S-Cam: A spectrophotometer for optical astronomy: Performance and latest results

S-Cam is a cryogenic optical camera for ground-based astronomy designed aro und a 6x6 array of superconducting tunnel junctions. It has been conceived as a technology demonstrator, aimed at proving the potential of a new gener ation of single photon counting detectors for ground-based telescopes and a s a possible precursor to a future space-based instrumentation. The camera is based on a 6x6 array of Ta-Al Josephson junctions, operating at about 35 0 mK and individually read out. For each detected photon, the absorption po sition, the arrival time, and the corresponding energy are measured. This a llows for recording an image and simultaneously obtaining spectrophotometri c information from the observed objects. In this article we provide an over view of the latest cryogenic detector performance, an up-to-date descriptio n of the S-Cam system, and a summary of the results obtained both during te sting at ESTEC and during actual observations at the William Herschel Teles cope in La Palma (Canary Islands, Spain). An example of the novel astronomi cal data obtained during the latest observation campaigns (December 1999 an d April 2000) is also described. (C) 2000 American Institute of Physics. [S 0034-6748(00)05112-1].