S-Cam 3: Optical astronomy with a STJ-based imaging spectrophotometer

S-Cam 3 is the third generation of a cryogenic camera, based on superconducting tunnel junctions (STJs), for ground-based optical astronomy, deployed at the 4.2m William Herschel Telescope (WHT) at La Palma (Spain). It exploits a 10 x 12 pixel array of Ta/Al STJs, covering a field of view of similar to 9 '' x 11 '' on the sky. The wavelength band extends from 330-750 nm, with a wavelength resolving power of similar to 10 at 500 nm. The detectors are operated at similar to 285 mK, achieved with a double stage He-4-He-3 sorption cooler. Each pixel has its own electronic readout chain at room temperature, with a JFET-based charge sensitive preamplifier. The instrument has undergone extensive testing and calibration, followed by the first observation campaign at La Palma in July 2004. This campaign has focused on point sources with time variability, exploiting the instrument's unique combination of spectrophotometry with high time resolution. (c) 2006 Elsevier B.V. All rights reserved.