THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT
1999

5. Longer-Term Plans

5.1. Multi-Object and Integral Field Spectroscopy

At the November 1999 UKIRT Board meeting the Head of Operations identified wide field spectroscopy as the most likely development path for the longer term future of UKIRT. It was considered that there was insufficient access to powerful widefield spectroscopic capabilities in the near IR to complement WFCAM and the VISTA project (neither of which will provide any spectroscopic capability), while initially Gemini will be concentrating on small-field observations exploiting its high-resolution performance, especially with adaptive optics. Four possible options were considered:

• A Giant Integral Field Unit (GIFU). With the telescope remaining at F/36, a field of 1.5 arcmin would be covered by an image-slicing system giving 0.5" pixels at spectral resolution R around 4000. This would require four separate channels (probably four individual spectrometers) each equipped with a 4k x 4k array or mosaic (possible developments for the NGST). This would be an expensive but extremely powerful instrument. (Some thought was given to alternative ways of effecting such a truly giant IFU. e.g. by the use of large fibre bundles. The resulting design was deemed impractical.)
• A Multiple Integral Field Unit (MIFU). At F/36, a system of 10-30 Multiple Deployable Integral Field Units (which have been the subject of a successful design study at the UKATC for Gemini and NGST) would exploit a field of about 6 arcmin. The deployable IFUs have an ``optical trombone'' design providing cold optics suitable for low-background work out to 5 µm. Several (probably 4) parallel unit spectrographs would be required. A UKIRT prototype for a Gemini system, using a single spectrometer, is an attractive possibility.
• A variant on the above would incorporate a change of the default F/ratio to F/16 (long considered on grounds of compatibility with Gemini as well as access to a larger FOV). This could offer a 19 arcmin field to the deployable IFUs.
• Some thought has also been given to a more traditional multi-slit system. The UKATC has produced outline designs for a system allowing cold masking plates to be employed and exchanged on a daily basis. Technological developments for the NGST may permit non-mask-based approaches, using solid-state micro-mirrors or micro-apertures to substitute for mask plates.

5.2. Adaptive Secondary Mirror (ASM)

An adaptive secondary remains of interest for the long-term future of UKIRT. Unfortunately supporting work at UCL for such a facility was not supported in the 1999 grants round and it is not clear that further progress will be possible.