To:sot_shift from: Dan Schwartz date: 25 July 99, 1030 EDT Subject: SOT shift report, Shift A3 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii -------- Shift A3. Start at 206:03:30 GMT = 11:30pm 24 July 99 SOT Lead DAS Spac/Aspect WAP FOT/Sci liason EM HRC MVZ,AR ACIS PPP (Times will be given in GMT on day 206) PLAN Activate vacuum monitor and measure pressure. Activate the EIO and IEPHIN Perform Solar array characterization Perform Earth scan #3 Evaluate orbit from IPS-1 burn EVENTS OBSID changed to 62495 at ~03:53, as planned. Turn vacuum monitor on at ~ 04:12. Readings show ~1.1x 10^-4 torr. We expect (from venting analysis and from TRW thermal vac data) that actual pressures are about 3x10^-6 at this time. Complete at 06:45 Offpoint solar arrays at 06:34. Complete around 0900. Start EIO activation, ~0700. Complete, looks good at 07:35. Pause before IEPHIN activation. EPHIN activation complete, ~0820. Performance shows an excellent low background outside the radiation belts. EPHIN detects the radiation belts (of course!) and in fact saturates. But that is because we are at such a low perigee, 1000 vs 10,000 km for final orbit, and because they used the large instead of small geometric factor. Format 2 at 09:03. ACIS focal plane = -118.9, same as always. ~0950 finish pitch to IRU bias dwell, prior to earth scan #3. LGA swap at 1041. Lose realtime telemetry momentarily. Early LOS from Goldstone at ~1300. They lost track momentarily and went to a predicted ephemeris which may not have been the latest data. Real time telemetry restored at 13:53. 14:30 starting maneuvers for Earth Scan #4 sequence. 1440 start SSR dump, at 1024. NOTES/ISSUES/PROBLEMS We have written a flight note to lower the set point on the ACIS focal plane in order to determine whether we currently are regulating the focal plane or whether we simply are in equilibrium at as cold a temperature as can be achieved. By changing the focal plane temperature from its current set point of -120.6 to -126.3 (TBR) we must see the focal plane temperature decrease by some amount, IF it is currently being regulated. This should be done AFTER opening the big vent valve, as there may still be some considerable gas inside the detector volume. A CARD constraint prohibits HRC HV turn-on while the vacuum monitor is above 10^-5 torr, UNLESS venting analysis and test indicate that the pressure at the detector housing is less than 10^-5 torr. The latter is the real requirement. In fact, both a venting analysis, and the pressure profile in thermal vacuum test at TRW indicate that the requisite vacuum is achieved before 7 days MET. However, the vacuum monitor did not read below 10^-5 torr until about 24 days in the TV test. So we should tie the HRC HV to the same reading of the vacuum monitor as occurred in TV test, and NOT to a reading of 10^-5. Earth Sensor #1. Some anomalies -- status bit set to valid data when clearly data isn't valid. Factory suggests power cycling unit. Orbit following IPS-1 burn is 72073.8km apogee, 1192.6km perigee, and 25hr 7min period. Apogee #3, and IPS burn #2, expected at 207:01:52 GMT. The delay of IPS burn #3 means we must rethink HRC and ACIS operations in the PET day 5 to 13 timeframe. ACIS wants to wait at least until after IPS-3 to start monitoring background (because the apogee is so different) so perhaps HRC-S internal calibration measurements can move somewhat earlier? TBN ------------------------------------------------------- Dan Schwartz, MS #3 das@head-cfa.harvard.edu phone: (617)495-7232 FAX: (617)495-7356 cell phone: (617)512-5627 pager: 800-759-8352 PIN 1636502 or e-mail 1636502@skytel.com -------------------------------------------------------