[Isocops] [Ibexhi] CAR : New P/L DESCENDING commands
Harald Kucharek
Harald.Kucharek at unh.edu
Mon Jun 28 21:39:20 EDT 2010
Hi Chelle,
Yes, please make sure we descend earlier. We cannot watch HK data live and
if so we cannot react when something unexpected happens. This margin is a
bit too small for my taste and we should not take any unnecessary risk.
Thanks for making that decision.
Best regards,
Harald
On 6/28/10 6:40 PM, "Reno, Michelle" <mreno at swri.edu> wrote:
> Hello All,
>
> Eberhard pointed out that the actual sun angle margin will be closer to 0.23
> when you take into account a 2-D sun. See below.
>
> Given this I would like to upload new DESCENDING commands and delete the ones
> onboard. Mark, please generate an STF that has us in HVSTANDBY by a predicted
> angle of 7.4 degrees. Attached is a partial CAR with the commands to be
> deleted and a spot for the ATS filename - Tim, please edit and redistribute.
>
> This orbit we will descend early. At an ISOC telecon we should discuss again
> (with feeling, as Nathan says) the reason for the prediction error prior to
> the burn and the actual off sun pointing planning limit.
>
> Thanks,
> Chelle
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Chelle Reno
> Austin Mission Consulting
> 106 E. 6th St. Ste. 939 Austin, TX 78701 (512) 704-3394 (o) (210) 478-7337
> (c)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> From: Eberhard Moebius [mailto:eberhard.moebius at unh.edu]
> Sent: Mon 6/28/2010 4:45 PM
> To: Reno, Michelle
> Cc: Eberhard Moebius
> Subject: Re: [Ibexlo] Quaternions post pointing burn
>
> Hi Chelle:
>
> The maximum angle is 8.12o. Please see the figure attached, which I produced
> at the time of the design. We raised the height of the cover over a certain
> angular range on the Sunward side so that the angle is guaranteed even if the
> spin axis is off in ecliptic latitude.
> However, it just occurs to me that the actual safe range for partial
> illumination by the Sun is only 7.87o (8.12 - 0.25) adjusted for the size of
> the Sun's disk in the sky of 0.5 degrees. That is why we went with 8 degrees +
> in the first place. SO, we are a little closer than I said, 0.23 degrees to
> the limb of partial illumination!
>
> As long as we stay away from that we are safe, but we shouldn't get closer.
> There is no additional margin beyond that, except that a little partial
> illumination will probably not immediately lead to a big jump in something,
> but we never tried that!!
>
> We should definitely take a look whether anything is changing in the sensor HK
> data when we approach this extreme angle. What has been the maximum that we
> actually went to up to now?
>
> With best regards
> 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
>
>
>
> From: Reno, Michelle
> Sent: Mon 6/28/2010 4:06 PM
> To: Mark Tapley; isocops at lists.sr.unh.edu; ibexhi at lists.sr.unh.edu;
> ibexlo at lists.sr.unh.edu
> Cc: michelle.reno at swri.org
> Subject: RE: Quaternions post pointing burn
>
> 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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----------------------------
Harald Kucharek
University of New Hampshire
Space Science Center
Morse Hall
39 College Road
Durham, NH 0324
USA
Phone: +1 603 862 2948
FAX : +1 603 862 0311
----------------------------
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