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REPORT OF THE AD HOC ADVISORY COMMITTEE
TO THE SSC DIRECTOR AND SIRTF PROJECT SCIENTIST
ON THE SIRTF RESPONSE TO THE WIRE FAILURE
On 29 and 30 April 1999 this committee was convened at IPAC by SIRTF
Science Center Director Tom Soifer and Project Scientist Mike Werner to
advise them on the appropriateness of making modifications to the current
SIRTF science program as a result of the loss of the IR sources that were
anticipated to come out of the WIRE surveys at 12 and 25 microns.
The specific charge given to the committee was to evaluate the impact of
the loss of the core WIRE high galactic latitude survey on SIRTF science
programs and to advise whether and how SIRTF and the SSC should undertake
actions to redress this situation so as to maximize the scientific return
from SIRTF.
The committee was given briefings by SSC, SIRTF Project, and WIRE
personnel on the characteristics and planned science programs of WIRE and
SIRTF, and the responsibilities and capabilities of the SSC and the SIRTF
instrument teams. Based upon the information presented to us, we have come
to the following conclusions:
- The science program of the WIRE mission was very important, and would
have made an essential contribution to characterization of the IR sky at
12 and 25 microns. Its sources would likely have been important target
objects for many of the programs to be carried out on SIRTF.
- Although SIRTF cannot duplicate the WIRE observing program, it does
have imaging capabilities at wavelengths which would produce a
representative sample of previously undetected sources in a modest amount
of observing time.
- The Legacy Science Program represents an excellent process by which
to produce outstanding science on SIRTF, provide early illustration of
SIRTF's capabilities to address a wide range of problems, and provide
early community access to a database that will aid significantly in
planning GO programs. These peer-reviewed projects should remain the
pillars of the early scientific program of SIRTF.
- The addition of a representative view of the mid-IR sky at a level
equivalent to that which WIRE would have provided represents a critical
augmentation of known IR sources to serve as targets for the detailed
studies that SIRTF will conduct. Given the estimated 5-year lifetime of
SIRTF, it is essential that this sample be acquired as soon as possible so
the broad community can optimize planning for early observing cycles.
- The loss of the expected WIRE source catalogs which would have
provided target lists for many types of SIRTF science makes it imperative
for the scientific success of SIRTF that a more fully capable pipeline
data processing system be in place at the SSC at the time of launch. The
currently planned pipeline would only produce calibrated, individual
images. The steps needed to identify and remove low-level cosmic rays, to
register overlapping images and to merge the images in a dither-set or map
together were all to be left to the user, as was the source extraction
optimized for final SIRTF images. The lack of these latter capabilities
will cause individual users to expend substantial, duplicative efforts
developing software of their own and will delay the release of initial
datasets, both of which will cause wasted effort. It is our belief that
the current level of effort is unlikely to provide for acceptable,
immediately scientifically usable data products when they will be needed,
and this situation needs to be addressed.
The committee discussed at some length the overarching topic of the
scientific impact of SIRTF during our two-day meeting, especially in the
context of the loss of the WIRE satellite and its primary science. We
remain excited about the tremendous scientific potential that SIRTF holds.
Achieving that potential will, however, require both additional effort and
funds. In particular, we believe it is vital that the science
observations on SIRTF be initiated with a brief survey that will provide
for a representative sample of sources for subsequent study. In addition,
we also believe the data processing pipeline at the SSC needs to be
upgraded to provide for a more rapid analysis of SIRTF imaging results. We
believe that both of these matters can be addressed straightforwardly, and
therefore we recommend to the SSC Director and SIRTF Project Scientist the
following actions.
RECOMMENDATIONS:
In response to the loss of WIRE and its effect on the SIRTF science
program, the Committee recommends that a special survey -- of order 100
hours duration - be carried out by SIRTF as its first observing program in
order to characterize the mid-IR sky to sensitivity levels two orders of
magnitude fainter than presently known. The wavelength coverage of MIPS
makes it the obvious instrument of choice to carry out this survey.
Although not replacing the WIRE survey, this program should yield a
quick-look, representative sample of ~1000 sources at 24 microns that are
essential for the planning of a wide range of SIRTF GO and Legacy Science
projects.
The SSC should take lead responsibility for planning and executing the
survey and for making survey data products available to the community so
this information can be used in the preparation of GO proposals for Cycle
2. In doing so, we strongly urge the SSC to seek involvement of the broad
community of potential SIRTF users and to ensure that the community is
represented in the definition of the survey.
Supporting this survey and releasing survey products to the community
immediately after their validation will require that the SSC develop a
full complement of software tools, including mosaicing, cosmic ray
rejection, and frame co-addition. These same tools are also critically
needed to ensure the early release of data arising from Legacy Science
projects which also contain essential information for planning Cycle 2 GO
programs. To accomplish this will require application of additional
pre-launch resources of order ~$4M as soon as possible. The benefits to
the community and the Legacy Science databases, and the enhanced software
toolbox that would emerge from early implementation of a shallow mid-IR
survey are large, and lead us to suggest that some of the enabling funding
may come from the (post-launch) GO and Legacy Science data analysis
funding pool. The committee believes that the ultimate responsibility for
guaranteeing the adequacy of SIRTF data reduction software resides with
the SSC, and in this role, we encourage them to avail themselves of
relevant expertise and software that exists in the community.
The prompt identification of survey fields is critical to planning Legacy
Science projects and GO programs and crucial complementary ground-based
programs. We therefore urge the SSC to work with the community to fully
characterize the survey and identify the target fields prior to autumn
1999.
Submitted by
R. Williams (Chair), N. Bahcall, C. Beichman, P.
Hacking, B. Jannuzi, J. Stauffer, S. Strom, D. Weedman
20 May 1999
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