Subject: The job of the LSST SWG

From: Michael Strauss

Submitted: Fri, 18 Jul 2003 11:53:00 -0400 (EDT)

Message number: 149 (previous: 148, next: 150 up: Index)

Thanks, Dave, for livening up the discussion on lsst-general; this is
exactly the kind of exchanges we need. 

Let me describe as clearly as I understand it, the SWG's job and how
it relates to the existing efforts on Pan-STARRS (by which I
specifically mean the currently funded IfA four-telescope design) and
the DMT (by which I mean specifically the monolithic 8.4m wide-field
telescope).  

  The LSST Science Working Group was formed on a mandate from the NSF
to flesh out the case for a major new optical survey facility with a
large A Omega.  Such a facility has been recommended for a variety of
science reasons by three decadal surveys, as you all know.  Our job,
as I see it, is to: 
   -Flesh out the science case for such a facility.
   -Assuming the science case is compelling (which is clearly the
       case), ask the extent to which it will remain compelling in, 
       say 8-10 years time (in light of Pan-STARRS, VISTA, and other
       similar facilities). 
  -If the answer to those two questions are yes, we can then ask what
       the appropriate design for the LSST should be.  I agree
       strongly with Dave that this should be heavily informed by the
       experience that Pan-STARRS will give.  I agree strongly with
       Sidney that the technical details of the DMT need further
       fleshing out, so that this sort of comparison should be done. 

  As the recent e-mail exchange has made clear, the phrase 'LSST' has
been confusingly used in two quite different senses.  From the point
of view of the Science Working Group, I use 'LSST' to refer to the
abstract notion of a facility with large A Omega.  Dave is right that
the website www.lsst.org defines the LSST as the DMT design, and that
it would be much clearer if the semantic distinction between the LSST
and the DMT were kept.  NOAO is exploring that design, and is part
what is called the LSST Corporation (which is focussed on the DMT
design), as it has every right to do.  The SWG is formally independent
of NOAO (indeed, it has no members on the NOAO staff for exactly this
reason; we do, however, have several members of the Pan-STARRS team,
including its PI, in the SWG.).  We can and should use the NOAO
expertise where appropriate, just as we have input from the Pan-STARRS
folks.

  Dave also expressed frustration with the vagueness of the SWG
effort, and the fact that writing this DRM is taking longer than it
should.  I share his concern, and indeed take the blame for this as
the chair of this group.  This is why I am so eager to get started on
the actual writing of the DMT, and why I have sent e-mail to each of
the SWG members asking them to write their specific pieces.  Dave also
asked for further discussion of the DMT-Pan-STARRS tradeoff. I
absolutely agree; the lsst-general mailing list is a fine forum for
that.  I also think that phrasing things in terms of figures of merit
is also valuable for this exercise, as I've mentioned earlier.
However, while the DRM should certainly have some discussion of this
issue, I don't think it is our job (at least at this stage) to make a
final decision on which approach (or perhaps a third one) is superior,
at least in the document we are drafting now.  

  Everybody, keep the e-mails coming.  These are important issues
which need to be talked through, and we all have thick enough skins
that I hope nobody is getting too bent out of shape about all of this.

			      -Michael Strauss


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