THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT
2000

3.4. Instruments

3.4.1. CGS4 (1-5 micron multiple-resolution spectrometer with 256256 array)

CGS4 was used for 44% of the PATT nights in semesters 00A and 00B, and 2000 was another successful year for this instrument, with only 0.3% of clear time lost to faults. In March, a new A/D converter was installed which fixed a minor but long-lived CGS4 problem: one channel was consistently dropping bits. Read noise was consistently excellent (in the mid-to-high 30-electron range) after this change was made. In July the echelle grating was replaced with the 150 l/mm grating, internal parts of the coldhead were replaced, the new CVFs were inspected and the grating mechanism was also inspected for brake wear. No problems were found and the engineering was completed smoothly.

CGS4 operated well under the new ORAC system with only a few minor problems, mostly involving aperture definitions and peakup. Initial ORACDR recipes for data reduction covered the basic observing modes of CGS4, and these proved to be ample for most purposes. The only notable data reduction issue was the discovery that for some months, the pipeline flux calibration routine had been incorrectly implemented. This was fixed shortly after it was discovered, the major surprise being the long delay before the problem was noticed. All affected observers were advised to re-calibrate their data off-line.

3.4.2. IRCAM/TUFTI (1-5 micron camera with 256256 array)

IRCAM was used for 12% of the PATT nights in semesters 00A and 00B. Half of the runs used IRPOL. All runs in semester 00A were affected by the persistent data-transfer problem known as ``BDS errors''. On the last IRCAM/TUFTI run of the semester, a hard failure of the waveform generator board resulted in continuous BDS errors. The board was replaced with the spare which after some work appeared to have finally cured the problem. However, when winter returned the errors also returned. In late January 2001 the cause was finally traced to the cooling fans in the ALICE rack, and investigations were beginning into how the fan arrangement might be altered.

Mechanically, IRCAM performed well through the year, with only two cryogenic incidents. In October/November the cryostat was warmed up and maintenance work was carried out on the filter wheels, which had been producing datum errors. The work was successful, reducing the lost time from more than two hours per semester to 0.6.

Transfer of IRCAM/TUFTI data acquisition over to the ORAC system was initiated in the first half of 2000, and successfully introduced to outside users at the start of 00B. Software changes were made to the new TCS and the new ORAC data acquisition system that made the instrument more robust and convenient to use.

3.4.3. UFTI (1-2.5 micron camera with 10241024 array)

UFTI was used for 38% of the PATT nights in semesters 00A and 00B and was the first instrument to achieve robust performance under ORAC. Initial problems with data acquisition and handling were quickly resolved. Documentation on the use of UFTI with ORAC was quickly made available on the UKIRT web pages. Links to the recipe descriptions are in fact links to cgi scripts which automatically generate the online documentation from the perl source comments; thus the documentation will never become out of step with the actual running systems.

A programme was begun to monitor bad pixels and to regularly update the UFTI bad-pixel mask used by ORAC-DR; in the initial state, 0.36% of the 1 million pixels in the UFTI array were flagged as ``bad'' by the bad-pixel mask. Initial results of the study indicated that, over a period of a few weeks, some pixels ``migrate'' across the good/bad cut-off; but that the bad-pixel mask nevertheless remains accurate to within 5%.

High humidity continued to cause condensation on the cryostat window, and a significant fraction of the small amount of UFTI time lost was to this cause. A fan was installed in front of the UFTI window in mid-December to aid in clearing condensation, and worked well immediately. The fan is always on; a heater is also available to remove condensation in need. Its use is not an option with the Fabry-Perot, which is highly temperature-sensitive. Towards the end of 00B, low level noise was seen and the array controller was swapped for the spare early in 2001. Some vignetting of the filters was seen in 00B and in March 2001 the instrument filter wheels were refurbished, solving the problem. After a power outage in November UFTI had cooling problems which were traced to a faulty coldhead, which was replaced.

Engineering was scheduled for early October when a number of filters would have been upgraded to ``Mauna Kea'' standards. The H 2-1S(1) filter, which gave elongated images, should also have been replaced. In the event, Infrared Engineering - the UK-based company contracted by JAC (and a number of other observatories) - were unable to deliver these filters and the engineering was postponed.

3.4.4. Accessories

UKIRT's support for polarimetry options on all instruments is unique among MK facilities. IRPOL, the facility polarimetry unit, also found favour with the visitor instrument TRISPEC. During the course of 2000, IRPOL was integrated with the new telescope control and data acquisition systems, and the first observer to use ORAC did so with IRCAM3 and IRPOL at the very beginning of Semester 00B. A number of ORAC template sequences and data reduction recipes are now offered for IRPOL imaging.

The (K-band) Fabry-Perot was used with UFTI for three projects in 00A and a further three in 00B. A simple shell script is now being used to speed up the alignment process. In addition, with the DVS, stable temperature conditions are reached within an hour or so of the start of each night. FP control with ORAC was commissioned in October; data reduction recipes and associated ORAC template observing sequences are now available. Use of UFTI+FP with ORAC is fully documented on the UKIRT web pages. Actively cooling and/or maintaining the 400 km/s FP (and indeed the higher-resolution FPs) at a fixed temperature might be an option if the FP and UFTI are to be offered after the arrival of UIST.

3.4.5. Visitor Instruments

Visitor instruments MAX and TRISPEC were used for 6% of the PATT nights in semesters 00A and 00B. Both performed quite well.

TRISPEC was allocated time at the end of August, just post-ORAC commissioning. Two PATT runs independent of the TRISPEC team were carried out, in addition to observations by Chrysostomou and the TRISPEC team and an engineering night allocated at the start of the run. The observing went reasonably well, and it was hoped that a further visit could be undertaken once some flexure issues were cured.

MAX, the MPIA thermal-IR camera, had a productive visit in December 2000. Images of Orion at 10 and 20 micron were completed once some instrument problems had been identified and cured. The thermal stability of UKIRT was praised by the MPIA team; this is a good sign for future use with Michelle.