INTERFEROMETRIC PROCESSING OF PALSAR WIDE-BEAM SCANSAR DATA Charles Werner, Urs Wegmüller, Othmar Frey, Maurizio Santoro Gamma Remote Sensing AG, Worbstrasse 225, CH-3073 Gümligen, Switzerland, http://www.gamma-rs.ch, cw@gamma-rs.ch ABSTRACT Processing of ScanSAR data for interferometric applications requires careful attention to the phase and position accuracy to obtain interferometric products with high correlation and continuous phase across the bursts. We describe an interferometric processing system developed for ScanSAR data acquired by the ALOS PALSAR instrument able to produce differential interferometric products with 350 km swath width that are without visible phase discontinuities between ScanSAR beams. 1. INTRODUCTION Between 2006 and 2011 the ALOS PALSAR acquired an impressive archive of ScanSAR data which are potentially suited also for SAR interferometry. The advantage of ScanSAR is the ability to achieve wide- swath coverage required for short repeat intervals with moderate increase of system complexity. Interferometry based applications are facilitated by wide swath widths permitting short repeat intervals and the potential for frequent acquisitions to reduce measurement errors due to atmospheric and ionospheric phase variability. ScanSAR successively illuminates parallel overlapping swaths with a burst of radar pulses. A sketch of the PALSAR acquisition modes is shown in Figure 1. Figure 1: PALSAR Acquisition Modes Table 1: PALSAR ScanSAR WB1 Mode Parameters Center Frequency (MHz) 1270 Chirp Bandwidth (MHz) 14 Polarization HH Incidence angle (deg.) 18 – 43.3 Swath Width (km) 350 Data Rate (Mbps) 120 PRF(Hz) swath dependent 1669 - 2315 Pulses per Burst swath dependent 247 - 355, 327 To access the high potential of the PALSAR ScanSAR archive we implemented a methodology for PALSAR ScanSAR raw processing and interferometry. In the following we explain the methodology used and show examples for both ScanSAR – Stripmap and ScanSAR – ScanSAR interferograms. This work is also of interest in the context of the planned Sentinel-1 [1] which will operate primarily using the Interferometric Wide-Swath mode. 2. PALSAR SCANSAR CHARACTERISTICS The PALSAR instrument operates in several modes including Stripmap single and dual-pol fine-beam (FBS, FBD), Quad-Pol (POL), and ScanSAR (WB1, WB2) as shown in Figure 1. The ScanSAR mode predominately used by PALSAR was WB1 with characteristics as shown in Table 1. ScanSAR operates by progressive illumination of overlapping swaths to build up the wide- swath. In the case of PALSAR, the illumination of each beam is for approximately 0.17 seconds. Each of the 5 beams has a different pulse repetition frequency (PRF) determined by the range and azimuth ambiguity constraints. The number of pulses in each burst varies due to the differing PRFs. The time that a point on the ground can be illuminated by the antenna, called the aperture time, determines the number of bursts that an echo from this point can be received and processed. For ScanSAR beam 4 the