ACE Weekly 02/13/2013 - 02/19/2013

All ACE spacecraft subsystems are performing as expected.

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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.

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OCRs:

None

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Activities:

Data Capture:  100%  DOY 041-049 2013


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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.

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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.