STEREO Weekly Meeting Minutes for 2016-02-23 (Week 08) ANNOUNCEMENTS ------------- * None INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally on the main lobe of the high gain antenna. * There are currently no communications with the Behind spacecraft. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 07 (Feb 15-21) * On day 046 (Feb 15), during the DSS-26 support for Ahead, turbo decoder lock was lost briefly at 2322z and again at 047-0040z. This anomaly resulted in the loss of 2 frames of SSR playback data. * On day 050 (Feb 19), the 6th uplink array test for STEREO using DSS-24, 25, and 26 with Ahead was successfully conducted by the DSN. The new configuration consisted of incorporating the frequency segmented acquisition sequence with three 34m stations using the 80 kW and two 20 kW transmitters along with the MOC sending no-op commands. At 2027z, no commands were sent for one command segment when the DSN command subsystem remained in “Interrupted” state when it should have transitioned to “Operational” after command modulation was turned on. The next command modulation off/on sequence cleared the issue. An approximate 12 dBm increase in received uplink power, as compared to a single 34m, was again demonstrated. 28 one kHz frequency segments were tested sending 9 commands each testing the battery recovery procedure with all expected no-op commands being received correctly using the 7.8125 bps uplink rate. See DR #G116965 for more information. * The Ahead observatory operated nominally during this week on the center of the HGA main lobe. The HGA feed assembly was at 114 degrees C and decreasing with the HGA angle at 8.2 degrees and increasing, with respect to the spacecraft-Sun line. * On day 046 (Feb 15), beginning at 1030z the G&C wheel speed avoidance algorithm failed to converge resulting in a 1.2 degree average roll error for three hours. Later that day, the algorithm failed to converge again at 1630z through 2230z with a 0.3 degree average roll error. This behavior had not been seen before. At the same time, there were also unusually large excursions in pitch and yaw. This resulted in affecting SECCHI images from all the telescopes, with the roll particularly affecting the HI images, and the pitch and yaw excursions particularly affecting the stray light pattern in COR1 images. * The average daily science data return for Ahead was 4.1 Gbits during this week. * On day 050 (Feb 19), during the DSS-43 70m support for Behind, 189 commands were sent for battery state of charge recovery. * On day 051 (Feb 20), during the DSS-26 34m support for Behind, using the 80 kW transmitter to minimize 70m contentions, 297 commands were sent for battery state of charge recovery. * On day 052 (Feb 21), during the DSS-43 70m support for Behind, 380 commands were sent for transmitter carrier recovery. No downlink signal was detected by the DSN. Due to the duration of the support and the increased commands for each step, only 19 of the 36 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. Week 08 (Feb 22-28) * The 85th momentum dump on Ahead was carried out successfully yesterday (Feb 22), with ignition at 22:00 UT. This was the fourth no-gyro momentum dump. Fine pointing was restored within two minutes, and the roll error was damped out within 20 minutes. * Turbo decoder lock was lost briefly yesterday (Feb 22), resulting in the loss of about 26 frames of data. * A 2.6 hour DSN ranging test will be carried out using station 15 later today (Feb 23). There will be no instrument commanding or SSR playback during this track. * Tomorrow, Feb 24, at 12:15 UT during the station 55 pass for Ahead, the control bandwidth will be changed in G&C RAM in an attempt to better control the roll error. The MOC will monitor this change over the next several weeks. * Ahead has 13 passes during the week, and overall coverage is nominal. There are four passes at 720 kpbs, three at 240 kbps, and six at 160 kbps. * Behind starts the week at an SPE angle of 9.9 degrees. Recovery efforts for Behind are on Friday, Saturday, and Sunday, Feb 26-28. The battery conditioning tracks will be carried out with the 80 kW transmitter on station 26. Week 09 (Feb 29-Mar 6) * On Thursday, Mar 3, the uplink margin on the Behind LGA with 70 meter stations returns to 6 dB at 7.8 bps. * Ahead has 13 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, seven at 240 kbps, and four at 160 kbps. * Behind starts the week at an SPE angle of 10.4 degrees. Recovery efforts for Behind are on Thursday, Friday, and Sunday, Mar 3-6. The battery recovery tracks will be carried out with the 80 kW transmitter on station 26. Week 10 (Mar 7-13) * Daylight Savings Time starts in the U.S. on Sunday, Mar 13. * Ahead has 13 passes during the week, and overall coverage is nominal. There are seven passes at 720 kbps, one at 360 kbps, two at 240 kbps, and three at 160 kbps. It is possible to go to 360 kbps with station 26 if the elevation is above 25 degrees for the entire pass. * Behind starts the week at an SPE angle of 10.9 degrees. Recovery efforts for Behind are on Friday, Saturday, and Sunday, Mar 11-13. The battery recovery tracks will be carried out with the 80 kW transmitter on station 26. Week 11 (Mar 14-20) * The first uplink array pass for Behind will be on Thursday, Mar 17. This will be a 4.75 hour battery recovery track using stations 24, 25, and 26. * A downlink source is needed to calibrate the stations for uplink array. Ahead will be used for this purpose just before the pass for Behind. To allow this to happen, Ahead will be commanded to the 160 kbps downlink rate at the end of the station 63 pass at 18:00 UT on Mar 17, instead of switching to the space weather beacon rate as usual. The switch to the beacon rate will be delayed until 22:25 UT. The 4.75 hour pass for Behind will be split between the calibration on Ahead for about 2 hours, with the rest on Behind. * Ahead has 11 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, two passes at 360 kbps, four passes at 240 kpbs, and two passes at 160 kbps. * Behind starts the week at an SPE angle of 11.4 degrees. Besides the phased array pass on Thursday, Mar 17, recovery efforts for Behind are on Friday, Saturday, and Sunday, Mar 18-20. The battery recovery tracks will be carried out with the 80 kW transmitter on station 26. All four passes are within 72 hours of each other. * After this week, recovery efforts for Behind will be reduced to every two weeks, with phased array attempts once per month. For the phased array attempts, one of the two battery recovery tracks will use the phased array configuration, and the other will be used for the carrier acquisition track. Week 12 (Mar 21-27) * A 2.75 hour DSN ranging test is scheduled for station 26 with Ahead on Mar 22. There will be no instrument commanding or SSR downlink during this pass. * The 86rd momentum dump for Ahead is scheduled for Wednesday, Mar 23, with ignition at 22:00 UT. This will be the 5th momentum dump without the gyros. * Ahead has 12 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, three passes at 360 kbps, three passes at 240 kbps, and two passes at 160 kbps. * Behind starts the week at an SPE angle of 11.9 degrees. There will be no passes for Behind. From this point on, attempts to contact Behind will occur only every other week, with phased uplink arrays used once per month. Week 13 (Mar 28-Apr 3) * A 2.6 hour DSN ranging test is scheduled for station 15 with Ahead on Monday, Mar 28. There will be no instrument commanding or SSR downlink during this pass. * Ahead has 9 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, four passes at 240 kbps, and one pass at 160 kbps. * Behind starts the week at an SPE angle of 12.3 degrees. Recovery efforts for Behind are on Friday, Saturday, and Sunday, Apr 1-3. The battery recovery tracks will be carried out with the 80 kW transmitter on station 26. Week 14 (Apr 4-10) * The 33rd SECCHI stepped calibration roll is scheduled for Tuesday, Apr 5, starting at 10:45 UT. This will be the midpoint roll. System momentum is expected to be around 4 N-m-s. This will be the second stepped calibration roll without the gyros. * On Wednesday, Apr 6, the LGA uplink margin on Ahead with 70 m stations will return to the nominal 6 dB at 7.8 bps. * A 2.6 hour DSN ranging test is scheduled for Sunday, Apr 10, with station 55. There will be no instrument commanding or SSR playback during this test. * Ahead has 11 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, one at 360 kbps, five at 240 kbps, and three at 160 kbps. * There are no passes for Behind during the week. Other * SECCHI asked about whether there have been any changes in the way the spacecraft treats the guide telescope data during the mission. The HI team is interested in this information in helping them understand their data. The guide telescope bias changes are handled internally within SECCHI. Otherwise, there have been no changes in the way the GT data are used. The MOC will send a list of dates when the G&C parameters were modified. There was a change in the boresight definition early in the mission to better align the spacecraft boresight with the GT, but this hasn't changed since then. A slow drift in attitude history data has been seen since launch, with a jump associated with solar conjunction. This is probably due to small changes in the alignment of various spacecraft components. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 08: M Feb 22 (053) Ahead: Momentum dump, 22:00 UT T Feb 23 (054) Ahead: DSN ranging test with station 15 W Feb 24 (055) T Feb 25 (056) F Feb 26 (057) S Feb 27 (058) S Feb 28 (059) ------------------------------------------------------------------------------- Scheduled activities for Week 09: M Feb 29 (060) T Mar 01 (061) W Mar 02 (062) T Mar 03 (063) Behind: Resume LGA uplink capability on 70 m DSN F Mar 04 (064) S Mar 05 (065) S Mar 06 (066) ------------------------------------------------------------------------------- Scheduled activities for Week 10: M Mar 07 (067) T Mar 08 (068) W Mar 09 (069) T Mar 10 (070) F Mar 11 (071) S Mar 12 (072) S Mar 13 (073) Daylight Savings Time starts in U.S. ------------------------------------------------------------------------------- Scheduled activities for Week 11: M Mar 14 (074) T Mar 15 (075) W Mar 16 (076) T Mar 17 (077) Ahead: Remain at 160 kbps between 18:00-22:25 UT Behind: First recovery attempt using uplink phased array F Mar 18 (078) S Mar 19 (079) S Mar 20 (080) ------------------------------------------------------------------------------- Scheduled activities for Week 12: M Mar 21 (081) T Mar 22 (082) Ahead: Ranging test with station 26 W Mar 23 (083) Ahead: Momentum dump, 22:00 UT T Mar 24 (084) F Mar 25 (085) S Mar 26 (086) S Mar 27 (087) ------------------------------------------------------------------------------- Scheduled activities for Week 13: M Mar 28 (088) Ahead: Ranging test with station 15 T Mar 29 (089) W Mar 30 (090) T Mar 31 (091) F Apr 01 (092) S Apr 02 (093) S Apr 03 (094) ------------------------------------------------------------------------------- Scheduled activities for Week 14: M Apr 04 (095) T Apr 05 (096) Ahead: SECCHI stepped calibration roll, 10:45 UT W Apr 06 (097) Ahead: Resume LGA uplink capability on 70 m DSN T Apr 07 (098) F Apr 08 (099) S Apr 09 (100) S Apr 10 (101) Ahead: Ranging test with station 55 ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2016: * May 16 Both: Post Solar Conjunction Assessment Review * Jul 5 Juno arrival at Jupiter * Dec Behind: Resume LGA downlink capability on 70 m DSN 2017: 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