STEREO Weekly Meeting Minutes for 2016-05-24 (Week 21) 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 20 (May 16-22) * The Ahead observatory operated nominally during this week on the center of the HGA main lobe. The HGA feed assembly was at 96 degrees C and decreasing with the HGA angle at 11.1 degrees and increasing, with respect to the spacecraft-Sun line. * On day 138 (May 17), during the DSS-25 support for Ahead, turbo decoder lock was lost intermittently beginning at 1643z through 1836z. This anomaly resulted in the loss of 6 frames of SSR data. * On day 139 (May 18), G&C fine pointing loss on Ahead was intermittent for 12 hours beginning at 1030z. This coincides when two of the wheels reached the wheel speed dead zone for zero speed avoidance. The wheel speed avoidance band about zero speed will be increased to 30.79 rads/second. This change was just uploaded to G&C RAM on Ahead today, Tuesday May 24. * On day 140 (May 19), during the DSS-25 support for Ahead, turbo decoder lock was lost briefly at 1833z. This anomaly resulted in the loss of 1 frame of SSR data. * On day 142 (May 21), during the DSS-25 support for Ahead, turbo decoder lock was lost intermittently beginning at 1627z through 1813z. This anomaly resulted in the loss of 3 frames of SSR data. * On day 143 (May 22), during the DSS-26 support for Ahead, turbo decoder lock was lost briefly at 1632z. This anomaly resulted in the loss of 1 frame of SSR data. * The average daily science data return for Ahead was 6.1 Gbits during this week. * No recovery tracks for Behind this week. As commands must be received to recover the Behind observatory, the first use of the newly developed DSN uplink arraying capability for Behind recovery operations occurred on March 17, 2016. The uplink array capability provides four times the uplink received power as a 70m station. The uplink array consists of using an 80 kW and two 20 kW transmitters from three 34m Goldstone sta tions, DSS-24, 25, and 26, with each uplink being precisely phase shifted to create a constructive interference. From testing with STEREO Ahead, an approximate 12 dBm increase in received uplink power, as compared to a single 3 4m, has been successfully demonstrated each time. As the Behind observatory may be rotating, a frequency segmented acquisition sequence will be used with the uplink array. For each use of the uplink array, as transponder feedback is required, the Ahead observatory is first used to calibrate the phased uplink array then the three stations are switched to point to the Behind observatory sending commands for recovery. The uplink array will be used twice monthly within a three day period, once for batteryrecovery and again for carrier recovery. The next use of the uplink array is scheduled for June 11th and 12th. * As time goes by, the ephemeris error increases degrading DSN antenna pointing. However, with time the spacecraft range also decreases improving RF communications and the ability for other assets to acquire data on Behind. Analysis indicates that the total RF gain change is significant and the probability of command success increases with time. Week 21 (May 23-29) * G&C wheel speed avoidance parameter uplinked to RAM Tuesday, May 24. * Thursday, May 26 PLASTIC will do real time commanding to adjust instrument performance starting at about 12:00 EDT. * The MOC will switch over the restricted IONET connect for three hours starting at 12:00 UT on Thursday, May 26. This should have no effect on operations. * Electrical maintenance will be carried out at the MOC during Memorial Day weekend. During this time, the MOC will be on generator power, starting at 5:00 PM EDT on Friday, May 27, through 8:00 PM EDT on Monday, May 30. Operations will not be affected. * Ahead has 14 tracks during the week, and overall coverage is nominal. There are three tracks at 720 kbps, seven at 240 kbps, and four at 160 kbps. * Behind starts the week at an SPE angle of 14.8 degrees. Recovery efforts for Behind are on Friday-Sunday, May 27-29. The battery recovery tracks will be undertaken with the 80 kW transmitter on station 26. The Allen Telescope Array will also be listening during the transmitter recovery track, along with station 14. Week 22 (May 30-Jun 5) * Monday, May 30, is Memorial Day, which is an APL holiday. * The 88th momentum dump on Ahead will be carried out on Tuesday, May 31, with ignition at 20:00 UT. This will be the seventh momentum dump without using the gyros. * Jun 2, the MOC will be loading new C&DH fault protection rules (version 2.3.19) and macros (version 1.1.29) to EEPROM. These changes are designed to provide better protection in case of the loss of one of the reaction wheels, or low solar array voltage. * Ahead has 12 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, three at 360 kbps, five at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 15.0 degrees. There are no passes for Behind during the week. Week 23 (Jun 6-12) * Ahead has 10 passes during the week, and overall coverage is nominal. There are 4 passes at 720 kbps, one pass at 360 kbps, four passes at 240 kbps, and one pass at 160 kbps. * Behind starts the week at an SPE angle of 15.1 degrees. * Uplink array attempts to recover Behind are scheduled for June 11, 12. Each pass will start out with Ahead for 1.9 hours for phase calibration. There will be no instrument calibration or SSR playback during these calibration passes. Following calibration, the stations will attempt to command Behind for 3.3 hours on June 11 for battery recovery, and for 5.3 hours on June 12 for carrier recovery along with station 14. The last 35 minutes will be below the 27.5 degree elevation limit, so a waiver has been requested. Otherwise, the broadcast power would be reduced from 80 to 60 kW. Week 24 (Jun 13-19) * Ahead has 12 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, four at 360 kbps, five at 240 kbps, and one at 160 kbps. * Behind starts the week at an SPE angle of 15.1 degrees. There are no tracks for Behind during the week. Week 25 (Jun 20-26) * Ahead has 10 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, two at 360 kbps, four at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 15.2 degrees. Recovery efforts for Behind are Monday-Wednesday, Jun 20-22. The battery recovery tracks will be undertaken with the 80 kW transmitter on station 26. Week 26 (Jun 27-Jul 3) * The 5th battery discharge operation on Ahead is scheduled for Monday, Jun 27, for about 2 hours starting at 17:00. * Ahead has 12 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, two at 360 kbps, four at 240 kbps, and three at 160 kbps. * Behind starts the week at an SPE angle of 15.2 degrees. There are no tracks for Behind. Week 27 (Jul 4-10) * Monday, July 4 is a holiday for APL. * Monday, July 4 is aphelion for Ahead. * The 89th momentum dump on Ahead is on Wednesday Jul 6 at 16:00 UT. This will be the eighth momentum dump without using the gyros. * Ahead has 15 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, two at 360 kbps, five at 240 kbps, and four at 160 kbps. * Behind starts the week at an SPE angle of 15.1 degrees. Recovery efforts for Behind are Friday-Sunday, Jul 8-10. The battery recovery tracks will be undertaken with the 80 kW transmitter on station 26. Station 14 will be used for carrier recovery on July 10. Other: * The MOC has put together the most recent sun pointing perfomance and put it out for review by the SECCHI Team Nathan: the SECCHI team has been discussing it and they have a proposed specification. He will send it to the MOC soon. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 20: M May 16 (137) T May 17 (138) W May 18 (139) T May 19 (140) F May 20 (141) S May 21 (142) S May 22 (143) ------------------------------------------------------------------------------- Scheduled activities for Week 21: M May 23 (144) T May 24 (145) W May 25 (146) T May 26 (147) F May 27 (148) S May 28 (149) S May 29 (150) ------------------------------------------------------------------------------- Scheduled activities for Week 22: M May 30 (151) Memorial Day T May 31 (152) Ahead: Momentum dump, 20:00 UT W Jun 01 (153) T Jun 02 (154) F Jun 03 (155) S Jun 04 (156) S Jun 05 (157) ------------------------------------------------------------------------------- Scheduled activities for Week 23: M Jun 06 (158) T Jun 07 (159) W Jun 08 (160) T Jun 09 (161) F Jun 10 (162) S Jun 11 (163) Behind: Phased array recovery attempt S Jun 12 (164) Behind: Phased array recovery attempt ------------------------------------------------------------------------------- Scheduled activities for Week 24: M Jun 13 (165) T Jun 14 (166) W Jun 15 (167) Ahead: STEREO Subsystem Assessment Review T Jun 16 (168) F Jun 17 (169) S Jun 18 (170) S Jun 19 (171) ------------------------------------------------------------------------------- Scheduled activities for Week 25: M Jun 20 (172) T Jun 21 (173) W Jun 22 (174) T Jun 23 (175) F Jun 24 (176) S Jun 25 (177) S Jun 26 (178) ------------------------------------------------------------------------------- Scheduled activities for Week 26: M Jun 27 (179) Ahead: Battery maintenance, 17:00 UT T Jun 28 (180) W Jun 29 (181) T Jun 30 (182) F Jul 01 (183) S Jul 02 (184) S Jul 03 (185) ------------------------------------------------------------------------------- Scheduled activities for Week 27: M Jun 04 (185) T Jun 05 (186) W Jun 06 (187) T Jun 07 (188) Ahead: Momentum dump, 16:00 UT F Jul 08 (189) S Jul 09 (190) S Jul 03 (185) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2016: * 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