UVCS MISSION LOG ---------------- Date: 21 April 2004 ----- Last revision: 23 April 2004 (Wu) -------------- File Name: 2004.04.21.a.log ----------- Compiled by: R. Wu ------------ UVCS Activity: UVCS in Safe Mode Due to SOHO ESR -------------- SOHO Activity: -------------- EOF Staff: M. Uzzo: Lead Scientist ---------- Y.-K. Ko: Commander M. Uzzo: Planner R. Wu Command file: No Commanding Activity: --------- 1) UVCS in Safe Mode Due to SOHO ESR Sequence: SCI_SPEC: SOHO appears to be in Low Rate upon coming up on DSS-54 pass at ~12:15 UT, 21 April 2004 indicating an ESR has taken place. UVCS Aperture Door is closed, and Detector Power is turned off. As of 13:00 UT, it is not known when the ESR occured. SAFETM on UVCS CmdHistory Page reads 04/21/04|05:38:06. SOHO back in Medium Rate at 12:45 UT UVCS TSU Substitution Heater (Circuit #84) turned on at approximately 13:25 UT using 60% default setting. NB: ESR occurred at 05:37 UT, 21 April 2004 From email received from SOC Wed, 21 Apr 2004 13:33:37 (UT): SOHO went into Emergency Sun Reacquisition mode at 05:37 UT this morning. The ESR was triggered by the FSPAAD (Fine Sun Pointing Attitude Anomaly Detector), most likely a spurious signal caused by a radiation hit to an LM139 comparator (the cause of several earlier ESRs, including the last one). We are in Medium Rate on the LGA using a 34m station, and recovery is proceeding. From email received from SOC Thu, 22 Apr 2004 00:24:57 (UT): SOHO entered RMW (Roll Maneuver Wheels) mode by 22:00 UT tonight. It is close to the normal roll attitude, but the Roll Steering Law (RSL) is not in effect. OBS_PROG: SCI_OBJ: OBJ: CMP_NAME: CMP_NUM: Duration: start: 2004.04.21.05:38 end: 2004.04.22.07:27 ONUMs = 21147 Instrument configuration: - Pointing: Sun center - Spacecraft Roll: 0 Degrees - Roll: 262 Degrees (922) - Mirror/Occulter: 5.0 Ro 1.5 mm overocculting - LYA Slit: 50 um - OVI Slit: 150 um - LYA GRTPOS: 128000 - OVI GRTPOS: 188310 - LYA HIGH VOLTAGE POWERED OFF - OVI HIGH VOLTAGE POWERED OFF - VLD HIGH VOLTAGE POWERED OFF - LYA DETECTOR POWERED OFF - OVI DETECTOR POWERED OFF - VLD DETECTOR POWERED OFF - OVI mask: OVI_str_188_225 in slot 5 Fits Files: GAP between 04/21/04|12:55:47( 7275) and 04/21/04|12:58:17( 7514) GAP between 04/21/04|15:48:11( 7456) and 04/21/04|15:50:40( 7697) GAP between 04/21/04|21:18:42( 6442) and 04/21/04|21:21:10( 6678) GAP between 04/22/04|02:55:14( 6013) and 04/22/04|02:58:21( 6306) 2) UVCS in Safe Mode Due to SOHO ESR Sequence: SCI_SPEC: While UVCS was still in Safe Mode from previous ESR, a second ESR occured at approximately 07:27 UT, 22 April 2004 due, apparently, to another spurious FSPAAD anomaly. UVCS Aperture Door is closed, and Detector Power is turned off. UVCS TSU Substitution Heater (Circuit #84) still on. A partial timeline (email from Michael Uzzo received on Thu, 22 Apr 2004 12:05:53 UT): 07:27 UT The ESR occurred. 08:30 UT D66 came up but being a 26m antenna it could not lock onto low rate signal. Uplink only. 09:13 UT D63 a 70m antenna brought out of maintenance for the downlink. 10:32 UT Spacecraft emergency was declared. NB: SOHO back in Medium Rate at ??:?? UT SOHO in CRP Mode at 15:24 UT. SOHO back in ESR at approximately 16:12 UT OBS_PROG: SCI_OBJ: OBJ: CMP_NAME: CMP_NUM: Duration: start: 2004.04.22.07:27 end: 2004.04.22.16:12 ONUMs = 21147 Instrument configuration: - Pointing: Sun center - Spacecraft Roll: 0 Degrees - Roll: 262 Degrees (922) - Mirror/Occulter: 5.0 Ro 1.5 mm overocculting - LYA Slit: 50 um - OVI Slit: 150 um - LYA GRTPOS: 128000 - OVI GRTPOS: 188310 - LYA HIGH VOLTAGE POWERED OFF - OVI HIGH VOLTAGE POWERED OFF - VLD HIGH VOLTAGE POWERED OFF - LYA DETECTOR POWERED OFF - OVI DETECTOR POWERED OFF - VLD DETECTOR POWERED OFF - OVI mask: OVI_str_188_225 in slot 5 Fits Files: GAP between 04/22/04|13:45:57( 1904) and 04/22/04|13:51:23( 2424) GAP between 04/22/04|14:25:36( 5713) and 04/22/04|14:28:53( 6027)