PALSAR Multi-Mode Interferometric Processing Charles Werner, Urs Wegmüller, Tazio Strozzi, Andreas Wiesmann, and Maurizio Santoro Gamma Remote Sensing, Worbstrasse 225, CH-3073 Gümligen, Switzerland, Email: cw@gamma-rs.ch Abstract The main objective of the project “ALOS PALSAR quality assessment, calibration, and validation research” (ALOS-RA-175) is to independently validate PALSAR data for applications focusing specifically on interferometry. As development platform we have developed an independent processing chain (GAMMA) that takes into account the specific features of the PALSAR instrument and data characteristics. In a first part the PALSAR data characteristics and the raw data processing we performed are discussed. In a second part we describe the processing techniques used to generate interferograms between single and dual polarization PALSAR data sets. 1. PALSAR RAW DATA CHARACTERISTICS AND SAR PROCESSING 1.1. PALSAR raw data characteristics For PALSAR fine-beam single-polarization mode (HH) acquisitions we found characteristics as shown in Table 1. The Doppler spectrum at the center of the swath, modulo the SAR pulse repetition frequency is shown in Figure 1. The Doppler ambiguity was resolved using the multi-look beat frequency (MLBF) algorithm as described by Cumming and Wong [2]. The Doppler centroid as a function of range was estimated by cross- correlation of adjacent lines and is shown in Figure 2. It is important to notice that such high Doppler Centroid values and significant range dependence of the Doppler Centroid was only observed during the initial phase. Later on zero-Doppler steering was applied very successfully, so that the Doppler Centroids determined were all close to zero. Table 1 ALOS PALSAR Fine-Beam raw data characteristics. Radar Center Frequency: 1270.000 MHz Polarization HH Range Bandwidth 28.000 MHz Chirp Duration 27 micro-sec. Range Sample rate (IQ) 32.000 MHz Number of range samples/echo 10304 Number of echoes 32421 Number of bits/sample 5 Pulse Repetition Frequency (PRF) 2159.827 Hz Figure 1. Azimuth spectrum at center-swath, modulo the SAR Pulse Repetition Frequency Figure 2. Doppler versus slant-range sample number (for a data set acquired early on before operation with zero Doppler steering). 1.2. SAR processing Level-1 complex signal samples were processed using the Gamma MSP to produce single-look complex (SLC) and multi-look intensity (MLI) images. In fine-beam mode the transmit chirp is 28 MHz and lasts 27 micro- seconds. The data were processed using a range-Doppler algorithm including secondary range migration. Autofocus confirmed that the effective along-track velocity determined from the state vectors was accurate at the level of .5 m/s. The antenna pattern provided are used for the radiometric calibration. A small section of a very early image processed with MSP showing the full range resolution and 3 azimuth looks is shown in Figure