Top End

Andy Adamson

Associate Director, UKIRT

A Weather Report

It is not often that a UKIRT Newsletter begins (and ends) with commentary on the weather, but the science impact of this dreadful winter on Mauna Kea is already significant. The last few months have seen a frustrating series of upper-level lows and associated fronts marching across the Pacific, bringing fog, ice and snow to the summit; and the end is not yet in sight. At the time of writing, the telescope is inaccessible with snow drifting up to six feet in places between HP and the summit ridge. Observing statistics for the past month are quite dire: in the four weeks ending on the 19th March UT, less than 40 hours of PATT observing has been undertaken. That this small amount of clear time has been spent getting more than ten different 06A projects underway is better than would have been achieved under a classical schedule, but that is little comfort. Astronomy on Mauna Kea is unquestionably in temporary hiatus, and the science output of the current Cassegrain block will inevitably fall well short of what would be expected in a "normal" year.

WFCAM and UKIDSS

The recent UKIDSS Early Data Release marked the culmination of a major effort on the part of the UKIDSS consortium, and the archive and pipeline providers in Edinburgh and Cambridge. Relatively small by comparison to the amount of UKIDSS data now in hand, even this release shows the potential of a coherent survey combined with an efficient instrument scheduled optimally. Taking up to 200Gbyte per night, WFCAM has of course easily eclipsed all previous UKIRT data-taking records. The total number of UKIDSS pixels observed in November 2005 alone equals the total number of pixels in the 2Mass survey. With early data now available on the WFCAM science archive and the follow-up potential starting to become clear, we look forward to even better data products and the next major data release in early July. Data coming from the telescope should also improve in quantity and quality: at present work is going on between the JAC and UK ATC to take advantage of faster PCs to significantly reduce overheads in the data acquisition. WFCAM returns to the telescope at the end of April, and engineering scheduled at the start of the block should help to improve image quality as a function of telescope attitude.

Changes at Cassegrain

With demand for the Cassegrain instruments remaining at a healthy level after the change to the alternating Cass/WFCAM "block" schedule, we continue to identify and implement improvements in their functions and operation. This issue reports on two new developments: the implementation of coronagraphic polarimetry via the installation of wire masks in the cold focal plane of UIST; and the essential elimination of "spectropolarimetry ripple" by changing the waveplate position angle sequence for spectropolarimetry. Chris Davis has also been carrying out further tests of slitless spectroscopy, which will be released for common use when fully characterized, and work is ongoing at the UK ATC to provide an SDSU controller / acquisition system for UIST. Besides being compatible with WFCAM, one of the expected benefits of this new controller will be the ability to read out the full UIST array in the thermal infrared.

Imiloa

Finally, the Imiloa Astronomy Center of Hawaii is the latest addition to University Park; for more details see Thor's report at the end of this issue. The JAC has been active in support of the development of materials for this centre, and we look forward to the full operation of the center over the coming years.