Subject: APO 3.5-m Users Committee minutes 3/8/04

From: Bruce Gillespie

Submitted: Fri, 12 Mar 2004 09:17:17 -0700

Message number: 753 (previous: 752, next: 754 up: Index)

					APO 3.5-m Users Committee Phonecon, 3/8/04

Attending:  Ed Turner, Michael Strauss, Bruce Gillespie, John Bally, 
Fred Hearty, Don York, Russet McMillan, Bruce Balick, Karl Glazebrook, 
Al Harper, Rene Walterbos

Absent:  Jon Holtzman

Minutes taken by Bruce Gillespie


Telescope/Instruments Report:

Bruce G and Russet said that the telescope has been performing 
reasonably well lately, and hasn't suffered from cold-weather problems 
recently because the weather has been milder.  The need for routine 
engineering work has increased somewhat since we have been clouded out 
during recent scheduled engineering time.

The facility instruments are largely working.  The echelle guider 
camera has a loaner controller to see if the occasional crashes go 
away.  GRIM2 still has the missing quadrant problem once in a while.  
DIS blue camera has some low-level noise pickup that has defied 
diagnosis so far.  SPIcam's control computer died, and a somewhat 
cobbled replacement system is now running it; a new ICC is being 


10th anniversary celebration:

Rene mentioned that we still need speakers for science talks at the 
workshops on 27 and 28 May, and we also still need invitee lists from 
most of the institutions.


Integral Field Spectrograph proposal:

John Bally reported that he hasn't heard any reaction from CFHT about 
their potential interest in the IFS.  He also is waiting for feedback 
from potential users at CU.  Bruce Balick reported that Connie Rockosi 
polled the UWash users, and found that they would "very, very much" 
like to use an IFS at APO, especially for spectroscopy of extended 
galaxies, halos, etc.  They note that the instrument would likely need 
bigger lenslets to reach the sky limit, probably ~3 arcsec.  An 
alternative would be to use fibers, say 300 for 3 arcsec apertures, or 
1500 for 1.5 arcsec.  In any case, grating selection is going to be 
tricky.  There are concerns about the CFH detector characteristics, 
e.g., CTE.

Michael Strauss reported that the Princeton user community thinks that 
the extragalactic science opportunities are great.  They are concerned, 
however, about the small throughput of the proposed system using small 
lenslets; the small lenslet design would mainly be useful only for 
emission line objects.  Also, they anticipate problems in optics design 
and manufacture.

Rene reported that Jon Holtzman found that the NMSU interest in the IFS 
would comprise about one-quarter to one-half of the NMSU use of the 
telescope.  For example, Rene would like to use it for emission-line 
work, especially at low spatial resolution.

John Bally pointed out that the detector pixel size drives the lenslet 
size.  Karl Glazebrook noted that you could bin the detector pixels so 
that the lenslets could be bigger.  John Bally added that one could use 
a fiber-optics front end to get large input pixels.  Al Harper noted 
that the size of the grating would be dependent on A-omega constraints.

Bruce Balick said that the IFS would be great for the kinematics of 
disks and halos, and clusters.  Don York emphasized that the instrument 
must be able to reach the sky limit to be widely useful.  Bruce Balick 
reminded us that we need to be careful to define the unique niche this 
instrument would fill on a 3.5-m telescope, given the competition.  He 
feels that the low-surface brightness, large input pixel, projects 
would be that niche.  Al Harper then noted that such an instrument 
would have a spectrograph as large as the ones built for 6-m and larger 
telescopes.  Bruce Balick said that a reasonable way to fund such a 
huge instrument would be to grant wide community access, ala TSIP.

Given the huge estimated cost, does it make sense to build a new 
detector instead of using the CFH12K?  John Bally thought no, because a 
comparable new detector would be very expensive compared to the CFH12K. 
  Bruce Gillespie noted the similarities in IFS to the proposed WIYN 
1-degree camera, where the expected instrument costs are comparable to 
the initial costs of their respective telescopes, and both filling a 
niche that only 4-m class telescopes can serve. John Bally discussed 
some of the possible reasons why existing IFSs have not been 
particularly productive, citing software complexity, limited detector 
size, and data-cube analysis problems.  Al Harper said if you're going 
to require that the instrument be usable to the sky limit, you will 
need to have optimal detectors.

Karl Glazebrook said he had sent a technical memo to John Bally about 
the IFS, and that he had not yet received any comments from the JHU 
users on the proposal.  Don York suggested we consider building it with 
a "dial-able" set of entrance apertures, which was endorsed by John 
Bally.  John also said that he hadn't heard anything from Bruce 
Woodgate, who has expressed interest in the IFS in the past.  Al Harper 
also said that he hadn't heard any feedback from the UChicago users, 
and he will poll them again.  There will be an opportunity to discuss 
this at Chicago on 17 April during a local users community meeting.

Ed Turner summarized the highlights of this discussion:  There is the 
issue of reaching the sky limit which may be achieved by using larger 
entrance pixels, and/or pixel binning on the detector.  Another issue 
is whether or not to use the CFH12K, or to plan to build a new 
detector.  The availability of the CFH camera is TBD anyway, so we 
should have a plan to build a new detector as backup, anyway.

Don York added that he could argue for the smaller pixels, e.g., the 
"red rectangle" and for galaxy spectra without contamination.  One 
question is how efficient the spectrograph needs to be--is the typical 
20% throughput good enough, or do you need to optimize the spectrograph 
for high throughput in a limited observing mode.

Ed Turner finished off by saying that we need to hear from CFHT about 
their interests, and that we should get a better guess at the total 
cost of the IFS before we invest too much more effort in the technical 
design.  John Bally said he would talk to CFHT, and that he would post 
a new version of his white paper with updates reflecting these 


CorMASS is coming (really):

Bruce Gillespie again reminded the user community that the low-res NIR 
spectrograph CorMASS is coming to the 3.5-m this spring, with 
commissioning runs now definitely scheduled for 3 - 7 May.  If users 
are interested in any tests or science commissioning experiments during 
this run, they should contact Bruce Gillespie (  
More information on the capabilities of CorMass will be posted soon.


New Instrument Call for Proposals:

Ed is preparing a CP for a new ARC instrument for the 3.5-m, which will 
have provisions for significant CIF funding support, plus an allowance 
of Director's Discretionary time for commissioning and science 
programs.  The proposals would be due this summer, with a late summer 
decision likely.  The CP will probably be issued within the next few 


NIC-FPS report:

Fred Hearty said that the engineering detector and controller would be 
going into service fairly soon, after they solve the problem they've 
encountered with cool-down rates.  The etalon mover is being build, and 
they will be testing the IR etalon this week.  The filter wheels are in 
test, and the dewar has passed its deflection tests.  The overall 
delivery schedule is unchanged, and they are working on a commissioning 
plan, and expect a turnover to APO for user science programs by 1 Oct 


Last month's minutes were approved without comment.

Next phonecon will be on Monday, April 19, 2004, at 11:30 AM Eastern 


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