[Isocops] Hawaii 21 March 1710

Mark Tapley mtapley at swri.edu
Mon Mar 21 14:59:02 EDT 2011


All,
	hm. Well, if the sun-acq maneuver had 
worked perfectly, it would have ended 
2011/03:20:23:03:00 pointing us directly at the 
sun.

[tapley at ena ~]$ ibex_rotate -o -u 1,0,0 -w ibex-sun -t 2011/03:20:23:03:00
Quaternion    +0.000000,+0.000000,+0.000000,+0.000000
  points axis  +1.000000,+0.000000,+0.000000
  towards ECI  +1.000000,+0.000000,+0.000000
  which is     R.A.   +0.000 Decl.  +0.000
  missing      R.A. +359.870 Decl.  -0.045 (ibex-sun)
  error is     R.A. +359.870 Decl.  +0.045
  for a total  0.137 deg

	At the time of the just completed pass, 
that pointing (R.A. +359.870 Decl.  -0.045 
(ibex-sun)) would aim us 0.865 degrees off the 
sun:

[tapley at ena ~]$ ibex_rotate -o -r +359.870 -d 
-0.045 -w ibex-sun -t 2011/03:21:19:22:00
Quaternion    +0.000000,+0.000000,+0.000000,+0.000000
  points axis  +1.000000,+0.000000,+0.000000
  towards ECI  +0.999997,-0.002269,-0.000785
  which is     R.A. +359.870 Decl.  -0.045
  missing      R.A.   +0.666 Decl.  +0.292 (ibex-sun)
  error is     R.A. +359.204 Decl.  +0.337
  for a total  0.865 deg

	Even allowing a 1 degree deadband, we 
should be 1.865 deg. off the sun now. The 
telemetry Tim sent looks like we are now 2.34 
degrees off the sun. Clearly the maneuver 
completed, but it looks like the deadband may 
have been closer to 1.48 degrees. That's bigger 
than we planned; I'll be very interested to see 
what the AST says about our spin axis when it 
comes back on-line.

	Descending is complete at 
2011/03:27:02:37:18; at that point, our sun angle 
would be 6.081 deg if the sun-acq were perfect.

[tapley at ena ~]$ ibex_rotate -o -r +359.870 -d 
-0.045 -w ibex-sun -t 2011/03:27:02:37:18
Quaternion    +0.000000,+0.000000,+0.000000,+0.000000
  points axis  +1.000000,+0.000000,+0.000000
  towards ECI  +0.999997,-0.002269,-0.000785
  which is     R.A. +359.870 Decl.  -0.045
  missing      R.A.   +5.468 Decl.  +2.335 (ibex-sun)
  error is     R.A. +354.402 Decl.  +2.380
  for a total  6.081 deg

	Add a 1-degree deadband, and we are OK 
(7.081 deg). Add a 1.48 deg deadband, and we are 
at 7.56 degrees, which is greater than the 7.25 
we have been looking at for a limit (but less 
than the angle at which housekeeping telemetry 
starts showing adverse effects, as in Orbit 114).
	Three-dimensional effects have not been 
considered in this, so I would not panic yet.


At 14:27 -0400 3/21/11, Tim Perry wrote:
>All,
>    The Hawaii support was failed due to a poor signal quality.  The Eb/No
>ranged from 1 to 17 db. Spacecraft looked nominal and the maneuver was
>successful.
>Eb/No: @ 1710  2k    3 to 14 db
>                @ 1715  2k    1 to 17 db
>                @  1732 2k    1 to 12 db
>USN PR 10,000
>Razor Issue I100-450   Intermittent data Hawaii 21 Mar 11 1710
>
>
>
>(Embedded image moved to file: pic05436.gif)
>
>Timothy E. Perry
>IBEX, GEMS Mission Ops Lead
>Orbital Sciences Corp
>Space Systems Group
>Office: (703) 406-5976
>Cell: (301) 606-1430
>perry.tim at orbital.com
>
>
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-- 
						- Mark     210-379-4635
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