STEREO Weekly Meeting Minutes for 2014-12-16 (Week 51) ANNOUNCEMENTS ------------- * There will be no STEREO operations telecon on Dec 30. 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 50 (Dec 8-14) * On day 348 (Dec 14), during the DSS-43 support for Ahead, turbo decoder lock was lost intermittently beginning at 1948z. This anomaly resulted in the loss of five frames of SSR data. * The Ahead observatory is operating on the first side lobe of the HGA to prevent overheating of the HGA feed assembly which is currently at 117 degrees C with the HGA angle at 7.4 degrees, with respect to the spacecraft-Sun line. * On day 343 (Dec 9), the 74th momentum dump on Ahead was executed successfully at 2030z, which imparted a delta V of 0.086 m/sec. * On day 348 (Dec 14), IMU-B was powered on at 1915z and temporary fault protection changes were loaded to C&DH RAM in preparation for changing the star tracker thermal electric cooler temperature set point in EEPROM. * On day 349 (Dec 15), during the DSS-43 support, the star tracker was taken off-line for four minutes at 0119z to change the thermal electric cooler temperature set point to -10 degrees C in the star tracker EEPROM. This change may result in quicker initial star field identification, thereby minimizing the “lazy” star tracker performance which contributed to the current STEREO BEHIND loss of communications anomaly. IMU-B was powered off at 0213z and the temporary changes to the fault protection rules were removed. Real-time science data, which was suspended from the telemetry downlink to allow for monitoring this change, was restored at 0342z. * The average daily science data return for Ahead, while operating on the first side lobe on the HGA, was 56 Mbits during this week. * Detailed status of the activities that occurred on the Behind loss of communication anomaly, which occurred on day 274 (Oct 1), are listed below. To ensure communications on the LGA during long term recovery efforts, the Behind track coverage have been reduced to 3 hour 70 meter supports for 3 days in a row each week. * On days 342 through 344 (Dec 8-10), during the DSN 70 meter supports, recovery commanding was conducted to ensure that the transmitter is in its operational configuration. 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 day 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 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. Week 51 (Dec 15-21) * A return-to-service track for station 14 was successfully carried out yesterday (Dec 15). Station 14 will be back online this Friday, which will relieve some of the scheduling pressure on the 70 meter stations. * PLASTIC will power down their entrance system tomorrow (Dec 17). The commands were uploaded this morning, and the command store buffer was dumped to confirm that the commands are onboard. * Ahead has 7 passes during the week, all at 10 kbps on the first side lobe in SWAVES-prime mode. * Behind has 3 passes during the week to attempt recovery, between Wednesday-Friday. * There was some discussion about commencing aberration corrections for the Behind passes. Normally, the DSN stations are configured to maximize the downlink signal. The DSN will start maximizing the uplink signal instead for the Behind recovery passes. This will increase the uplink gain by 4-5 dB, while the downlink gain will be decreased. Week 52 (Dec 22-28) * Thursday, Dec 25, is Christmas. APL will be closed Dec 25-26 for the holiday. * The station 14 pass on Saturday, Dec 27, has been changed to a Project Interface Test pass to test out a new version of the downlink software. There will be no instrument commanding or SSR playback during this pass. However, realtime telemetry will be available. A longer 4.2 hour support is scheduled for later in the day. * Ahead has 9 passes during the week, all at 10 kbps on the first side lobe in IMPACT-prime mode. * Behind has 3 passes during the week to attempt recovery, between Monday-Wednesday. Week 01 (Dec 29-Jan 4) * APL will be closed Jan 1-2 for the New Year holiday. * The HGA angle bias for the Ahead spacecraft will be updated on Jan 4 in preparation for second-side lobe operations in the following week. Instruments should configure their instruments for the 3 kbps downlink rate in advance of the switch on Jan 5. The change in angle bias will result in the last few minutes of the track being lost. POC queues will be disabled 20 minutes before the end of the track. * A question was asked when the instruments should change their rates. The MOC requests that the change occur before the 19:55 UT start of the pass on Jan 5. There are two passes on Jan 4 which can be used for instrument commanding. SECCHI stated that they would handle the rate change the same way they do the 34 meter passes. * SECCHI stated that they wished to try to downlink their telemetry during the SSR playback periods on the second side lobe. They suggest trying this on one of the tracks about a week after the start of second side lobe operations, to see if it has any adverse affect on any of the other instruments or spacecraft. It was pointed out that there's also an uplink sweep about 40 minutes into the track that will result in a 1-2 minutes drop in telemetry. * Ahead has 8 passes during the week, all at 10 kbps on the first side lobe in SWAVES-prime mode. * Behind has 3 passes during the week to attempt recovery, between Tuesday-Thursday. Week 02 (Jan 5-11) * Second side lobe operations at 3 kbps on Ahead start Monday, Jan 5. The uplink rate will also drop to 125 bps. * The 75th momentum dump on Ahead is scheduled for Tuesday, Jan 6, with ignition at 13:00 UT. This is earlier than normal because of the lower target used for the previous momentum dump. * On Wednesday, Jan 7 the restricted IONet at APL will be down for maintenance for three hours starting at 15:30 UT. This should not effect operations, as there are no passes during this time. * Ahead has 10 passes during the week, six at 3 kbps on the second side lobe, and four at 633 bps. * Behind has 3 passes during the week to attempt recovery, between Friday-Sunday. Week 03 (Jan 12-18) * Ahead has 9 passes during the week, all at 3 kbps on the second side lobe. * Behind has 3 passes during the week to attempt recovery, between Monday-Wednesday. Week 04 (Jan 19-25) * If the Behind spacecraft has been recovered by this time, preparations for superior solar conjunction would begin on Jan 19, starting with the instruments powering down. The SSR would be played back on Jan 20, and on Jan 22, the spacecraft would be reset to rotate at 5 degrees per minute. * Regardless of the state of the spacecraft, DSN coverage for Behind ends on Jan 26. * Ahead has 10 passes during the week, nine at 3 kbps, and one at 633 bps. * Behind has 3 passes during the week to attempt recovery, on Thursday, Friday, and Sunday. Week 05 (Jan 26-Feb 01) * A dry run for the Solar Conjunction Readiness Review will be held on Jan 29. The review itself is scheduled for Feb 12. * Ahead has 8 passes during the week, seven at 3 kbps, and one at 633 bps. Overall coverage is short about 6.2 hours, with no passes currently scheduled on Monday or Thursday, where the gaps in coverage are about 36 hours. The MOC is looking into scheduling ESA stations to fill in the gaps. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 51: M Dec 15 (349) Ahead: Star tracker temperature set-point reset Ahead: Return-to-service track for D14 T Dec 16 (350) W Dec 17 (351) T Dec 18 (352) F Dec 19 (353) S Dec 20 (354) S Dec 21 (355) Notes: * Ahead operating on first side lobe, in SWAVES-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 52: M Dec 22 (356) T Dec 23 (357) W Dec 24 (358) T Dec 25 (359) Christmas F Dec 26 (360) S Dec 27 (361) Ahead: PIT test with station station 14. S Dec 28 (362) Notes: * Ahead operating on first side lobe, in IMPACT-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 01: M Dec 29 (363) T Dec 30 (364) W Dec 31 (365) T Jan 01 (001) New Year F Jan 02 (002) S Jan 03 (003) S Jan 04 (004) Ahead: Update HGA angle bias for second side lobe operations. Notes: * Ahead operating on first side lobe, in SWAVES-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 02: M Jan 05 (005) Ahead: Start of second side operations. T Jan 06 (006) Ahead: Momentum dump, 13:00 UT W Jan 07 (007) T Jan 08 (008) F Jan 09 (009) S Jan 10 (010) S Jan 11 (011) Notes: * Ahead operating on second side lobe. ------------------------------------------------------------------------------- Scheduled activities for Week 03: M Jan 12 (012) T Jan 13 (013) W Jan 14 (014) T Jan 15 (015) F Jan 16 (016) S Jan 17 (017) S Jan 18 (018) Notes: * Ahead operating on second side lobe. ------------------------------------------------------------------------------- Scheduled activities for Week 04: M Jan 19 (019) T Jan 20 (020) W Jan 21 (021) T Jan 22 (022) F Jan 23 (023) S Jan 24 (024) S Jan 25 (025) Notes: * Ahead operating on second side lobe. ------------------------------------------------------------------------------- Scheduled activities for Week 05: M Jan 26 (026) T Jan 27 (027) W Jan 28 (028) T Jan 29 (029) Solar Conjunction Readiness Review dry run. F Jan 30 (030) S Jan 31 (031) S Feb 01 (032) Notes: * Ahead operating on second side lobe. ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2015: * Jan 6 Behind: HGA on 2nd side lobe * Jan 12 Behind: Test with 34 meter at 633 bps * Jan 19 Behind: Instrument power down * Jan 20 Behind: Replay SSR * Jan 22 Behind: Reset into 5 degrees/minute rotation mode. * Jan 22 - Mar 23 Behind: Spacecraft behind Sun * Feb 12 Solar Conjunction Readiness Review * 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