ACE Weekly 02/20/2013 - 02/26/2013

All ACE spacecraft subsystems are performing as expected.

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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.

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OCRs:

None

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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


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Anomalies:

None


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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
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.