THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT
1999

3.4. Instruments

3.4.1. CGS4 (1-5 µm multiple resolution spectrometer with 256 x 256 array)

GS4 operated extremely successfully throughout 1999, with only 0.5% of clear time lost to faults in semester 99A and 1.2% lost in 99B. Read noise was kept consistently low (40 electrons and below, down to 25 for long exposures). The new CVFs survived four thermal cycles without any sign of the crazing of which the manufacturers, OCLI, had warned. The 40 lines/mm grating remains the workhorse grating. The echelle was in use for one month at the beginning of 99A, but was replaced by the 150 lines/mm grating for the rest of the semester. The echelle was put back in place in November 1999 for the winter star-formation period. Two recurrent problems were cured during 1999: blackbody unit datum failures and inaccurate grating settings (cured by removing debris from the grating datum wheel brakes). A minor problem with the offset angle between the one and two-pixel slits manifested itself to the detriment of a polarimetry run in 99B; the method by which the offset angle is measured has been improved. Following the successful integration of UFTI with ORAC and the clear gain in efficiency offered by ORAC control, it was decided that CGS4 would be controlled by ORAC from May 2000 onward.

3.4.2. IRCAM3 (1-5 µm camera with 256 x 256 array)

IRCAM was used for 15% of the PATT nights in Semester 99A, and in its re-engineered form for 4% of the PATT time in Semester 99B. After a cryogenically eventful semester in which compressor problems caused two warmups, IRCAM spontaneously warmed up the night before its final removal from the telescope for conversion to a smaller pixel scale appropriate for thermal imaging with the upgraded telescope. The new format was successfully commissioned at the start of semester 99B, and sensitivity appears to be good. Transformations between photometric systems (old IRCAM to TUFTI with new consortium filters) were determined and a programme to increase the number of L' standards was begun in semester 99B. The M-band performance is still being determined. IRCAM data are now reduced using ORACDR; recipes suited for high-background imaging were implemented during commissioning. There were two ongoing sources of faults with the instrument - a datum problem with one filter wheel and ALICE BDS errors. The ALICE electronics were refurbished in June as part of an ongoing investigation of this long-running problem (which was present at delivery of the instrument). While the IRCAM ALICE controller shows BDS errors, the CGS4 system does not, for reasons that are not yet understood. As the CGS4 ALICE produces lower read noise, that rack will be kept with CGS4 until such time as matching the noise performance becomes possible. Following the successful integration of UFTI with ORAC and the clear gain in efficiency offered by ORAC control, it was decided that IRCAM would be controlled by ORAC from May 2000 onward.

3.4.3. UFTI (1-2.5 µm camera with 1024 x 1024 array)

UFTI was used for 32% of the PATT nights in Semester 99A, and for 37% of the PATT nights in 99B. The instrument was initially ``shared-risk'' and shake-down of the system continued to the end of 99A. Documentation improved, the number of data reduction recipes increased, and operational procedures were consolidated, throughout the period. In April the polarimetry prism was installed. Re-engineering in January and April improved the reliability of the filter wheel mechanisms. Photometric transformations were determined to the old UKIRT Standards JHK system; work on the UFTI IZ system is ongoing. UFTI has demanding memory and processor requirements, particularly for large-area mosaics. This revealed itself in a number of failures of the summit data reduction (and some impact on other instruments' reduction systems), which were mitigated by installation of additional memory, the provision of ``basic'' reduction recipes which bypass some of the more advanced steps, and the installation of less leaky algorithm packages.

3.4.4. Accessories

1999 was an eventful year for polarimetry, with IRPOL commissioned in two new modes. Commissioning of IRPOL with UFTI took place in June 1999. At near-infrared wavelengths (J--K) the efficiency and instrumental polarization were measured to be good (around 99% and below 0.5% respectively). Polarimetry may be possible in the I and Z-bands if a suitable flat fielding method can be developed. IRPOL was also used, for the first time, with CGS4 and the medium-resolution (150 l/mm) grating in semester 99B. Some difficulty was encountered in aligning the orthogonally polarized (e- and o-) beams with the CGS4 slit, but this issue is now better understood and a more precise alignment procedure was developed. L- and M-band characterization measurements were obtained in 99B; these indicate that the (wavelength-dependent) efficiency levels are high: >90% in both bands. IRPOL remains a popular add-on facility with all of the instruments at UKIRT, and UKIRT's spectropolarimetry and imaging polarimetry capability remains unique on Mauna Kea. Of the 42 PATT proposals awarded time in 99B, 5 requested IRPOL (3 with CGS4, one of these -- a starred project -- at M-band); a sixth University of Hawaii project also used IRPOL with UFTI for 5 consecutive nights.

The 350 km/s Fabry-Perot interferometer was not used in 1999.

3.4.5. Visitor Instruments

Two visitor instruments saw time on UKIRT in 1999. MAX, the MPIA camera, returned to UKIRT in December 1999. This run was not a success instrumentally, with various communications problems preventing significant observing, and the team fell back to UKIRT facility instruments. MICS, the Japanese ten-micron imager/spectrometer, was not made available since the MICS team remains committed to COMICS development for Subaru. TRISPEC (PI: Sato) was not allocated time by PATT in Semester 99A. Further proposals were submitted for 00A, and it is likely that TRISPEC will see UKIRT time in February/March 2000. MIRAC (PI: Hoffmann) was not awarded time on UKIRT in 99A. It will be at the MMT for an extended period and is unlikely to come to UKIRT in 2000.