Subject: Minutes of June 9, 1997 Users' Cmte Mtg

From: elt@astro.Princeton.EDU

Submitted: Wed, 11 Jun 1997 09:49:23 -0400 (EDT)

Message number: 146 (previous: 145, next: 147 up: Index)

ARC 3.5-m user's committee meeting, June 9, 1997


Hobbs, Klaene (for Bruce Gillespie), Turner, Secker, Stubbs, Walterbos (minutes)
Absent: Uomoto, Straus


1. Shut down plan

Aimed at addressing some aspects of 3-yr plan work, but more so to
address problems discovered during Dec 96 work, and maintenance.

Is long shut down the best way to do it? Scheduling shut down is not
trivial, because human resources are limited. A long shut down is not
optimally efficient, however, series of short shut downs is not
efficient either because bringing facility back on-line every time
takes time too.

Is this the last major shutdown for a while for the 3.5-m? No, because
there will be many issues from the 3-yr plan, including a new
secondary, that will require further shutdowns. There may also be an
annual maintenance shut down.  But it is the goal for the August
shutdown to accomplish goals that require the primary to be out. Also,
future shutdowns will be aimed for summer scheduling, and probably
restricted to a few weeks.

It is planned that about 3 to 4 FTEs will be working on average on the
3.5-m activities planned during the shut down.

2. Community meeting

Meeting time: would be nice if it were in advance of late Nov BoG
meeting. Walterbos will distribute general announcement with proposed
time slots and setup. Perhaps friday/saturday meeting is best, to
allow for less expensive airfares. Turner will provide his schedule
with constraints.

Possible topic of discussion could include scheduling. Other topics
would include status of telescope and instrumentation. Status of 3-yr
plan, new instrumentation, science presentations.

3. Secondary

Negotiations for polishing of the new secondary continue. It is hoped
that an agreement may be reached soon.

We are still considering testing of current secondary to make sure it
is well below spec and causes significant image degradation. There is
strong indirect evidence that the secondary is at fault, but it would
be better to have direct proof of that.

4. HST SPIKE software to schedule telescope

HST representatives will send a proposal to the 3.5-m Director for
making this software suitable for use of the 3.5-m scheduling. Current
scheduling is time consuming and not optimal.

There was some discussion on scheduling and notification time of
schedules for users. SPIKE might allow more flexible scheduling on
short notice.

UW: some users prefer scheduling blocks of time, with individual
institutions filling in schedule for their own users.

5. 3-yr plan update.

Stubbs (UW) reported a study of FWHM of image quality as a function of
zenith angle. Date were obtained during good seeing. Best images were
0.9", although seeing was believed to be much better, since images
degraded to only 1.3" seeing at 3 airmasses (in Johnson R). The image
degradation with increasing zenith angle was much smaller than before
before primary support was fixed, suggesting that significant progress
was made.  Best images of 0.9" demonstrate limit of current optics.

Guider may be installed during next week's shut down. Rotator may need
work because torque is too low. This could be a problem with
installation of guider. Baffling will be next.

Focus jumps may occur due to thermal effects related to wind direction
shifts accompanied by changing air temperature. So focus changes may be
real. Suggests that thermal management needs further discussion. Users
are encouraged to note temperature conditions and changes in wind
direction or speed during focus jumps.

Telescope throughput seems to hold stable (few percent decrease noted,
which may be in the noise). Ledlow (NMSU) has helped in instructing
observing specialists in reducing throughtput measurements to enable
regular monitoring.

Minutes of previous meeting approved as posted.

Next meeting: July 14, 1997.

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