Astronomical instrumentation

Abstract:

We describe the design of a 2^nd generation instrument for the ESO VLT which will deliver a unique multiple deployable integral field capability in the near-infrared (1-2.5μm). The science drivers for the instrument are presented and linked to the functional specification. The baseline instrument concept is described with emphasis on technological innovations. Detailed discussions of specific technologies, and ongoing prototype studies, are described in separate papers.

Abstract:

The MUSE (Multi Unit Spectroscopic Explorer) instrument is a second-generation integral-field spectrograph candidate for the VLT, operating in the visible and near IR wavelength range (0.465-0.93 μm). It is combining a large 1' × 1' Field of View with a spectral resolution of 3000 and a spatial resolution of 0.2" coupled to a sophisticated ground-layer Adaptive Optics (AO) system. After a brief summary of the major instrumental requirements, we will focus on the opto-mechanical design of MUSE, including core subsystems such as the Fore-Optics, the Image Slicers and the Spectrographs, the Structure and the Calibration Unit. The most creative trends of the instrument will be underlined, such as the specific choices adopted to reduce the costs, weight and volume of the Slicer and Spectrograph units, that need to be manufactured and installed on the VLT Nasmyth platform into twenty-four replicas. Finally, a realistic estimate of the expected performance (in both throughput and image quality), and the future development program for the forthcoming detailed design phase will be presented.

Abstract:

The VISTA IR Camera has now completed its detailed design phase and is on schedule for delivery to ESO's Cerro Paranal Observatory in 2006. The camera consists of 16 Raytheon VIRGO 2048×2048 HgCdTe arrays in a sparse focal plane sampling a 1.65 degree field of view. A 1.4m diameter filter wheel provides slots for 7 distinct science filters, each comprising 16 individual filter panes. The camera also provides autoguiding and curvature sensing information for the VISTA telescope, and relies on tight tolerancing to meet the demanding requirements of the f/1 telescope design. The VISTA IR camera is unusual in that it contains no cold pupil-stop, but rather relies on a series of nested cold baffles to constrain the light reaching the focal plane to the science beam. In this paper we present a complete overview of the status of the final IR Camera design, its interaction with the VISTA telescope, and a summary of the predicted performance of the system.

Abstract:

FMOS is a near-IR OH-suppressed multi-fibre fed spectrograph for the Subaru telescope. The spectrograph will accept 200 optical fibres from the ECHIDNA positioner system at the 30arcmin Prime focus of the telescope. We will describe the recent activities here in the UK in progressing the instrument from its conceptual phase through detailed design and into manufacture. A variety of technical areas will be described including: the opto-mechanical system design and construction, development of the HAWAH-II detector control system, the thermal system design & control and OH suppression techniques.

Abstract:

We describe the source subtraction strategy and observations for the extended Very Small Array, a CMB interferometer operating at 33 GHz. A total of 453 sources were monitored at 33 GHz using a dedicated source subtraction baseline. 131 sources brighter than 20 mJy were directly subtracted from the VSA visibility data. Some characteristics of the subtracted sources, such as spectra and variability, are discussed. The 33-GHz source counts are estimated from a sample selected at 15 GHz. The selection of VSA fields in order to avoid bright sources introduces a bias into the observed counts. This bias is corrected and the resulting source count is estimated to be complete in the flux-density range 20-114 mJy. The 33-GHz source counts are used to calculate a correction to the VSA power spectrum for sources below the subtraction limit.