Subject: Minutes, 06/19/00 3.5m User's Committee meeting

From: strauss@astro.Princeton.EDU

Submitted: Mon, 26 Jun 2000 15:14:54 -0400 (EDT)

Message number: 440 (previous: 439, next: 441 up: Index)

  Apache Point Observatory 3.5m User's Committee Meeting
		June 19, 2000

Attending: Alan Uomoto, Mark Klaene, Jeff Brown, Lew Hobbs, Ed Turner,
Michael Strauss, Chris Stubbs, Rene Walterbos

******Status of the new topend******************

Status of new topend to be built by Ed Kibblewhite and colleagues,
which would also include a laser beacon mounted on back of the

Stubbs: It turns out that it is quite difficult to mount the laser
beacon, so Kibblewhite and collaborators are now going to mount it on
the primary mirror cell.  Once they made this decision, their
involvement in the secondary support system vanished. 
  So designing and building the new topend is squarely back in the
observatory's court.  Windshake in the current system is a big
problem, and is currently the biggest contributor to site seeing.  We
need to make a rigid system, and find a way to mount the secondary to
 We need to decide whether to start from scratch, or whether to
retrofit what we've got.  The problem is not with the truss, but
rather with the topend itself, which shakes by wind-driven oscillation. 

  Ed Kibblewhite continues to try to produce a high-order
adaptive-optics system, with the aspiration of delivering 0.1" images
in K.  Note that we really don't have instrumentation that can take
advantage of such a development, and we should actively be thinking
about it: how should we as an observatory capitalize on the
possibility of AO?  Can we be a leader in this field? 

  Kibblewhite and Stubbs agree that the next high-priority instrument
should be a wide-field near-IR imager.   Note that in the f/10 beam,
a standard pixel size of IR cameras will be of order 0.1".  So with a
bit of reimaging optics, we can be critically sampled with 0.1" images. 
But the ARC community as a whole needs to have the discussion of what
instrument they would like to have, and then ask the question: who's
going to build it?  where's the money to come from?  (Stubbs:
"Michael, why are you looking at me?")

Mark Klaene: We are in the process of putting together requirements
for the new topend, and are actively looking for input from the
committee.  The draft requirements can be found on the web at:

**************Planning for the future****************

Ed Turner:
  We need a new version of the strategic plan over the next few
months; where are we going to put our energies over the next few

Among the major items under discussion are the following.  Note that
we can't do all of this; we need to prioritize this list: 

The new topend; see above. 

Remember we still have cracks in the primary mirror.  We need either
to fix them (probably by soaking them in acid, which will stabilize
them, but it requires turning the entire mirror upsidedown), or
convince ourselves, with inspections to be carried out this summer,
that they are stable and therefore not problematic for the time

A new instrument, either a state-of-the-art near-IR imager, or
something else. 

The DIS upgrade. 

Stubbs' large-format optical imaging camera. 

Upgrading the echelle with a new detector (a 2048^2 15 micron pixel
chip has been suggested), and improving the guider to work to fainter

Chaos (Ed Kibblewhite's adaptive optics system)

The planned UC/JHU instrument. 

Tony Tyson's Big Throughput Camera from the 4m at Tololo is now
"sitting in a closet"; do we want to take advantage of this? 

We should think about a community meeting to discuss all this. A
possibility of doing this to coincide with Sloan Dedication in early

Strauss: Perhaps someone should come up with a strawman prioritization
of all of this; this will give us all something to start with. 

**************What the DIMM actually measures**************

Many have wondered what the relationship is between the DIMM seeing
measurements, and the actual seeing on the 3.5m.  Armin Rest from UW
carried out some experiments: he ran two versions of DIMM at different
locations (3.5m dome and its current "standard" location), while the
3.5m was observing with SPICAM.  There was good correlation between
the 3.5m and DIMM seeing, with the DIMM sitting in the dome, but there
was poor correlation between the two DIMMs.  This implies that in the
location the DIMM currently lives, there is a lot of local seeing
effects.  So the current DIMM is actually not very useful in practice.
We're considering putting a DIMM on the SDSS observing platform, and
carrying out further tests to see what's correlated with what.

  Last month's minutes are approved. 

  Next meeting, 11:30 Eastern time,  July 17, 2000

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