CHAPTER 11
The RADARSAT Geophysical Processor System
R.KwOK
Contents
11.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 235
11.1.1 Ice Motion ........... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 237
11.1.2 Ice Age/Thickness Distribution ............................. 237
11.1.3 Melt Onset/Freeze-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 238
11.1.4 Open-Water Fraction .................................... 239
11.1.5 Backscatter Histograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239
11.2 Sea Ice Algorithms ....................................... 239
11.2.1 Lagrangian Ice Motion ................................... 240
11.2.2 Ice Age/Thickness Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 241
11.2.3 Summer Open Water Fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 249
11.2.4 Melt Onset/Freeze-Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 250
11.3 RGPS Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 251
11.3.1 Database Tables ........................................ 252
11.3.2 Products ............................................. 252
11.3.3 Sampling Issues and Measurement Errors . . . . . . . . . . . . . . . . . . . . .. 254
11.4 The RGPS System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 255
11.5 Summary and Discussion .................................. 256
References ................................................ 256
11.1
Introduction
The RADARSAT Geophysical Processor System (RGPS) is a data processing system for
the analysis of synthetic aperture radar (SAR) data of sea ice acquired by the Canadian RADARSAT satellite (Raney et al. 1991). RADARSAT was launched in November of
1995 into a 24-day repeat cycle, an orbit configuration which provides near repeat coverage of the high latitudes at 3- and 7-day intervals. The SAR sensor has a number of
imaging modes, one of which illuminates a wide swath (460 km) designed for large
scale mapping of the Earth's surface. The science plan of the Alaska SAR Facility calls
for weekly coverage of the Arctic Ocean. With this mode, the coverage of the Arctic
Ocean every 7 days (Fig. 1) with 100 m pixels produces approximately 1 GB of image
data daily. In an effort to make this large volume of SAR data more useful to the scienAnalysis of SAR Data of the Polar Oceans
Edited by C. Tsatsoulis and R. Kwok
© Springer-Verlag Berlin Heidelberg 1998
The RADARSAT Geophysical Processor System
R.KwOK
Contents
11.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 235
11.1.1 Ice Motion ........... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 237
11.1.2 Ice Age/Thickness Distribution ............................. 237
11.1.3 Melt Onset/Freeze-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 238
11.1.4 Open-Water Fraction .................................... 239
11.1.5 Backscatter Histograms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 239
11.2 Sea Ice Algorithms ....................................... 239
11.2.1 Lagrangian Ice Motion ................................... 240
11.2.2 Ice Age/Thickness Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 241
11.2.3 Summer Open Water Fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 249
11.2.4 Melt Onset/Freeze-Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 250
11.3 RGPS Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 251
11.3.1 Database Tables ........................................ 252
11.3.2 Products ............................................. 252
11.3.3 Sampling Issues and Measurement Errors . . . . . . . . . . . . . . . . . . . . .. 254
11.4 The RGPS System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 255
11.5 Summary and Discussion .................................. 256
References ................................................ 256
11.1
Introduction
The RADARSAT Geophysical Processor System (RGPS) is a data processing system for
the analysis of synthetic aperture radar (SAR) data of sea ice acquired by the Canadian RADARSAT satellite (Raney et al. 1991). RADARSAT was launched in November of
1995 into a 24-day repeat cycle, an orbit configuration which provides near repeat coverage of the high latitudes at 3- and 7-day intervals. The SAR sensor has a number of
imaging modes, one of which illuminates a wide swath (460 km) designed for large
scale mapping of the Earth's surface. The science plan of the Alaska SAR Facility calls
for weekly coverage of the Arctic Ocean. With this mode, the coverage of the Arctic
Ocean every 7 days (Fig. 1) with 100 m pixels produces approximately 1 GB of image
data daily. In an effort to make this large volume of SAR data more useful to the scienAnalysis of SAR Data of the Polar Oceans
Edited by C. Tsatsoulis and R. Kwok
© Springer-Verlag Berlin Heidelberg 1998