ACE Weekly 11/14/2012 - 11/20/2012 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude SK-63 Date 11/19/2012 11/19/2012 DOY 324 2012 324 2012 Thrusters 2R 4R+ 4R- 1A 2A Duration 9:58 min 56.016 sec Start 15:54:49z 17:15:35z Stop 16:04:47z 17:16:31z HGAStart -8.46deg +9.08deg HGAStop +9.08deg +9.28deg SunStart 9.16deg 15.22deg SunStop 15.22deg 15.39deg SpinStart 5.0856rpm 5.0881rpm SpinStop 5.0881rpm 5.0704rpm Nutation 0.15deg 0.23deg Firing 51 pulses Continuous FuelUsed 0.1609lbs 0.1952lbs FuelRemain 118.0996lbs 117.9044lbs FinalSCMass 1352.359lbs 1352.164lbs The next attitude maneuver is scheduled for Tuesday 11/27/2012. ======================================================================== OCRs: DOY 320 (11/15/2012) 2053-2058z SIS-049 5 cmds Disabled noisy M1B HV strips # 18 & 30 and raise their threshold. As the instrument is warmer (Oct-Mar near perihelion), some strips have increased leakage current and noisy data. There are a total of 512 strips in the two SIS telescopes. So far 40 strips have been disabled since launch and 2 VLSI readout channels were not working at launch. M1B detector now has maximum number of strips that can be disabled and the threshold on all M1B strips has been raised. ======================================================================== Activities: Data Capture: 100% DOY 316-323 2012 We have had limited DSN antenna time this past week. Viewperiods from several missions are beginning to overlap. A new moon meant that the GRAIL viewperiod overlapped with L1. And winter months give reduced views for Northern Hemisphere antennas (Goldstone & Madrid). When we are behind in the playback, we don't worry about redumping every small gap. On DOY 322, there were 2 gaps resulting in 4 seconds of missing data. But by coincidence, we were in a pass for the corresponding time and have real-time science data to cover the playback gaps. Therefore we continue our current streak of 5+ months of perfect data capture (since 5/9/2012). The WS1 certification test on 11/20/2012 was successful. No DSN time was available for this day, the data was successfully converted and sent to ASC for level-zero processing. We have found a solution to the NOAA processing of SIS data. By holding onto the telemetry for a few seconds before sending it, NOAA successfully processed the SIS data. WS1 is delivering the data to the MMOC much faster than DSN. On a somewhat related note, there may be some issues between data forwarding and the mmoc_fanout that should be investigated. ======================================================================== Anomalies: DOY 320 11/13/2012 S-ACE-0655 G12-0016 IN_TASK set after SIS OCR The ITOS system is configured with an IN_TASK variable so that other tasks know if they can start. After the SIS commanding, a known ITOS issue contributed to the IN_TASK variable to be set to one. (The ITOS issue is that critical commands cause ITOS to "go" through wait statements in halted procs.) The only commanding left was end-of-pass state of health checks and recorder redumps. These were performed on the following pass. IMPACT: Manual intervention to clean up proc after pass. No data loss. ======================================================================== Average Sun Angles With Weekly Attitude Maneuvers Dates Avg SEV Avg Sun Sun-SEV (indicates extra s/c tilt) ----------- ------- ------- ---------------------------------- 10/18-10/23 5.1deg 11.0deg 5.9deg 10/23-10/28 3.3deg 9.3deg 6.0deg 10/28-11/06 2.0deg 7.3deg 5.3deg 11/06-11/13 3.8deg 8.4deg 4.6deg 11/13-11/20 6.3deg 10.3deg 4.0deg ACE is moving away from the sun-earth line (larger sun-earth-vehicle angle, SEV) which allows for larger sun angles over the next 5 weeks. After mid-December, the L1 orbit will bring ACE back towards the sun-earth line (smaller SEV angles). The following is background information that will be included in each weekly report. The project has accepted the SWEPAM team proposal to keep the spacecraft at larger sun angles with weekly attitude maneuvers. The SWEPAM-Ion instrument has a series of channel electron multipliers (CEMs) and larger sun angles allows more responsive CEMs to measure the solar wind. The maximum sun angle follows the Sun-Earth-Vehicle angle (SEV). The SEV angle is determined by the size/shape of the orbit around L1. When the spacecraft antenna is pointed directly towards earth, the spacecraft's sun angle will be equal to the Sun-Earth-Vehicle angle. With weekly maneuvers, the sun angle can be kept ~6deg more than the SEV angle. This results in the spacecraft antenna aspect angle being kept between 5 and 9 degrees and never pointing directly back at earth. For reference, the SWEPAM team prefers sun angles above 13 degrees. With the current size of the L1 orbit, the sun angle will be above 13 degrees for ~45% of the time.