Remote Sensing Physics: An Introduction to Observi ng Earth from Space

Acronyms xiii

Preface xix

About the Companion Website xxi

1 Introduction to Remote Sensing 1

1.1 How Remote SensingWorks 4

References 9

2 Satellite Orbits 11

2.1 Computation of Elliptical Orbits 15

2.2 Low Earth Orbits 16

2.3 Geosynchronous Orbits 23

2.4 Molniya Orbit 27

2.5 Satellite Orbit Prediction 29

2.6 Satellite Orbital Trade-offs 29

References 31

3 Infrared Sensing 33

3.1 Introduction 33

3.2 Radiometry 33

3.3 Radiometric Sensor Response 37

3.3.1 Derivation 37

3.3.2 Example Sensor Response Calculations 40

3.3.3 Response of a Sensor with a Partially-Filled FOV 41

3.4 Blackbody Radiation 41

3.4.1 Planck's Radiation Law 41

3.4.2 Microwave Blackbody 43

3.4.3 Low-Frequency and High-Frequency Limits 44

3.4.4 Stefan-Boltzmann Law 44

3.4.5 Wein's Displacement Law 44

3.4.6 Emissivity 45

3.4.7 Equivalent Blackbody Temperature 45

3.5 IR Sea Surface Temperature 45

3.5.1 Contributors to Infrared Measurements 45

3.5.2 Correction of Low-Altitude Infrared Measurements 47

3.5.3 Correction of High-Altitude Infrared Measurements 49

3.6 Atmospheric Radiative Transfer 50

3.7 Propagation in Seawater 55

3.8 Smooth Surface Reflectance 58

3.9 Rough Surface Reflectance 61

3.10 Ocean Thermal Boundary Layer 63

3.11 Operational SST Measurements 66

3.11.1 AVHRR Instrument 67

3.11.2 AVHRR Processing 69

3.11.3 AVHRR SST Algorithms 70

3.11.4 Example AVHRR Images 71

3.11.5 VIIRS Instrument 72

3.11.6 SST Accuracy 76

3.11.7 Applications 77

3.12 Land Temperature - Theory 78

3.13 Operational Land Temperature 81

3.14 Terrestrial Evapotranspiration 86

3.15 Geologic Remote Sensing 88

3.15.1 Linear Mixture Theory and Spectral Unmixing 90

3.16 Atmospheric Sounding 92

References 96

4 Optical Sensing - Ocean Color 101

4.1 Introduction to Ocean Color 101

4.2 Fresnel Reflection 105

4.3 Skylight 108

4.4 Water-Leaving Radiance 108

4.5 Water Column Reflectance 111

4.5.1 Pure Seawater 114

4.5.2 Case 1Waters 114

4.5.3 Case 2Waters 115

4.6 Remote Sensing Reflectance 116

4.7 Ocean Color Data - Case 1Water 119

4.7.1 Other Uses of Ocean Color 120

4.8 Atmospheric Corrections 121

4.9 Ocean Color Satellite Sensors 125

4.9.1 General History 125

4.9.2 SeaWiFS 132

4.9.3 MODIS 133

4.9.4 VIIRS 136

4.10 Ocean Chlorophyll Fluorescence 139

References 145

5 Optical Sensing - Land Surfaces 149

5.1 Introduction 149

5.2 Radiation over a Lambertian Surface 149

5.3 Atmospheric Corrections 153

5.4 Scattering from Vegetation 154

5.5 Normalized Difference Vegetation Index 158

5.6 Vegetation Condition and Temperature Condition Indices 164

5.7 Vegetation Indices from Hyperspectral Data 165

5.8 Landsat Satellites 166

5.9 High-resolution EO sensors 170

5.9.1 Introduction 170

5.9.2 First Generation Systems 170

5.9.3 Second Generation Systems 172

5.9.4 Third Generation Systems 172

5.9.5 Commercial Smallsat Systems 173

References 182

6 Microwave Radiometry 185

6.1 Introduction to Microwave Radiometry 185

6.2 Microwave Radiometers 185

6.3 Microwave Radiometry 187

6.3.1 Antenna Pattern 188

6.3.2 Antenna Temperature 189

6.3.3 Examples 190

6.4 Polarization 191

6.4.1 Basic Polarization 191

6.4.2 Jones Vector 192

6.4.3 Stokes Parameters 193

6.5 Passive Microwave Sensing of the Ocean 194

6.5.1 Atmospheric Transmission 195

6.5.2 Seawater Emissivity 195

6.5.3 Fresnel Reflection Coefficients, Emissivity, and Skin Depth 196

6.5.4 Sky Radiometric Temperature 197

6.5.5 Sea Surface Brightness Temperature 199

6.5.6 Wind Direction from Polarization 202

6.6 Satellite Microwave Radiometers 203

6.6.1 SMMR 204

6.6.2 SSM/I and SSMI/S 205

6.6.3 SSM/I Wind Algorithm 207

6.6.4 AMSR-E 208

6.6.5 WindSat 210

6.7 Microwave Radiometry of Sea Ice 213

6.8 Sea Ice Measurements 219

6.9 Microwave Radiometry of Land Surfaces 224

6.10 Atmospheric Sounding 229

References 232

7 Radar 235

7.1 Radar Range Equation 235

7.2 Radar Cross-Section 239

7.3 Radar Resolution 242

7.4 Pulse Compression 246

7.5 Types of Radar 250

7.6 Example Terrestrial Radars 251

7.6.1 Weather Radars 251

7.6.2 HF SurfaceWave Radar 254

References 255

8 Altimeters 257

8.1 Introduction to Altimeters 257

8.2 Specular Scattering 260

8.3 Altimeter Wind Speed 263

8.4 Altimeter SignificantWave Height 266

8.5 Altimeter Sea Surface Height 269

8.5.1 Introduction 269

8.5.2 Pulse-limited vs Beam-limited Altimeter 269

8.5.3 Altimeter Pulse Timing Precision 270

8.5.4 Altimeter Range Corrections 270

8.6 Sea Surface Topography 274

8.7 Measuring Gravity and Bathymetry 280

8.8 Delay-Doppler Altimeter 281

References 284

9 Scatterometers 287

9.1 OceanWaves 287

9.2 Bragg Scattering 293

9.3 RCS Dependence on Wind 297

9.4 Scatterometer Algorithms 300

9.5 Fan-Beam Scatterometers 303

9.6 Conical-Scan Pencil Beam Scatterometers 306

9.7 Conical-Scan Fan-Beam Scatterometers 311

References 313

10 Synthetic Aperture Radar 315

10.1 Introduction to SAR 315

10.2 SAR Azimuth Resolution 319

10.2.1 Doppler Time History 319

10.2.2 Azimuth Extent, Integration Time, and Doppler Bandwidth 322

10.2.3 Azimuth Resolution 322

10.2.4 SAR Timing, Resolution, and Swath Limits 324

10.2.5 The Magic of SAR Exposed 325

10.3 SAR Image Formation and Image Quality 326

10.4 SAR Imaging of Moving Scatterers 329

10.5 Multimode SARs 332

10.6 Polarimetric SAR 333

10.6.1 Polarimetric Response of Canonical Targets 333

10.6.2 Decompositions 334

10.6.3 Compact Polarimetry 336

10.7 SAR Systems 337

10.7.1 Radarsat-1 339

10.7.2 Envisat 339

10.7.3 PALSAR 339

10.7.4 Radarsat-2 339

10.7.5 TerraSAR-X 339

10.7.6 COSMO-SkyMed 341

10.7.7 Sentinel-1 343

10.7.8 Radar Constellation Mission (RCM) 343

10.7.9 Military SARs 343

10.8 Advanced SARs 346

10.8.1 Cross-Track Interferometry 346

10.8.2 Along-Track Interferometry 347

10.8.3 Differential Interferometry 350

10.8.4 Tomographic Interferometry 351

10.8.5 High-Resolution, Wide-Swath SAR 351

10.9 SAR Applications 353

10.9.1 SAR Ocean SurfaceWaves 353

10.9.2 SAR Winds 359

10.9.3 SAR Bathymetry 365

10.9.4 SAR Ocean InternalWaves 371

10.9.5 SAR Sea Ice 376

10.9.6 SAR Oil Slicks and Ship Detection 378

10.9.7 SAR Land Mapping Applications and Distortions 386

10.9.8 SAR Agricultural Applications 392

References 395

11 Lidar 399

11.1 Introduction 399

11.2 Types of Lidar 399

11.2.1 Direct vs Coherent Detection 400

11.3 Processes Driving Lidar Returns 401

11.3.1 Elastic Scattering 401

11.3.2 Inelastic Scattering 402

11.3.3 Fluorescence 403

11.4 Lidar Range Equation 403

11.4.1 Point Scattering Target 403

11.4.2 Lambertian Surface 404

11.4.3 Elastic Volume Scattering 404

11.4.4 Bathymetric Lidar 404

11.5 Lidar Receiver Types 406

11.5.1 Linear (full waveform) Lidar 406

11.5.2 Single Photon Lidar 407

11.6 Lidar Altimetry 408

11.6.1 NASA Airborne Topographic Mapper 408

11.6.2 Space-Based Lidar Altimeters (IceSat-1 & 2) 409

11.6.3 Bathymetric Lidar 410

11.7 Lidar Atmospheric Sensing 410

11.7.1 ADM-Aeolus 411

11.7.2 NASA CALIOP 414

References 417

12 Other Remote Sensing and Future Missions 419

12.1 Other Types of Remote Sensing 419

12.1.1 GRACE 419

12.1.2 Limb Sounding 419

12.2 Future Missions 420

12.2.1 NASA Missions 421

12.2.2 ESA Missions 422

12.2.3 Summary 423

References 424

Appendix A Constants 425

Appendix B Definitions of Common Angles 427

Appendix C Example Radiometric Calculations 431

Appendix D Optical Sensors 437

D.1 Example Optical Sensors 439

D.1.1 Photodiodes 440

D.1.2 Charge-Coupled Devices 442

D.1.3 CMOS Image Sensors 444

D.1.4 Bolometers and Microbolometers 444

D.2 Optical Sensor Design Examples 446

D.2.1 Computing Exposure Times 446

D.2.2 Impact of Digitization and Shot Noise on Contrast Detection 448

References 449

Appendix E Radar Design Example 451

Appendix F Remote Sensing Resources on the Internet 459

F.1 Information and Tutorials 459

F.2 Data 459

F.3 Data Processing Tools 460

F.4 Satellite and Sensor Databases 460

F.5 Other 460

Appendix G Useful Trigonometric Identities 461

Index 463