STEREO Weekly Meeting Minutes for 2015-02-10 (Week 07) ANNOUNCEMENTS ------------- * None. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating on the second 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 06 (Feb 2-8) * On day 034 (Feb 3), during the DSS-43 support for Ahead, monitor data was not received by the MOC for the duration of the support due to a failed multicast router at JPL. This anomaly resulted in a delay of 32 minutes for commanding. See DR# N109857 for more information. * On day 035 (Feb 4), during the DSS-63 support for Ahead, turbo decoder lock was lost intermittently between 1539z through 1559z. This anomaly resulted in the loss of 10 frames of real-time data. * The Ahead observatory is operating on the second side lobe of the HGA to prevent overheating of the HGA feed assembly which is currently at 109 degrees C with the HGA angle at 9.2 degrees, with respect to the spacecraft-Sun line. * On day 034 (Feb 3), the SSR playback of spacecraft data was extended to the duration of each 70 meter station support during HGA second side lobe operations. This was done to monitor spacecraft health and safety as the previous playback duration was insufficient. With the change, the MOC is slowly starting to catch up with the SSR playback. * On day 037 (Feb 6), PLASTIC tested the entrance system at 2105z to determine the cause of an increasing power supply current indication. They will be discussing the results of their tests and their plans at a meeting later today (Feb 10). * The average daily science data return for Ahead, while operating on the second side lobe on the HGA, was 15 Mbits during this week. * Detailed status of the activities that occurred on the Behind loss of communication anomaly, which occurred on day 2014-274, are listed below. * The Behind observatory entered superior solar conjunction at the two degree SPE angle on day 022 (Jan 22). Recovery efforts will resume post solar conjunction on day 082 (Mar 23) with increasing the ground transmit power through arraying uplink stations and implementing the Failure Review Board recommendations which are starting to come in. * 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 day 2014-274, 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 and initial G&C simulations, it is highly suspected that the observatory is rotating about the principal axis of inertia 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. Recovery from a negative power state is also being investigated. While the recovery and analysis efforts continue on Behind, as the Ahead observatory will enter superior solar conjunction in March, the primary focus of the engineering team is on developing operational configuration changes to add robustness to the G&C rate sensor usage to ensure the Ahead observatory’s continued safety. * Once communications are restored and the anomaly resolved, the Behind observatory will be returned to nominal science data collection as soon as it is safely possible. Week 07 (Feb 9-15) * The 76th momentum dump on Ahead was successfully carried out this morning (Feb 10), starting at 15:30 UT. It was pointed out that the IMU is turned on as part of the momentum dump, and that this was the first time the IMU has been turned on since the code patch to protect against bad data marked good. The laser was not on long enough for a comparison against the limb monitor. * DSCOVR is scheduled for launch later tonight (Feb 10), at 23:05 UT. The DSCOVR launch delays have already impacted one DSN support for STEREO. If the DSCOVR launch is delayed until tomorrow, then a STEREO support on Mar 1 will be increased by about an hour. * The solar conjunction readiness review is scheduled for Thursday, Feb 12, starting at 8:30 A.M at APL. * The final ephemeris update for Ahead before solar conjunction will be written to EEPROM on Thursday, Feb 12. * Ahead has 7 passes during the week, all at 3 kbps. The previously scheduled 34 meter passes have been given up to the DSCOVR mission. Overall 70 meter coverage is short about 7 hours spread throughout the week. * No passes are scheduled for Behind due to superior solar conjunction. Week 08 (Feb 16-22) * Ahead has 7 passes during the week, six at 3 kbps and one at 633 bps. Overall 70 meter coverage is short 4.5 hours between Tuesday to Sunday. * No passes are scheduled for Behind due to superior solar conjunction. Week 09 (Feb 23-Mar 1) * Ahead has 7 passes during the week, all at 3 kbps. Overall coverage is short 4.25 hours between Monday-Thursday. * No passes are scheduled for Behind due to superior solar conjunction. Week 10 (Mar 2-8) * Daylight saving time begins on the US east coast at 07:00 UT on March 8. * On Wednesday, Mar 4, at 15:00 UT, the restricted IONet at APL will be taken down while the prime router is replaced. * Ahead has 8 passes during the week, seven at 3 kbps, one at 633 kbps. Overall coverage is nominal. * No passes are scheduled for Behind due to superior solar conjunction. Week 11 (Mar 9-15) * On Thursday, Mar 12, during overlapping tracks for 34 meter stations 24 and 25, there will be an uplink array test with Ahead. There will be telemetry downlink, but no commanding during this time. This test is in preparation for Behind recovery efforts. Arraying the stations together is expected to increase the uplink signal strength by 3 dB. * Ahead has 12 passes during the week, six at 3 kbps and six at 633 kbps (five without overlap). Overall 70 meter coverage is short 4 hours between Monday-Wednesday. * No passes are scheduled for Behind due to superior solar conjunction. Week 12 (Mar 16-22) * Preparations for solar conjunction on Ahead will start during the week. The SPE angle will be 2.2 degrees at the beginning of the week, approaching 2 degrees toward the end of the week. * The 77th momentum dump on Ahead is scheduled for Tuesday, Mar 17, with ignition at 23:00 UT. The system momentum target will be 13 N-m-s, selected to minimize the chance of an autonomous momentum dump during the solar conjunction period. * The instrument teams (except SWAVES) are requested to start configuring their instruments between Mar 16-19 for power down. IMPACT, PLASTIC, and SECCHI will be powered off via time-tagged command on Friday, Mar 20, at 16:00 UT. The SPE angle will be 2.1 degrees. At such a small angle, the X-band may be affected. * Scheduled track coverage for Behind has been reallocated to Ahead. * Ahead has 13 passes during the week, and overall coverage is nominal. * There was some discussion about the difference between the SPE angle (Sun-Platform-Earth), which is the angle as seen from the spacecraft, and the SEP angle (Sun-Earth-Platform), which is the angle as seen from Earth. All MOC planning is done in terms of the SPE angle. At the moment, these two angles are almost the same, with the SEP angle being about 0.1 degrees smaller than the SPE angle. Week 13 (Mar 23-29) * Both spacecraft will be at an SPE angle of 2 degrees at the start of the week, with Ahead going into solar conjunction, and Behind coming out of it. * Monday, Mar 23, will be the last nominal 3 kbps pass before solar conjunction. This pass will be used to reset the SSR pointers. * On Tuesday, Mar 24, at 16:00 UT, the spacecraft will be commanded to reset into solar conjunction mode, and no more commands will be sent to the spacecraft. * The passes for the remainder of the week will be monitoring the signal from the spacecraft. Most of these supports will be on one of the low gain antennae, and there will be little signal margin even with the 70 meter stations. * The first hard command loss timer reset should occur on Friday, Mar 27, at 16:20 UT. The HGA antenna will also be bumping up against the soft stop angle, so the signal will be expected to fade after that. * Ahead has 7 passes during the week, and overall coverage is nominal. * The optimal pass schedule for Behind recovery has not yet been determined. * If command uplink is lost before the planned spacecraft reset on Mar 24, the spacecraft will autonomously reset itself into the same configuration when the hard command loss timer triggers after three days. The reason for commanding the reset is to know when the spacecraft will be switching between the high and low gain antennae. The MOC still plans to inform Green Bank Observatory about the anticipated antenna schedule during superior solar conjunction. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 07: M Feb 09 (040) T Feb 10 (041) Ahead: Momentum dump, 15:30 UT W Feb 11 (042) T Feb 12 (043) Solar Conjunction Readiness Review F Feb 13 (044) S Feb 14 (045) S Feb 15 (046) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 08: M Feb 16 (047) T Feb 17 (048) W Feb 18 (049) T Feb 19 (050) F Feb 20 (051) S Feb 21 (052) S Feb 22 (053) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 09: M Feb 23 (054) T Feb 24 (055) W Feb 25 (056) T Feb 26 (057) F Feb 27 (058) S Feb 28 (059) S Mar 01 (060) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 10: M Mar 02 (061) T Mar 03 (062) W Mar 04 (063) T Mar 05 (064) F Mar 06 (065) S Mar 07 (066) S Mar 08 (067) Start of daylight savings time in U.S. Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 11: M Mar 09 (068) T Mar 10 (069) W Mar 11 (070) T Mar 12 (071) Ahead: Uplink array test with stations 24 and 25. F Mar 13 (072) S Mar 14 (073) S Mar 15 (074) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 12: M Mar 16 (075) T Mar 17 (076) Ahead: Momentum dump, 23:00 UT W Mar 18 (077) T Mar 19 (078) F Mar 20 (079) Ahead: Instrument power down (except SWAVES), 16:00 UT S Mar 21 (080) S Mar 22 (081) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 13: M Mar 23 (082) T Mar 24 (083) Ahead: Reset into solar conjunction mode, 16:00 UT W Mar 25 (084) T Mar 26 (085) F Mar 27 (086) S Mar 28 (087) S Mar 29 (088) Notes: * Ahead operating on second side lobe. No commanding after the reset on Mar 24. The signal will continue to be monitored during the week, but the signal margin may be too low to lock on. ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2015: * Jan 22 - Mar 23 Behind: Spacecraft behind Sun * Feb 12 Solar Conjunction Readiness Review * Mar DAWN - Ceres arrival * 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 * Aug 17 Ahead: HGA on 1st side lobe * Nov 10 Ahead: HGA on main lobe, offpoint 1 degree Ahead: SSR playback and reconfiguration, S/C checkout * Nov 12 Ahead: Instrument recommissioning * Nov 20 Behind: HGA on 1st side lobe * Dec 30 Ahead: HGA on main lobe 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 * 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 2019: * Mar Ahead: Switch downlink rate to 240 kbps * Apr Behind: Switch downlink rate to 240 kbps 2020: * May Behind: Switch downlink rate to 360 kbps * Jun Ahead: Switch downlink rate to 360 kbps * Jun Behind: Switch downlink rate to 480 kbps * Sep Ahead: Switch downlink rate to 480 kbps 2021: * Jul Behind: Switch downlink rate to 720 kbps * Aug Ahead: Switch downlink rate to 720 kbps