STEREO Weekly Meeting Minutes for 2014-10-28 (Week 44) ANNOUNCEMENTS ------------- * First side lobe operations on Ahead have been extended through Dec 7. * To allow instrument teams to track the recording until the data is played back in Dec 2015, once the HGA is back on the main lobe, the SSR full prediction data product plot, on the MOC SDS and GSFC SSC website, has been modified to display the percent full indication of the IMPACT, PLASTIC, and SWAVES SSR partitions during side lobe operations after each track. * The MOC is starting to plan to use 34 meters to bring down spacecraft housekeeping and instrument space weather data at 633 bps. See below for details. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating on the first side lobe of the HGA to prevent overheating of the feed assembly. * There are currently no communications with the Behind spacecraft. See below for details. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 43 (Oct 20-26) * On day 296 (Oct 23), during the DSS-43 support for Ahead, turbo decoder lock was lost intermittently between 2005z and 2013z. The anomaly resulted in the loss of 315 frames of data. During this time, DSN reported fluctuating receiver, SNR and SNT readings. Coincidentally, transmitter drive on occurred at 2005z. See DR #C110651 for more information. * On day 297 (Oct 24), no real-time science telemetry was downlinked from Ahead as the scheduled 70 meter support with DSS-14 was changed to a 34 meter support with DSS-55 in support of the STEREO Behind communication recovery. * On day 298 (Oct 25), no real-time science telemetry was downlinked from Ahead as the scheduled 70 meter support with DSS-14 was changed to a 34 meter support with DSS-55 in support of the STEREO Behind communication recovery. * On day 299 (Oct 26), no real-time science telemetry was downlinked from Ahead as the scheduled 70 meter support with DSS-14 was changed to a 34 meter support with DSS-55 in support of the STEREO Behind communication recovery. * On day 293 (Oct 20), DHS release 1.1.9 was loaded to C&DH RAM and EEPROM on Ahead. This release contained a RTDFD table correction to ensure that the real-time SWAVES science telemetry continues to be downlinked after a momentum dump during side lobe operations. * On day 294 (Oct 21), MOps macro release 1.1.25 was loaded to C&DH RAM on Ahead. This release updated the SSR playback ratio from 2 to 3 for spacecraft playbacks during side lobe operations. * On day 295 (Oct 22), Fault Protection release 2.3.16 was loaded to C&DH RAM and EEPROM on Ahead. This release contained an enhancement rule to conserve IMU lifetime by powering off the IMU after 2 hours if the star tracker is on-line and a change to protect against simultaneous star tracker and IMU anomalies. * The average daily science data return for Ahead, while operating on the first side lobe on the HGA, was 31 Mbits during this week. * On day 297 (Oct 24), NASA Science Mission Directorate was briefed by GSFC and JHU/APL on the Behind loss of communications anomaly. A Failure Review Board will be convened by GSFC to understand the failure and ensure that the Ahead observatory is protected against a similar anomaly. * Detailed status of the activities that occurred this week on the Behind loss of communication anomaly, which occurred on day 274, are listed below. The project has requested 3 hour 70 meter DSN supports every 21 hours through day 313 to re-establish communications. This ensures that communications on an LGA will be attempted daily. * On days 293 through 299 (Oct 20-26), during the DSN 70 meter support for Behind each day, contingency commanding continued with ensuring that IMU-A is disabled as it has failed. No signal was received by the DSN radio science receivers. * Significant findings to date: 1. Analysis of the three DSN extracted telemetry frames from the carrier signal just before the planned observatory reset/anomaly occurred on October 1st, showed nominal performance of the spacecraft, i.e., no anomalies, IMU off, and the star tracker providing an attitude solution. 2. Post reset, from the very limited telemetry, three packets, extracted from the carrier signal by the DSN, the X-axis gyro on IMU-A had failed. Unfortunately, this telemetry contained only G&C anomaly data and no spacecraft summary data, i.e., the state of the RF, G&C, fault protection and other subsystems is not known at the time of the anomaly. With a failed IMU and the star tracker being off-line for an undetermined duration, the sun sensors will keep the observatory pointed at the Sun, though the G&C will not have any roll knowledge, and cannot roll the observatory as part of the safing configuration to re-establish communications on the LGAs. From analysis of this telemetry, it is highly suspected that the observatory is rotating due to an autonomous momentum dump initiated by bad gyro data flagged good, but this has not yet been confirmed. 3. At least two anomalies occurred post reset, the star tracker not promoting to AAD mode and the X-axis gyro failure. Unfortunately, due to the number of possible combinations, the STEREO fault protection system is not designed for simultaneous failures. * The cause and effect analysis of the loss of communications from the LGAs is continuing. G&C simulations using the bad gyro data flagged good are continuing to better understand the potential impact to the observatory state. Twelve samples of these data were extracted from the post-reset telemetry. Recovery from a negative power state is also being investigated. * Once communications are restored and the anomaly resolved, the operational plan for exiting the solar conjunction testing will continue to return the BEHIND observatory back to nominal science data collection as soon as safely possible. * The MOC is using the G&C simulations to try to work out what state the observatory could end up in. This will take time. One possibility is that the spacecraft could have initiated an autonomous momentum dump. If the spacecraft ended up rotating about the principle axis of inertia, the solar arrays could be pointed away from the Sun. * The MOC is starting to shift their effort to ensuring the health of the Ahead spacecraft, not only looking at preventing the same thing happening on Ahead, but also what other steps can be taken to make the spacecraft more robust. * A question was raised about station 14 apparently getting intermittent carrier lock on Sunday. This was determined to not be the signal from the STEREO spacecraft, and occured on the wrong wavelength. * The HGA feed horn temperature on Ahead is currently 112 C at an antenna angle of 8.4 degrees. The temperature has been tracking right where the models say it should be. It's therefore been decided to extend first side lobe operations on Ahead through Dec 7. * The SSR prediction plots have been modified to allow the in situ teams to monitor the data being recorded during side-lobe operations. See the announcement above for details. * The MOC is planning to start using 34 meter stations to bring down spacecraft housekeeping and instrument space weather data at 633 bps. The track coverage isn't there yet. The DFD tables are being developed. The IMPACT, PLASTIC, and SWAVES instruments will have their normal beacon telemetry rates. The SECCHI rate will be throttled back to give room for the spacecraft housekeeping packets. The MOC is currently planning on asking for 8 hours per day of DSN time on the 34 meter stations. The consensus was that more time, if possible, would be even better for space weather forecasting. This 34 meter time is intended to be in addition to the 70 meter time that we're already getting, not as a replacement. Week 44 (Oct 27-Nov 2) * Daily savings time in the U.S. ends on Sunday, Nov 2. * Ahead has 6 passes during the week on the first side lobe, in IMPACT-prime mode. Four of the passes are at 10 kbps, and two are using 34 meter stations at 633 bps, on Wednesday and Friday. * Behind has 9 passes scheduled during the week, all using 70 meter stations, approximately 21-24 hours apart. Week 45 (Nov 3-9) * The 73rd momentum dump on Ahead will be carried out on Nov 5, starting at 21:00 UT. * Ahead has 7 passes during the week, all at 10 kbps on the first side lobe, in SWAVES-prime mode. * Behind has two 70 meter passes during the week, on Tuesday and Friday. After this week, Behind will be on the original DSN schedule. Some of these passes may be reassigned to Ahead, with the proviso that recovery operations continue on Behind. Week 46 (Nov 10-16) * Ahead has 7 passes during the week, all at 10 kbps on the first side lobe, in IMPACT-prime mode. * Behind has 7 passes during the week, all on 70 meter stations, roughly one day apart. Week 47 (Nov 17-23) * Behind will reach the HGA soft stop on Nov 19. * Ahead has 7 passes during the week, all at 10 kbps on the first side lobe, in SWAVES-prime mode. * Behind has 7 passes during the week, all on 70 meter stations. A 1.7 hour return-to-service track for station 63 is scheduled for day 327 (Nov 23). Week 48 (Nov 24-30) * Ahead has 8 passes during the week, all at 10 kbps on the first side lobe, in IMPACT-prime mode. Coverage is short by two hours Monday-Wednesday. * Behind has 6 passes during the week. If the Behind spacecraft is recovered by then, overall coverage will be short by 4.4 hours. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 44: M Oct 27 (300) T Oct 28 (301) W Oct 29 (302) T Oct 30 (303) F Oct 31 (304) S Nov 01 (305) S Nov 02 (306) End of daily savings time in U.S. Notes: * Emergency DSN contacts for Behind requested through Nov 9. * Ahead operating on first side lobe, in IMPACT-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 45: M Nov 03 (307) T Nov 04 (308) W Nov 05 (309) Ahead: Momentum dump, 21:00 UT T Nov 06 (310) F Nov 07 (311) S Nov 08 (312) S Nov 09 (313) Notes: * Emergency DSN contacts for Behind requested through Nov 9. * Ahead operating on first side lobe, in SWAVES-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 46: M Nov 10 (314) T Nov 11 (315) W Nov 12 (316) T Nov 13 (317) F Nov 14 (318) S Nov 15 (319) S Nov 16 (320) Notes: * Ahead operating on first side lobe, in IMPACT-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 47: M Nov 17 (321) T Nov 18 (322) W Nov 19 (323) Behind: HGA antenna reaches soft stop T Nov 20 (324) F Nov 21 (325) S Nov 22 (326) S Nov 23 (327) Behind: Return-to-service track with D63. Notes: * Ahead operating on first side lobe, in SWAVES-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 48: M Nov 24 (328) T Nov 25 (329) W Nov 26 (330) T Nov 27 (331) F Nov 28 (332) S Nov 29 (333) S Nov 30 (334) Notes: * Ahead operating on first side lobe, in IMPACT-prime mode. ------------------------------------------------------------------------------- Upcoming events: 2014: * Nov 19 Behind: HGA hits soft stop * Nov 28 Behind: SSR reconfiguration * Dec 1 Behind: HGA on 1st side lobe * Dec 8 Ahead: HGA on 2nd side lobe * Dec 8 Behind: Test with 34 meter at 633 bps, both side lobes 2015: * Jan 6 Behind: HGA on 2nd side lobe * Jan 12 Behind: Test with 34 meter at 633 bps * Jan 20 Behind: Instrument power down * Jan 22 - Mar 23 Behind: Spacecraft behind Sun * Mar DAWN - Ceres arrival * Mar 22 Ahead: Instrument power down * Mar 23 - Apr 06 Behind: S/C SSR Playback at 3 kbps * Mar 24 - Jul 07 Ahead: Spacecraft behind Sun * Mar 30 Behind: Instrument power on * Apr 25 Behind: HGA on 1st side lobe * Jul DAWN - End of nominal mission * Jul 8 Behind: HGA on 2nd side lobe * Jul 7-28 Ahead: S/C SSR Playback at 3 kbps * Jul 14 Ahead: Instrument power on * Sep 24 Ahead: HGA on 1st side lobe * Nov 20 Behind: HGA on 1st side lobe * Dec 29 Ahead: HGA on main lobe, offpoint 1 degree Ahead: SSR playback and reconfiguration, S/C checkout * Dec 31 Ahead: Instrument recommissioning 2016: * Jan 2 Behind: HGA on main lobe Behind: SSR playback and reconfiguration, S/C checkout * Jan 5 Behind: Instrument recommissioning * Jan 27 Both: HGA calibration * Feb 19 Ahead: HGA on main lobe * Mar 16 Both: Post Solar Conjunction Assessment Review * Jul 5 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