Simon C. Craig

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 Visible and Infrared Survey Telescope for Astronomy (VISTA): Design, technical overview, and performance

The VISTA project was made possible by funding from the UK Joint Infrastructure Fund (JIF) and PPARC (later STFC).

A new era of wide-field submillimetre imaging: on-sky performance of SCUBA-2

SCUBA-2 is the largest submillimetre wide-field bolometric camera ever built. This 43 square arc- minute field-of-view instrument operates at two wavelengths (850 and 450 microns) and has been installed on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. SCUBA-2 has been successfully commissioned and operational for general science since October 2011. This paper presents an overview of the on-sky performance of the instrument during and since commissioning in mid- 2011. The on-sky noise characteristics and NEPs of the 450 μm and 850 μm arrays, with average yields of approximately 3400 bolometers at each wavelength, will be shown. The observing modes of the instrument and the on-sky calibration techniques are described. The culmination of these efforts has resulted in a scientifically powerful mapping camera with sensitivities that allow a square degree of sky to be mapped to 10 mJy/beam rms at 850 μm in 2 hours and 60 mJy/beam rms at 450 μm in 5 hours in the best weather.

Project VISTA: a review of its progress and overview of the current program

The Visible and Infrared Survey Telescope for Astronomy (VISTA) project started in 2000 following a Joint Infrastructure Fund award (JIF) to a consortium of 18 UK Universities . The JIF proposal was for a 4 metre class telescope with the ability to mount a visible and an infrared wide field camera. The UK Astronomy Technology Centre successfully tendered for the management of the project of developing and building the telescope in two phases. The initial phase was intended to review the proposed design and carry out a conceptual study. The second phase being the development, manufacture and commissioning of this design. As a result of the first phase, a conceptual design based on an f/1 primary mirror telescope and cold baffle IR camera has been developed. The IR Camera focal plane has been sized to accommodate sixteen 2k × 2k IR detectors, putting VISTA at the forefront of IR Survey Astronomy. The project team have developed this conceptual design into formal ITTs to allow the design and manufacture to commence. The telescope will be sited at the ESO Observatory in Paranal and is due for completion in 2006.

The Advanced Technology Solar Telescope: design and early construction

The National Solar Observatory’s (NSO) Advanced Technology Solar Telescope (ATST) is the first large U.S. solar telescope accessible to the worldwide solar physics community to be constructed in more than 30 years. The 4-meter diameter facility will operate over a broad wavelength range (0.35 to 28 μm ), employing adaptive optics systems to achieve diffraction limited imaging and resolve features approximately 20 km on the Sun; the key observational parameters (collecting area, spatial resolution, spectral coverage, polarization accuracy, low scattered light) enable resolution of the theoretically-predicted, fine-scale magnetic features and their dynamics which modulate the radiative output of the sun and drive the release of magnetic energy from the Sun’s atmosphere in the form of flares and coronal mass ejections. In 2010, the ATST received a significant fraction of its funding for construction. In the subsequent two years, the project has hired staff and opened an office on Maui. A number of large industrial contracts have been placed throughout the world to complete the detailed designs and begin constructing the major telescope subsystems. These contracts have included the site development, AandE designs, mirrors, polishing, optic support assemblies, telescope mount and coudé rotator structures, enclosure, thermal and mechanical systems, and high-level software and controls. In addition, design development work on the instrument suite has undergone significant progress; this has included the completion of preliminary design reviews (PDR) for all five facility instruments. Permitting required for physically starting construction on the mountaintop of Haleakalā, Maui has also progressed. This paper will review the ATST goals and specifications, describe each of the major subsystems under construction, and review the contracts and lessons learned during the contracting and early construction phases. Schedules for site construction, key factory testing of major subsystems, and integration, test and commissioning activities will also be discussed.

Construction status of the Daniel K. Inouye Solar Telescope

We provide an update on the construction status of the Daniel K. Inouye Solar Telescope. This 4-m diameter facility is designed to enable detection and spatial/temporal resolution of the predicted, fundamental astrophysical processes driving solar magnetism at their intrinsic scales throughout the solar atmosphere. These data will drive key research on solar magnetism and its influence on solar winds, flares, coronal mass ejections and solar irradiance variability. The facility is developed to support a broad wavelength range (0.35 to 28 microns) and will employ state-of-the-art adaptive optics systems to provide diffraction limited imaging, resolving features approximately 20 km on the Sun. At the start of operations, there will be five instruments initially deployed: Visible Broadband Imager (VBI; National Solar Observatory), Visible SpectroPolarimeter (ViSP; NCAR High Altitude Observatory), Visible Tunable Filter (VTF (a Fabry-Perot tunable spectropolarimeter); Kiepenheuer Institute for Solarphysics), Diffraction Limited NIR Spectropolarimeter (DL-NIRSP; University of Hawaii, Institute for Astronomy) and the Cryogenic NIR Spectropolarimeter (Cryo-NIRSP; University of Hawaii, Institute for Astronomy). As of mid-2016, the project construction is in its 4th year of site construction and 7th year overall. Major milestones in the off-site development include the conclusion of the polishing of the M1 mirror by University of Arizona, College of Optical Sciences, the delivery of the Top End Optical Assembly (L3), the acceptance of the Deformable Mirror System (Xinetics); all optical systems have been contracted and are either accepted or in fabrication. The Enclosure and Telescope Mount Assembly passed through their factory acceptance in 2014 and 2015, respectively. The enclosure site construction is currently concluding while the Telescope Mount Assembly site erection is underway. The facility buildings (Utility and Support and Operations) have been completed with ongoing work on the thermal systems to support the challenging imaging requirements needed for the solar research. Finally, we present the construction phase performance (schedule, budget) with projections for the start of early operations.

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.

Performance of the SCUBA-2 dry dilution refrigerator: 4 years of operation at the JCMT

Cryogen free or ‘dry’ dilution refrigerators that integrate a cryocooler such as a two stage pulse tube to replace the conventional liquid helium bath and 1K pot, have become a practical alternative for cooling astronomical detectors to mK temperatures and offer many advantages. SCUBA-2, the new submillimetre camera in operation at the JCMT, on the summit of Mauna Kea, Hawaii, was one of the first instruments to use such a fridge design. The dry dilution fridge for SCUBA-2 has now been in service for almost 4 years during commissioning at JCMT. In the most recent astronomical commissioning phase, the dilution fridge was in continuous operation for 10 months with no loss of base temperature or cooling power, cooling the SCUBA-2 detector arrays to below 100mK while maintaining a further 100Kg of enclosure, shields and SQUID amplifiers at 1K. In this paper we review some of the lessons from operating a dry dilution fridge at the JCMT and the necessary changes that have been incorporated. We present the performance of the fridge and discus its role in ensuring the success of SCUBA-2.

Vista IR camera: conceptual design

This paper describes the conceptual design for a near infrared camera for the Visible and Infrared Survey Telescope for Astronomy (VISTA). VISTA is a 4m class survey telescope that is being designed to perform pre-planned, ground-based astronomical surveys of the Southern sky from ESOs Cerro Paranal Observatory in Chile. The IR Surveys will be carried out in the J, H and Kshort wave-bands at fainter magnitudes than those produced by the current generation of survey telescopes. To maximise throughput and survey efficiency, the camera has been completely integrated with the overall optical design with the telescope mirrors providing the power and the camera optics the wavefront correction. The camera design employs a non-traditional approach to control stray light by using cryogenic baffles rather than the more traditional cold-stop approach. The very large optical field available, 1.6° diameter with a plate scale of approximately 57μm/arcsec, means that the focal plane can accommodate sixteen 2k×2k IR detectors thus forming the largest IR focal plane used in ground based astronomy to date. The 67 Mpixel focal plane will generate a significant data rate. Each exposure will comprise 270 MB and a typical night will generate 400 GB.

JCMT Telescope structure modifications and facility upgrades for SCUBA-2 instrument

The James Clerk Maxwell Telescope (JCMT) on the summit of Mauna Kea is currently undergoing significant structural upgrade in order to accommodate the new generation instrument SCUBA-2 (Submillimeter Common-User Bolometric Array) which is being developed by the United Kingdom Astronomy Technology Centre (UK ATC). This four tonne instrument will be located at the Nasmyth focus of the telescope and will require five large auxiliary external warm mirrors to be installed on the telescope structure and in the receiver cabin along with dedicated automatically deployable tertiary mirror. The carousel of the observatory building as well as the original telescope structure was not designed for an instrument of this mass and complexity. The whole left Nasmyth platform of the telescope has to be removed and rebuilt in order to accommodate the instrument, its support structure and the warm optics. The floor of the observatory has to be reinforced and fitted with rail system and a scissor lift in order to handle the installation of the instrument on the telescope and removal from the telescope for maintenance. Details are given of particular challenges associated with handling, mechanical interfacing, optical alignment, design of the external warm mirrors mounts and the tertiary mirror deployment mechanism for SCUBA-2.