Subject: Minutes of May 12 APO User's Committee Meeting

From: strauss@astro.Princeton.EDU

Submitted: Tue, 13 May 1997 15:01:45 -0400 (EDT)

Message number: 143 (previous: 142, next: 144 up: Index)

   Minutes of APO 3.5m User's Committee Phone Conference
		  Monday, May 12, 1997

   Attending: Tom Harrison (standing in for Walterbos), Alan Uomoto,
Bruce Gillespie, Ed Turner (Chair), Michael Strauss (taking minutes),
Chris Stubbs, Jeff Secker (arriving late).  Ed Kibblewhite, standing in
for Hobbs, did not attend.

  Current status of Three-year Plan
  Current status of DIS. 
  Optical counterparts to Gamma-ray bursts; what shall we do with
     targets of opportunity?
  The Future of DSC
  Upcoming negotiations with WSMR
		Three Year Plan

Stubbs: new Primary Mirror Support system is in, and seems to rectify
the major problems with the old system.  It is now stable as it
stands, although there is still some work to be done.  Some aspects of
the installation could have gone better; management of the effort
might have been better.  One of the issues that has come up is
collimation.  Focus has become much sharper; as you go out of focus,
things degrade much more rapidly, a sign of poor collimation.  We need
a proper method of collimating the telescope.

  Gillespie: With the old system, there were probably several tenths
of arcsecond image degradation due to mirror support wobbling,
especially at 2 airmasses and above.  

Poor weather has meant that we have not yet fully tested this system
on the sky.  In particular, the automatic focus change with airmass
probably needs to be recalibrated with new system.

  Next big thing: New guider with 1K thinned chip, 4 times the field
of view of the present system.  This should make quite a difference;
we hope to be able to pick up a guide star anywhere in the sky at
arbitrary position angle.  This upgrade is planned for June, during a
5-night engineering run. 

  A big shutdown for the entire month of August (monsoon season) is
planned for a wide range of engineering tasks.  The engineers are
asking for a ten-day extension of this into September.  Note that we
do not have resources for KPNO-like shutdowns, wherein large numbers
of people are swarming over the telescope, fixing many things
  A question to the committee: how painful is this shutdown likely to
be, and in particular, how difficult would it be to see it extended
  Turner will be out at the site at the end of the week to talk to
people about the schedule for the shutdown.
  Alan says that this seems a too long shutdown, given that long
shutdown periods tend to be a bit inefficient.  In any case, we need
to see what would actually be done during those ten days, and see what
the efficiencies are. 
  Turner et al will discuss this, and send a note about this to the
user's committee at the end of the week.

Walterbos has sent around an e-mail about current status of DIS.  Excerpts

>The readnoise on the red side of DIS is much higher than it was before, 
>between 22 and 30 electrons, rather than 15. Even in a recent Halpha 
>imaging run the data were READnoise limited. It will be next to impossible
>to be skynoise limited in spectroscopic mode. Even at the nominal 15  e 
>this may be the case, but that is still a factor up to two better S/N for
>same integration time.

>The issue is, will DIS chips be replaced, and when? Given the need for 
>funding for the secondary, we fear that we may be stuck with DIS in its
>current mode for another couple of years; this would eliminate much of 
>gain obtained by the throughput advantage after re-alum. for the red side.
>Clearly, replacing the chips would be the best solution and might avoid
>a long hunt to fix problems with a very old chip. However, the time scale
>for this replacement is the crucial issue.

  Uomoto: The high read noise is probably an electronics problems;
it would require roughly 2 weeks of a skilled electronics technician's
time (who is familiar with the electronics of this system) to diagnose
and fix this.
  Gillespie: There are several possible people who could work on this:
Richard Luccinio, Jim Gunn (when he's down at APO for the Sloan
camera), or the new electronics technician who is being hired to
replace Brinkmann (who has moved over to SDSS).
  It has long been a hope to use Sloan electronics for the DIS.
Uomoto is building the ability to generate Sloan electronics for CCDs
in his lab.
  Hope to get Advanced Camera chips into the DIS some time in the next
year, or perhaps some Loral-like 2Kx4K chips from Stubbs.

  Walterbos has also indicated interest in wider slits, up to 4", for
spectroscopy of diffuse objects. 

  Slits are ~$1600 each.  We have 1.5" and 2" slits in progress.  If
these turn out well, we can ask the same outfit to make 4" slits as well.
Walterbos (via Harrison) will tell us exactly what he needs.

  Very high-dispersion gratings: Not yet converged on exactly what we
want here.  These cost ~$5-6K each.  Bruce Balick is very
enthusiastic, as are a number of people at UW.  Another possibility is
to use the echelle for the same science (i.e., take out the
cross-disperser, and operate the echelle in long-slit mode in a single
order with an order-sorting filter).  Of course, the echelle is not
in operation yet, while DIS is.

  Stubbs: There now exist CCDs with read noise less than 1 electron.
If we were to have one of these on the echelle, this would be an
instrument competitive with high-res instruments on much larger
telescope, even Keck.  These chips have 15 micron pixels; that could
be really exciting.  We had some discussion about whether the
possibility of getting such a chip would be worth delaying the echelle

  Medium-resolution gratings: when these come in, we probably do not
want to be in the position of having to switch gratings (between
medium, and low) in the middle of the night, as this is a non-trivial
task.   Thus people applying for DIS time will need to indicate which
resolution they would prefer, and Ed Turner, as scheduler, will have
more work putting together programs that do not require a switch of
grating in the middle of the night. 

			Target of Opportunity Programs Turner: 
  On Friday morning, Beppo-SAX found a gamma-ray burst with a good
position; an optical counterpart has been found.  Over the weekend, Turner
tried to organize people to observe with APO.  This organizational
effort worked, in that people were agreeable to using the telescope
for these observations.  However, it took a huge amount of Turner's
time, and and in the end, the
weather was poor; no observations were made.  Ideas are being floated
around how to use APO to observe these objects synoptically.  How do
we set up a system to exploit the flexibility of our telescope to
follow these very exciting objects?  There will be a proposal written
soon for this.
  Harrison: We should definitely put together a multi-institution
proposal to follow-up these things up.  There are people at each of
the institutions have a particular interest in these things.
  XTE is also interested in following these things up, and generating
good positions, so we may get as much as 10 of these a year.
  It is difficult to plan, because we don't know enough about these
objects yet to know how they vary.

  Whatever we do, we have to avoid wasting telescope time.  We need up
front a description of how this will work, and who is in charge of
making sure the data are taken.  We need a target of opportunity plan,
that all observers will know about.

  Stubbs and Margon will draft a policy document for how this should
be done; we'll discuss this when we have that in front of us.
Gillespie: look at what HST does for target of opportunity problems.

Gillespie: Will DSC be available for third quarter? Fermilab people
have a last set of observations that they want to use it for.

Stubbs: drift-scan capabilities with SPICAM have not been fully tested
on sky yet.

  DSC will not be available as a backup for SPICAM in 3Q; it will not be
kept cold all the time.

  Gillespie and Turner will meet with the WSMR folks on Thursday to
discuss details of agreements with the observatory.  We plan to ask
them to pay a base fee per quarter,
just to be involved.
  Also, they tend to give details of their observing needs only a few
days in advance.  Negotiations on how much advance warning is needed.
  We need to clarify policies to the user's community.

  There is a possibility that a vBNS link capability will exist
between APO and essentially all APO sites (other than Washington
State) which might improve throughput over the internet by a factor of
as much of 5!

  Craig Loomis has taken over from Jim Fowler as an interim systems
manager for the mountain, until someone can be hired permanently for
the position.

  Last month's meeting approved. 

  Next meeting is June 9, 1997. 12:30 EDT

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