The AGILE silicon tracker: Pre-launch and in-flight configuration

AGILE is an ASI (Italian Space Agency) Small Scientific Mission dedicated to high-energy astrophysics which was successfully launched on April 23,2007. The AGILE instrument is composed of three main detectors: a Tungsten-Silicon Tracker designed to detect and image photons in the 30 MeV-50 GeV energy band, an X-ray imager called Super-AGILE operating in the 18-60 keV energy band, and a Mini-Calorimeter that detects gamma-rays and charged particles energy deposits between 300 key and 100 MeV. The instrument is surrounded by an anti-coincidence (AC) system. In this paper, we present the noise characterization and the front-end configuration of the Silicon Tracker. Two crucial (and unique, among gamma-ray astrophysics missions) characteristic of the AGILE Silicon Tracker are the analog signal acquisition (aimed at obtaining an optimal angular resolution for gamma-ray imaging) and the very small dimension of the instrument (the total height including the active elements is similar to 21 cm and therefore the Silicon Tracker is the lightest and most compact gamma-ray imager sent in orbit). The results presented in this paper were obtained during the AIV (Assembly. Integration and Verification) pre-launch testing phase and during the post-launch commissioning phase. The AGILE Silicon Tracker has been optimally configured with a very good response of the frontend system and of the data acquisition units.