The SIR-C/X-SAR Italian experiments at Matera: Instrumentation and measurement results

This paper presents results related to the shuttle imaging radar C and X-and synthetic aperture radar (SIR-C/X/-SAR) Italian experiments carried out at the calibration backup supersite CBI (Matera, in southern Italy). C-, L- and X-band active radar calibrations (ARC) were deployed for radiometric analysis of the microwave instrument on board the NASA space shuttle. The main objectives of this investigation - namely, ground instrumentation validation, image quality assessment, and radiometric calibration - are accomplished by making measurements from the signatures of the ARCs, whose radar cross section (RCS) was known from laboratory measurements. The expected RCS of each deployed target, as seen by the sensor, is reconstructed on the radiometrically calibrated images, taking into account the uncertainties in the measurements made on the impulse response function and the accuracy of the laboratory tests. Numerical results derived from the standard single-look complex (SLC) products provided by the Jet Propulsion Laboratory and by the German and Italian processing and archiving facilities show good performance of the ARCs and of the SAR processors, also indicating acceptable stability of the calibration parameters of SIR-C and X-SAR. A simple self-organizing clustering algorithm is applied to the areas centered on the ARCs to obtain histograms of scattering properties of bare and ploughed soil. The comparison with backscattering statistics databases gives good agreement with the backscatter data derived from the calibrated SAR imagery.