[DSC-Weekly] Dawn DSC tagup: Meeting Thursday, July 17 at 0800 PDT (1700 CEST) MeetingId=0000

Tue Jul 22 17:34:27 PDT 2014

Pablo,

We had expected Jupiter to still be a suitable target based on your previous email pasted below. Also, there is no requirement for spectral calibration of Ceres prior to OpNav 1 so that is not a factor in target selection.

The reason Jupiter had been suggested as an alternative for Ceres during the DSC Tag-up was because observing Ceres requires us to thrust in a direction that is more damaging to the interplanetary cruise trajectory than thrusting in the direction needed to observe Jupiter. Using Jupiter as a target removes one 180 deg turn from the IPS calibration which saves hydrazine, and it also shortens the entire IPS calibration because the portion at Ceres pointing had to be extended to mitigate the impact to NAV of not pointing in the optimal direction for the FT2 calibration. There is also a significant decrease in the degradation of the IPS calibration to use Jupiter as a target rather than Ceres. The off-nominal direction for NAV is only 3.5 deg so they were willing to execute the entire FT2 calibration at the Ceres attitude thus eliminating the tight 8-hour pointing constraint from the activity. We could arrive at Ceres possibly two days earlier using Jupiter as a target.

Is Jupiter really an unacceptable target or just less preferable? We need to have a final decision on the target selection before next Tuesday. NAV has been folding the impact of the IPS calibration into their cruise trajectory design for the last two months in order to mitigate the impact of the thrust perturbations from this activity. We are kicking off the dc075 sequence next Wednesday and NAV needs to anticipate what the thrusting in dc077 will be in order to optimize the dc075 trajectory for Ceres. While we had accepted the cost of designing the activity to use Ceres as a target prior to realizing the Jupiter option, everyone has been working very hard on the flight team side to minimize the hydrazine cost of this and all other cruise activities.

Best regards,
Carol

From: <Gutierrez-Marques>, Pablo <gutierrez at mps.mpg.de<mailto:gutierrez at mps.mpg.de>>
Date: Wednesday, June 5, 2013 4:53 AM
To: Carol A Polanskey <Carol.A.Polanskey at jpl.nasa.gov<mailto:Carol.A.Polanskey at jpl.nasa.gov>>, "Raymond, Carol A (3220)" <carol.a.raymond at jpl.nasa.gov<mailto:carol.a.raymond at jpl.nasa.gov>>, "Rayman, Dr. Marc D (3100)" <marc.d.rayman at jpl.nasa.gov<mailto:marc.d.rayman at jpl.nasa.gov>>, Steven Joy <sjoy at igpp.ucla.edu<mailto:sjoy at igpp.ucla.edu>>
Cc: "Nathues Dr., Andreas" <nathues at mps.mpg.de<mailto:nathues at mps.mpg.de>>, "Ripken Dr., Joachim" <ripken at mps.mpg.de<mailto:ripken at mps.mpg.de>>, "Hall, Ian" <hall at mps.mpg.de<mailto:hall at mps.mpg.de>>
Subject: Dawn dates for stray light investigation

Dear all,

Andreas reported on the discussion of when and how an observation of a quasi-extended source would be possible for the purpose of characterizing the stray light patterns on FC, and asked me to investigate when the geometric conditions could be fulfilled.

The result is that Jupiter will be usable as a stray light source all the way to Ceres, whereas Ceres itself would be usable (from the considerations of size) between beginning of May 2014 at a distance of 1e7 km and end of September 2014 at a distance of 2e6 km. According to our calculations at this point the apparent diameter of Ceres would exceed five (5) pixels and would become too big to be used as a stray light source.

Concerning the number of pointing stations, we already mentioned last time this activity was de-scoped due to the complexity that a single pointing for 3-4 hours would already be better than nothing, but the goal would be to have three different pointings to determine the variation of the stray light patters with the position of the lit pixel.

Please let us know if there is a window where this activity could be conducted.

Regards,
Pablo

From: <Gutierrez-Marques>, Pablo <gutierrez at mps.mpg.de<mailto:gutierrez at mps.mpg.de>>
Reply-To: "dscweekly at igpp.ucla.edu<mailto:dscweekly at igpp.ucla.edu>" <dscweekly at igpp.ucla.edu<mailto:dscweekly at igpp.ucla.edu>>
Date: Friday, July 18, 2014 1:29 AM
To: "dscweekly at igpp.ucla.edu<mailto:dscweekly at igpp.ucla.edu>" <dscweekly at igpp.ucla.edu<mailto:dscweekly at igpp.ucla.edu>>, "Ripken Dr., Joachim" <ripken at mps.mpg.de<mailto:ripken at mps.mpg.de>>, "Hall, Ian" <hall at mps.mpg.de<mailto:hall at mps.mpg.de>>, "yamashita at psi.edu<mailto:yamashita at psi.edu>" <yamashita at psi.edu<mailto:yamashita at psi.edu>>, "Hall, Andrew S (397J)" <Andrew.S.Hall at jpl.nasa.gov<mailto:Andrew.S.Hall at jpl.nasa.gov>>
Subject: Re: [DSC-Weekly] Dawn DSC tagup: Meeting Thursday, July 17 at 0800 PDT (1700 CEST) MeetingId=0000

Hi Carol,

Joachim mentioned from yesterday’s teleconference the possibility to perform the stray light calibration with Jupiter instead of Ceres as currently planned.

We have considered the case and found that the circumstances are not so promising. As of today, Jupiter has an apparent diameter of 1.5 pixels, which is slightly below the spec, and it is getting worse with time. Additionally, Ceres has, in comparison with Jupiter, the advantage of allowing spectral calibration.

All in all the team believes that Jupiter is not a suitable alternative to Ceres for the stray light calibration.

Kind regards,
Pablo

From: dscweekly-bounces at igpp.ucla.edu<mailto:dscweekly-bounces at igpp.ucla.edu> [mailto:dscweekly-bounces at igpp.ucla.edu] On Behalf Of Polanskey, Carol A (394E)
Sent: Thursday, July 17, 2014 4:47 PM
To: dscweekly at igpp.ucla.edu<mailto:dscweekly at igpp.ucla.edu>; Ripken Dr., Joachim; Hall, Ian; yamashita at psi.edu<mailto:yamashita at psi.edu>; Hall, Andrew S (397J)
Subject: [DSC-Weekly] Dawn DSC tagup: Meeting Thursday, July 17 at 0800 PDT (1700 CEST) MeetingId=0000

Note that Marc, Keri and Drew will probably not be dialing in because of the ORT (Operations Readiness Test).

Agenda

  *   Short questions from instrument teams that would not otherwise be covered
  *   ORT report –  C. Polanskey
  *   dc074/dc075 status – K. Bean/C. Polanskey
  *   dc077 status – C. Polanskey/S. Joy
  *   RC3 ISB update status – S. Joy
  *   LAMO ISB  – X. Liu
Sequence Development Milestones:
07/09/14 LAMO ISB MPST Pass 1 products released (da801, 900, 901)
07/18/14 dc074 command conference
07/24/14 LAMO ISB MPST Pass 1 products released (da902, 903)
07/??/14 LAMO ISB MPST Pass 1 Review meeting
07/30/14 dc075 MPST Kick-off
08/01/14 dc075 MPST Pass 1 inputs due
08/05/14 dc075 MPST Pass 1 review meeting
08/15/14 dc075 MPST Pass 2 review meeting
08/21/14 Ceres Risk Review
09/03/14 dc077 Pre-Build Kick-off
09/05/14 dc077 Pre-Build SciTOL due
09/10/14 dc077 Pre-Build instrument inputs due
09/10/14 dc077 Tabletop meeting
09/12/14 dc077 Pre-Build review package #1
09/17/14 dc077 Pre-Build instrument inputs update
09/19/14 dc077 Pre-Build review package #2
09/23/14 dc077 Pre-Build checklists due
09/24/14 dc077 Walkthrough meeting
09/24/14 dc077 MPST Kick-off
09/26/14 dc077 MPST Pass 1 inputs due
09/30/14 dc077 MPST Pass 1 products released
10/01/14 dc077 MPST Pass 1 review package
10/06/14 dc077 MPST Pass 1 review meeting
10/10/14 dc077 MPST Pass 2 review meeting
10/13/14 dc077 uplink of products
10/14-17/14 Science Team Meeting
Get ready for Ceres

Next instrument activity:
07/21/2014 dc073 HGA pass GRaND playback (power off occurs earlier during thrusting)
08/18/2014 dc074 HGA pass FC2 Checkout & FC1 FSW
09/15 /2014 dc075 HGA pass FC1 Checkout playback
10/27-31/2014 dc077 Straylight Calibrations, GRaND

Procedure for telecon participation
--------------------------------------------------------
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-OR-
-- From JPL telephones, dial 4-3434
-- From local, off-Lab telephones, dial (818) 354-3434
-- From long distance (USA), use the following procedure:
     1. Dial (800) 367-5754
     2. Upon hearing the tones, press 5-7-5 (the numbers for J-P-L)
     3. At the second dial tone, press 4-3434 When prompted, dial the
        meeting code: 0000
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