The James Clerk Maxwell Telescope (JCMT), the world's 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 observer's 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.
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.
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.
A 350GHz 4 × 4 element heterodyne focal plane array using SIS detectors is presently being constructed for the JCMT. The construction is being carried out by a collaborative group led by the MRAO, part of the Astrophysics Group, Cavendish Laboratory, in conjunction with the UK-Astronomy Technology Centre (UK-ATC), The Herzberg Institute of Astrophysics (HIA) and the Joint Astronomy Center (JAC). The Delft Institute of Microelectronics & Sub-micron Technology (DIMES) is fabricating junctions for the SIS mixers that have been designed at MRAO.
Working in conjunction with the 'ACSIS' correlator & imaging system, HARP-B will provide 3-dimensional imaging capability with high sensitivity at 325 to 375GHz. This will be the first sub-mm spectral imaging system on JCMT - complementing the continuum imaging capability of SCUBA - and affording significantly improved productivity in terms of speed of mapping. The core specification for the array is that the combination of the receiver noise temperature and beam efficiency, weighted optimally across the array will be <330K SSB for the central 20GHz of the tuning range.
In technological terms, HARP-B synthesizes a number of interesting and innovative features across all elements of the design. This paper presents both a technical and organizational overview of the HARP-B project and gives a description of all of the key design features of the instrument. 'First light' on the instrument is currently anticipated in spring 2004.
The Joint Astronomy Centre (JAC) operates the James Clerk Maxwell Telescope (JCMT), the world's largest sub-mm telescope, and the United Kingdom Infrared Telescope (UKIRT), the world's 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.
The JCMT, the world's 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.
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.
From 1991 until 1997, the 3.8m UK Infrared Telescope (UKIRT) underwent a programme of upgrades aimed at improving its intrinsic optical performance. This resulted in images with a FWHM of 0."17 at 2.2 μm in September 1998. To understand and maintain the improvements to the delivered image quality since the completion of the upgrades programme, we have regularly monitored the overall atmospheric seeing, as measured by radial displacements of supaperture images (i.e. seeing-generated focus fluctuations), and the delivered image diameters. The latter have been measured and recorded automatically since the beginning of 2001 whenever the facility imager UFTI (UKIRT Fast Track Imager) has been in use.
In this paper we report the results of these measurements. We investigate the relation between the delivered image diameter and the RMS atmospheric seeing (as measured by focus fluctuations, mentioned above). We find that the best seeing occurs in the second half of the night, generally after 2am HST and that the best seeing occurs in the summer between the months of July and September. We also find tha the relationship between Zrms and delivered image diameter is uncertain. As a result Zrmsfrequently predicts a larger FWHM than that measured in the images.
Finally, we show that there is no correlation between near-infrared seeing measured at UKIRT and sub-mm seeing measured at the Caltech Submillimetre Observatory (CSO).
The upgraded 3.8 m UK Infrared Telescope employs active control of the primary mirror figure and secondary mirror alignment to constrain intrinsic wavefront errors, currently to approximately 180 nm, while a fast guider controls a tip- tilt secondary to remove telescope vibrations and tracking errors. It routinely produces images with FWHM below 0.'5 at 2.2 micrometers wavelength (the K-band). The best fully-sampled image yet recorded has FWHM equals 0.'171 and is believed still to be the best ever achieved by a ground-based telescope without the use of higher-order adaptive optics.
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.
The paper describes the manufacture and testing of a lightweighted Zerodur secondary mirror for the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. The 313 mm diameter mirror is mounted on a Piezo platform for fast tip/tilt corrections. Therefore, the mirror mass has to be minimized to achieve high dynamic properties of the adaptive tip/tilt platform. The goal was to test the convex secondary without large auxiliary optics (Hindle sphere). We measured the mirror through the back surface using a small null lens system. A special transparent and highly homogeneous Zerodur was used for this purpose. We demonstrate that grinding a honeycomb structure and acid-etching of the back side of the mirror does not affect the figure of the polished convex surface.
The upgraded 3.8 m UK Infrared Telescope is now provided with: (1) tip-tilt image stabilization by a light-weighted secondary mirror on piezo-electric actuators, controlled by a fast guider sampling at >= 40 Hz on guide stars V m6; (2) active primary mirror figure and secondary mirror alignment control, via a regularly-maintained look-up table; (3) active focus measurements and correction by the fast guider, supplementing a focus maintenance model which corrects for elastic and thermal changes; (4) ventilation of the 2600 m3 dome by 16 apertures totalling 50 m2; (5) insulation of the underside of the concrete dome floor; and (6) internal air circulation during the day, to reduce heating of the upper telescope steelwork.
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.
The 3.8 m UK Infrared Telescope has been the focus of a program of upgrades intended to deliver images which are as close as possible to the diffraction limit at (lambda) equals 2.2 micrometers (FWHM equals 0.'12). This program is almost complete and many benefits are being seen. A high-bandwidth tip-tilt secondary mirror driven by a Fast Guider sampling at <EQ 100 Hz effectively eliminates image movement as long as a guide star with R < 16.m5 is available within +/- 3.'5 of the target. Low-order active control of the primary mirror and precision positioning of the secondary, using simple lookup tables, provide telescope optics which are already almost diffraction limited at (lambda) equals 2 micrometers . To reduce facility seeing the dome has been equipped with sixteen closable apertures to permit natural wind flushing, assisted in low winds by the building ventilation system. The primary mirror will soon be actively cooled and the concrete dome floor may be thermally insulated against daytime heating if fire safety concerns can be resolved. Delivered images in the K band now have FWHM which is usually <EQ 0.'8, frequently <EQ 0.'6 and quite often approximately 0.'3. Examples of the latter are shown: these approximate the resolution achieved by NICMOS on the HST. We estimate that the productivity of the telescope has approximately doubled, while its oversubscription factor has increased to > 4.
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.
The United Kingdom Infra-Red Telescope (UKIRT) has recently undergone the first major upgrade program since its construction. One part of the upgrade program was an adaptive tip-tilt secondary mirror closed with a CCD system collectively called the fast guide system. The installation of the new secondary and associated systems was carried out in the first half of 1996. Initial testing of the fast guide system has shown great improvement in guide accuracy. The initial installation included a fixed integration time CCD. In the first part of 1997 an integration time controller based on computed guide star luminosity was implemented in the fast guide system. Also, a Kalman type estimator was installed in the image tracking loop based on a dynamic model and knowledge of the statistical properties of the guide star position error measurement as a function of computed guide star magnitude and CCD integration time. The new configuration was tested in terms of improved guide performance nd graceful degradation when tracking faint guide stars. This paper describes the modified fast guide system configuration and reports the results of performance tests.
The 3.8 m UK infrared telescope (UKIRT) is currently the focus of an upgrades program to improve its imaging performance, ideally to approach its diffraction limit in the near-IR at 2.2 micrometer, with FWHM approximately 0.'12. This program is now in its late stages. All the new systems have been designed, most have been manufacture and many have been installed. A new top end carries an adaptive tip-tilt secondary mirror with active precision alignment, which, with low-order active control of the primary mirror, should provide the desired intrinsic optical performance. The adaptive tip- tilt system will correct image motion from telescope vibrations and drive errors and from atmospheric wavefront tilt; delivered images are expected regularly to be less than 0.'5 over wide fields, and within a factor 2 or so of the diffraction limit, at least inside an isoplanatic patch of order an arcmin radius. To reduce facility seeing the primary mirror has been equipped with a ventilation system and will receive a 5 kW cooling system; the dome is being equipped with sixteen closable apertures to permit natural wind flushing, which can be assisted by the building air handling system in low winds. It is hoped that facility seeing -- excluding boundary layer effects -- will be imperceptible during approximately 85% of observable time. The upgraded UKIRT should be well capable of exploiting fully the very best conditions on Mauna Kea.
The United Kingdom Infra-Red Telescope (UKIRT) is currently undergoing its first major upgrade since its construction. The upgrades program consists of an adaptive tip-tilt and focus system closed with a CCD system at rates of up to a few hundred hertz, an active primary support system, extensive dome thermal work, and other miscellaneous improvements. This paper outlines how we propose to control the new systems, and how these systems are integrated into the existing telescope control system.
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.
In the 1970s the pioneering thin-mirror 3.8 m United Kingdom Infrared Telescope (UKIRT) of the UK Science and Engineering Research Council (SERC) was conceived as a low-cost `light bucket', with an 80% encircled-energy diameter <EQ 3'. However the delivered primary mirror had an 80 encircled- energy diameter of approximately 1' and the telescope has regularly delivered sub-arc-second images. To exploit this quality and to keep UKIRT competitive in a 21st century of 8-meter telescopes, in 1991 the SERC initiated an ambitious Upgrades Program, with the goal of routinely providing near- diffraction limited images at 2.2 microns. The major elements of the program are an adaptive tip-tilt secondary system, an active five-axis secondary collimation system, an upgraded primary mirror support system providing active control of the main optical aberrations, and modifications to the telescope and its enclosure to reduce or eliminate dome and mirror seeing, so as to take advantage of the excellent natural seeing on Mauna Kea. This paper outlines the overall project goals, the proposed strategies for upgrading the telescope and the progress to date.
A large telescope spends over 70 per cent of its time observing isolated objects on the telescope axis -an excessive waste of the available field of view. This paper describes a CCD camera which images the off-axis light on the William Herschel Telescope whilst an on-axis observer uses the telescope as normal. This enables a major background survey to be performed at minimal cost, and with no additional observing time. The cost of the system is about $150,000; by doubling the use of a telescope which costs $10,000 per night to run it pays for itself within a matter of weeks. Implementing similar systems on the new generation of large telescopes would ensure that the quality of background surveys will automatically keep pace with the advancing telescope technology.