ACE Weekly 02/20/2013 - 02/26/2013 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude Date 02/26/2013 DOY 057 2013 Thrusters 2R 4R+ 4R- Duration 6:17 min Start 15:40:47z Stop 15:47:04z HGAStart -8.61deg HGAStop +8.95deg SunStart 16.61deg SunStop 13.57deg SpinStart 5.0820rpm SpinStop 5.0834rpm Nutation 0.19deg Firing 32 pulses FuelUsed 0.1056lbm FuelRemain 116.0332lbm FinalSCMass 1350.293lbm The next attitude maneuver is scheduled for Tuesday 03/05/2013. ======================================================================== OCRs: None ======================================================================== Activities: Data Capture: 100% DOY 048-055 2013 The 5th operational pass (since 11/01/2012) with WS1 was on Thursday 02/21/2013 (DOY 052). The pass had been shortened by 1 hour after a request from Themis. No issues with the pass. DSN antenna time has been becoming more available. * GRAIL mission ended in December. * Northern hemisphere views (Goldstone & Madrid) are growing longer. But there are still remaining DSN contention issues. * Continue overlapping views with other missions (Mars,Messenger,Stereo) Voyager 1&2 views are no longer overlapping however. * DSN DSS-43 and DSS-54 are still down for repairs ======================================================================== 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 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 02/19-02/26 14.3deg 8.8deg 5.5deg 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.