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

Abstract

S-Cam is a cryogenic optical camera for ground-based astronomy designed around a $\text{6×6}$ array of superconducting tunnel junctions. It has been conceived as a technology demonstrator, aimed at proving the potential of a new generation of single photon counting detectors for ground-based telescopes and as a possible precursor to a future space-based instrumentation. The camera is based on a $\text{6×6}$ array of Ta–Al Josephson junctions, operating at about 350 mK and individually read out. For each detected photon, the absorption position, the arrival time, and the corresponding energy are measured. This allows for recording an image and simultaneously obtaining spectrophotometric information from the observed objects. In this article we provide an overview of the latest cryogenic detector performance, an up-to-date description of the S-Cam system, and a summary of the results obtained both during testing at ESTEC and during actual observations at the William Herschel Telescope in La Palma (Canary Islands, Spain). An example of the novel astronomical data obtained during the latest observation campaigns (December 1999 and April 2000) is also described.