STEREO Weekly Meeting Minutes for 2018-03-13 (Week 11) ANNOUNCEMENTS ------------- * Attempts to recover Behind will shift to back to a monthly schedule from the current weekly schedule. Weekly attempts will end in week 16, and the monthly attempts will pick up in week 20. * The recovery track for Behind on Sunday, Mar 18, will be the last with radio science receiver support on a routine basis. 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 10 (Mar 5-11) * On day 064 (Mar 5), during the DSS-35 level-3 support for Ahead, turbo decoder lock was lost briefly at 0428z. Also, during this support the VC6 and VC7 IDR data file transfer stopped at 0500z through 0740z. The IDR data files were retransmitted offline by the DSN on DOY 066 and all Mercury transit data was recovered. This anomaly resulted in the loss of eight frames of SSR data. * On day 068 (Mar 9), during the DSS-55 support for Ahead, turbo decoder lock was lost briefly at 1400z and again at 1505z. This anomaly resulted in the loss of two frames of SSR data. * On day 069 (Mar 10), during the DSS-55 support for Ahead, turbo decoder lock was lost intermittently from 1559z through 1602z. This anomaly resulted in the loss of 931 frames of SSR data. See DR #M110503 for more information. * On day 069 (Mar 10), during the DSS-14 support for Ahead, turbo decoder lock was lost briefly 2042z. This anomaly resulted in the loss of one frame of SSR data. * On day 064 (Mar 5), the SECCHI instrument successfully observed the 2nd Mercury transit of the Sun from 0225z through 0527z. The SECCHI team reports that Mercury was visible in both EUVI and COR1 images. * On day 064 (Mar 5), the 107th momentum dump on Ahead was executed successfully at 1600z, which imparted an estimated delta V of 0.104 m/sec. This was the 26th momentum dump that did not use the IMU. After thruster operations completed, there was a 0.18 degree of roll angle error which was dampened out over the next 15.8 minutes. Fine pointing stabilized 3.0 minutes after completion of the momentum dump. * The average daily science data return for Ahead was 6.1 Gbits during this week. * On day 065, during a 2.2 hour 4 kHz carrier recovery support with DSS-43, 200 commands were transmitted during the support. No carrier was detected by either the DSN station or the radio science receiver team after attempting to power on the TWTA for 30 minutes. Transitioned to battery recovery operations for the remainder of the support which consists of repeatedly sweeping a 4 kHz uplink range and sending commands for IEM switched power and PDU 1553 interface bus off. * On day 066, during a 3.25 hour 4 kHz battery recovery search pattern support with DSS-43, 320 commands were transmitted during the support. All 7 points on the pattern were covered twice. * On day 070 during a 3.25 hour 4 kHz carrier recovery search pattern support with DSS-43, commanding was delayed by 40 minutes due to a transmitter issue. 260 commands were transmitted during the support for carrier recovery. No carrier was detected by either the DSN station or the radio science receiver team. The last 3 points on the pattern were only covered once due to the transmitter anomaly. Three commands must be received sequentially to power on the transmitter. See DR #C113270 for more information. Week 11 (Mar 12-18) * Acquistion was about 1 hour late during the station 55 support for Ahead this morning (Mar 13). The SSR pointers were repositioned to minimize data loss. * 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 was carried out yesterday (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). These will be the last supports with the radio science receiver on a routine basis. 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 17 passes during the week, and overall coverage is nominal. A previously scheduled station 14 pass early on Saturday has been deleted. There are seven passes at 720 kbps, five at 360 kbps, and five 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). Week 16 (Apr 16-22) * The TESS launch is scheduled for late Monday, Apr 16. This is expected to have minimal impact on the STEREO DSN schedule. * Ahead has 17 passes during the week, and overall coverage is nominal. There are six tracks at 720 kbps, five at 360 kbps, and six at 240 kbps. * Search pattern recovery tracks for Behind are scheduled for Tuesday, Apr 17 (battery), and Friday, Apr 20 (carrier). A nominal 4 kHz recovery sequence is scheduled for Sunday, Apr 22. * This is the last week for weekly attempts to recover Behind. Monthly attempts will pick up in week 20. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- 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) ------------------------------------------------------------------------------- Scheduled activities for Week 16: M Apr 16 (106) T Apr 17 (107) Behind: Recovery track, DSN 14 (search pattern, battery) W Apr 18 (108) T Apr 19 (109) F Apr 20 (110) Behind: Recovery track, DSN 43 (search pattern, carrier) S Apr 21 (111) S Apr 22 (112) Behind: Recovery track, DSN 14 (4 kHz) ------------------------------------------------------------------------------- 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