Subject: Re: 3.5-m Users Committee minutes 3/19/07

From: Stephane Beland

Submitted: Tue, 20 Mar 2007 15:49:25 -0400

Message number: 1021 (previous: 1020, next: 1022 up: Index)

Everybody,

I would like to clarify a couple of points from Bruce's minutes from  
the Users Committee meeting.

> Colorado (Bally) - John talked about the recent fast sub-frame  
> observing mode for NIC-FPS, which was implemented to support the  
> Pluto occultation.  One glitch discovered is that if you ask for  
> full-frame exposures with Fowler sampling set to a large number,  
> the instrument control computer crashes.  ...

The problem showed up when clicking on the "Abort" button in the  
NICFPS Expose window in the TUI while doing a large set of NFS  
exposures.
Doing a large number of NFS full-frame exposures works fine (as long  
as you don't abort).  I'll look into this a will let everybody know  
when a fix is in place.


>
> New plans for NIC-FPS - Bally:
> ...
>   o The science-grade chip will most likely be sent to Rockwell to  
> connect some leads that will enable reading all 16 channels of the  
> array.  This will reduce the read noise by allowing much faster  
> multiple-read Fowler sampling, which we can't do now with the  
> single-channel readout.  Also, the video cards in the Leach  
> controller will be replaced to handle the extra channels.  There is  
> some risk in having Rockwell work on the chip, but it is considered  
> to be minimal, and the engineering-grade chip is a suitable backup  
> if something bad happens to the science-grade chip.
> ...

Saying that the engineering grade chip is "a suitable backup" is a  
long stretch.  We have NO characterization data on this chip: we  
don't know what the QE is, the read noise, dark current, well depth,  
etc.  There is a small but obvious cosmetic defect in the middle of  
the chip that we know doesn't flatten out.  This is an engineering  
chip for a reason. I still believe the risk in adding the wires to be  
small since this is a process that Rockwell does on every chip they  
produce.


Stéphane Béland
Senior Professional Research Assistant
University of Colorado at Boulder
Center for Astrophysics and Space Astronomy
(303)-492-3657
sbeland@colorado.edu



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