STEREO Weekly Meeting Minutes for 2018-01-09 (Week 2) 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 1 (Jan 1-7) * On day 003 (Jan 3), during the DSS-14 support for Ahead, the uplink was delayed 9 minutes due to a transmitter issue. The transmitter was recalibrated and the uplink was established at 1954z. This anomaly resulted in the loss of 9 minutes of commanding and two-way tracking data and 4196 frames of real-time and SSR data, equivalent to a few seconds at the 720 kbps rate. See DR# G118783 for more information. * On day 004 (Jan 4), during the DSS-55 support for Ahead, turbo decoder lock was lost intermittently between 1353z and 1411z. This anomaly resulted in the loss of 11 frames of SSR data. * On day 005 (Jan 5), during the DSS-34 support for Ahead, turbo decoder lock was lost briefly at 0734z and 0845z. This anomaly resulted in the loss of 4 frames of SSR data. * On day 005 (Jan 5), during the DSS-63 support for Ahead, telemetry lock was lost intermittently between 1744z and 1808z due to rain at the Madrid complex. This anomaly resulted in the loss of 41,527 frames of real-time and SSR data, which is equivalent to about 8.5-9 minutes at the 720 kbps rate. See DR# M110420 for more information. * The average daily science data return for Ahead was 6.8 Gbits during this week. * On day 001 (Jan 1), during a 4 hour 1 kHz battery recovery support for Behind with DSS-14, 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 002 (Jan 2), 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. * On day 005 (Jan 5), 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 007 (Jan 7), during a 3 hour 4 kHz carrier recovery search pattern support for Behind with DSS-14, commanding was interrupted for 14 minutes between 1629z and 1643z due to a configuration issue at the station. See DR# G118795 for more information. This anomaly prevented 20 carrier recovery commands from being transmitted, and resulted in 1 of 7 points on the pattern not being covered twice. Overall, 300 commands were transmitted during the support for carrier recovery. No carrier was detected by either the DSN station or the radio science receiver team. Three commands must be received sequentially to power on the transmitter. Week 2 (Jan 8-14) * Ahead has 14 tracks during the week, and overall coverage is nominal. There are seven tracks at 720 kbps, one at 360 kbps, four at 240 kbps, and two at 160 kbps. * A recovery pass for Behind battery recovery using the 1 kHz frequency acquisition sequence was carried out this morning using station 63. The antenna brakes engaged, which caused about a one hour delay before the pass could resume. Between the antenna brakes problem, and the pass duration, a total of 170 commands were sent, corresponding to only 8 of the 36 frequency segments being covered. * An additional recovery attempts for Behind using the 1 kHz frequency acquisition sequence for carrier recovery is scheduled for Friday, Jan 12. A search pattern for battery recovery is scheduled for Sunday, Jan 14. * DSN reports that a new procedure has been implemented to make recovery search patterns easier. Week 3 (Jan 15-21) * Jan 15 is the Martin Luther King Day holiday. Government offices will be closed, but APL will remain open. * Ahead has 16 tracks during the week, and overall coverage is nominal. There are six tracks at 720 kbps, one at 360 kbps, eight at 240 kbps, and one at 160 kbps. * A carrier recovery search pattern track for Behind is scheduled for Tuesday, Jan 16. Recovery tracks using the 1 kHz frequency acquisition sequence are scheduled for Thursday, Jan 18 (battery), and Saturday, Jan 20 (carrier). Week 4 (Jan 22-28) * The fourth SECCHI HI stray light calibration maneuver is scheduled for Tuesday, Jan 23, starting at 17:00 UT. This maneuver involves off-pointing in the Y axis direction by a little over a degree. The sequence will run for about 1.75 hours. System momentum will be about 9 N-m-s. This will be the first time this calibration will be carried out without gyros. * SECCHI raised a question about the possibility of going through zero wheel speed during the HI calibration maneuver. It's difficult to predict what the wheel speeds will be, but none of the wheels should go through zero for the HI calibration. There was also some discussion about the strategy for scheduling stepped calibration rolls to avoid zero wheel speeds. * SECCHI also pointed out that the HI calibration maneuver is not yet in the weekly schedule. The updated weekly schedule should be out this week, possibly today. * The 106th momentum dump is scheduled for Thursday, Jan 25, with ignition at 15:30 UT. This will be the 25th dump without gyros. This is a week or so early, due to scheduling constraints. * On Wednesday, Jan 24, Behind would resume 125 bps uplink on LGA assuming nominal operations. * Ahead has 13 tracks during the week, and overall coverage in nominal. There are seven tracks at 720 kbps, two at 360 kbps, and four at 240 kbps. * Weekly recovery operations for Behind continue. A battery recovery search pattern track is scheduled for Tuesday, Jan 23, and the corresponding carrier recovery search pattern track will be on Friday, Jan 26. On Sunday, Jan 28, a battery recovery 1 kHz sweep sequence is scheduled. Week 5 (Jan 29-Feb 4) * Ahead has 14 tracks during the week, and overall coverage is nominal. There are eight tracks at 720 kbps, five at 240 kbps, and one at 160 kbps. * A carrier seach pattern track for Behind is scheduled for Monday, Jan 29. The previous Behind track was actually a battery 1 kHz sweep sequence, but the track duration did not support a carrier search pattern. The 1 kHz sweep sequences will be used on Wednesday, Jan 31 (battery), and Friday, Feb 2 (carrier). A battery recovery search pattern will be carried out on Sunday, Feb 4. Week 6 (Feb 5-11) * Ahead has 16 tracks during the week, and overall coverage is nominal. There are seven tracks at 720 kbps, one at 360 kbps, and eight at 240 kbps. * Nominal 4 kHz recovery tracks for Behind are scheduled for Monday, Feb 5, and Wednesday, Feb 7. A 1 kHz carrier recovery track is scheduled for Friday, Feb 9, and a battery recovery search pattern track is scheduled for Sunday, Feb 11. Week 7 (Feb 12-18) * Ahead has 15 tracks during the week, and overall coverage is nominal. There are eleven tracks at 720 kbps, two at 360 kbps, and two at 240 kbps. * A carrier recovery search pattern track for Behind is scheduled for Tuesday, Feb 13, and 1 kHz recovery tracks are scheduled for Friday, Feb 16 (battery), and Sunday, Feb 18 (carrier). * Station 43 comes back online. Week 8 (Feb 19-25) * The 42nd SECCHI stepped calibration roll is scheduled for Tuesday, Feb 20, starting at 12:30 UT. This will be the midpoint roll. System momentum will be 4 N-m-s. * Ahead has 14 tracks during the week, and overall coverage is nominal. There are eight tracks at 720 kbps, four at 360 kbps, and two at 240 kbps. * Recovery search pattern tracks for Behind are scheduled for Tuesday, Feb 20 (battery) and Wednesday, Feb 21 (carrier). 1 kHz frequncy acquisition sequence recovery tracks are scheduled for Saturday, Feb 24 (battery) and Sunday, Feb 25 (carrier). Other * The DSN optimized their ability to extract telemetry from low signals, and managed to find 18 additional telemetry frames from the attempt to recovery Behind in 2016. Many of these frames were on the HGA and contain four packets per frame. The MOC is still analyzing these data. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 02: M Jan 08 (008) T Jan 09 (009) Behind: Recovery track, DSN 63 (1 kHz, battery) W Jan 10 (010) T Jan 11 (011) F Jan 12 (012) Behind: Recovery track, DSN 63 (1 kHz, carrier) S Jan 13 (013) S Jan 14 (014) Behind: Recovery track, DSN 14 (search pattern, battery) ------------------------------------------------------------------------------- Scheduled activities for Week 03: M Jan 15 (015) Martin Luther King Day T Jan 16 (016) Behind: Recovery track, DSN 63 (search pattern, carrier) W Jan 17 (017) T Jan 18 (018) Behind: Recovery track, DSN 14 (1 kHz, battery) F Jan 19 (019) S Jan 20 (020) Behind: Recovery track, DSN 63 (1 kHz, carrier) S Jan 21 (021) ------------------------------------------------------------------------------- Scheduled activities for Week 04: M Jan 22 (022) T Jan 23 (023) Ahead: SECCHI HI stray light calibration offpoint, 17:00 UT Behind: Recovery track, DSN 63 (search pattern, battery) W Jan 24 (024) T Jan 25 (025) Ahead: Momentum dump, 15:30 UT Behind: Recovery track, DSN 14 (search pattern, carrier) F Jan 26 (026) S Jan 27 (027) S Jan 28 (028) Behind: Recovery track (1 kHz, battery) ------------------------------------------------------------------------------- Scheduled activities for Week 05: M Jan 29 (029) Behind: Recovery track, DSN 63 (search pattern, carrier) T Jan 30 (030) W Jan 31 (031) Behind: Recovery track, DSN 63 (1 kHz, battery) T Feb 01 (032) F Feb 02 (033) Behind: Recovery track, DSN 63 (1 kHz, carrier) S Feb 03 (034) S Feb 04 (035) Behind: Recovery track, DSN 63 (search pattern, battery) ------------------------------------------------------------------------------- Scheduled activities for Week 06: M Feb 05 (036) Behind: Recovery track, DSN 63 (4 kHz) T Feb 06 (037) W Feb 07 (038) Behind: Recovery track, DSN 14 (4 kHz) T Feb 08 (039) F Feb 09 (040) Behind: Recovery track, DSN 63 (1 kHz, carrier) S Feb 10 (041) S Feb 11 (042) Behind: Recovery track, DSN 14 (search pattern, battery) ------------------------------------------------------------------------------- Scheduled activities for Week 07: M Feb 12 (043) T Feb 13 (044) Behind: Recovery track, DSN 14 (search pattern, carrier) W Feb 14 (045) T Feb 15 (046) F Feb 16 (047) Behind: Recovery track, DSN 63 (1 kHz, battery) S Feb 17 (048) S Feb 18 (049) Behind: Recovery track, DSN 63 (1 kHz, carrier) ------------------------------------------------------------------------------- Scheduled activities for Week 08: M Feb 19 (050) T Feb 20 (051) Ahead: SECCHI calibration roll, 12:30 UT Behind: Recovery track, DSN 63 (search pattern, battery) W Feb 21 (052) Behind: Recovery track, DSN 43 (search pattern, carrier) T Feb 22 (053) F Feb 23 (054) S Feb 24 (055) Behind: Recovery track, DSN 63 (1 kHz, battery) S Feb 25 (056) Behind: Recovery track, DSN 63 (1 kHz, carrier) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2018: * Mar 5 Ahead: Mercury transit 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