STEREO Weekly Meeting Minutes for 2016-04-19 (Week 16) ANNOUNCEMENTS ------------- * A sudden decrease in the scattered light level in the COR1-A telescope was seen between 01:05 and 01:10 UT on Apr 13. It is theorized that a small dust particle came off of the objective lens. Since the decrease was in particular directions, symmetrically placed around the approximately 4 and 10 o'clock positions, the ejected dust particle is assumed to have been elongated, since elongated particles will tend to scatter most strongly in directions perpendicular to the direction of elongation. This is the first time that a significant sudden decrease in scattered light has been seen in COR1. The usual behavior is a sudden increase due to a new particle landing on the objective. The COR1 team is interested in knowing whether any of the other teams saw anything unusual in their data around the time of this event. 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 15 (Apr 11-17) * On day 103 (Apr 12), during the Ahead support with DSS-26, the transmitter tripped off-line at 104-0126z due to a coolant flow alarm. The alarm was cleared and the pass remained downlink only for the last 34 minutes to prevent data loss. This anomaly resulted in the loss of 34 minutes of commanding and two-way tracking data. All SSR data were received. See DR# G117040 for more information. * On day 104 (Apr 13), during the DSS-26 support for Ahead, turbo decoder lock was lost briefly at 2257z. This anomaly resulted in the loss of 2 frames of SSR data. * On day 106 (Apr 15), during the DSS-25 support for Ahead, turbo decoder lock was lost briefly at 2329z. This anomaly resulted in the loss of 11 frames of SSR data. * On day 107 (Apr 16), during the DSS-63 support for Ahead, turbo decoder lock was lost intermittently beginning at 1140z through 1143z due to heavy rain at the Madrid complex. This anomaly resulted in the loss of 5597 frames of real-time and SSR data, which is equivalent to about 2 minutes worth of data for each of the instruments. See DR# M109299 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 107 degrees C and decreasing with the HGA angle at 9.8 degrees and increasing, with respect to the spacecraft-Sun line. * On day 103 (Apr 12), fine pointing on Ahead intermittently dropped out for a 15 hour period from 0315z through 1816z due to zero wheel speed avoidance. All four momentum wheels were close to zero momentum. The effects of this were particularly noticeable in the SECCHI COR1 data. * On day 107 (Apr 16), the Ahead observatory was used to phase calibrate the 2nd uplink array, using DSS-24, 25, and 26 for 1.9 hours, to support the array use for STEREO Behind battery recovery. A 12 dB gain in uplink AGC was observed in the spacecraft transponder data. No SSR playback was conducted as the phasing of transmitters would have caused periodic dropped frames. * On day 108 (Apr 17), the Ahead observatory was used again to phase calibrate the 3rd uplink array, using DSS-24, 25, and 26 for 1.9 hours, to support the array use for STEREO Behind carrier recovery. From 10 to 12 dB gain in uplink AGC was observed in the spacecraft transponder data. No SSR playback was conducted as the phasing of transmitters would have caused periodic dropped frames. * The average daily science data return for Ahead was 5.0 Gbits during this week. * On day 107 (Apr 16), the 2nd uplink array for STEREO Behind recovery was conducted using DSS-24, 25, and 26. The uplink array was phase calibrated using the Ahead observatory first for 1.9 hours then the arrayed stations were switched to point to the Behind observatory. The configuration consisted of with the three 34m stations at the Goldstone complex using the 80 kW and two 20 kW transmitters incorporating the frequency segmented acquisition sequence with the MOC sending commands for battery recovery. 324 commands covering 36 frequency segments were sent for battery state of charge recovery. * On day 108 (Apr 17), the 3rd uplink array for STEREO Behind recovery was conducted using DSS-24, 25, and 26. The uplink array was phase calibrated using the Ahead observatory first for 1.9 hours then the arrayed stations were switched to point to the Behind observatory. The configuration consisted of with the three 34m stations at the Goldstone complex using the 80 kW and two 20 kW transmitters incorporating the frequency segmented acquisition sequence with the MOC sending commands for transmitter carrier recovery. 640 commands covering 32 frequency segments were sent. The DSN 70m station, DSS-43, and the Allen Telescope Array observed concurrently, however, no downlink signal was detected. At approximately 2323z, the command production state remained in the "interrupted" state even though command modulation was enabled and should have been ready for commanding. The anomaly resulted in the loss of commanding for one frequency segment. See DR# G117052 for more information. * The next uplink array use for Behind is scheduled for May 13 and 14. Week 16 (Apr 18-24) * Heavy rain in Madrid this morning (Apr 19) resulted in the loss of most of the 4.3 hour station 65 pass for Ahead. The MOC plans to reposition the pointers during the subsequent station 25 pass from California to minimize data loss. * Ahead has 14 tracks during the week, and overall coverage is nominal. There are two tracks at 720 kbps, ten at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 13.5 degrees. There are no passes for Behind during the week. Week 17 (Apr 25-May 1) * The 87th momentum dump on Ahead is scheduled for Thursday, Apr 28, with ignition at 20:00 UT. This will be the 6th momentum dump without using the gyros. * Ahead has 12 tracks during the week, and overall coverage is nominal. There are three tracks at 720 kbps, one at 360 kbps, five at 240 kbps, and three at 160 kbps. * Behind starts the week at an SPE angle of 13.8 degrees. Recovery efforts for Behind are on Monday-Wednesday, Apr 25-27. The battery recovery tracks will be undertaken with the 80 kW transmitter on station 26. Week 18 (May 2-8) * There will be a return to service track with station 14 for 4 hrs at 720 kbps on Saturday, May 7. There will be no instrument commanding or SSR playback during this track. The use of 720 kbps is to test the nominal operating state. * Ahead has 10 track during the week, and overall coverage is nominal. There are two tracks at 720 kbps, two at 360 kbps, five at 240 kbps, and one at 160 kbps. * Behind starts the week at an SPE angle of 14.1 degrees. There are no tracks for Behind during the week. Week 19 (May 9-15) * Ahead has 12 tracks during the week, and overall coverage is nominal. There are three tracks at 720 kbps, two at 360 kbps, five at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 14.4 degrees. Phased uplink array passes for Behind recovery are scheduled for May 13 and 14. The first 1.9 hours each day will be with Ahead to calibrate the antenna phasing. There will be no instrument commanding or SSR playback during these calibration passes. These passes with Ahead show up in the DSN schedules, so the NOAA antenna partners will know when Ahead will or will not be in space weather broadcast mode. The subsequent pass durations for Behind will be 3.2 hours on May 13 for battery recovery, and 5.3 hours on May 14 for carrier recovery. The last 47 minutes will be below 27.5 degrees elevation, so there will need to be either a waiver, or a decrease in broadcast power from 80 to 40 kW. The Allen Telescope array will listen for any signal from Behind, along with DSN station 14. Week 20 (May 16-22) * Ahead has 13 tracks during the week, and overall coverage is nominal. There are two tracks at 720 kbps, two at 360 kbps, five at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 14.6 degrees. There are no tracks for Behind during the week. Week 21 (May 23-29) * 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 8:00 PM EDT on Friday, May 27. 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. * 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. * 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. * There are no passes for Behind during the week. Other * The MOC expressed gratitude to the DSN team for the uplink array tracks over the previous weekend. This is not yet an operational configuration for the DSN, and a lot of effort is required to make it happen. * The post solar conjunction STEREO Subsystem Assessment Review is scheduled for Wednesday, Jun 15, starting at 9 AM EDT. Telecon access will be available using the same dial-in information as for the regular Tuesday telecons. The MOC will send out slides one or two days before the review. Some expected topics of discussions will be the occasional losses of fine pointing, and the HGA feed temperature. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 16: M Apr 18 (109) T Apr 19 (110) W Apr 20 (111) T Apr 21 (112) F Apr 22 (113) S Apr 23 (114) S Apr 24 (115) ------------------------------------------------------------------------------- Scheduled activities for Week 17: M Apr 25 (116) T Apr 26 (117) W Apr 27 (118) T Apr 28 (119) Ahead: Momentum dump, 20:00 UT F Apr 29 (120) S Apr 30 (121) S May 01 (122) ------------------------------------------------------------------------------- Scheduled activities for Week 18: M May 02 (123) T May 03 (124) W May 04 (125) T May 05 (126) F May 06 (127) S May 07 (128) Ahead: Return-to-service track with station 14 S May 08 (129) ------------------------------------------------------------------------------- Scheduled activities for Week 19: M May 09 (130) T May 10 (131) W May 11 (132) T May 12 (133) F May 13 (134) Behind: Phased array recovery attempt S May 14 (135) Behind: Phased array recovery attempt S May 15 (136) ------------------------------------------------------------------------------- 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) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2016: * Jun 15 STEREO Subsystem 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