Performance of the L- and P-band Subsystems of the F-SAR Airborne SAR Instrument

The F-SAR airborne SAR instrument represents the successor of the E-SAR system of the German Aerospace Center (DLR), which has been extensively used in the last three decades. Its development was triggered by the current demand for data being simultaneously acquired at different wavelengths and polarisations, as well as by the demand for very high resolution in the order of decimetres. F-SAR is a modular development utilising the most modern hardware and commercial off the shelf components. As for E-SAR DLR’s Dornier DO228-212 aircraft is the first choice as platform for the new system. Although the F-SAR system is still under development, since some years it is already taking over some of the operational duties of the old E-SAR system. With the recently completed L-band and P-band subsystems, F-SAR is now ready for fully replacing the E-SAR. This paper presents the new L-band subsystems and analyses its performance based on fully polarimetric imagery acquired during recent system test and calibration campaigns. The maiden flight of the new F-SAR P-band system has been postponed to spring 2012, first results will be shown in the conference presentation. Special emphasis is placed on the system calibration and the associated quality control including the achieved spatial resolution and radiometric accuracy in the different bands. 1 F-SAR instrument design and status F-SAR is designed to operate fully polarimetrically at X-, C-, S-, Land P-bands and will provide singlepass polarimetric interferometric capabilities in Xand S-bands. Repeat-pass PolInSAR is a standard measurement mode for the other bands. Range resolution is determined by the available system bandwidth. While components limit system bandwidth to 100MHz at P-band, a step-frequency approach is adopted to achieve up to 760MHz effective signal bandwidth at X-band to satisfy the requirement for very high resolution [2]. An overview of the general design parameters can be found in Tab. 1. Tab.1: F-SAR technical characteristics. Band X C S L P1 / P2 RF (GHz) 9.6 5.3 3.25 1.325 0.35/0.45 Bw [MHz] 760 400 300 150 100/50 PRF [kHz] 5 5 5 10 10 PT [kW] 2.5 2.2 2.2 0.9 0.9 Rg res [m] 0.2 0.4 0.5 1.0 1.5 Az res. [m] 0.2 0.3 0.35 0.4 1.5 Channels 4 2 2 2 2 Fig. 1: High-resolution polarimetric X-band image acquired by F-SAR A special antenna mount was designed to fix planar array antennas to the aircraft. In fully-fledged multifrequency configuration, it holds seven right-looking dual polarised antennas: three in X-band, one in Cband, two in S-band and one in L-band. The P-band antenna will be mounted under the nose of the aircraft. The antenna mount has the important advantage of making it easy to change the antenna configuration EUSAR 2012