Shift M49 Start at 251:18:00 GMT = 14:00, 08 Sept 1999 EDT End at 252:02:00 GMT = 22:00 08 Sept 1999 EDT See http://asc.harvard.edu/acis/SOT_reports/sot-shift.html, or /proj/ascwww/AXAF/extra/science/htdocs/acis/SOT_reports/Sep_08_1999_M49.txt. (Times will be given in GMT: hhmm or ddd:hhmm, In general times are rough, not precise.) STAFFING -------- SOT Lead Robert Cameron FOT-SI ACIS Yousaf Butt HRC PLAN ---- Run p12 load (NOTE: The best laid plans aft gang agley, more than somewhat). EVENTS ------ Nominal DSN contact: 251:2220 to 252:0200, DSN-54 (Madrid). Chandra transmitter turn-on command sent at 2205. Why not have the transmitter always powered? TRW would need a Technical Directive from MSFC to study this. 2210: OBSID: 62390. 7 stars being tracked. No fids. Format 2. No fid light current. FLCA is on. ACA image slot 3 is in re-acquire. SIM TT at step 92903 (ACIS-I). Daily load is stopped. Holding on bright stars. 2240: OFLS doing a pattern match to find our location. 2318: SSR playback complete. 2320 - 2328: loss of comm. JPL comm problem, not with Madrid. 2348: recycle command server. 2355: Execute CAP 385 for ACIS. First Bias after P12 stop. 252:0005: Obsid = 62415. 0029: Run CAP 387: HRC Anti-co HV turn-off. HRC confirms HV off. 0037: Step 7 of CAP 385. ACIS stop science. ACIS has decided to skip their second bias frame. 0041: CAP 388. Dither turn-off. 0043: Step 8 of CAP 386. ACIS Stop science and power down video boards. 0056: Run Step 1 of CAP 70. This disables the RADMON process, to simulate a step in the daily load for HRC, and to allow simple recovery of HRC science after the radiation zone exit. 0119: Run CAP 389, to recover the accurate PCAD estimated quaternion. Disable SCS 31 (attitude/rate error safe mode trigger). 0129: Need to run SCS 38, to "idle" the ACA, before sending ACA search commands. AONMMODE sent. Activate SCS 38. AONPMODE sent. 4 of 5 stars acquired. Good one-shot attitude update of about 2 arcsec. It's not clear why the guide-only star in slot 2 was not found. 0200: DSN LOS NOTES/ISSUES/PROBLEMS --------------------- Initial diagnosis: the first maneuver in P12 failed the acquisition stars and fell back to bright stars and stopped the daily load. The first maneuver was 63 degrees, mostly yaw. The starting quaternion (from the end of P11) was screwed up because the fid light/guide star mix up. ACIS SOH: running some video boards. But ACIS seems to be ok. HRC SOH: half voltage on. Radiation starts at 252:0237. Madrid comm goes through to 0200. Reasonably solid. Instrument safing: ACIS: collect 2 bias frames, stop science and turn off video boards. CAP is being prepared. Obsids 62415 and 62414 allocated to ACIS for bias frames and video shutdown. HRC: turn off anti-co voltage. MCP HV at half voltage, which is ok for radiation. CAP will be prepared for this. Recovery from bright star hold scenario: OFLS has located us on the sky through pattern matching. We are about 170 arcsec from the correct location. PCAD will go to NMM, upload new estimated quaternion and target quaternion, and command a maneuver to the correct target. Earth and moon occultation are not a problem with the incorrect attitude. The attitude recovery will be done in the present contact. Mission planning to consider how to pick up timeline. Options: 1. start P12 from top (since HRC focus measurements didn't start). 2. Keep p13 fixed in time (because of coordinated HST observation with HRC-I) and chop p12. 0048: CXC mission planning recommends keeping the start of P12, containing HRC-S/LETG focus on Capella, and truncating the end of P12, and keeping P13 as is. There will be a meet-me telecon for review of the P12 load rebuild. The call in number is 888 592 9602 Pass code: 14785 The time is midnight, 0000 EDT, on 9 Sept. More concerns: at the current attitude we are supposed to hold until 252:12:40, we will violate the bright Earth constraint on the ACA. The Earth limb will be at 20 degrees from the ACA line of sight at the start of comm at 1025 GMT, and will decrease to 5 degrees at 1240 GMT. If the bright earth spoils stars in the ACA, we will fall through bright star hold, and go to normal sun mode (and stop the already stopped P12, but cause another P12 replan). Plan: command NMM immediately after the AOS. Stay in gyro hold for 2+ hours. Upload P12d, and wait until first maneuver in P12d at 1240 GMT. PCAD expectation is that 2+ hours of gyro hold will not cause excessive attitude drift, nor bias estimate uncertainty increase, to the extent that the first P12d maneuver will fail. The first P12d maneuver is about 60 degrees, in yaw. NOTE: We cannot maneuver early to the first attitude in P12d, because compounding the problem is a SIM translation, from ACIS to HRC, which is supposed to happen at the end of the first maneuver, but which would happen in NPM if we maneuvered early, and possibly cause attitude/rate error constraint violations in NPM. Similar concerns apply to the LETG motion which is also at the start of P12d. Review of fid/star and star/star separations in P12d shows no problems. This is checked with the PERL script /proj/rad1/ska/perl/mg_check.pl, on the MP Guide Star product file mg252:1203.sum. HRC-S fid light positions have been updated in the ODE, and are used in the P12d build. Ref: CAP 391. New ACIS-S focus position = -468 steps, has been updated in the ODE and is in use. Ref: CAP 392.