[Isocops] [Ibexlo] Quaternions post pointing burn

[Eberhard Moebius]

Hi Chelle:

I don't see any problems with that. It is still more than 0.5 degree away from the Sunshield design limit.

Eberhard

Eberhard Möbius
Space Science Center and Department of Physics
Department Chair
University of New Hampshire
Morse Hall, 8 College Road
Durham, NH 03824

Phone: 1 603 862 3097
Fax: 1 603 862 0311

On Jun 28, 2010, at 5:06 PM, Reno, Michelle wrote:

> Thanks Mark. I agree we should leave the current DESCENDING times; 7.64 degrees off sun pointing is higher than desired (7.5 degree planning limit) but less than the actual max limit of 8.0 degrees.
>  
> Hi or Lo, please speak up by noon 6/29 if you are uncomfortable with this. The only planned opportunity to change these is the apogee contact early on 6/30.
>  
> Chelle
>  
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Chelle Reno
> Austin Mission Consulting
> 106 E. 6th St. Ste. 939
> Austin, TX  78701
> (512) 704-3394 (o)
> (210) 478-7337 (c)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> From: Mark Tapley [mailto:mtapley at swri.edu]
> Sent: Mon 6/28/2010 2:05 PM
> To: isocops at lists.sr.unh.edu
> Cc: michelle.reno at swri.org
> Subject: Quaternions post pointing burn
> 
> 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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