Polarimetric imaging with the 91GHz radiometer SPIRA

The Scanning Polarimetric Imaging Radiometer (SPIRA) is a passive microwave imaging system operating around 91 GHz. It consists of a two orthogonally polarized receiver channels and an analog adding correlator network with 2 GHz bandwidth, which can measure all four Stokes parameters simultaneously by scanning the scene with an offset parabolic reector on an elevation over azimuth scanner. In October 2008 the SPIRA instrument has participated in the joint Swiss-German Radiometer Experiment Thun where it has been operated in parallel with two PMMW systems of Fraunhofer Institut für Hochfrequenzphysik und Radartechnik and an IR camera. During this measurement campaign different camouage kits, vehicles and persons with hidden threats have been observed together with reference objects. This paper gives an overview of the three different instruments and discusses selected images of the joint measurement campaign.