|Working Group Recommendations
EIS Pilot Public Imaging Survey
A. Renzini reported on the status of the wide field imager at the 2.2m (WFI@2.2). The delivery of the detectors is on schedule, and the instrument will be installed at the telescope in September 1998. ESO aims at allowing the scientific use of the new facility starting November 1, 1998, though delays cannot be excluded due to late delivery of the detectors. In any event, it is expected that the WFI@2.2 will become available at least for the second half of Period 62. The next call for proposals (to be issued on March 1, 1998) will include the WFI@2.2. Taking into account collecting area, field of view, throughput and QE of the CCDs, the camera will be a factor more efficient than NTT/EMMI. The 2.2m telescope will be the first telescope of its class to be fully dedicated to wide field imaging, worldwide, thus offering a unique opportunity to the ESO community. It is also important to notice that the data flow rate from the WFI@2.2 will be several times higher than that of all other optical instruments at ESO telescopes on La Silla (the WFI@2.2 will have 67 million pixels, against 34 million pixels of all other optical instruments together). All in all, in 1999 the data flow from La Silla will be 4-5 times higher than in 1998.
Under these circumstances it appears that at least during 1999 the bottleneck for wide field imaging will no more be represented by the available telescope time (and corresponding raw data), but by the ability to properly and timely process this tremendously increased data flow rate. The experience that has been accumulated with EIS will be precious to start coping with this problem, offering a working survey pipeline able to process frames producing coadded, mosaiced, photometrically and astrometrically calibrated images and object catalogs. However, the EIS survey pipeline needs to be significantly upgraded in order to be able to deal with images made of 8 slightly disjoint subimages, one for each chip of the WFI@2.2. An evaluation of the resources necessary to this upgrade is currently under way.
Renzini emphasized that a relatively modest incremental effort is required if one dwells on the expertise now accumulated by the EIS Team. A public pilot survey with the WFI@2.2 in Period 62 would then provide the focus for the pipeline upgrade, with also the aim of making the pipeline portable towards the community, the philosophy of ESO public surveys being that every products (including software tools) are made publicly available. Besides producing the immediate advantages for the VLT science of such a survey, the goal will therefore be to spread within the community the capability of dealing with large numbers of very large format images such as those produced by the WFI@2.2 (and later by the 2.5m telescope on Paranal, the VST), and to efficiently produce surveys, no matter whether public or private. Instrumental to make the survey pipeline practically portable is the wide participation in the EIS Team of astronomers and scientists from the community. Otherwise, the production of a fully documented, platform independent pipeline would require resources that are not available, or an impractically long time. Instead, the return to the home institution of well trained EIS Team members will be essential for a most efficient use of these new facilities. Institutes and groups interested in an extensive use of the WFI@2.2 should be encouraged to participate in the EIS Team activity through the EIS Visitor Programme, while planning for the necessary hardware investment at home. For this latter aspect, concern was also expressed for the capability of the community to take prompt advantage of the WFI@2.2 during 1999.
Finally, Renzini emphasized how this effort for the WFI@2.2 is essential to prepare for a prompt scientific use of the VST in 2001, when the new telescope will mark another quantum jump in the wide field imaging capability (a factor of compared to the WFI@2.2!). A long discussion followed on the policies to be followed for future surveys. Various issues were treated also in a closed session restricted to the non-ESO members of the WG and resulted in the following results.
Definition of a public survey: a survey that the WG recognizes of compelling interest for the ESO community, in particular in view of the maximization of the scientific outcome of the VLT, and is not likely to be covered by ``private'' proposals. A public survey makes the data available immediately, has to contain in the proposal a detailed description of the products and the distribution policy. Successful examples of public surveys are EIS, the HDF or the recent radio surveys FIRST and NVSS.
Collaboration between ESO and institutes in the community is highly recommended. Interchange of people and expertise between ESO and the institutes has proved to be highly effective (e.g. the DENIS experience transported in the EIS).
A call for ideas to the ESO community should be issued as soon as possible using channels of communication as broad as possible. The answers to the call should be collected by the WG which will study the ways to stimulate collaboration, integrate the scientific aims into general interest programs in the framework of the ESO possibilities in terms of manpower, budget, data distribution and contribute with own ideas in order to maximize the scientific output of the survey. The ideas for public surveys should reach the WG with some advance (about 2-3 months before the deadline for normal proposals) for discussion and integration of the goals. In this way the WG will be able to improve its task of sensing what are the feelings of the community and define a baseline for public surveys with hopeful collaboration between ESO and the community.
The competition among all the possible survey proposals should be encouraged: a public survey proposal, after being endorsed by the WG, should go through the OPC and compete with the other proposals. The WG recommends that there should be neither special rights like e.g. a special presentation to the OPC nor special priorities in the scheduling because of the publicity. Scheduling should be done on the basis of scientific priorities only. The scientific priorities will be, of course, determined by OPC. In future, the Chairman of the OPC should be ex officio a member of the WG.
The WG recommends that up to 1/3 of the total time available at the 2.2m telescope is dedicated to public surveys.
As a pilot project for the first quarter of 1999 the WG recommends the completion of the EIS survey in the originally planned bands with the addition of a long wavelength filter (the z band nm) especially suited for observations in grey time. The WFI camera of the 2.2m should also be used to reach a fainter limiting magnitude in the I band and to observe a deep field in order to explore what are the limiting capabilities of this facility.
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Last update: Oct 30, 2000