[asac] information for charge3

[Christine Wilson]

Hi everyone,

Here is some information for Charge 3 for tomorrow's telecon. Sorry for 
the relatively short notice.

Chris W.

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Some initial thoughts on Charge 3
Chris Wilson, 2 August 2005

The text of Charge 3 for the October 2005 ASAC meeting is as follows:

"Following from your Sept. 2004 discussions, the ASAC is invited to continue
developing proposed "demonstration science" guidelines or policies. The
ultimate goals include:
       a. providing a proposed framework (rationale, principles) that
 	 establish the value to the astronomical community of
 	 accomplishing demonstration science as you envision it during
 	 the early operations era; and
       b. facilitating evaluation of the concept, its proposed timeline
 	 and the planning for its implementation during a period when
 	 demand for ALMA construction and operational resources will
 	 likely be high"

(I find the wording of the Charge from the Board difficult to interpret. 
Ewine reads it as (a) why do we need science demonstration at all? and (b) 
if we need it, how should it be implemented?)

In this note, I will try to synthesize the issues as I see them related to 
demonstration science. This discussion is based on a summary of relevant 
information from several documents relating to demonstration science. I 
have already circulated that summary to the Charge 3 subcommittee and I 
can make it available to the whole ASAC if desired. (This note has been 
modified to include some comments from the Charge 3 subcommittee.)

The concept of "demonstration science" first appears in the May 2004 ASAC 
report, where we recommended that the ALMA project focus on exploiting its 
high resolution and high frequency capability to maximize its early 
science impact. We recommended that these projects have community 
involvement and recognized that multi-configuration observations would be 
required. We also identified two categories of science demonstration 
projects: public demonstration images for publicity and the general 
public, and science demonstration projects to demonstrate ALMA's 
capabilities to the general community.

In the September 2004 ASAC report, we elaborated on demonstration science 
by recommending that they be carried out from end-to-end by a team of 
community astronomers and ALMA experts. We also cautioned that it would be 
unwise to attempt this too soon, as it would be hard to demonstrate ALMA's 
superior capabilities with only a few antennas. We suggested that 
demonstration science should take place before the first open call for 
proposals and that demonstration science should be delayed until ALMA has 
about 16 antennas.

The draft ALMA Commissioning and Science Verification Plan (2004-09-03) 
covers the period up to but not including Early Science. It describes 
demonstration science as being part of the science verification process. 
Science verification, in general, tests the system end-to-end (from 
proposal submission to final science) and involves outside observers. The 
document also says that very limited reconfiguration will occur during 
early commissioning (that is, the commissioning before early science) and 
notes that scheduling the multiple array configurations required to 
produce pretty pictures for demonstration science is a concern.

In reading these three documents, it becomes apparent that there is some 
confusion on what is meant by demonstration science and what is meant by 
science verification and how the two are related. We suggest replacing the 
original term "demonstration science" with the following two definitions:

   Science verification = end-to-end test of an ALMA mode done using a science
 	  project proposed by an external user

   First Pubic Images = large-scale project whose primary intention is to
 	  convince wider community/public of the value of ALMA

I will try to use these two definitions consistently in the rest of this 
note.

So, the fundamental difficulty we are facing is this: we would like to 
produce pretty images for our First Public Images both for publicity and 
to demonstrate the power of ALMA to the wider astronomical community. 
Ideally, this would take place before proposals are due for the first open 
call for proposals to encourage the community to use ALMA. However, if 
Early Science starts with only 6-8 antennas in the array, it will be 
difficult to make pretty images with good publicity value. So the question 
becomes, how important is it to spend a lot of time moving the telescopes 
to different configurations so that we can make nice, sensitive images 
with lots of spatial scales? And is this important enough to delay the 
start of Early Science, or to shift project effort from commissioning and 
science verification to taking data for the First Public Images?

One thing we should consider is whether the first public images should be 
deferred until ALMA has more antennas and making images is easier. In this 
case, we would be putting off the publicity side of ALMA for a little 
while. But I think we could still demonstrate what ALMA can do to the 
astronomical community by what will come out of science verification. Each 
mode of ALMA that is used for early science will be tested by one or more 
projects in an end-to-end fashion. Some of these projects (particularly 
the high frequency ones and high resolution ones) may be sufficient to get 
the wider astronomical community interested in ALMA. The APEX 
commissioning experience suggests that it will be possible to have a big 
impact with observations at high frequency because the site is so much 
better than Mauna Kea. The science verification that is proposed is 
absolutely necessary (no one wants to advertize a mode of observing 
without having tested it first), and so the ASAC doesn't have to defend 
the need for this (although North Americans and Japanese may not as used 
to this formal mode of operating as Europeans are).

If we go this route, more thinking is required about how the community 
involvement in the science verification process is managed. The CSV 
document says that the science verification team is responsible for the 
selection of a small number of proposals of scientific interest. It would 
be good to supplement them with a proto-TAC or an advisory group with a 
broad range of scientific interests. ALMA staff would need to be involved 
to assess feasibility and the process would need to be light and nimble. 
We could look at how other telescopes have managed calls for commissioning 
ideas and see how they did it. Again based on the APEX experience, we 
should expect a strong response to any call for science verification 
projects. One issue to be considered later is whether science verification 
projects will be limited to a single configuration or allowed two 
configurations (i.e. compact and extended).It would also be possible to 
identify this science verification phase as the start of early science 
observing (as the ASAC recommended in an earlier report, I think Sept 
2004).

I think the main thing we lose in the short term with this approach is the 
publicity value of pretty images. We should not underestimate the 
importance of producing one or more splashy images suitable for the 
general public, funding agencies, etc. However, we might be able to retain 
this capability, if only for one particular image, by careful choice of 
science verification projects. For example, I imagine the project will 
need to commission all the configurations that are offered in early 
science. If the ALMA project was careful to always observe some unique 
southern source (eta Carina, the Galactic Center, or Cen A spring to mind) 
in small mosaic mode with the appropriate correlator setup in each of the 
6 early science configurations at one of the higher frequencies (Band 7 or 
9), that ought to produce a pretty spectacular image. This approach 
assumes that entire configurations are commissioned, not just individual 
pads one at a time (which might result in configurations that are not 
optimal for imaging).

The Board says that one of our ultimate goals should be to provide the 
rationale and principles that establish the value to the astronomical 
community of "demonstration science" in the early operations era. If we 
adopt my scheme above (very limited pretty "First Public Images" coupled 
with thorough science verification of all early science modes), I think it 
is very easy to establish the value to the community (although I think we 
still need to think about justifying the pretty image). If we want to 
stick with the more elaborate version of "demonstration science" outlined 
in the two earlier ASAC reports, we need to think hard how to justify 
them.

The Board also says that another goal should be to facilitate the 
evaluation of the concept of "demonstration science", its proposed 
timeline, and planning for its implementation. Again, timeline is easy in 
the scaled-back version (the CSV team needs to do science verification in 
any case). Ditto for evaluating the concept, I think. Planning for its 
implementation needs some work i.e. how to get the word out to the 
community, how to pick which project to do, etc. A couple of wrinkles are 
when to commission Band 5 (which may be under pressure due to ALMA's slip 
relative to Herschel) and whether and when to include the Japanese 12m 
antennas in the early science arrays.