THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT 2003-2004

3.2. Telescope Usage

Semesters 03A and 03B were relatively normal semesters, with CGS4, UFTI and UIST available. Semester 03A ended a month early so that the primary could be realuminised. Due to changes in the WFCAM delivery schedule (see Chapter 4), semesters 04A and 04B merged into one semester running from January 16th to September 26th 2004, at which point UKIRT was closed for WFCAM commissioning. Michelle was offered (and CGS4 removed) for the period February to April 2004. The weather was particularly bad in March 2004 with 65% of the month lost to weather.

In semester 03A UKIRT became flexibly scheduled. The ultimate goal is completion of high-priority programmes, but also programmes requiring the best conditions should be given the best chance of being done in those conditions. It is required that observers who come to the telescope should have a good chance to carry out their own programme while retaining a significant degree of discretion in selecting programmes for execution. These goals and requirements are achieved by giving Principal Investigators of highly rated programmes summit occupancy for a period of time in excess of their allocation. They can observe their own programme unless a PATT-approved override is called, or conditions are too poor or they have used their allocation, in which case programmes are taken from the queue. The observer can choose between the top few projects to avoid an excessive number of instrument changes, or to avoid a mode with which they are unfamiliar. Some programs were scheduled classically in 03A - either because of complexity (e.g. spectropolarimetry) or because the target had to be monitored at fixed intervals. In semesters following 03A this was handled differently - complex programmes were given observer status and monitoring programs were scheduled so that they became available at appropriate times, with a buffer of a few nights to allow for poor weather.

The JAC OMP software automates many of the flexible observing tasks. These include selecting an observation suitable for the weather conditions, bookkeeping, and notification of principal investigators when data has been obtained for their project. A feedback system is provided and data can be obtained via the web.

Flexible scheduling was successful from the start - in 03A the average completion rate was 77%, and for the top 10 ranked programmes it was 94%. Over half of the programmes were more than 95% complete, and almost three-quarters were over 50% complete. Semester 03B had worse weather conditions than 03A but nevertheless the average completion rate was over 70%. The weather was also poor in 2004 and by the end of July 2004 the completion percentage for all projects was 60%. The following plots shows the 03A and 03B completion statistics and the 04A completion statistics.

The following table summarizes telescope usage for semesters 03A, 03B,and 2004, covering the period February 1, 2003 to September 26, 2004. Fault rate remained low through 03A and 03B, but during 2004 telescope systems became somewhat unreliable, as described in the next section.