The Square Kilometre Array (SKA)

Abstract:

In this paper, we report on calibration and polarisation performance of the 2PAD digital beamforming system, a pathfinder instrument for large-N, high-frequency phased-array radio instruments, in particular the Square Kilometre Array (SKA) radio telescope. We review the design of the digital system, and report on instrumental calibration approaches. © 2010 IEEE.

Abstract:

Wide-field multi-object spectroscopy is a high priority for European astronomy over the next decade. Most 8-10m telescopes have a small field of view, making 4-m class telescopes a particularly attractive option for wide-field instruments. We present a science case and design drivers for a wide-field multi-object spectrograph (MOS) with integral field units for the 4.2-m William Herschel Telescope (WHT) on La Palma. The instrument intends to take advantage of a future prime-focus corrector and atmospheric-dispersion corrector (Agocs et al, this conf.) that will deliver a field of view 2 deg in diameter, with good throughput from 370 to 1,000 nm. The science programs cluster into three groups needing three different resolving powers R: (1) high-precision radial-velocities for Gaia-related Milky Way dynamics, cosmological redshift surveys, and galaxy evolution studies (R = 5,000), (2) galaxy disk velocity dispersions (R = 10,000) and (3) high-precision stellar element abundances for Milky Way archaeology (R = 20,000). The multiplex requirements of the different science cases range from a few hundred to a few thousand, and a range of fibre-positioner technologies are considered. Several options for the spectrograph are discussed, building in part on published design studies for E-ELT spectrographs. Indeed, a WHT MOS will not only efficiently deliver data for exploitation of important imaging surveys planned for the coming decade, but will also serve as a test-bed to optimize the design of MOS instruments for the future E-ELT. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

We describe the results of a Phase A study for a single field, wide band, near-infrared integral field spectrograph for the European Extremely Large Telescope (E-ELT). HARMONI, the High Angular Resolution Monolithic Optical & Nearinfrared Integral field spectrograph, provides the E-ELT's core spectroscopic requirement. It is a work-horse instrument, with four different spatial scales, ranging from seeing to diffraction-limited, and spectral resolving powers of 4000, 10000 & 20000 covering the 0.47 to 2.45 μm wavelength range. It is optimally suited to carry out a wide range of observing programs, focusing on detailed, spatially resolved studies of extended objects to unravel their morphology, kinematics and chemical composition, whilst also enabling ultra-sensitive observations of point sources. We present a synopsis of the key science cases motivating the instrument, the top level specifications, a description of the opto-mechanical concept, operation and calibration plan, and image quality and throughput budgets. Issues of expected performance, complementarity and synergies, as well as simulated observations are presented elsewhere in these proceedings[1]. © 2010 Copyright SPIE - The International Society for Optical Engineering.