Nicholas P. Rees

UFTI: the 0.8 - 2.5 μm fast track imager for the UK infrared telescope

In 1996, it was proposed to build a near-infrared imager for the 3.8-m UK Infrared Telescope in Hawaii, to exploit the 1024 pixel format detectors that were then becoming available. In order to achieve a fast delivery, the instrument was kept simple and existing designs were reused or modified where possible. UFTI was delivered within 2.5 years of the project start. The instrument is based around a 1k Rockwell Hawaii detector and a LSR Astrocam controller and uses the new Mauna Kea optimized J,H,K filter set along with I and Z broad-band filters and several narrow-band line filters. The instrument is cooled by a CTI cry-cooler, while the mechanisms are operated by cold, internal, Bergelahr stepping motors. On UKIRT it can be coupled to a Fabry-Perot etalon for tunable narrow-band imaging at K, or a waveplate for imaging polarimetry through 1-2.5 μm; the cold analyzer is a Barium Borate Wollaston prism. UFTI was designed to take full advantage of the good image quality delivered by UKIRT on conclusion of the upgrades program, and has a fine scale of 0.09 arcsec/pixel. It is used within the UKIRT observatory environment and was the first instrument integrated into ORAC, the Observatory Reduction and Acquisition Control System. Results obtained during instrument characterization in the lab and over the last 3 years on UKIRT are presented, along with performance figures. UFTI has now been used on UKIRT for several hundred nights, and aspects of instrument performance are discussed.

Design status of WFCAM: a wide-field camera for the UK Infrared Telescope

An update on the design status of the UKIRT Wide Field Camera (WFCAM) is presented. WFCAM is a wide field infrared camera for the UK Infrared Telescope, designed to produce large scale infrared surveys. The complete system consists of a new IR camera with integral autoguider and a new tip/tilt secondary mirror unit. WFCAM is being designed and built by a team at the UK Astronomy Technology Centre in Edinburgh, supported by the Joint Astronomy Centre in Hawaii. The camera uses a novel quasi-Schmidt camera type design, with the camera mounted above the UKIRT primary mirror. The optical system operates over 0.7 - 2.4 μm and has a large corrected field of view of 0.9° diameter. The focal plane is sparsely populated with 4 2K x 2K Rockwell HAWAII-2 MCT array detectors, giving a pixel scale of 0.4 arcsec/pixel. A separate autoguider CCD is integrated into the focal plane unit. Parallel detector controllers are used, one for each of the four IR arrays and a fifth for the autoguider CCD.

ORAC: a modern observing system for UKIRT

The steady improvement in telescope performance at UKIRT and the increase in data acquisition rates led to a strong desired for an integrated observing framework that would meet the needs of future instrumentation, as well as providing some support for existing instrumentation. Thus the Observatory Reduction and Acquisition Control (ORAC) project was created in 1997 with the goals of improving the scientific productivity in the telescope, reducing the overall ongoing support requirements, and eventually supporting the use of more flexibly scheduled observing. The project was also expected to achieve this within a tight resource allocation. In October 1999 the ORAC system was commissioned at the United Kingdom Infrared Telescope.

Sharing code and support between heterogeneous telescopes: the UKIRT and JCMT joint software projects

UKIRT and JCMT, two highly heterogeneous telescopes, have been embarking on several joint software projects covering all areas of observatory operations such as observation preparation and scheduling, telescope control and data reduction. In this paper we briefly explain the processes by which we have arrived at such a large body of shared code and discuss our experience with developing telescope-portable software and code re-use.

The JCMT observing queue and recipe sequencer

The James Clerk Maxwell Telescope (JCMT), the worlds largest sub-mm telescope, will soon be switching operations from a VAX/VMS based control system to a new, Linux-based, Observatory Control System1 (OCS). A critical part of the OCS is the set of tasks that are associated with the observation queue and the observing recipe sequencer: 1) the JCMT observation queue task 2) the JCMT instrument task, 3) the JCMT Observation Sequencer (JOS), and 4) the OCS console task. The JCMT observation queue task serves as a staging area for observations that have been translated from the observers science program into a form suitable for the various OCS subsystems. The queue task operates by sending the observation at the head of the queue to the JCMT instrument task and then waits for the astronomer to accept the data before removing the observation from the queue. The JCMT instrument task is responsible for running up the set of tasks required to observe with a particular instrument at the JCMT and passing the observation on to the JOS. The JOS is responsible for executing the observing recipe, pausing/continuing the recipe when commanded, and prematurely ending or aborting the observation when commanded. The OCS console task provides the user with a GUI window with which they can control and monitor the observation queue and the observation itself. This paper shows where the observation queue and recipe sequencer fit into the JCMT OCS, presents the design decisions that resulted in the tasks being structured as they are, describes the external interfaces of the four tasks, and details the interaction between the tasks.

JCMT observatory control system

The JCMT, the worlds largest sub-mm telescope, has had essentially the same VAX/VMS based control system since it was commissioned. For the next generation of instrumentation we are implementing a new Unix/VxWorks based system, based on the successful ORAC system that was recently released on UKIRT. The system is now entering the integration and testing phase. This paper gives a broad overview of the system architecture and includes some discussion on the choices made. (Other papers in this conference cover some areas in more detail). The basic philosophy is to control the sub-systems with a small and simple set of commands, but passing detailed XML configuration descriptions along with the commands to give the flexibility required. The XML files can be passed between various layers in the system without interpretation, and so simplify the design enormously. This has all been made possible by the adoption of an Observation Preparation Tool, which essentially serves as an intelligent XML editor.

Active Optics at UKIRT

The 3.8 m United Kingdom Infrared Telescope (UKIRT) has recently installed active control of the primary mirror figure, taking advantage of aspects of the original mirror design, which permits the correction of low order aberrations. In this paper, we present results from a campaign of all-sky wavefront sensing carried out UKIRT. As a result of the campaign, a lookup table is being used to correct for attitude dependent astigmatism, while fixed corrections are applied to trefoil and spherical aberrations. Coma is removed by secondary mirror alignment. A continuous, model based, correction of focus for thermal and elastic effects is also applied. Accurate focus is now maintained throughout an observing night.

Photon counting versus CCD sensors for wavefront sensing: performance comparison in the presence of noise

Using simulations of time evolving speckle patterns we investigate the performance of three different wavefront sensors--a Shack-Hartmann sensor, a curvature sensor and an intensity moments based sensor. We compare the performance of these systems using detectors with two different levels of read noise--0 electronics read noise, corresponding to a photon counting detector and 5 electrons read noise, corresponding to a CCD. We also look at the effect of different source photon rates. For the UKIRT Upgrades program we will address the question which of the three wavefront sensors is optimal. We will also present a new simulation method for time-evolving speckle patterns using two turbulent layers.

Progress on the UKIRT Upgrades programme

All the major components of the United Kingdom Infra-Red Telescope (UKIRT) Upgrades program are now in place. The thrust of the program has shifted to developing the new telescope capabilities so that performance is maintained under real observing conditions. This paper presents an overview of the current state of affairs and focuses on how we have implemented the secondary mirror and fast guide systems and how we control the active primary mirror system to minimize the telescope aberrations.

JCMT/UKIRT Telescope Control System

The Joint Astronomy Centre (JAC) operates the James Clerk Maxwell Telescope (JCMT), the worlds largest sub-mm telescope, and the United Kingdom Infrared Telescope (UKIRT), the worlds largest telescope dedicated solely to infrared astronomy. Although these two telescopes investigate different regions of the electro-magnetic spectrum and have different mounting arrangements, the JAC (in collaboration with the Anglo-Australian Observatory) has developed the Portable Telescope Control System (PTCS) software so that it can be used on both JAC telescopes. The benefit of this work is increased efficiency, reduced maintenance time, and reduced personnel costs as a result of using a common code base on both JAC telescopes. During the next year, the PTCS will be enhanced as part of the JCMT Observatory Control System (OCS) project so that configuration information can be transmitted to the PTCS via XML files. This will simplify the PTCS interface and expedite the implementation of the OCS. This paper gives an overview of the PTCS, describes its use on both telescopes, and indicates how XML files will be used to configure the telescope prior to the start of an observation.