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UKIRT's Instruments

Several instruments to measure infrared radiation (e.g., cameras for making images, spectrometers, polarimeters) may be simultaneously mounted at UKIRT's four Cassegrain focus stations.

Current instruments

There are two current imagers (i.e, cameras): IRCAM3 and UFTI. IRCAM3 is the third generation of a design which began with the world's first infrared imager at an astronomical facility, the InfraRed CAMera, "IRCAM", which was completed at Royal Observatory, Edinburgh, (ROE: now the UK Astronomy Technology Centre, UKATC) in 1985. IRCAM3 uses an array of 256x256 Indium Antimonide (InSb) detectors, sensitive to radiation from &lt1 to 5.4 microns. It originally covered an area 72 arcsec square with individual pixels 0.280 arcsec square, but an upgrade undertaken in the late 1990s reduced the pixel scale to 0.08 arcseconds and the field of view to 23 arcseconds, with a view to improving the sensitivity to thermal-infrared radiation. IRCAM also preserves the capability to take images at a very fast frame rate for making shift-and-add images, a technique which has proved especially useful for making very high resolution pictures of moderately bright objects

UFTI is a high-resolution near-infrared imager built specifically to take advantage of the UKIRT image quality, which is second to none for infrared telescopes without adaptive optics. Built at the University of Oxford, UFTI employs a 1024x1024 array of mercury cadmium telluride (HgCdTe) detectors sensitive between ~1 and 2.5 microns wavelength. This offers a larger field of view (92 arcsec square) with finer resolution (0.090 arcsec pixels) than does IRCAM.

The main spectrometer is the pioneering CGS4 (Cooled Grating Spectrometer Mk 4), built at the ROE in 1986-1991. Like the IRCAMs this is sensitive to light from 1 to 5 microns wavelength. CGS4 offers moderate- to high-resolution spectra of single objects or a slice of sky up to 90 arcseconds across. First commissioned in 1991 and upgraded in 1995, CGS4 on UKIRT remains one of the most powerful facility of its kind in the world, now offering spectroscopy with spatial resolution of 0.6 arcsec and spectral resolutions from R~400 up to R~35,000.

In the mid-IR wavelengths from ~7 microns to ~25 microns spectroscopy and aperture photometry are provided by  Michelle , an imager and spectrometer containing a two-dimensional 300x400 array of thermal-infrared (arsenic-doped silicon - Si:As) detectors. This instrument can provide spectra at five different resolutions in the 10 and 20 micron atmospheric windows, or imaging in both broad and narrow-band filters.  The atmosphere is generally transparent from 7 to 13 microns and quite often also from 18 to 25 microns. Michelle will be shared between UKIRT and Gemini-North.

Visiting astronomers from time to time bring their own (private) instruments on observing campaigns to UKIRT. 

Future instruments

In 2002 a "workhorse" instrument, the UKIRT Imager SpecTrometer UIST (which is also one of the Western Isles, or Outer Hebrides, of Scotland) will come into service at UKIRT. This will offer medium resolution spectroscopy at wavelengths between 1 and 5 microns and includes an "Integral Field" mode which will provide a spectrum of every spot on a square area of sky, probably about 5 arcseconds square. (High resolution spectroscopy may remain available with CGS4.)

Initially UIST will use a 1024x1024 array of InSb detectors, thus offering sensitivity over the same wide wavelength range as IRCAM but with much bigger field of view and better spatial resolution. Spectrosopy will be available in long-slit mode across a single atmospheric window and with a short (10-12 arcsec) slit across 2 or 3 windows at once.

Further enhancements to UIST are likely to include its equipment with a larger 2048-square array, either built of 4 of the 1024-square InSb detectors on a single multiplexer or, perhaps more likely, a monolithic 2048-square array of HgCdTe material, tailored to provide sensitivity over wavelengths from 1 to 5 microns. Such devices are under development for the Next Generation Space Telescope (NGST) project, and we hope that UIST will benefit from this work.

Under consideration: Widefield IR Instrument

Part of the programme approved by the Williams Panel was the development of a capability for widefield astronomy on UKIRT. 

Equipping any large telescope to observe a very large field of view while retaining good image quality is challenging; it is even more so in the Infrared, where the images are still better but there are more constraints on the design (such as a high fraction of cryogenic components and a shortage of optical materials which are usable over the wide bandwidths involved).

The Wide field camera project (WFCAM) was formally approved by PPARC in Jan 2001, and is now well on the way to completion; we anticipate delivery in late 2003.