STEREO Weekly Meeting Minutes for 2018-02-27 (Week 9) ANNOUNCEMENTS ------------- * None INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally on the main lobe of the high gain antenna. * Behind has transitioned to a weekly schedule to attempt to recover the spacecraft. Passes are scheduled approximately every three days to keep within the 72 hour command loss timer. Typically, two of those days use a search pattern consisting of two diamonds, based on the estimated uncertainty in the ephemeris. The double diamond pattern is executed twice, once to send commands, and then again 40 minutes later to listen for the carrier. An additional pass uses the standard configuration. In some cases, the older "1 kHz" frequency acquisition sequence is used, with one day for battery recovery, and another for carrier recovery. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 8 (Feb 19-25) * On day 052 (Feb 21), during the DSS-63 support for Ahead, the receiver dropped lock causing a loss of telemetry intermittently from 1755z through 1854z due to the antenna brakes engaging from low film height alarms. The SSR pointers were repositioned and all SSR data were recovered on the next track. This anomaly caused the loss of 32 minutes of real-time telemetry and 44 minutes of tracking data. See DR #M110472 for more information. * On day 055 (Feb 24), during the DSS-14 support for Ahead, turbo decoder lock was lost intermittently from 0227z through 0248z due to the transmitter tripping offline. This anomaly resulted in the loss of 21 minutes of commanding and tracking data and 5220 frames of SSR data. See DR #G118968 for more information. * On day 055 (Feb 24), during the DSS-63 support for Ahead, the receiver dropped lock causing a loss of telemetry intermittently from 1559z through 1636z due to the antenna brakes engaging from low film height alarms. This anomaly caused the loss of 11 minutes of real-time telemetry and tracking data and 28,348 frames of SSR data. See DR #M110476 for more information. * On day 051 (Feb 20), the 42nd SECCHI stepped calibration roll was executed at 1230z for midpoint in the Ahead orbit. This was the 11th SECCHI stepped calibration roll to be conducted without gyro use. * The average daily science data return for Ahead was 6.7 Gbits during this week. * On day 051 (Feb 20), during a 3 hour 4 kHz battery recovery search pattern support for Behind with DSS-63, 320 commands were transmitted during the support. All 7 points on the pattern were covered twice. * On day 052 (Feb 21), during a 3.25 hour 4 kHz carrier recovery search pattern support for Behind with DSS-43, 320 commands were transmitted during the support for carrier recovery. No carrier was detected by either the DSN station or the radio science receiver team. All 7 points on the pattern were covered twice. Three commands must be received sequentially to power on the transmitter. * On day 055 (Feb 24), during a 4 hour 1 kHz battery recovery support for Behind with DSS-63, 306 commands were transmitted for battery state of charge recovery. Due to the duration of the support, only 34 of the 36 frequency segments were commanded. * On day 056 (Feb 25), during a 4 hour 1 kHz carrier recovery support for Behind with DSS-63, 440 commands were sent for transmitter carrier recovery. No carrier was detected by either the DSN station or the radio science receiver team. Due to the duration of the support and the increased commands for each step, only 22 of the 36 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. * Recently the DSN refined their telemetry extraction process from low signal levels and was able to deliver 18 new frames from the BEHIND recovery, all post momentum dump. While nothing new was discovered, much of the following observations confirm what was known: - Battery temperature was at 52.72 deg C (upper telemetry limit), probably higher due to an overcharge condition - Latch valve telltales appear to be functioning - Last-minute commands sent to shed main bus load were received as the main bus current dropped about 6A - The IMU was flagged invalid throughout the period - The star tracker was tracking and enabled throughout After all commanded thruster firing had terminated the angle between the angular momentum vector and sun vector steadily increased at ~0.03 deg/min. This tends to further support the hypothesis that something was being expelled. Week 9 (Feb 26-Mar 4) * The GOES-S launch is scheduled for Thursday afternoon. * Ahead has 10 tracks during this week, and overall coverage is nominal. There are six tracks at 720 kbps, one at 360 kbps, and three at 240 kbps. * Recovery search pattern tracks for Behind are scheduled for Tuesday, Feb 27 (battery) and Friday, Mar 2 (carrier), and a 1 kHz frequency acquisition sequence recovery track is scheduled for Sunday, Mar 4 (battery). Week 10 (Mar 5-11) * The second Mercury transit for Ahead is on Monday, Mar 5. The SSC estimates that Mercury will transit through the EUVI field-of-view between approximately 23:20 UT on Mar 4 and 8:15 UT on Mar 5, and through the COR1 field-of-view between 17:30 UT on Mar 4 and 14:30 UT on Mar 5. The MOC calculates that Mercury will cross the solar disk between 02:25 and 05:27 UT on Mar 5. Two DSN tracks on that day have been promoted to level 3 on station 35 and station 55. * The 107th momentum dump is scheduled for Monday, Mar 5, starting at 16:00 UT. This is the 26th dump without the gyros. * Daylight savings time in the U.S. begins Sunday, Mar 11. * Ahead has 13 tracks during this week, and overall coverage is nominal. There are two tracks at 720 kbps, four at 360 kbps, and seven at 240 kbps. * A nominal 4 kHz recovery track for Behind is scheduled for Tuesday, May 6. Search pattern tracks are scheduled for Thursday, Mar 8 (battery), and Saturday Mar 10 (carrier). Week 11 (Mar 12-18) * Ahead has 15 tracks during the week, and overall coverage is nominal. There are six tracks at 720 kbps, two at 360 kbps, six at 240 kbps, and one at 160 kbps. * A battery recovery search pattern track for Behind is scheduled for Monday, Mar 12, and a nominal 4 kHz carrier recovery track is scheduled for Wednesday, Mar 14. 1 kHz frequency acquisition recovery tracks are scheduled for Friday, Mar 16 (battery), and Sunday, Mar 18 (carrier). Week 12 (Mar 19-25) * Ahead has 13 tracks during the week, and overall coverage is nominal. There are eight tracks at 720 kbps, and five at 240 kbps. * Search pattern recovery tracks for Behind are scheduled for Tuesday, Mar 20 (battery) and Wednesday, Mar 21 (carrier). A 1 kHz frequency acquisition sequence battery recovery track is scheduled for Saturday, Mar 24. Week 13 (Mar 26-Apr 1) * Passover begins Friday, March 30 and goes through April 7. Good Friday is March 30, and April 1 is Easter. * March 31 is aphelion for the Behind S/C. * Ahead has 16 tracks during the week, and overall coverage is nominal. There are six tracks at 720 kbps, four at 360 kbps, and six at 240 kbps. * A 1 kHz frequency acquisition sequence carrier recovery track is scheduled Monday, Mar 26. Search pattern recovery tracks are scheduled for Wednesday, Mar 28 (battery), and Saturday, Mar 31 (carrier). A 1 kHz frequency acquisition sequence battery recovery track is scheduled for Sunday, Apr 1. Week 14 (Apr 2-8) * Ahead has 15 passes during the week, and overall coverage is nominal. There are eight passes at 720 kbps, five at 360 kbps, and two at 240 kbps. * Carrier recovery search pattern tracks for Behind are scheduled for Monday, Apr 2, and Saturday, Apr 7. A 1 kHz frequency acquisition battery recovery track is scheduled for Wednesday, Apr 4. Week 15 (Apr 9-15) * The 108th momentum dump on Ahead is scheduled for Tuesday, Apr 10, with ignition at 15:00 UT. This will be the 27th dump without gyros. * Ahead has 15 passes during the week, and overall coverage is nominal. There are six tracks at 720 kbps, three at 360 kbps, and six at 240 kbps. * Search pattern recovery tracks for Behind are scheduled for Monday, Apr 9 (battery) and Wednesday, Apr 11 (carrier). 1 kHz frequency acquisition recovery tracks are scheduled for Friday, Apr 13 (battery) and Sunday, Apr 15 (carrier). Other * TESS launch is currently scheduled for Apr 16. * The Senior Review has come out, and STEREO Ahead was favorably seen. * SECCHI is planning to do a GT-driven off-point to characterize the current position of the COR1 occulter. This off-point will be up to 60 arc seconds, and will take less than an hour. The MOC will look into what needs to be done in terms of coordination. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 09: M Feb 26 (057) T Feb 27 (058) Behind: Recovery track, DSN 14 (search pattern, battery) W Feb 28 (059) T Mar 01 (060) F Mar 02 (061) Behind: Recovery track, DSN 14 (search pattern, carrier) S Mar 03 (062) S Mar 04 (063) Behind: Recovery track, DSN 14 (1 kHz, battery) ------------------------------------------------------------------------------- Scheduled activities for Week 10: M Mar 05 (064) Ahead: Mercury transit, 02:25-05:27 UT Ahead: Momentum dump, 16:00 UT T Mar 06 (065) Behind: Recovery track, DSN 43 (4 kHz) W Mar 07 (066) T Mar 08 (067) Behind: Recovery track, DSN 43 (search pattern, battery) F Mar 09 (068) S Mar 10 (069) Behind: Recovery track, DSN 43 (search pattern, carrier) S Mar 11 (070) Daylight Savings Time begins in US ------------------------------------------------------------------------------- Scheduled activities for Week 11: M Mar 12 (071) Behind: Recovery track, DSN 14 (search pattern, battery) T Mar 13 (072) W Mar 14 (073) Behind: Recovery track, DSN 14 (4 kHz) T Mar 15 (074) F Mar 16 (075) Behind: Recovery track, DSN 43 (1 kHz, battery) S Mar 17 (076) S Mar 18 (077) Behind: Recovery track, DSN 14 (1 kHz, carrier) ------------------------------------------------------------------------------- Scheduled activities for Week 12: M Mar 19 (078) T Mar 20 (079) Behind: Recovery track, DSN 14 (search pattern, battery) W Mar 21 (080) Behind: Recovery track, DSN 14 (search pattern, carrier) T Mar 22 (081) F Mar 23 (082) S Mar 24 (083) Behind: Recovery track, DSN 43 (1 kHz, battery) S Mar 25 (084) ------------------------------------------------------------------------------- Scheduled activities for Week 13: M Mar 26 (085) Behind: Recovery track, DSN 43 (1 kHz, carrier) T Mar 27 (086) W Mar 28 (087) Behind: Recovery track, DSN 43 (search pattern, battery) T Mar 29 (088) F Mar 30 (089) S Mar 31 (090) Behind: Recovery track, DSN 14 (search pattern, carrier) S Apr 01 (091) Behind: Recovery track, DSN 14 (1 kHz, battery) ------------------------------------------------------------------------------- Scheduled activities for Week 14: M Apr 02 (092) Behind: Recovery track, DSN 14 (search pattern, carrier) T Apr 03 (093) W Apr 04 (094) Behind: Recovery track, DSN 43 (1 kHz, battery) T Apr 05 (095) F Apr 06 (096) S Apr 07 (097) Behind: Recovery track, DSN 14 (search pattern, carrier) S Apr 08 (098) ------------------------------------------------------------------------------- Scheduled activities for Week 15: M Apr 09 (099) Behind: Recovery track, DSN 14 (search pattern, battery) T Apr 10 (100) Ahead: Momentum dump, 15:00 UT W Apr 11 (101) Behind: Recovery track, DSN 14 (search pattern, carrier) T Apr 12 (102) F Apr 13 (103) Behind: Recovery track, DSN 43 (1 kHz, battery) S Apr 14 (104) S Apr 15 (105) Behind: Recovery track, DSN 43 (1 kHz, carrier) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2019: * Mar Ahead: Switch downlink rate to 240 kbps for 34 meter * Apr Behind: Switch downlink rate to 240 kbps for 34 meter 2020: * May Behind: Switch downlink rate to 360 kbps for 34 meter * Jun Ahead: Switch downlink rate to 360 kbps for 34 meter * Jun Behind: Switch downlink rate to 480 kbps for 34 meter * Sep Ahead: Switch downlink rate to 480 kbps for 34 meter 2021: * Jul Behind: Switch downlink rate to 720 kbps for 34 meter * Aug Ahead: Switch downlink rate to 720 kbps for 34 meter 2022: 2023: * May 5 Behind: Mercury transit * Jul 17 Behind: Closest approach to Earth * Aug 13 Ahead: Closest approach to Earth 2024: 2025: * Apr 7 Ahead: Mercury transit 2026: 2027: * Feb 1 Behind: Mercury transit 2028: 2029: * Jun 30 Ahead: Mercury transit