THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT
2000

5. Longer-Term Plans

5.1. Multi-Object and Integral Field Spectroscopy

Options for multi-object spectroscopy were explored during 2000. The most promising was a version of the Gemini Infrared Multi-Object Spectrometer (GIRMOS) design, which offers roving integral field units (IFUs) positionable anywhere in a large field. Four pickoffs could feed one spectrometer; a UKIRT-sized version could accommodate four spectrometers, offering 16 roving IFUs in one field. The possibility of a single giant IFU (GIFU) was also explored. Four 2048 HgCdTe arrays similar to those intended for WFCAM could offer up to 32k low-dispersion spectra (each 512 pixels long), which would allow a FOV of around 1 arcmin at a spatial resolution of 0.5 arcseconds. Full utilisation of these spectra would require an array of microlenses, using fixed fibre feeds. However, since even 1024 lenslet-fibre arrays do not exist, a more practical solution is offset lenslet arrays, which do not exploit the available pixels as efficiently, a concern since pixel numbers still set the performance limits of infrared instruments. These options have not been pursued further because the financial situation makes the necessary support unlikely. However they may have their role in a mainly-wide-field future for the telescope.

5.2. Adaptive Secondary Mirror (ASM)

Further consideration was given to equipping UKIRT with an Adaptive Secondary Mirror, in many ways the most attractive AO option for an infrared telescope, and the most simple to integrate with UKIRT's instrument suite. This was pursued with the UCL Optics group and a grant application was made for related technical developments. This was not successful, and since the UKIRT group does not have the resources to undertake such work, these plans have been shelved.

5.3. The OHANA Project

The OHANA concept proposes interferometric coupling of 3 to 10 m class telescopes on Mauna Kea, taking advantage of breakthroughs with AO and coherent transport of light with optical fibres. Science cases have been presented in the areas of AGNs, YSOs, Cepheids and brown dwarfs. For YSOs for example, OHANA should be able to probe the inner accretion disk and determine its size. A measurement of the diameter of a brown dwarf would give fundamental information and could be achieved using the full resolution and the largest pupils; in the H-band the resolution would be 425  microarcseconds. An implementation study was initiated in 2000. The proposed timescales are: by March 2001 demonstrate beam extraction from AO foci with fibres and routing to ground; in 2002 achieve first coupling of a pair of telescopes leading to fringes; in 2003 complete array capability. UKIRT has an important contribution to offer as it is at the southern end of the summit complex. An AO system would be required. The ICSTM optics group has expressed interest in providing an AO system suitable for feeding UKIRT's signal to the delay line ``switchyard'', probably at Keck.