S-Cam: An Imaging Spectro-Photometer Based on Superconducting Tunnel Junctions

S-Cam is a cryogenic camera for ground-basedastronomy using Superconducting Tunnel Junctions(STJs). It has been designed as a technologydemonstrator, aiming to prove the potential of a newgeneration of single photon counting detectors at aground-based telescope. The camera has a field of viewof about 4.0 × 4.0 arcsec2 and it is based on a6 × 6 array of Ta-Al Josephson junctions, operating atabout 350 mK and individually read-out. For eachdetected photon, the absorption position, the arrivaltime and the corresponding energy are measured. Inthis paper we provide an overview of the cryogenicdetector performance, a description of the S-Camsystem and a summary of the results obtained bothduring testing at ESTEC and during the firstobservations at the William Herschel Telescopein La Palma (Canary Islands, Spain). Initialastronomical results on the Crab pulsar are presentedalong with an outlook on future activities.