Microwave Radiometer Systems Design and Analysis Second Edition -- Contents -- Preface xi -- 1 Introduction 1 -- 2 Summary 3 -- 3 The Radiometer Receiver: Sensitivity and Accuracy 7 -- 3.1 What Is a Radiometer Receiver? 7 -- 3.2 The Sensitivity of the Radiometer 7 -- 3.3 Absolute Accuracy and Stability 9 -- 4 Radiometer Principles 13 -- 4.1 The Total Power Radiometer (TPR) 13 -- 4.2 The Dicke Radiometer (DR) 14 -- 4.3 The Noise-Injection Radiometer (NIR) 16 -- 4.4 The Correlation Radiometer (CORRAD) 18 -- 4.5 Hybrid Radiometer 20 -- 4.6 Other Radiometer Types 21 -- 5 Radiometer Receivers on a Block Diagram Level 25 -- 5.1 Receiver Principles 25 -- 5.1.1 Direct or Superheterodyne 25 -- 5.1.2 DSB or SSB with or without RF Preamplifier 26 -- 5.2 Dicke Radiometer 27 -- 5.2.1 Microwave Part 27 -- 5.2.2 The Noise Figure and the Sensitivity of the Radiometer 29 -- 5.2.3 The IF Circuitry and the Detector 30 -- 5.2.4 The Extreme Signal Levels 32 -- 5.2.5 The LF Circuitry 33 -- 5.2.6 The Analog-to-Digital Converter 34 -- 5.2.7 On the Sampling in the Radiometer: Aliasing 37 -- 5.3 The Noise-Injection Radiometer 38 -- 5.4 The Total Power Radiometer 40 -- 5.4.1 DSB Receiver without RF Preamplifier 40 -- 5.4.2 SSB Receiver with RF Preamplifier 42 -- 5.5 Stability Considerations 43 -- 6 The DTU Noise-Injection Radiometers Example 47 -- 7 Polarimetric Radiometers 55 -- 7.1 Polarimetry and Stokes Parameters 55 -- 7.2 Radiometric Signatures of the Ocean 57 -- 7.3 Four Configurations 57 -- 7.3.1 Polarization Combining Radiometers 57 -- 7.3.2 Correlation Radiometers 60 -- 7.4 Sensitivities 62 -- 7.5 Discussion of Configurations 64 -- 7.6 The DTU Polarimetric System 64 -- 8 Synthetic Aperture Radiometer Principles 69 -- 8.1 Introduction 69 -- 8.2 Practical Considerations 72 -- 8.2.1 RF Processing 72 -- 8.2.2 Basic Equation 73 -- 8.2.3 Image Processing 74.

8.2.4 Sensitivity 75 -- 8.3 Example 76 -- 9 Calibration and Linearity 81 -- 9.1 Why Calibrate? 81 -- 9.2 Calibration Sources 82 -- 9.3 Example: Calibration of a 5-GHz Radiometer 86 -- 9.4 Linearity Measured by Simple Means 87 -- 9.4.1 Background 88 -- 9.4.2 Simple Three-Point Calibration 89 -- 9.4.3 Linearity Checked by Slope Measurements 92 -- 9.4.4 Measurements 93 -- 9.5 Calibration of Polarimetric Radiometers 96 -- 10 Sensitivity and Stability: Experiments with Basic Radiometer Receivers 99 -- 10.1 Background 99 -- 10.2 The Radiometers Used in the Experiments 100 -- 10.3 The Experimental Setup 101 -- 10.4 5-GHz Sensitivity Measurements 102 -- 10.5 Stability Measurements 103 -- 10.5.1 Discussion of the 5-GHz DR Results 103 -- 10.5.2 The 5-GHz DR with Correction Algorithm 105 -- 10.5.3 The 17-GHz NIR Results 109 -- 10.5.4 Discussion of the TPR Results 111 -- 10.5.5 Back-End Stability 113 -- 10.6 Conclusions 114 -- 11 Radiometer Antennas and Real Aperture Imaging Considerations 117 -- 11.1 Beam Efficiency and Losses 117 -- 11.2 Antenna Types 119 -- 11.3 Imaging Considerations 121 -- 11.4 The Dwell Time Per Footprint Versus the Sampling Time in the Radiometer 125 -- 11.5 Receiver Considerations for Imagers 130 -- 12 Relationships Between Swath Width, Footprint, Integration Time, Sensitivity, Frequency, and Other Parameters for Satellite-Borne, Real Aperture Imaging Systems 133 -- 12.1 Mechanical Scan 134 -- 12.2 Push-Broom Systems 139 -- 12.3 Summary and Discussion 140 -- 12.4 Examples 143 -- 12.4.1 General-Purpose Multifrequency Mission 143 -- 12.4.2 Coastal Salinity Sensor 143 -- 12.4.3 Realistic Salinity Sensor 144 -- 13 First Example of a Spaceborne Imager: A General-Purpose Mechanical Scanner 147 -- 13.1 Background 147 -- 13.2 System Considerations 149 -- 13.2.1 General Geometric and Radiometric Characteristics 149.

13.2.2 Instrument Options 152 -- 13.2.3 Baseline Instrument Specifications 156 -- 13.2.4 Instrument Layout and Receiver Type 156 -- 13.3 Receiver Design 157 -- 13.3.1 The Direct Receivers (10.65-36.5 GHz) 157 -- 13.3.2 The 89-GHz DSB Receivers 158 -- 13.3.3 Integrated Receivers: Weight and Power 159 -- 13.3.4 Performance of the Receivers 160 -- 13.3.5 Critical Design Features 161 -- 13.4 Antenna Design 163 -- 13.5 Calibration and Linearity 165 -- 13.5.1 Prelaunch Radiometric Calibration 165 -- 13.5.2 On-Board Calibration 166 -- 13.6 System Issues 167 -- 13.6.1 System Weight and Power 167 -- 13.6.2 Data Rate 168 -- 13.7 Summary 169 -- 14 Second Example of a Spaceborne Imager: A Sea Salinity/Soil Moisture Push-Broom Radiometer System 171 -- 14.1 Background 171 -- 14.2 The Brightness Temperature of the Sea 172 -- 14.3 The Brightness Temperature of Moist Soil 175 -- 14.4 User Requirements for Geophysical and Spatial Resolution 177 -- 14.4.1 Salinity Measurements 177 -- 14.4.2 Soil Moisture Measurements 177 -- 14.5 A 1.4-GHz Push-Broom Radiometer System 177 -- 14.5.1 Sensitivity Considerations 177 -- 14.5.2 The 1.4-GHz Noise-Injection Radiometer Receiver 178 -- 14.5.3 Antenna Considerations 181 -- 14.5.4 Layout of the System 181 -- 14.6 Calibration 184 -- 14.7 A Disturbing Factor: The Faraday Rotation 186 -- 14.7.1 The Faraday Rotation 186 -- 14.7.2 Correction Based on Knowing the Rotation Angle 187 -- 14.7.3 Correction Based on the Polarization Ratio 189 -- 14.7.4 Consequences for Instrument Design 191 -- 14.7.5 Circumventing the Problem by Using the First Stokes Parameter 191 -- 14.8 Other Disturbing Factors: Space and Atmosphere 192 -- 14.8.1 Space Radiation 192 -- 14.8.2 Atmospheric Effects 193 -- 14.9 Summary 193 -- 15 Examples of Synthetic Aperture Radiometers 197 -- 15.1 Introduction 197 -- 15.2 Implementation of Synthesis 198.

15.3 Airborne Example: ESTAR 200 -- 15.3.1 Hardware 200 -- 15.3.2 Image Reconstruction 204 -- 15.3.3 Calibration 205 -- 15.3.4 Discussion 207 -- 15.3.5 Example of Imagery 208 -- 15.4 Spaceborne Examples 211 -- 15.4.1 HYDROSTAR 211 -- 15.4.2 SMOS 214 -- Acronyms 219.