AMICA, an astro-mapper for AMS

The alpha magnetic spectrograph (AMS) is a composite particle detector to be accommodated on the International Space Station (ISS). AMS is mainly devoted to galactic, charged cosmic rays studies, antimatter and dark matter searches. Besides the main, classical physics goals, capabilities in the field of GeV and multi-GeV gamma astrophysics have been established and are under investigation by a number of groups. Due to the unsteadiness of the ISS platform, a star-mapper device is required in order to fully exploit the intrinsic arc-min angular resolution provided by the silicon tracker. A star-mapper is conceptually an imaging, optical instrument able to autonomously recognize a stellar field and to calculate its own orientation with respect to an inertial reference frame. AMICA (Astro Mapper for Instruments Check of Attitude) on AMS is responsible for providing real-time information that is going to be used off-line for compensating the large uncertainties in the ISS flight attitude and the structural degrees of freedom. In this paper, we describe in detail the AMICA sub-system, the accommodation/integration issues and the in-flight alignment procedure adopting identified galactic (Pulsars) and extra-galactic (AGNs) sources.