To: sot_shift Subject: SOT shift report, Shift A8 Date: Fri, 30 Jul 1999 08:57:53 -0400 From: Dan Schwartz ------------- Shift A8. Start at 211:01:30 GMT = 0930 pm 29 July 99 End 9:20am 30 July SOT Lead DAS Spac/Aspect WAP FOT/Sci liason EM HRC MJ,RK,JG,MVZ,SSM,GA,JHC ACIS PPP,RB,FB,MP,MWB (Times will be given in GMT on day 211. In general times are rough, not precise.) PLAN Turn on HRC-I high voltage and check rates. DONE Turn on HRC-S high voltage. DONE (not on full) check antico enable/disable check edge/center blank enable/disble Take ACIS event histograms. DONE Measure vacuum monitor. Perform SSR dump Perform Big Yaw maneuver, assess slosh effects. Make ACIS internal cal source measurements. EVENTS 04:40. Update yaw attitude ~.75 deg. Update bias ~.25 deg/day. HRC-I is turned back on around 01:30. Shows same counting rate as last night, around 160 per sec (no antico). Go up one more HV step and get about 210 per sec. HRC-S High voltage is being ramped up, and shows similar behaviour to HRC-I. At 1500v gets about 110 counts/sec, ~04:20. Next step: ~150 counts/sec TARGET HV = 1750V 05:10. Turn on antico. Rates do not seem to decrease (maybe by ~10 per sec). OBSID 62796. 05:30. OBSID 62973 to test edge/center blank enable/disable. 05:43: Finish HRC procedures. Turn down High Voltage. HRC team plans to stand down further instrument activities until vacuum monitor shows a definitive pressure decrease, or for a few days. 05:45 Start CAP 109, test 1b. This sets SIM flexure heater control at +25 deg C. Control at +25 for ~ 2 hours. Proceed to CAP 109, test 1c. Set the SIM flexure heater control at +30 deg. We find that the internal SIM software only has a thermistor calibration curve which goes up to +25 deg, so the temperature control saturates at that level. Test 1c is terminated. We need to investigate whether the A/D of the thermistor would allow a software patch to extend the calibration curve up above 30 deg C, so that we could test whether we have control margin. 06:02. Go to format 4, SSR subformat. Start SSR-A playback 06:07. Finish 06:44. Go into PCAD subformat. Switch to format 2, ~06:20. Terminate ACIS event histogram acquisition. Start ACIS internal cal source measurment. New OBSID 62775 start 06:35. Internal cal source measurement doesn't start until ~07:50 due to preparation and review of updated scripts for SAP 61049. Use parameter block WT000DC014 Use OBSID 62774 at 10:21 for second run of the internal cal source. Use parameter block WT000E4014. OBSID 62773 expected to be send at 12:50 to complete the current sequence of ACIS internal cal source measurements. Perform Big Yaw maneuver to assess slosh effects, 08:33. Finish maneuver at 09:13. Vacuum monitor on for most of shift. Reading 1.2 10^-5 torr. Turned off at 12:30 NOTES/ISSUES/PROBLEMS The qualitative similarity of the HRC-I and HRC-S behavour argues that the high counting rates are due to external effects, probably high pressure, and not due to a problem in the detector. HRC will be postponing planned activities over the next couple of days (at least). Need to replan to use more time for ACIS. Flight note 138 on the vacuum monitor argues that the lower pressure readings we have been seeing are the valid data. The higher pressure readings are interpreted as outgassing of contaminants in or near the gauge -- this explains that the first times it was turned on it stayed in low pressure only briefly, until it warmed and started outgassing, whereas now when it is cleaner it reads low for a long time, heats up and reads high pressure for a relatively shorter time and then returns to the lower pressure. A flight note is being prepared on the flexure heater test. Bill Podgorski notes that the fid lights move around with several tenths arcsec amplitude, following the limit cycles of the flexure heaters. This suggests that we might want to leave the flexures uncontrolled -- we first need to complete CAP 109 test 1a where we assess the flexure temperatures at 55 and 65 degree pitch angles. There was a good deal of discussion of proposed CAP 106 to update the spacecraft inertia tensor. The relatively small changed was challenged as being worth the "risk" of doing a K-constant patch to the flight software. Eventually was approved to do at start of next shift. ------------------------------------------------------- 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 -------------------------------------------------------