Calibrating and optimizing the imaging of the SuperAGILE experiment

SuperAGILE (SA) is the hard X-ray monitor of the AGILE small satellite mission, launched on 23^rd April 2007. The monitor is based on four one-dimensional coded-mask detectors. In spite of the compactness (45×45×15 cm³) and lightness (5 kg), the experiment has high angular resolution (6 arcmin) and point source location accuracy (<2 arcmin, for bright sources) for every position in the Field Of View (FOV). To achieve these imaging performances, considerable efforts were made for the alignment procedures during the assembly of the experiment itself, and with the rest of the satellite. Mechanical alignment were measured during all the assembly phases and before the launch campaign. Moreover, a specific campaign was performed in the laboratory with radioactive calibration sources to calibrate the imaging response on ground. A on-orbit calibration campaign was performed using the Crab Nebula. Due to the huge satellite wobbling (1 deg) and continuous slewing (1 deg/day), a refined attitude correction strategy has been implemented on photon-by-photon data to maintain the high imaging performances. In this paper we summarize all the activities we performed for calibrating and optimizing the imaging capabilities, from the assembly of the experiment to the on-orbit calibrations and we show the results achieved.