ACE Weekly 12/05/2012 - 12/11/2012 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude Date 12/11/2012 DOY 346 2012 Thrusters 2R 4R+ 4R- Duration 7:39 min Start 22:31:25z Stop 22:39:04z HGAStart -8.78deg HGAStop +8.95deg SunStart 14.04deg SunStop 18.80deg SpinStart 5.0738rpm SpinStop 5.0756rpm Nutation 0.09deg Firing 39 pulses FuelUsed 0.1265lbs FuelRemain 117.4928lbs FinalSCMass 1351.753lbs The next attitude maneuver is scheduled for Tuesday 12/18/2012. ======================================================================== OCRs: None ======================================================================== Activities: Data Capture: 100% DOY 337-344 2012 ACE had an operational pass with WS1 on Friday 12/7/2012 (DOY 342). There was a data flow issue with mmoc_fanout in the first ~10 minutes of the pass. The problem was resolved by restarting ACE data forwarding and didn't recur. Time will be needed to resolve the issue. Antenna time with WS1 was requested for Wednesday 12/19/2012. There are 4 hours from the beginning of the ACE view to the beginning of the LRO passes, but a 45 minute Themis D pass sits in the middle of that time. We'll keep the shortened 2.5 hour pass with DSS-27 and catch up on the science playback a few days later. As reported last week, we are currently in a period of limited antenna time (12/9-12/14 and 12/17-12/20). Playback will fall behind by 30-60 minutes (5-10 hours of science data). No data loss is expected. The reasons for limited antenna time are: * GRAIL viewperiod at DSN overlaps ACE (new moon) * LRO viewperiod at WS1 overlaps ACE (new moon) * DSN DSS-54 antenna down for repairs * Short northern hemisphere views (Goldstone & Madrid) during winter * Mission views overlapping in December and January (Mars,Voyager,etc) ======================================================================== Anomalies: None ======================================================================== Average Sun Angles With Weekly Attitude Maneuvers Dates Avg Sun Avg SEV Sun-SEV (indicates extra s/c tilt) ----------- ------- ------- ---------------------------------- 10/18-10/23 11.0deg 5.1deg 5.9deg 10/23-10/28 9.3deg 3.3deg 6.0deg 10/28-11/06 7.3deg 2.0deg 5.3deg 11/06-11/13 8.4deg 3.8deg 4.6deg 11/13-11/20 10.3deg 6.3deg 4.0deg 11/20-11/27 12.7deg 8.6deg 4.1deg 11/27-12/04 14.9deg 10.1deg 4.8deg 12/04-12/11 16.0deg 10.9deg 5.1deg 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 average sun angle can be kept 4-6deg 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.