Pamela

PAMELA is a satellite-borne experiment designed to study charged particles in the cosmic radiation with a particular interest in antiparticles. The experiment is collecting data since July 2006 on board of the Russian Resurs DK1 satellite, which travels along a semipolar elliptical orbit arount the Earth. The PAMELA apparatus includes a magnetic spectrometer, which is composed of 6 planes of silicon microstrip detectors dipped in an almost-uniform magnetic field generated by a permanent magnet made of Nd-Fe-B alloy. The spectrometer has been designed to determine precisely the rigidity (up to 1 TeV) and the absolute charge (up to Z=6) of particles crossing the detector. In the first part a short review of the magnetic spectrometer design is given and the main spectrometer operations in flight are described. The main topic of this article is the procedure to measure the rigidity, described in the second part. Particular focus is put on the position-finding algorithm. In fact, recent theoretical and experimental results have shown that in case of inclined tracks a significant systematic shift can be present, if the proper algorithm is not applied. Finally, some preliminary results are presented.