THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT
2001-2002

3.4. Established Instrumentation

3.4.1. CGS4 (1-5µm multiple-resolution spectrometer with 256x256 array)

In 2001 CGS4 performed well, with lost time being dominated by IEEE bus problems. It was discovered that the algorithm used to calculate the CGS4 instrument aperture for non-zero slit position angles was incorrect; this was fixed using measurements taken during a QA night. In 2002 there was a fault in a cable in the calibration unit, and some grounding-related noise problems, all of which were resolved.

In April 2001 the 150 l/mm grating was replaced with the echelle and this is expected to be the long term configuration; no further major engineering is planned. In semester 02B CGS4 was moved from the South to the North port to allow UIST installation at the South. Subsequently a slit-wheel datum problem was traced to a broken wire and subsequently to burnt wiring internal to the cryostat, requiring CGS4 to be warmed up. The telescope schedule was changed to avoid losing time to this fault.

3.4.2. IRCAM/TUFTI (1-5µm camera with 256x256 array)

IRCAM was used for 6% of the PATT and UH nights in semester 01A and 9% in 01B. In 2002 the WHIRCAM electronics were shipped to UKIRT from La Palma; these provided useful spares for IRCAM and CGS4.

The well-known data transfer problem known as a "BDS error" was traced in late January 2001 to the cooling fans in the ALICE rack; extremely few errors occurred if the fans were off. In 2001 intermittent array noise was seen; various connections were cleaned and the array performance returned to normal. The closed-cycle cooler chillers failed twice after mains power glitches, although no observing time was lost. It was determined that power glitches were causing the compressor to turn off because it was slaved through the PLC; a direct slaving cable was installed. The 3.1µm ice filter was replaced but still found to be poor, indicating that ice was forming in the cryostat. Given the limited projected lifetime of IRCAM no repair was attempted.

After the arrival of MICHELLE in 2001, IRCAM shared the East port with the wavefront sensor. The instruments were switched several times during 01B, but at the end of the semester IRCAM was removed for an extended period and then offered for two months of 02A before being permanently removed on August 28th 2002. The IRCAM series of imagers were heavily used at UKIRT for more than fifteen years. The first IRCAM was commissioned in 1986 and had a 58x62 InSb array. It replaced the single channel photometers UKT6 and UKT9, which were formally retired in 1994. In this same year, 1994, IRCAM was upgraded to a 256x256 InSb array and fitted with a new array controller. In 1998, following the successful commissioning of UFTI, IRCAM's optics were changed to produce a smaller pixel scale of 0.08arcsec/pixel, which made better use of the improved image quality of the telescope and made observing in the thermal more efficient. The IRCAM series served UKIRT well.

3.4.3. UFTI (1-2.5µm camera with 1024x1024 array)

UFTI was used for 57% of the allocated PATT nights in semester 01A, 48% of 01B, 36% of 02A and 32% of 02B. At the start of 01A intermittent horizontal banding was seen on the array, and one of the filter wheels began to fail, resulting in vignetting and gradients across the images. UFTI was warmed up in April 2001 and the filter wheel gears were cleaned; since then the filter wheel problem has not recurred. The intermittent noise problem was eventually traced to a poor connection in one of the controller cables. In 01B the familiar "negative-countdown" bug was traced to an EPICS-related task and cured. In November two of the array quadrants were found to be blank, a problem traced to broken connectors in a cable between the array controller and the cryostat. In mid-December and again in January, bias structure and irregular striping were seen across the array. The controller was swapped and sent away for maintenance. In 02A an entire night was lost due to a combination of a failed controller and an incorrectly-seated cable. In August 2002 the instrument was warmed up to replace O-rings and patch vacuum leaks.

3.4.4. Accessories

In semester 01A linear and circular polarimetry data were acquired with TRISPEC and IRPOL as part of three PATT projects. IRPOL was also used with IRCAM in a fourth PATT programme. In 01B IRPOL was used in one (IRCAM) project. In 02A IRPOL was used as part of a backup programme for a MICHELLE project; four hours were lost to a failure of the waveplate drive. This was the first time this particular type of fault had resulted in lost telescope time. On troubleshooting, it was found that a fuse had failed and that the motor controllers for IRPOL were not powered up. The IRPOL EPICS window has been modified so that loss of IRPOL control is now reported to the TSS and the waveplate is visually inspected and reset to datum at the beginning of each IRPOL night. In 02B IRPOL was used for two projects, including 10µm spectropolarimetry with MICHELLE.

The Fabry-Perot was particularly popular in 01A, being employed in four separate programmes. Recently developed scripts and ORAC recipes worked well. In 01B the FP was used once, in 02A it was not used and in 02B it was used twice.