ACE Weekly 02/13/2013 - 02/19/2013 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude Date 02/19/2013 DOY 050 2013 Thrusters 2R 4R+ 4R- Duration 5:31 min Start 17:23:11z Stop 17:28:42z HGAStart -8.40deg HGAStop +8.91deg SunStart 14.54deg SunStop 12.29deg SpinStart 5.0807rpm SpinStop 5.0822rpm Nutation 0.18deg Firing 28 pulses FuelUsed 0.0936lbm FuelRemain 116.1388lbm FinalSCMass 1350.399lbm The next attitude maneuver is scheduled for Tuesday 02/26/2013. ======================================================================== OCRs: None ======================================================================== Activities: Data Capture: 100% DOY 041-049 2013 ======================================================================== Anomalies: None ACE crossed the ecliptic plane on 2/6/2013. When ACE is on the ecliptic plane, it is more difficult to maintain larger sun angles. The sun angle will be increasing over the next month as ACE moves away from the ecliptic plane and towards the bottom corner of the L1 Lissajous orbit. ======================================================================== 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 12/11-12/18 16.8deg 11.3deg 5.5deg 12/18-12/27 16.5deg 10.7deg 5.8deg 12/27-01/03 16.0deg 9.1deg 6.9deg 01/03-01/08 15.2deg 7.2deg 8.0deg 01/08-01/15 13.8deg 6.0deg 7.8deg 01/15-01/22 12.3deg 4.0deg 8.3deg 01/22-01/29 10.6deg 2.4deg 8.2deg 01/29-02/05 9.1deg 3.2deg 5.9deg 02/05-02/12 8.4deg 5.1deg 3.3deg 02/12-02/19 12.2deg 7.0deg 5.0deg 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 4-8deg 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.