[Isocops] Quaternions post pointing burn

Mark Tapley mtapley at swri.edu
Mon Jun 28 15:05:11 EDT 2010


All,
	Chelle asked me to look at the pointings subsequent to 
delivery of the quaternion resulting from the sun-pointing burn.

	From the Goat Herder orbit 82 which Tim emailed:

Q1	-0.15279000	ActNor.EstInrToBdy[0]
Q2	-0.52037700	ActNor.EstInrToBdy[1]
Q3	-0.78616500	ActNor.EstInrToBdy[2]
Q4	0.29632300	ActNor.EstInrToBdy[3]

	Checking how close the maneuver was to pointing at the sun:

[tapley at ena ~]$ ibex_rotate -o -z 
-0.15279000,-0.52037700,-0.78616500,0.29632300, -w ibex-sun -t 
2010-06-27T10:55:12.782Z
Quaternion    -0.152790,-0.520377,-0.786165,+0.296323
  points axis  +0.000000,+0.000000,+1.000000
  towards ECI  -0.068163,+0.908755,+0.411726
  which is     R.A.  +94.290 Decl. +24.313
  missing      R.A.  +96.080 Decl. +23.340 (ibex-sun)
  error is     R.A.   +1.791 Decl.  +0.974
  for a total  1.906 deg

	this agrees with the Goat herder, which says 1.901 degrees. 
Hmmm, not very close.
	If we look at the situation at the time of descending macros, 
taking that time from the STF (looking at the last of the commands),


[tapley at ena ~]$ ibex_rotate -o -z 
-0.15279000,-0.52037700,-0.78616500,0.29632300, -w ibex-sun -t 
2010-07-03T15:10:51.000Z
Quaternion    -0.152790,-0.520377,-0.786165,+0.296323
  points axis  +0.000000,+0.000000,+1.000000
  towards ECI  -0.068163,+0.908755,+0.411726
  which is     R.A.  +94.290 Decl. +24.313
  missing      R.A. +102.498 Decl. +22.926 (ibex-sun)
  error is     R.A.   +8.209 Decl.  +1.387
  for a total  7.647 deg

7.647 degrees should still be OK, though close. I would say let it 
ride, unless -Hi or -Lo teams are not happy with that big an angle.

-- 
						- Mark     210-379-4635
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