STEREO Weekly Meeting Minutes for 2017-05-09 (Week 19) ANNOUNCEMENTS ------------- * None. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally on the main lobe of the high gain antenna. * Attempts to recover Behind have transitioned back to a monthly schedule. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 18 (May 1-7) * There was a data gap for all instruments on day 126 (May 6) due a processing issue at the DSN. Almost all of the missing data has now been filled in, but there's still 30 minutes of SECCHI data which is still missing. MOC is looking into recovering those 30 minutes. * On day 120 (Apr 30) fine pointing was lost on Ahead four times at 0703z, 1304z, 1603z, and 1904z and again on 121-0403z. These occurrences are associated with transients that occurred as pairs of wheels (wheels 3 & 4) passed through zero simultaneously. There was some ping-ponging of the wheels passing through zero that occurred at approximately the Speed Avoidance computation interval (3 hours) or multiples thereof. In total, there were 108 occurrences of the Fine Specs Met flag being zero on day 120 which is well within the 3-sigma jitter specification. These transients can occur with no gyro operations and are not indicative of any problem with the spacecraft G&C. * The average daily science data return for Ahead was 6.2 Gbits during this week. * Planning continues for recovery of the Behind spacecraft. There will be a planning meeting on Thursday, May 11, starting at 9:00. The MOC is getting ready for the anticipated change to recover Behind in the fall, going over lessons learned from the last attempt and comments from the review committee. * On Thursday, May 4, SECCHI starte a special observing campaign for two weeks starting on Thursday, May 4. This campaign involves taking extra HI-2 images at shorter exposure times. The extra images are only a small delta on their current rate, and will be absorbed into their overall planning. In addition, they will also be substituting one of the 195 A beacon images for a 304 A image once every two hours. This is to support a study of using the 304 A data to augment flux transport simultations to forecast the evolution of active regions. Week 19 (May 8-14) * The track for tomorrow, May 10, has been shifted earlier by 3.6 hours, and shortened from 5 to 4 hours. This is to support Goldstone observations of a newly discovered asteroid. This change led SECCHI to upload a new schedule to avoid reaching 100% full on their buffer. They were successful in uploading the new schedule, but time was short. * DSN stations will be unavailable for a large part of the day on Thursday, May 11 for an exercise in preparation for DSN "Follow the Sun" operations. STEREO Ahead has passes just before and just after this exercise, so no problems are anticipated. * Ahead has 9 tracks during the week and overall coverage is nominal. There are 8 passes at 720 kbps, and one at 160 kbps. * The recovery attempt for Behind during the week will use the uplink array configuration on Saturday and Sunday, May 13-14, to officially validate the technique. The configuration uses stations 24, 25, and 26 at Goldstone for uplink, with the 80 kW transmitter on station 26, and the 70 meter station 14 for downlink. The first 1.9 hours will be used with STEREO Ahead for calibration. There will be no SSR playback or instrument commanding during these Ahead passes. After calibration, the stations will switch to Behind for 2.8 hours on Saturday, and 3.7 hours on Sunday, as well as station 14 for 3.4 hours with the Radio Science Receiver. A waiver has been requested for station 26 dipping below the 27.5 degree limit for 45 minutes starting at 22:15 UT on Sunday. Week 20 (May 15-21) * Ahead has 12 passes during the week, and overall coverage is nominal. There are eight passes at 720 kbps, one at 360 kbps, one at 240 kbps, and two at 160 kbps. * There are no passes for Behind during the week. Week 21 (May 22-28) * The 99th momentum dump on Ahead is scheduled for Monday, May 22, with ignition at 14:00 UT. This will be the 18th momentum dump with using the gyros. The dump is being scheduled a week or so early due to track coverage limitations. * Ahead has 8 passes during the week, and overall coverage is nominal. There are seven passes at 720 kbps, and one at 240 kbps. * There are no passes for Behind during the week. Week 22 (May 29-Jun 4) * Monday, May 29, is Memorial Day, which is a holiday at APL. * There will be an upgrade of the restricted IOnet on Thursday, June 1, between 11-19 UT. This will occur between tracks, and is expected to have no effect. * Ahead has 8 tracks during the week, and overall coverage is nominal. There are seven tracks at 720 kbps, and one at 160 kbps. * There are no tracks for Behind during the week. Week 23 (Jun 5-11) * Monday, Jun 5, 14-20 UT, is a backup date for the IOnet upgrade scheduled for the previous Thursday. This will also be between tracks. * Ahead has 9 tracks during the week, and overall coverage is nominal. There are six tracks at 720 kbps, one at 240 kbps, and two at 160 kbps. * Recovery tracks for Behind are scheduled for Friday, Saturday, and Sunday, Jun 9-11. The first two tracks will use the 80 kW transmitter on station 26. The last track will use station 43, and will include the Radio Science Receiver. Week 24 (Jun 12-18) * STEREO Ahead reaches aphelion on Jun 13. * The 39th SECCHI stepped calibration roll is scheduled for Tuesday, Jun 13, starting at 09:15 UT. System momentum is expected to be 1 N-m-s. This will be the eighth calibration roll without gyros. * Battery discharge maintenance will be carried out on Ahead on Wednesday, Jun 14, for 2 hours starting at 15:00 UT during a track. The battery state of charge will be taken down to 86-88% for testing. This is not expected to affect science operations. * Ahead has 10 tracks during the week, and overall coverage is nominal. There are six tracks at 720 kbps, three at 240 kbps, and one at 160 kbps. * There are no tracks for Behind during the week. Week 25 (Jun 19-25) * Ahead has 10 tracks during the week, and overall coverage is nominal. There are six tracks at 720 kbps, and four at 240 kbps. * There are no tracks for Behind during the week. Other * SECCHI would like the Ahead DSN schedule to be arranged so that the recorder will be empty the day before the total solar eclipse on August 21, on a best effort basis for a high nominal return. The MOC will send SECCHI the planned schedule for that date, and SECCHI will look it over to see if it meets their needs. * It was pointed out that SOHO also had some telemetry drop out on day 126, and that this was the second week in a row for them. It's not known whether this is related to the STEREO drop out or not. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 19: M May 08 (128) T May 09 (129) W May 10 (130) T May 11 (131) DSN stations down for "Follow the Sun" exercise F May 12 (132) S May 13 (133) Behind: DSN uplink array recovery attempt S May 14 (134) Behind: DSN uplink array recovery attempt ------------------------------------------------------------------------------- Scheduled activities for Week 20: M May 15 (135) T May 16 (136) W May 17 (137) T May 18 (138) F May 19 (139) S May 20 (140) S May 21 (141) ------------------------------------------------------------------------------- Scheduled activities for Week 21: M May 22 (142) Ahead: Momentum dump, 14:00 UT T May 23 (143) W May 24 (144) T May 25 (145) F May 26 (146) S May 27 (147) S May 28 (148) ------------------------------------------------------------------------------- Scheduled activities for Week 22: M May 29 (149) Memorial Day T May 30 (150) W May 31 (151) T Jun 01 (152) F Jun 02 (153) S Jun 03 (154) S Jun 04 (155) ------------------------------------------------------------------------------- Scheduled activities for Week 23: M Jun 05 (156) T Jun 06 (157) W Jun 07 (158) T Jun 08 (159) F Jun 09 (160) S Jun 10 (161) S Jun 11 (162) ------------------------------------------------------------------------------- Scheduled activities for Week 24: M Jun 12 (163) T Jun 13 (164) Ahead: Aphelion. SECCHI calibration roll, 09:15 UT W Jun 14 (165) Ahead: Battery discharge maintenance, 15:00 UT T Jun 15 (166) F Jun 16 (167) S Jun 17 (168) S Jun 18 (169) ------------------------------------------------------------------------------- Scheduled activities for Week 25: M Jun 19 (170) T Jun 20 (171) W Jun 21 (172) T Jun 22 (173) F Jun 23 (174) S Jun 24 (175) S Jun 25 (176) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 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 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