Subject: Response to your email of 2003-07-15

From: D. C. Jewitt

Submitted: Wed, 16 Jul 2003 13:11:49 -1000 (HST)

Message number: 140 (previous: 139, next: 141 up: Index)

>>  As you know, the LSST Science Working Group has as its principal job
>>to produce a Design Reference Mission (DRM) for the telescope, which
>>will describe the science goals for the telescope, lay out how these
>>drivers might be met with the LSST facility, and determine the
>>characteristics of the facility and the observing program necessary to
>>meet these goals.  The SWG has been rather inactive since our meeting
>>in Tucson in March, for which I am to blame; we've lost a fair amount
>>of momentum since then.  It is time to pick that momentum up, and it
>>is with that in mind that I sent around a suggested outline for the
>>DRM a few weeks ago
>>(http://astro.princeton.edu/~dss/LSST/lsst-general/msg.131.html).  I
>>writing to you now to find out how you will be able to contribute.
>>You have been somewhat inactive since we saw you in Princeton for the
>>October meeting, but your input continues to be very much needed.

******
Hi Michael: 
Let me be completely frank, since I think that's the best way forwards.
The trouble is that the LSST SWG is too big and has spent too much time
in diffuse round-table discussions.  What should have been done in a
few months looks like it's going to drag into its second year, I'm
afraid.  Few people (and certainly not yours truly) can maintain the
intense focus that is needed for writing the DRM over such a long
period:  all the energy is being sucked out of this thing by the overly
long timescale.  Even worse, the implicit => decade-long timescale that
seems to have been adopted for building LSST means that the SWG
tardiness has no big impact on the overall project.  But there's no
reason to do it this way: a big project doesn't necessarily imply a
very drawn-out SWG.  In fact, the science case for LSST is rather
obvious.  The document could have been written by a smaller group and
much faster.

******

>>Gary Bernstein has already put together a discussion of observing
>>cadences for KBO's
>>(http://astro.princeton.edu/~dss/LSST/lsst-general/msg.114.html), but
>>this needs expansion, especially in terms of laying the broad
>>scientific goals and the need for LSST.  This is something where your
>>expertise would be very much needed.  Please contact Gary directly to
>>coordinate your efforts on this with him. 

******
Yes, I already interacted with Gary on this.  He did a great job on the
KBOs and the KBO text is as good as it needs to be for the DRM, in my
view.  Remember, we're talking about the science we'd like to do 10
years hence and the KBO field is a rapidly changing one.  None of us
has sufficient forecasting ability to warrant a more detailed KBO
write-up than the one we have.

******
>>  One thing that we have not discussed much in the SWG, but that you
>>might be interested in, is main belt asteroid science with the LSST.
>>It is not one of our principal science drivers, but may be worth
>>including some brief discussion of this in the DRM as a natural
>>side-benefit of the LSST data.  

******
No, my view is that the main-belt asteroid science is of limited
interest in the context of LSST.  I'm not saying there's no science
there - of course there is.  But I do not see the main-belt as a driver
of LSST in any way.  You'll notice that main-belt is not listed as a
science driver in the Decadal Report, whereas NEOs and KBOs are drivers
(actually, they are the top two listed drivers).  On the other hand,
I'm totally open to somebody else pushing main-belt science if they 
want to.

******
>>  Another area where your contribution could be particularly valuable
>>is the discussion of the comparison between Pan-STARRS and the LSST.
>>As you may have seen in the exchange between Tyson and Kaiser
>>(http://astro.princeton.edu/~dss/LSST/lsst-general/msg.137.html),
>>feelings can run high on this subject.  The whole business of figures
>>of merit does strike me as an appropriate way to go here, however, and
>>should be expanded further.  I would definitely like to include
>>*something* along the lines of Tony's comparison document in the DRM,
>>and would like your take (and contribution, if appropriate) on all of
>>this.  

******
Here's another place where I want to be completely frank.  Before I
joined this SWG, Jeremy Mould and Sidney Wolff both personally assured
me that the design of LSST was not fixed and, in particular, was not
predetermined to be the DMT monolithic mirror design.  You've even told
me that yourself.  However, nothing that I have seen or heard from NOAO
has given the slightest indication that the LSST will be anything other
than the DMT with a different name.   Indeed, the not-so-subtle
morphing of http://www.dmtelescope.org into http://www.lsst.org tells
that story clearly enough.

Why do I care?  In a nutshell, because I think this strategy puts the
LSST in great danger.  I'm completely committed to the idea of LSST as
a public, all-sky, rapid-cadence facility with the broadest possible
science mission.  I worked hard to push this on the McKee/Taylor and
Belton decadal reviews, and with some success.  But nowhere in these
recommendations is the design predicated on DMT: the assumption was
that the best design will naturally float to the top.  My concern is
that there is no place within NOAO's version of LSST for this to
happen, because the design is essentially already fixed.  This matters
because it renders LSST vulnerable to being undercut by Pan STARRS or
any other aggressive design that may emerge in the long decade before
LSST becomes active.

So, I see no point in re-entering the DMT vs Pan STARRS debate: the
issues have been discussed and the LSST = DMT equation has already been
made by NOAO.  But I am very nervous that this is a needlessly
dangerous route.  Effectively, LSST is taking the bus to Alaska on the
assumption that the airplane won't take off.

To be specific: imagine that Pan STARRS works as advertised and ask
what would be the impact on solar system science.  Pan STARRS would
scoop the cream in the Kuiper Belt, on the Centaurs and comets, and
would detect a significant fraction of the accessible potentially
hazardous objects.  These objects would have multi-epoch astrometry and
orbits and maybe multi-color photometry before LSST opens the dome.
Then LSST is left with the task of mopping up the rest...hardly a very
inspiring justification for a national facility.  Sure, mopping up will
produce surprises and worthy science but it doesn't represent the
"shining beacon" of scientific leadership that we should expect from NOAO.
That's the core problem I envision for the existing LSST.

What I would much prefer is for NOAO to be truly open to other ideas,
particularly ideas that allow LSST to be built faster and to be more
competitive.  It doesn't have to be a multi-aperture design, it doesn't
have to be OTCCDs, but it seems to me that these are both good ideas
that would put a more easily scalable LSST on-line faster, possibly
more cheaply, and which would give both LSST and this SWG some real zip.

******
>>  I hope to hear from you soon about how to proceed on all of this.
>>Let me suggest that you send your response to the
>>lsst-general mailing list, so that all can join in the discussion and
>>know what you're thinking about.

Done.  Flame away!

******
Regards

Dave



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