Subject: Minutes of the November User's Committee Meeting

From: Michael Strauss

Submitted: Mon, 27 Nov 1995 15:15:15 -0500

Message number: 27 (previous: 26, next: 28 up: Index)

	Minutes to APO 3.5m User's Committee
	 Phone Conference, November 13, 1995

  Attending: Julie Lutz, Jack Burns, Bruce Gillespie, Ed Turner,
Michael Strauss, Don York, Chris Stubbs, Lew Hobbs, Kurt Anderson (at
the end)

  1. Report from Bruce Gillespie on status of telescope, shutdown.
  2. Overview of the budget. 
  3. Who decides when things get fixed? (we didn't get to this this month).
  4. Discussion of the number of instrument changes on any given

  Gillespie: Sent around fax of subset of overheads for board meeting.
Includes statistics on fraction of hours that are usable. Over 50%,
integrated from November 94. Would be useful also to tabulate those
nights in which people are gathering data, but because weather is poor
or instruments are not working properly, the data are not
scientifically useful.

  Shutdown: We cannot change out the cracked enclosure wheel; the
force required to remove the wheel shaft exceeds the initial estimated
upper limit of ~25 tons of force by a factor of four. This starts
getting rather dangerous. So the problem remains; how do we fix this?
A possibility of fixing the wheel in place; a proposal to do
this. However, this doesn't address the initial (still unknown) cause
of the cracks. Whatever the solution is will require another shutdown.

  The two drive and idler boxes in azimuth drives have been taken out,
and damaged bearings have been replaced; everything relubricated. By
November 15, expect to have everything together again, and all can be
retuned. Also, reduce altitude servo impulses down by a factor of two,
to reduce the 20 Hz problem.

  Power sources for all microprocessor controllers on the telescope
were switched from utility power to uninterruptable power supplies.

  Calibration lamps are now pointing down on the primary mirror cover,
allowing calibrations to be done in real time without opening and
closing the shutter covers. (Mirror covers still do need to be closed
manually; making this automatic will actually be non-trivial).

  The guider limit is now ~16 mag. Capability exists for finding the
position angle that puts such a star in the guider. There is a 512^2
device may or may not have superior performance in terms of
sensitivity. We would love to return 1024^2 chip to Spectrosource and
have them fix the high read-noise problem, or simply get a new chip
from another, more reliable vendor. Discussion of whether to put 512^2
device on telescope to test it.

  There now exists a slit-viewing camera to be installed on DIS by the
end of the month. Will create FITS images which can be moved over the
net by anonymous ftp.

  DSC is now back to Fermilab for a variety of upgrades and repairs to
electronics, in particular to remove spurious charge effects. There
are also unremovable flat field features (problem with the chip?);
contamination within dewar needs to be cleaned out. Stubbs: SITe is
now offering grade 2 2Kx2K chips (24 microns) for $27K (half-price!)
(grade 1 is $45K); we should think about buying one of these. All
orders must be in by the end of the year. Could we use one of these
for the DSC? Funds from UW and FNAL is a possibility to pay for this.

Dewars for DIS are being pumped to tighten up vacuum.

AMBER instrument is supposed to arrive soon.

Laser beacon device for CHaos scheduled for arrival in December. 

Seeing of DIS is systematically higher than for DSC, GRIM, which
presumably is due to the undersampling of the DIS. 

Best seeing ever seen on this telescope is 0.9"; budget for telescope
contribution to this is 0.5". Hartmann test shows that half of the
error budget is taken up in optics, the other half is due to "other":
mechanical jitter, collimation, and enclosure and site seeing. There
are strong suspicions that the optics problems are due to the
secondary. Practically speaking, we are pretty sure that it is indeed
the secondary. To clinch it, one can look whether particularly deviant
rays from the Hartmann test come from particularly rough areas on the
secondary.  Doing Hartmann testing on the primary alone will require a
big project putting a prime focus instrument on the telescope. Another
approach would be to rotate the secondary 120 degrees. We also don't
have a hard price for replacement of the secondary (we cannot get a
serious bid until we have a firm budgetary committment; a chicken and
egg problem). Board will look at this at their meeting on November 20,
but they won't have all the necessary information to make a firm

Telescope is scheduled to be on-line for users Sunday night. But if it
is cloudy for the next week, all the commissioning will not be done
by that time.

	Budget (to be presented to board at their meeting next week)

Issues to be discussed above the line (as part of standard operations):
  $30K for director's discretionary funds.
  $5K for consulting fees for Remark software updates (Lowenstein,
  Alternatively, bring in an independent programmer ($60K/year; it is
a full-time job for 2 years) to put all of this onto a firmer, better
documented, form, moving away from the Macintosh. And what if
Lowenstein and/or Yanny leave Chicago? A strong desire to put this
underneath the control of Apache Point itself. A high priority, just
below importance of the secondary (see below). The trade-offs are

Big-budget items "below the line" (i.e., not part of standard
  New Secondary: $250K (but this number is quite uncertain; an
estimate by Pat Waddell gives $400K). When are we going to do this?
The longer it takes, the more the money requirements get spread out
(and the greater the confidence that we will actually meet specs).
There was strong agreement that we are willing to take a longer time
in exchange for a stronger guarantee that we will meet specs.

  Instrument Rotator: $25K.  A second instrument rotator would allow us
to keep a second imaging instrument permanently mounted and, coupled
with automated tertiary rotation, make very fast instrument changes.
The original concept for the telescope envisaged multiple instrument
rotators and permanently mounted instruments instead of the current
system of manual changes of the NS2 instrument.

Discussion of how money is exchanged between institutions (in
particular, APO and UW) for specific engineering tasks.

The board has the unenviable task of making decisions between all the
various budget items, given the reality of a finite budget.

Bruce Gillespie will fed-ex budget to board members this afternoon.

How can we minimize the number of instrument changes on a given night?
Ed will keep this in consideration as he makes up the schedule. The
tradeoff is the loss of time when an instrument is changed, versus the
flexibility of being able to move from instrument to instrument. With
this in mind, we can have our cake and eat it too if we could move a
tertiary mirror to go from instrument to instrument.

Stubbs: With HETE gamma-ray satellite going up soon, it would be
wonderful to be able to point the telescope with optical imager at
gamma-ray bursts, pre-empting existing programs. 3.5m scheduling and
time-sharing is not well-suited for doing such sorts of programs; it
is worth thinking about how to allow this to be done.

Idea at last meeting of each institution ranking their proposals in
two categories: high priority (must be scheduled) and intermediate
priority (squeeze it in where you can) has met with disapproval. 

 Some discussion on requirement that observers spend three nights on
the mountain before they are permitted to observe remotely.  A
question of efficiency, not safety (you can't destroy the telescope
observing remotely!). A possibility that new people observe remotely
with a faculty member observing with them. Keep in mind that the
observatory staff are not in a position to train students who come
alone to the site.

Next meeting December 11.

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