Subject: 04/15/02 APO 3.5m user's committee meeting minutes

From: strauss@astro.Princeton.EDU

Submitted: Wed, 17 Apr 2002 15:50:04 -0400 (EDT)

Message number: 567 (previous: 566, next: 568 up: Index)

  Apache Point Observatory 3.5m User's Committee Meeting
		April 15, 2002

Attending: Bruce Gillespie, Ed Turner, Michael Strauss, Lew Hobbs, Jon
Holtzman, Rene Walterbos, Chris Stubbs, Alan Uomoto, Bruce Balick,
Jon Morse

        o DIS upgrade status and plans
        o NIC-FPS PDR report
        o Summer shutdown plan
        o Other CIF projects status
        o WIYN 1-degree imager workshop

*************** DIS upgrade status and plans ***************

The new DIS chips and electronics are in place, and the instrument has
now been used for science by a variety of groups.  As reported
earlier, one of the lenses on the blue camera has the wrong coating.
A new lens has been ordered, and will be installed April 24-26 (during
bright run).  At this time, we will also install an electronics
upgrade that allows synchronous readout, and will improve readnoise
properties.  At that point, the first phase of the upgrade will be

  Stubbs: there is one other feature is not yet understood.  Every
once in a while, there is a bias jump on some rows; it comes out with
row-by-row bias subtraction.  We'll keep an eye on it, and see if we
can diagnose the problem.

   The next step will be improvements in optics, which will improve
sampling and vignetting.  This work is planned for the summer
shutdown.  There is a possibility also to fix the infamous throughput
problem, i.e., the non-transmittal of light below 3850A, at the same

  There has not been much feedback from the users about the new DIS.
Erika Ellingson says that she is able to go significantly deeper than
she was able to before.  But please broadcast your experience (to the
mailing lists, or to Ed Turner, Chris Stubbs, Jon Holtzman, and Jeff
Morgan), so that we know what works and what doesn't.

     *************** NIC-FPS Preliminary Design Review report ***************
  Jon Morse at Colorado is PI.  Jon Holtzman, Bruce Gillespie and John
Barentine of APO attended the PDR meeting.  The PDR was successful and
productive. The CDR will be mid-summer.  The biggest question is the
choice of detector.  The standard choice was a new Hawaii Rockwell 1K
chip.  It is quite expensive.  Raytheon has been promising a similar
product for some time, but they only have test units thus far, so this
would be quite a risky approach.  So the decision was to go ahead with
the newer version of the Rockwell Hawaii chip.  This will afford
better read noise, higher QE, low latency, and sub-framing than the
older Hawaii chip.

  Gillespie: Filter choices were discussed.  The baseline filter set
is 5 filters (J H K_s, and narrow-band filters at Fe II 1.64 microns
and H_2 2.12 microns), but the current design can hold 18 filters in the filter
wheels.   There have been quite a few suggested filters to add from
the ARC consortium, more than there are slots available. 
   -How will we pay for these additional filters?  They are not cheap,
	and only the five baseline filters are budgetted at the moment. 
   -How do we decide on which ones we need? 
   -Do we want a third filter wheel?  This is possible, but will add
       considerably to the cost of the instrument, and delay the
       optical design. 

Can the Fabry-Perot replace the narrow-band filters?  Not really,
because the FP has R = 10,000, and needs a 0.5% NB filter in concert
for order-sorting.

  Can we get discounts for the filters by bulk-ordering with other

  Note that GRIM will stick around along as it stays alive (i.e., it
will not be retired once NIC-FPS comes on line), so all the
filters that are currently available will continue to be available. 

  There was some discussion about whether one needs a shutter with
this instrument, and how one might read out the chip (without a
shutter) in such a way that there are no gradients across the field,
and that added noise is kept to a minimum. Which readout rates are

  Morse will post details about the instrument on the web soon; this
will be announced to apo35-general.

******************** Summer shutdown plan ********************

  Planning is underway for the summer shutdown.  The tentative dates
for the shutdown are July 15-August 30, which is longer than normal.
The big items will be a realuminization of the primary and repairing
the shutter motor drives.

******************** Other CIF projects status ********************
Uomoto has put together a description of a low and medium infrared
spectrograph, optimized for point sources (a slit 30" long), available
on the web at:

This instrument will be built by Alan and his team in collaboration
with the University of Chicago.  

They plan to use an "old" Hawaii chip.  They plan to get the
instrument on the mountain in mid-2004.  Alan emphasizes that this is
a straightforward instrument; there are no show-stoppers or
particularly difficult items as potential schedule-breakers.

  Stubbs and York are discussing the possible use of chips that Chris
Stubbs has available for an upgrade to the echelle.

  **************** WIYN 1-degree imager workshop ******************
A workshop was held at KPNO last week to discuss a next-generation
wide-field imager for WIYN.  As Stubbs emphasized, with our f/10 focal
plane, it is difficult to rationalize building a wide-field imager at
APO, and so the possibility of collaboration with WIYN is quite

Gillespie and Doherty went to the workshop.  The plan is to build a
32K square imager, with a 1 degree field of view.  The timescale for
first light would be of order 5 years from now.  They have identified
a number of science drivers; we may be able to help them with
identifying further drivers (such as star formation studies). 

  The last meetings' minutes were approved. 

  The next meeting will be held at 11:30 AM EDT on May 13. 

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