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 keV 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 ∼ 21 cm and therefore the Silicon Tracker is the lightest and most compact γ ‐ 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.