satellite was not in safemode, and steady:
                    - moved HRI into focus; switched on

     As usual, satellite was disturbed by moving the detector carroussell,
     and became transient for short periods; at the end of the contact
     the satellite was steady again.

  14:54      AGO   - steady at the beginning, Earth block at the end of this
                       contact (like on DoY 237)
                   - HRI off due to SAA

  22:10:30   WHM1  transient (contact during ROSAT night)                      T
  23:49:15   WHM2  transient (contact during ROSAT night)                      T


Sat 1998-08-29 (DoY 241)

  01:29:15   WHM3  steady at the very end of the contact (3 min night, 4 min day)
  03:09:00   WHM4  partially steady starting at the middle of the contact 
                     (shortly after night)
  04:48:30   WHM5  continuously steady starting at the middle of the contact
                                                                               
     Still no safemode.


    Slew to various targets (during the weekend).
    Return to nominal timeline (at the beginning of next week)

  Targets for the weekend:

!--------------------------------------------------------------------------
!  iror  d ao iprp t# p t cc  PI         target    tr ts td   ra      dec
!
! 202805 H  8 9134  1 2 1 WG GUENTHER   V 773 TAU  10  0  0  63.600  28.189
! 300598 H  8 2644  4 2 0 US COOL       NGC 4372  103  0  0 186.439 -72.659
! 601104 H  8 9082  1 3 0 WG JUNKES     NGC 1800   40  0  0  76.608 -31.955
!--------------------------------------------------------------------------

  The start times for slews were taken from the nominal short term timeline;
  this should exclude any forbidden slews (esp. slews during night).

  11:11:41         safemode triggered (S27)

    Directly after ROSAT night: presence in CSS1 and CSS3
    Shortly afterwards: sun presence is lost in CSS1 and CSS3;
       CSS2 gets presence, whicht triggers the safemode.

    Thus not performed:

[ 13:06:30   ----  slew to 601104                                         ]
[                    - short slew (61 deg)                                ]
[                    - night and Earth block are coincident               ]
[                        (currently no aquisition during night)           ]
[                    - a large fraction of the belts and Earth blocks are ]
[                        coincident                                       ]
[                    - close to 90 deg offset from the Sun                ]


Sun 1998-08-30 (DoY 242)

  04:40:30   WHM5  recovery from safemode

     'WFC Source' flag was not commanded due to limited time.

  05:14:30   ----  slew to 202805
                     - exactly as scheduled in the short term timeline
                     - timecritical observation (coordinated)

? 11         DSN   uplinked 'WFC Source' flag command



  16:28:15   ----  slew to 300598
                     - long slew (126 deg)
                     - worse sun angle


eof