From 2004 onwards, the major instruments on UKIRT will be WFCAM, UIST, and Michelle. WFCAM will take the majority of the UK-owned time (two thirds), scheduled in advance in large blocks, in order to enable major surveys to be carried out. Of that WFCAM time, approximately 80% will be used for the UKIDSS survey (see below) and the remaining 20% will be open to competitive allocation through the PATT system.
The UKIRT Infrared Deep Sky Survey (UKIDSS) is the second major organised activity connected with WFCAM, along with the camera project itself, and the pipeline/archive project. The aim of UKIDSS is to undertake a substantial public survey programme over seven years, designed and implemented by a large consortium of astronomers at many different institutions. The UKIDSS web page is at http://www.ukidss.org. The science goals are summarised in two recent papers by Steve Warren[2,3]. The Principal Investigator (PI) is Andy Lawrence (Edinburgh University) and the Consortium Survey Scientist (CSS) is Steve Warren (Imperial College). Seventy astronomers are members, mostly from UK universities, plus a small number from Japan. The consortium meets regularly and every one has full voting rights on key issues, but in practice most of the work is done by a small number of working groups. As part of joining ESO, the UK has agreed that all the data from this public survey programme will be made available to astronomers from all ESO member states. We are now actively encouraging additional ESO members for both the full consortium and key working groups. The consortium has no proprietary rights. The policy specified by the UKIRT Board is that survey data will be freely available to astronomers from all ESO member states in the first instance, and to the rest of the world eighteen months after each successive release.
The UKIDSS project is not an end-to-end private enterprise, like SDSS. Neither is it a traditional public service programme, operated entirely by an observatory on behalf of a community. Rather, it is a kind of altruistic super-open-time proposal. The telescope and camera are public UKIRT facilities, whose construction, maintenance, and operation are the responsibility of UKATC and JAC. The UKIDSS consortium is a collection of private individuals who proposed to the UKIRT Board that a very large survey should be carried out by themselves, but on behalf of the whole community, with no proprietary ownership of the data by the consortium. The agreed responsibilities of the consortium are for scientific design and implementation of the survey, in the context of a working camera, and a working data pipeline system (see below). The UKIDSS concept was first proposed in 1998, alongside the camera project itself, with a final full scientific proposal to the UKIRT Board in March 2001 requesting 1200 nights spread over seven years. The programme is approved subject to rolling review and should begin in early 2004.
The scientific goals of UKIDSS are summarised elsewhere in these proceedings, but we will give a brief flavour here. It is not a single survey, but a suite of five surveys with a kind of ``wedding cake structure''. There are three very large shallow surveys totalling almost 7000 sq.deg. to a depth of K=18-19 : the Large Area Survey (LAS) covering a significant fraction of the SDSS area; the Galactic Plane Survey (GPS) covering much of the Milky Way visible to UKIRT at ; and the Galactic Cluster Survey (GCS), covering many key large open clusters. Next there is a smaller but deeper survey, the Deep Extragalactic Survey (DXS) covering 35 sq.deg. to K=21, over four selected areas with substantial multiwavelength data available. Finally there is the Ultra Deep Survey (UDS) covering 0.75 sq.deg. to a depth of K=23, centred on the Subaru Deep Field, which also has a wealth of very deep multiwavelength data available or imminent. Each one of these component surveys is two orders of magnitude larger than exisiting surveys to comparable depth. The prime purpose of all the surveys is to produce a legacy database that will fuel many scientific projects for years to come, but the design has been optimised with a number of specific goals in mind. These include detection of z=7 quasars and the epoch of re-ionisation; discovery of the very nearest and smallest sub-stellar objects; the shape of the initial mass function, and its environmental dependence; large scale structure and the value of the equation of state parameter ; the growth of large scale structure at z=0, z=1, and z=3; the abundance of high redshift ellipticals; and the connection between EROs, AGN, and high-z ellipticals.