Helen McGregor

Scuba-2: The 10 000 pixel bolometer camera on the james clerk maxwell telescope

SCUBA-2 is an innovative 10000 pixel bolometer camera operating at submillimetre wavelengths on the James Clerk Maxwell Telescope (JCMT). The camera has the capability to carry out wide-field surveys to unprecedented depths, addressing key questions relating to the origins of galaxies, stars and planets. With two imaging arrays working simultaneously in the atmospheric windows at 450 and 850µm, the vast increase in pixel count means that SCUBA-2 maps the sky 100–150 times faster than the previous SCUBA instrument. In this paper we present an overview of the instrument, discuss the physical characteristics of the superconducting detector arrays, outline the observing modes and data acquisition, and present the early performance figures on the telescope. We also showcase the capabilities of the instrument via some early examples of the science SCUBA-2 has already undertaken. In February 2012, SCUBA-2 began a series of unique legacy surveys for the JCMT community. These surveys will take 2.5years and the results are already providing complementary data to the shorter wavelength, shallower, larger-area surveys from Herschel. The SCUBA-2 surveys will also provide a wealth of information for further study with new facilities such as ALMA, and future telescopes such as CCAT and SPICA.

The cryo-mechanical design of SCUBA-2: a wide-field imager for the James Clerk Maxwell Telescope

The SCUBA-2 instrument is a new wide-field imager under development for the James Clerk Maxwell Telescope on Mauna Kea in Hawaii and due to be operational in 2006. The instrument has two separate focal planes and is designed to observe simultaneously at wavelengths of 450 and 850μm. The instrument cryostat will weigh around 2500kg and has a volume of approximately 2.4x1.8x2.0m. The two detector arrays are operated at ~100mK and are surrounded by a cold enclosure at ~1K. Both the arrays and cold enclosure are cooled by a novel, liquid cryogen-free dilution refrigerator. To reduce the thermal background on the arrays to a minimum the main optics structure, weighing in excess of 450kg, must be cooled to less than 15K. A pair of low vibration pulse tube coolers are used to cool this structure and a radiation shield at ~60K. This paper describes the cryo-mechanical design of SCUBA-2 and discusses some of the issues and techniques needed to both cool the instrument within a reasonable timescale, and operate it in the required temperature regime

Cryogenic magnetic shielding for SCUBA-2

SCUBA-2 is a new wide-field submillimeter continuum instrument being commissioned on the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. SCUBA-2 uses large-scale arrays of superconducting bolometers with SQUID- (superconducting quantum interference device) based multiplexing and amplification. The sensitivity of the devices that compose the detector arrays to magnetic fields is such that magnetic shielding, consisting of superconducting and high-permeability materials, was fitted to the detector enclosure at 1 K to reduce the magnetic field strength at the focal plane. This paper describes the design and construction of the cryogenic shielding, and presents verification measurements. The shielding performance was found to meet the instrument requirements, and compared well to the modelled results.

EAGLE: an MOAO fed multi-IFU working in the NIR on the E-ELT

EAGLE is an instrument for the European Extremely Large Telescope (E-ELT). EAGLE will be installed at the Gravity Invariant Focal Station of the E-ELT, covering a field of view of 50 square arcminutes. Its main scientific drivers are the physics and evolution of high-redshift galaxies, the detection and characterization of first-light objects and the physics of galaxy evolution from stellar archaeology. These key science programs, generic to all ELT projects and highly complementary to JWST, require 3D spectroscopy on a limited (~20) number of targets, full near IR coverage up to 2.4 micron and an image quality significantly sharper than the atmospheric seeing. The EAGLE design achieves these requirements with innovative, yet simple, solutions and technologies already available or under the final stages of development. EAGLE relies on Multi-Object Adaptive Optics (MOAO) which is being demonstrated in the laboratory and on sky. This paper provides a summary of the phase A study instrument design.

Opto-mechanical design of SCUBA-2

This paper describes the opto-mechanical design of a large instrument for sub-mm, SCUBA-2, to be commissioned at JCMT. The scientific requirements, specially the large fov and the constraints of the telescope mechanical structure, lead to a complex optical design using freeform aluminium mirrors . The mechanical design is also challenging with large modules to be mounted and aligned in the telescope as well as the cryogenic instrument containing the mirrors, the filters, the dichroics and the detector modules. The cryogenic isostatic mounting, the structural and thermal designs are presented. This includes details of the fabrication of the structure and design of a shutter mechanism for operation at 4K. The results of the first AIV cool-down are also presented.

SCUBA-2: Engineering and Commissioning Challenges of the World's Largest sub-mm Instrument at the JCMT

Over preceding conferences, the design and implementation of the SCUBA-2 (Sub-millimeter Common-User Bolometric Array 2) instrument hardware has been described in detail. SCUBA-2 has been installed on the James Clerk Maxwell Telescope (JCMT) for over two years and its hardware has been successfully commissioned. This paper describes the culmination of this process and compares the optical/mechanical design and test expectations of the instrument hardware against the performance achieved in the field.

GLT receiver commissioning at JCMT and future JCMT instrumentation

The Greenland Telescope (GLT) project and the East Asian Observatory (EAO) successfully commissioned the first light GLT instrument at the James Clerk Maxwell Telescope (JCMT) in Hawaii, prior to transferring the instrument to Greenland. The GLT instrument which comprises of a cryostat with three cartridge-type receivers (at 86GHz, 230GHz and 345GHz) was installed into the receiver cabin of JCMT and operated in three modes: - (a) Regular JCMT observing with the GLT instrument, using ACSIS, (JCMT’s autocorrelation spectrometer) as the backend and JCMT software for telescope control, data reduction, pointing and antenna focus adjustment. (b) Single dish observations of astronomical spectral line sources, recording data onto mark 6 recorders for offline data reduction. (c) eSMA interferometer array observations at 230GHz in conjunction with the SMA. In this paper, we report on the installation and integration of the GLT instrument at JCMT, present results from commissioning and show how the success of the GLT instrument commissioning fits with our plans for future instrumentation at JCMT.

Automated metrology simulator for multi-objects instruments

The most challenging of the metrology needs of multi-objects instruments is the registration of the pupil on the deformable mirror which corrects the wavefront errors. Pick-off mirrors in multi-objects instruments and specially spectrographs (MOS) require accurate positioning and simultaneous viewing of the pupil on the deformable mirror (DM) and the focal plane image on the image slicer at the sub-micron level. A laboratory test prototype simulating the telescope (E-ELT), the beam steering mirror (BSM) and the pupil imaging mirror (PIM), is presented to confirm the correct positioning of the pupil on the DM and to provide the movements of the moveable optical elements to achieve it. The opto-mechanical design and testing of this prototype is shown. The BSM stages (Goniometric cradle, Rotation, & Linear) provide the key mechanical system elements, with precision alignment, resolution, and repeatability . The design and behaviour of the control system is discussed; the ultimate aim of which is to adjust the BSM and PIM to correct for any slight mis-positioning of the pick-off mirror and any temporal drift of all the components to achieve the required alignment. The control system can also cope with flexure effects when required.

SCUBA-2: A Large-Format CCD-Style Imager for Submillimeter Astronomy

We describe the capabilities of SCUBA-2, the first CCD-like imager for submillimeter astronomy, and the technologies that make it possible. Unlike previous detectors using discrete bolometers, SCUBA-2 has two dc-coupled, monolithic arrays with a total of ~10,000 bolometers. SCUBA-2’s absorber-coupled pixels use superconducting transition edge sensors operating at ~ 120mK for photon-noise limited performance and a SQUID time-domain multiplexer for readout. It will offer simultaneous imaging of an 8 × 8 arcmin field of view at wavelengths of 850 μm and 450 μm. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, SCUBA-2 will also act as a pathfinder for submillimeter interferometers such as ALMA. SCUBA-2 will begin operation on the JCMT in 2006.