CryoSat Product Handbook Catherine Bouzinac CryoSat Product Handbook Table of Content 1. Introduction ...................................................................................................................... 6 1.1. Purpose and Scope of this User Guide ........................................................................................ 6 1.2. The CryoSat Mission and its Characteristics ................................................................................ 6 1.3. Principles Of Operation .............................................................................................................. 8 1.4. SIRAL Characteristics ................................................................................................................. 11 1.5. Data Access and Data ProcessinG Tools ...................................................................................... 12 2. Discussion of Data Parameters ........................................................................................ 13 2.1. Spacecraft Orbit and Orientation .............................................................................................. 13 2.1.1. DORIS ......................................................................................................................................... 14 2.1.2. Orbit Data Processing ................................................................................................................ 14 2.1.3. Satellite Reference Frame and Processing Reference Frame .................................................... 14 2.1.4. Mispointing ................................................................................................................................ 17 2.1.5. Centre of Mass ........................................................................................................................... 17 2.2. Spacecraft Time and Location .................................................................................................... 17 2.2.1. Reference Ellipsoid .................................................................................................................... 17 2.2.2. Some Basic Altimetry Terms ...................................................................................................... 17 2.2.1. Geoid and Mean Sea Surface ..................................................................................................... 18 2.2.2. Sea Surface Height Anomaly ...................................................................................................... 19 2.2.3. Freeboard .................................................................................................................................. 19 2.2.4. Timestamps ................................................................................................................................ 19 2.2.5. Latitude, Longitude and Altitude ............................................................................................... 20 2.2.6. DORIS Ultra Stable Oscillator Drift ............................................................................................. 20 2.2.7. Satellite Velocity Vector ............................................................................................................. 20 2.2.8. Reference Orbit ......................................................................................................................... 20 2.2.9. Ground Tracks ............................................................................................................................ 21 2.2.10. Illuminated Areas ..................................................................................................................... 23 2.3. Instrument Corrections and Noise ............................................................................................. 26 2.3.1. Automatic Gain Control ............................................................................................................. 26 2.3.2. Signal Phase Corrections ............................................................................................................ 26 2.3.3. Phase Slope Correction .............................................................................................................. 27 2.3.4. Hamming Weighting Function for SAR Azimuth FFT .................................................................. 27 2.3.5. Noise .......................................................................................................................................... 32 2.3.6. Echo Saturation .......................................................................................................................... 32 2.3.7. Application of Corrections ......................................................................................................... 32 2.4. Doppler Correction .................................................................................................................... 33 2.5. RetrackinG and Parameters Derived From Echo Shape ............................................................... 33 2.5.1. Range Window and Window Delay ........................................................................................... 33 2.5.2. Reception Period ....................................................................................................................... 33 2.5.3. Range Window Sampling ........................................................................................................... 33 2.5.4. Echo Positioning and Scaling ...................................................................................................... 35 2.5.5. Retracking .................................................................................................................................. 35 Page 2 CryoSat Product Handbook 2.5.6. Backscattering ............................................................................................................................ 37 2.5.7. Peakiness ................................................................................................................................... 37 2.5.8. Effects of Terrain ........................................................................................................................ 38 2.5.1. Interferometric Mode ................................................................................................................ 38 2.5.2. Significant Wave Height ............................................................................................................. 39 2.5.3. Sea State Bias ............................................................................................................................. 39 2.5.4. Wind Speed ................................................................................................................................ 39 2.6. RanGe Corrections for Atmospheric Effects ................................................................................ 39 2.6.1. Dry and Wet Tropospheric Corrections ..................................................................................... 39 2.6.2. Inverse Barometric Correction ................................................................................................... 40 2.6.3. Dynamic Atmospheric Correction .............................................................................................. 40 2.6.4. Ionospheric Correction .............................................................................................................. 40 2.6.5. Derivation of Corrections ........................................................................................................... 41 2.6.6. Application of Corrections to Range .......................................................................................... 41 2.7. RanGe Corrections for Tidal Effects ............................................................................................ 41 2.7.1. Ocean Tide ................................................................................................................................. 41 2.7.2. Ocean Loading Tide .................................................................................................................... 42 2.7.3. Solid Earth Tide .......................................................................................................................... 42 2.7.4. Geocentric Polar Tide ................................................................................................................ 42 2.7.5. Application of Corrections to Range .......................................................................................... 42 2.8. DerivinG RanGe .......................................................................................................................... 42 2.8.1. Geophysical Corrections by Surface .......................................................................................... 43 2.8.2. Surface Type .............................................................................................................................. 44 2.8.3. Level-2 Application .................................................................................................................... 44 2.9. Models Used ............................................................................................................................. 44 2.9.1. Static Auxiliary Data Files ..........................................................................................................