THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT
1997

3.4. Instruments

3.4.1. CGS3 (10 and 20 m 32-channel low resolution spectrometer)

CGS3 was used successfully on approximately 24 nights during the year. Despite the successful demonstration of MICS at UKIRT (see below), some demand for CGS3 remains because of its 20m capability, which MICS does not possess. There has been no further development work on CGS3 and none is envisaged before its retirement, which is anticipated to be at the end of 1998.

3.4.2. CGS4 (1-5 m multiple resolution spectrometer with 256256 array)

Apart from the first part of the year and a brief period in December 1997, CGS4 operated highly successfully in all modes and continued to be the subject of considerable praise by a number of visiting astronomers. The slit rotation mechanism, which had hampered observations during the latter part of 1996 and continued to inconvenience or limit some kinds of observations in early 1997, was fixed in April 1997 and has operated very well since then. For the most part other faults with the instrument were minor and were addressed quickly. However in late 1997 a period of intermittently unstable array performance culminated in a failure of one of the four readout channels in December. An emergency warm-up of the dewar was required to repair the fault, which turned out to be a broken resistor on the array circuit board. The schedule was rearranged so that no visitors lost observing time. Semester 97B saw the first use of the long camera, which provides a pixel scale better suited for UKIRT's improved image quality, and a 40 l/mm grating (replacing the workhorse 75 l/mm grating) that allows moderate resolution and wide wavelength coverage with the new pixel scale.

3.4.3. IRCAM3 (1-5 m camera with 256256 array)

IRCAM3 operated remarkably smoothly, with no major faults occurring during the year and the performance of the instrument benefited from the improved image quality delivered by the telescope, but the coarse pixel scale (0.28 arcseconds/pixel) of the instrument led to increasing use of the 2X magnifier by the end of the year. The various instrument accessories, and the unusual data acquisition mode snapshot, were employed successfully during the year. The total amount of time lost during 1997 was approximately 10 hours and was due mostly to communications breakdowns between the instrument and the VAX data acquisition software. Two observing programmes which used the snapshot mode with the 5X magnifier suffered from lower than expected sensitivity. This was later determined to be a feature of the magnifier, which originally was intended for image quality tests and which does not decrease the background per pixel when installed. Correct information concerning this is now on the IRCAM3 web pages.

Design work began on a modification to IRCAM3 to convert its plate scale to a smaller one that is more appropriate for imaging in the thermal infrared. Thermal IR imaging is expected to become the primary function of IRCAM3 once the new 10241024 UKIRT Fast Track Imager (UFTI) is delivered in 1998.

3.4.4. Accessories

Both the K band Fabry-Perot (FP) interferometer and IRPOL2 were used several times during 1997 and both performed excellently. Improved software was installed to considerably speed up the FP alignment process. The polarimetry data reduction software was enhanced in several respects.

3.4.5. Visitor Instruments

An integral field unit (IFU) for the J and H bands, designed and built at the University of Durham, was commissioned at UKIRT with CGS4 in Semester 97A. The unit has 72 fibres and reformats a 4 6 patch of sky onto the slit of CGS4. Poor weather prohibited accurate information from being obtained but the performance of the IFU was promising. Additional commissioning time for the instrument has been scheduled early in Semester 98A.

The MPIA thermal IR camera, MAX, had two very successful one-week runs at UKIRT, a third in which poor weather resulted in the observers using CGS4 instead, and another during which a number of technical problems led to considerable lost time. MIRAS, an Australian mid-infrared camera equipped with a polarimeter had a moderately successful observing run in July 1997, although electronic pickup noticeably reduced its sensitivity.

An agreement was reached whereby MICS, a Japanese prototype camera/spectrometer for 8-13 m, is to be offered to UKIRT observers with minimal restrictions in exchange for the opportunity for Japanese astronomers to gain experience in observing at thermal IR wavelengths. Tests of MICS were performed in engineering time at UKIRT in March and September 1997. In March the performance of the instrument was poor and it was judged unsuitable for scientific use at UKIRT. The September test showed that most of the problems with the instrument had been addressed and that its performance was much better. The instrument was to be made available to the community beginning in Semester 98A.

Commissioning and science time for COHSI, a revolutionary fibre-optic J and H band spectrometer built at Cambridge University, which rejects OH line emission, was rescheduled for semester 98A.