STEREO Weekly Meeting Minutes for 2012-10-23 (Week 43) ANNOUNCEMENTS ------------- * It is planned to switch to IMU-2 on Behind on Monday, Oct 29. See below for details. * The nominal telemetry rate on Behind will be dropping to 120 kbps starting in week 45. * Significant coverage shortfalls for the Behind spacecraft are expected starting during week 46 and continuing through the end of the year. See below for details. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * All subsystems on both spacecraft are nominal. However, IMU-1 on Behind is aging, and will be switched to IMU-2. See below for details. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 42 (Oct 15-21) * On day 292 (Oct 18), during the DSS-55 support for Ahead, the command bind was lost for three minutes 0534z, 0630z, and again at 0948z. See DR# M106952 for more information. A spare board was installed at station 55 on Friday, Oct 19. There has been one pass since then (Monday, Oct 22) without any repeat of the problem. * On day 293 (Oct 19), during the DSS-55 support for Ahead, the command bind was lost for three minutes at 0544z, 0630z, and again at 0836z. Also during the support, turbo decoder lock was lost briefly at 0752z. This anomaly resulted in the loss of one frame of SSR data. See DRs# M106955 and N108479 for more information. * On day 293 (Oct 19), during the DSS 15 support for Ahead, turbo decoder lock was lost briefly at 1700z. This anomaly resulted in the loss of one frame of SSR data. See DR# N108481 for more information. * On day 294 (Oct 20), during the DSS 63 support for Ahead, turbo decoder lock was lost briefly at 0606z. This anomaly resulted in the loss of eleven frames of SSR data. See DR# N108480 for more information. * On day 289 (Oct 15), SWAVES conducted real-time commanding on Ahead at 1400z to perform a system reboot to activate flight software version 4.12. * On day 291 (Oct 17) during the DSS-63 support for Behind, turbo decoder lock was lost briefly at 1113z and again at 1253z. This anomaly resulted in the loss of nine frames of SSR data. See DR# N108475 for more information. * On day 292 (Oct 18), the SSR science partitions on Behind filled as follows: SWAVES reached 100% full at 0815z for 10.6 hours. The primary cause was the accumulated shortage of track time throughout the week. * On day 294 (Oct 20), the SSR science partitions on Behind filled as follows: SWAVES reached 100% full at 0407z for 14.1 hours. IMPACT reached 95% full at 0941z for 8.5 hours. The primary cause was the accumulated shortage of track time throughout the week. * The average daily SSR playback volume during the week was 5.0 gigabits for Ahead, and 4.3 gigabits for Behind. Week 43 (Oct 22-28) * The second refresh of the IMU EEPROMs will be performed during the week. The EEPROMs for IMU1 on both spacecraft will be refreshed on Wednesday, Oct 24, and those for IMU2 on both spacecraft will be refreshed on Thursday, Oct 25. * IMU-2 on Behind was powered on yesterday (Oct 22) to monitor diagnostics in preparation for possibly switching over to it next week. See below for details. So far the data look good. * Oct 25 is the sixth launch anniversary of STEREO. * A software reset of the IMPACT/PLASTIC IDPU on Behind is scheduled for Saturday, Oct 27, during the station 15 pass. This will change the IDPU to run off of EEPROM to avoid bit-flip errors. This change has already been implemented on Ahead. It will take several hours to bring all the high voltages back up. * Ahead has 70 meter passes on Monday, Oct 22 (D63, D14), Tuesday, Oct 23 (D14), Wednesday, Oct 24 (D14), Friday, Oct 26 (D63), Saturday, Oct 27 (D63), and Sunday, Oct 28 (D63, D43 at 720 kbps). There are 14 passes during the week, and overall coverage is nominal. * Behind has 70 meter passes on Tuesday, Oct 23 (D63), Wednesday, Oct 24 (D63), Thursday, Oct 25 (D63), Friday, Oct 26 (D43), and Sunday, Oct 28 (D63). There are seven passes during the week, and overall coverage is nominal. An ESA New Norcia pass is scheduled for Monday, Oct 22. Week 44 (Oct 29-Nov 4) * The 51st momentum dump on Ahead is scheduled for Tuesday, Oct 30, with ignition at 16:00 UT. * Daylight savings time ends in the U.S. on Sunday, Nov 4. * Ahead has 70 meter passes on Monday, Oct 29 (D14), Tuesday, Oct 30 (D14), Wednesday, Oct 31 (D14), Friday, Nov 2 (D14), Saturday, Nov 3 (D63, D43), and Sunday, Nov 4 (D63). There are 11 passes during the week, and overall coverage is nominal. * Behind has 70 meter passes on Monday, Oct 29 (D14), Tuesday, Oct 30 (D63, D14), Thursday, Nov 1 (D63), Friday, Nov 2 (D43), Saturday, Nov 3 (D14), and Sunday, Nov 4 (D14). There are 9 passes during the week, and overall coverage is nominal. An ESA New Norcia pass is scheduled for Friday, Nov 2. Week 45 (Nov 5-11) * The nominal telemetry rate for Behind with 34 meter stations will drop from 160 kbps to 120 kbps starting Monday, Nov 5. The telemetry rate for high elevation passes will drop from 240 kbps to 160 kbps. The same change will be made for Ahead next spring. * The 46th momentum dump on Behind is scheduled for Tuesday, Nov 6, starting at 21:00 UT. * The times for the Ahead station 55 pass on Tuesday, Nov 6 have been shifted. Because of this, the pass will be carried out at 160 kbps. * Ahead has 13 passes during the week, and overall coverage is nominal. There are 70 meter passes on Monday, Nov 5 (D63), Tuesday, Nov 6 (D14), Wednesday, Nov 7 (D14), Friday, Nov 9 (D63), and Saturday, Nov 10 (D63, D43 at 720 kbps). An ESA New Norcia pass is scheduled for Sunday, Nov 11. * Behind has 8 tracks during the week, and overall coverage is nominal. There are 70 meter passes on Monday, Nov 5 (D63), Tuesday, Nov 6 (D14), Wednesday, Nov 7 (D43 at 720 kbps), Thursday, Nov 8 (D63), Friday, Nov 9 (D63), Saturday, Nov 10 (D14), and Sunday, Nov 11 (D14). The station 34 pass on Friday, Nov 9, will be the first pass to be carried out at 120 kbps, and the only one scheduled during the week. Week 46 (Nov 12-18) * Ahead has 14 passes during the week, and overall coverage is nominal. There are 70 meter passes on Tuesday, Nov 13, and Saturday, Nov 17, both using station D14. * Behind has 9 passes during the week, and overall coverage has a significant shortage of 16.3 hours over the course of the week. This is due to several stations going down for maintenance all at the same time. Station 43 will be down for six months. Station 54 will be down for about a month, and is expected to be back up on day 344 (Dec 9). The ESA New Norcia station will also be going down for maintenance. Coverage will be scant for the entire week, but will be particularly tight on Monday, Nov 12, and Thursday, Nov 15. 70 meter stations are scheduled for Tuesday, Nov 13 (D14), Thursday, Nov 15 (D63), Saturday, Nov 17 (D14), and Sunday, Nov 18 (D63). The station 24 pass on Monday, Nov 12, and the station 34 pass on Friday, Nov 17, will be carried out at 160 kbps. An ESA Cebreros pass is scheduled for Monday, Nov 12. A weekly schedule for week 46 will be out later today (Oct 16) to assist the instrument teams in planning. Coverage shortfalls for Behind are expected to continue through the end of the year. Week 47 (Nov 19-25) * Thursday, Nov 22 is Thanksgiving. Both Thursday and Friday, Nov 22-23, are holidays at APL. * Ahead has 15 passes during the week, and overall coverage is nominal. 70 meter passes are scheduled for Monday, Nov 19, Wednesday, Nov 21, and Thursday, Nov 22, all using station 14. * Behind has 8 passes during the week, and coverage is short 18.2 hours. The biggest gap in coverage (30 hours) starts Wednesday, Nov 21 into the next day. Data return will be affected through to Sun, Nov 25. 70 meter passes are scheduled for Monday, Nov 19, Tuesday, Nov 20, and Saturday, Nov 24, all using station 63. Other * IMPACT plans to reduce their bit rate on Behind as part of their realtime commanding on Saturday, Oct 27. Their initial plan is to reduce the volume of their burst rate data. If that is not sufficient, the next step is to eliminate burst rate data entirely. * SWAVES plans to reduce their telemetry rate on Nov 1 in preparation for the change in downlink rate. * Given the severe telemetry shortages anticipated starting in week 45, all the instrument teams should consider reducing their telemetry rates. * Behind will continue to be in contention for DSN coverage with other missions until February next year. After that, the Ahead spacecraft will be in contention. * The station 45 and 15 X-band masers are currently red. They are expected to be fixed on day 298 at 05:00 and 23:00 respectively. If not, a signal loss of 2 dB is expected, which is within STEREO's margin. * A potential problem has been identified with IMU-1 on STEREO Behind. The two STEREO spacecraft were each launched with two redundant IMUs. IMU-1 on Ahead failed 3 months after launch, and the spacecraft is currently operating using IMU-2. Recently, the laser intensity on one of the axes on Behind has been observed to be tailing off. This has been identified as a lifetime issue on the laser. The laser intensity increases for the first few years, then levels off, and then eventually falls. Laser intensities were all nominal back in January, but one axis has recently started to fall. A projection made on Oct 11 predicts that the laser intensity will drop below a usable level sometime between late November and January. It has been decided to switch to IMU-2 before IMU-1 fails, to preserve what life it has left. IMU-2 has been turned on, and its telemetry is being monitored. A go/nogo decision will be made on Friday, and the switch to IMU-2 is scheduled for Monday, Oct 29, during the station 14 pass. The other laser intensities on the two spacecraft have been observed to level, but are not yet dropping. If both IMUs fail, spacecraft attitude can be maintained using a combination of the star tracker and guide telescope data--this mode was tested back in June 2007. COORDINATED OBSERVATIONS ------------------------ ------------------------------------------------------------------------------- Scheduled activities for Week 43: M Oct 22 (296) T Oct 23 (297) W Oct 24 (298) T Oct 25 (299) F Oct 26 (300) S Oct 27 (301) Behind: IMPACT/PLASTIC software reset S Oct 28 (302) ------------------------------------------------------------------------------- Scheduled activities for Week 44: M Oct 29 (303) Behind: Switch to IMU-2 T Oct 30 (304) Ahead: Momentum dump, 16:00 UT W Oct 31 (305) T Nov 01 (306) F Nov 02 (307) S Nov 03 (308) S Nov 04 (309) End of daylight savings time in U.S. ------------------------------------------------------------------------------- Scheduled activities for Week 45: M Nov 05 (310) Behind: Switch downlink rate to 120 kbps T Nov 06 (311) Behind: Momentum dump, 21:00 UT W Nov 07 (312) T Nov 08 (313) F Nov 09 (314) S Nov 10 (315) S Nov 11 (316) ------------------------------------------------------------------------------- Scheduled activities for Week 46: M Nov 12 (317) T Nov 13 (318) Total solar eclipse, south Pacific W Nov 14 (319) T Nov 15 (320) F Nov 16 (321) S Nov 17 (322) S Nov 18 (323) ------------------------------------------------------------------------------- Scheduled activities for Week 47: M Nov 19 (324) T Nov 20 (325) W Nov 21 (326) T Nov 22 (327) Thanksgiving F Nov 23 (328) S Nov 24 (329) S Nov 25 (330) ------------------------------------------------------------------------------- Upcoming events: 2013: * May 3 Ahead: Switch downlink rate to 120 kbps * Dec 12 Ahead: Mercury transit 2014: * Jan 20 Behind: End use of 480 kbps on 70 m DSN subnet * Apr 21 Behind: Resume use of 480 kbps on 70 m DSN subnet * Apr 29 Behind: Mercury transit * Oct 15 Behind: End use of 480 kbps on 70 m DSN subnet 2015: * Feb DAWN - Ceres arrival * Jan 20 - Mar 28 (TBC) Behind: Spacecraft behind Sun * Mar 17 - Jul 14 (TBC) Ahead: Spacecraft behind Sun * Jul 2 Behind: Resume use of 480 kbps on 70 m DSN subnet * Aug 25 - Oct 19 (TBC) Behind: Spacecraft behind Sun * Sep 25 Behind: End use of 480 kbps on 70 m DSN subnet * Jul DAWN - End of nominal mission 2016: * Apr 3 Behind: Resume use of 480 kbps on 70 m DSN subnet * Jul Juno arrival at Jupiter 2017: * Jul 11 Ahead: Switch downlink rate to 160 kbps * Jul 22 Behind: Switch downlink rate to 160 kbps 2018: * Mar 5 Ahead: Mercury transit