ACE Weekly 01/30/2013 - 02/05/2013 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude Date 02/05/2013 DOY 036 2013 Thrusters 2R 4R+ 4R- Duration 5:15 min Start 18:07:07z Stop 18:12:28z HGAStart -8.74deg HGAStop +8.89deg SunStart 9.77deg SunStop 7.70deg SpinStart 5.0744rpm SpinStop 5.0756rpm Nutation 0.06deg Firing 27 pulses FuelUsed 0.0907lbm FuelRemain 116.5488lbm FinalSCMass 1350.809lbm The next attitude maneuver is scheduled for Tuesday 02/12/2013. ======================================================================== OCRs: None ======================================================================== Activities: Data Capture: 100% DOY 020-027 2013 The WS1 antenna (18-meter; part of the Near Earth Network) was used for the pass on Wednesday 1/30 and on Friday 2/1. These are the 3rd and 4th operational passes with WS1. ACE will use WS1 whenever DSN time is limited and WS1 time is available. The LRO mission is the prime user of WS1. We expect to use WS1 a couple of times each month. With the spacecraft antenna angle pushed to 8-9 degrees, the WS1 EbN0 has been between 2 and 2.5dB. During the Wednesday pass, the EbN0 dropped to ~1.3dB for ~10 minutes and a little bit of data was missed (<1%). The data was captured through redumps, but this provides a small indication of where WS1 might not be able to process ACE high-rate data. ======================================================================== 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 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.