[Comm2011] Fwd: PPRS-049927-Updated-VST-OMEGACAM-Possible drift of IA donuts during IA loop - centering algoriithm robust?-Science Operations
Konrad Kuijken
kuijken at strw.leidenuniv.nl
Sat Sep 7 23:25:07 CEST 2013
Begin forwarded message:
> From: Paranal_AREmail <esoarspl at eso.org>
> Subject: PPRS-049927-Updated-VST-OMEGACAM-Possible drift of IA donuts during IA loop - centering algoriithm robust?-Science Operations
> Date: September 7, 2013 23:24:44 GMT+02:00
> To: kuijken at strw.leidenuniv.nl
> Reply-To: Paranal_AREmail <esoarspl at eso.org>
>
> Problem number PPRS-049927 in the Paranal PRS has now been updated.
> The new details of the ticket are listed below.
> This is for your information only.
>
>
> Problem Number : PPRS-049927
>
> Creation Date : 2013-03-23 18:31:07 by Steffen Mieske (vst at eso.org)
> Type : Problem
> Keywords : Possible drift of IA donuts during IA loop - centering algoriithm robust?
> Priority : Necessary
> Deadline :
> Status : Assigned
>
> ----- Minor Change Section ---------------------
>
> -------------------------------------------------
>
> Location : VST
> Area/Instrument Type : INSTRUMENTS
> System/Instrument : OMEGACAM
> Sub-system : SOFTWARE
>
> Assigned to Group : Science Operations
> Assigned to Person : smieske
> CC List :
> kuijken at strw.leidenuniv.nl
> tszeifer at eso.org
> smieske at eso.orgVst_Omega_Notification
> uweilenm at eso.org
> msterzik at eso.org
> vst at eso.org
> par-vst at eso.org
> acarlier at eso.org
> akaufer at eso.org
> par-tios at eso.org
> Vst_all
> tios-omega at eso.org
> pietro.schipani at oacn.inaf.it
> tios-vst at eso.org
>
> Telescope Downtime : 00:00
> Workload (hrs.) : 2
> Detailed Description :
> Dear Ricardo,
>
> could you verify please how the (re-)centering algorithm of the boxes of the IA CCD works? We have seen a few times either a jump of the donut from the center a bit towards the outskirts of the box, or a slow drift. The drift was apparently happending during guiding, but it is not 100% clear. [it was an observation from Konrad Kuijken who did the photo I sent you, but he did not 100% clearly remember whether it was during science or during aquisition]
>
> As a first step it would be good to verify at which places in the SW the OS actually changes the box position of the IA star, for a recentering. I was up to now only aware of a recentering that happens after the very first box readout in the aquisition. At least this is where one typically sees a recentering: the pick object in aquisition may have been a bit inaccurate and thus the first box readout is used to re-center correctly the box.
>
> In other places of the IA sequences, my interpretation of a motion of the IA donut would have been that the telescope is actually moving. Now we got a bit suspicious whether there is a continuous recentering of the box running that may not be robust.
>
> Thanks for your help in this first step of analysis,
> Steffen
>
> PS: I include Konrad in CC who found the occurences.
>
> ----- Worklog & Comments Section ---------------
>
> Worklog and Comments :
> 2013-07-18 23:45:02 rschmutz
> The IA star centers are obtained with the CENTROI command.
> This command is only executed by the acquisition template, during the IA acquisition step.
>
> The IA box positions are also updated:
>
> 1) In the acquisition template, during the IA acquisition step, after the user made a manual selection
> of the IA stars (the manual selection is done after the CENTROI command).
>
> 2) Between exposures, when the IA stars are manually re-selected.
>
> 3) During offsets (with the OFFSAD command sent to ociaServer):
> Note that the offset is specified in RA,Dec coordinates, which have to be converted into
> detector coordinates according to the current telescope position and pixel scale, to so
> compute the offset in pixels (in x,y coordinates).
> If this conversion is not 100% correct, then you could evtl. see a shift of position of the
> IA stars within the box.
> The accuracy of this conversation could evtl. be verified on-sky performing offsets always
> in the same direction. While doing this, the IA star should stay on the center of the box.
> 2013-08-16 21:20:06 rschmutz
> Ticket assigned back to the OmegaCAM IS.
> Assignee changed: smieske
> Assigned to Group Changed: Science Operations
> Modified By: rschmutz
> Modified Date: 2013-08-16 21:20:05
> Assignee changed: smieske
> Assigned to Group Changed: Science Operations
> Modified By: rschmutz
> Modified Date: 2013-08-16 21:20:05
> 2013-09-07 21:22:16 smieske
> I would like to do some tests of this in my next shift starting Sept. 30.
>
> Steffen
>
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