Synthetic Aperture Radar Systems and Signal Processing Radarrr

Synthetic Aperture Radar – Systems and Signal Processing Radarrr rr r Radio Detection and Ranging WW II, England. Military use measure backscattered amplitude and distance to target High power, sharp pulse -> low power, FM-CW chirp signal Navigation radar Weather radar Ground Penetrating Radar Imaging radar cf) LIDAR (Light detection and Ranging)

Synthetic Aperture Radar – Systems and Signal Processing Imaging Radar Different Eyes microwave, UHF, VHF surface roughness and dielectric constant Microwave Ranging All-weather Cloud-free Side-looking Active System Day and night imaging independent of solar illumination

Synthetic Aperture Radar – Systems and Signal Processing Aperture Optics : Diameter of the lens or mirror. The larger the aperture, the more light a telescope collects. Greater detail and image clarity will be apparent as aperture increases. 2. 4 m Hubble Space Telescope 10 m Keck, Hawaii 16. 4 m VLT (Very Large Telescope), Chile 50 m Euro 50 100 m OWL (Over. Whelmingly Large T. )

Over. Whelmingly Large Telescope

Synthetic Aperture Radar – Systems and Signal Processing Real Aperture vs. Synthetic Aperture • Real Aperture : resolution ~ Rλ/L • Synthetic Aperture: resolution ~ L/2 Irrespective of R Smaller, better? ! - Carl Wiley (1951)

Synthetic Aperture Radar – Systems and Signal Processing ERS– 1/2 SAR Image Acquisition L: 10 m, D: 1 m Altitude: 785 km, sun-synchronous orbit Ground Velocity: 6. 6 km/s Look Angle: Right 17 -23 (20. 355 mid-swath) Slant Range: 845 km (mid-swath) Frequency: C- Band (5. 3 GHz, 5. 6 cm) Footprint : 100 km x 5 km Incidence Angle: 19 – 26 (23 mid-swath) Sampling Rate: 18. 96 MHz Pulse duration: 37. 1 s Range gate: ~ 6000 s Sampling Duration: ~ 300 s (5616 samples) Inter-pulse period: ~ 600 s ( upto 10 pulses) Pulse Repetition Frequency: 1700 Hz Data Rate: 105 Mb/s (5 bits/sample)

Synthetic Aperture Radar – Systems and Signal Processing SAR Systems Spaceborne SAR SEASAT-A (USA, 1978), SIR-A (USA, 1981), SIR-B (USA, 1984), SIR-C/X-SAR (USA, Germany, Italy, 1994), ALMAZ-1 (Russia, 1991 -1993), ERS-1(EU, 1991 -2000), ERS-2 (EU, 1995 -), JERS-1 (Japan, 1992 -1998), Radarsat-1 (Canada, 1995 -), SRTM (USA/Germany, 2000), ENVISAT (EU, 2002), RADARSAT-2 (Canada, 2005), PALSAR (Japan, 2004), Light. SAR (US)*, Terra. SAR (Germany)*, Micro. SAR(EU)* Airborne SAR TOPSAR (JPL, USA), IFSARE(ERIM/Intermap, USA), DO-SAR(Donier, Germany), E-SAR(DLR, Germany), Ae. S-1(Aerosensing, Germany), AER-II (FGAN, Germany), C/X-SAR (CCRS, Canada), EMISAR (Denmark), Ramses (ONERA, France), ESR (DERA, UK) Planetary SAR Magellan (US, 1990 -1994), Titan Radar Mapper (US, 2004), Arecibo Antenna, Goldstone antenna * Under development

Synthetic Aperture Radar – Systems and Signal Processing SAR System Modes Target – the Earth or planets Vehicle – stationary, airborne, satellite, or spaceship Mode – monostatic and/or bistatic Carrier frequency – X, C, S, L, and/or P bands Polarisation – HH, VV, VH, HV (single-pol, dual-pol, full-pol) Imaging geometry – strip, scan, spot <examples> SIR-C/X-SAR: space shuttle, mono, L/C/X, full-pol. ERS-1/2, Envisat: Earth satellite, mono, C, VV. SRTM: space shuttle, mono/bistatic, C/X, HH/VV. Arecibo Antenna: planetary, stationary, mono/bi, multi-bands, multi-pol. Magellan, Cassini SAR: Venus and Titan, mono, S, HH. AIRSAR/TOPSAR: airborne, mono/bi, L/C/P, full-pol

Synthetic Aperture Radar – Systems and Signal Processing ENVISAT Launched 2002. 2. 28 C-band, Multpol, multi-mode Data : Envisat Announcement of Opportunity

Synthetic Aperture Radar – Systems and Signal Processing Image Domain Range (R) 5616 pixels, 100 km Azimuth (s) 28, 000 lines, 106 km

Synthetic Aperture Radar – Systems and Signal Processing Range Compression Linear Chirp Signal Chirp autocorrelation Function Matched Filtering For ERS-1/2, Pulse duration (T): 37. 1 s Bandwidth : 15. 5 MHz Half power width of autocorrelation function: 0. 065 s Pulse Compression Ratio: 575 (ERS-1/2) Ground Range Resolution: 12. 5 m Input Range FFT Range Matched Filtering Range i. FFT

Synthetic Aperture Radar – Systems and Signal Processing Range Migration Flight Path Point Target Linear (Range Walk) Azimuth FFT Quadratic (Range Curvature)

Synthetic Aperture Radar – Systems and Signal Processing Range Migration Compensation Range (R) Azimuth (s) After Range Walk Compensation Range Migration

Synthetic Aperture Radar – Systems and Signal Processing Azimuth Compression Synthetic Aperture Real Aperture Doppler Shift (Linear Chirp Pulse) : wavelength For ERS-1/2, L: Antenna length Coherent Integration Time (S): 600 ms (5 km footprint) Azimuth footprint width: 5 km (ERS-1/2) Matched Filtering Bandwidth: 1260 Hz Half power width of autocorrelation function: 0. 8 ms Pulse Compression Ratio: 756 (ERS-1/2) Azimuth Resolution: 5 m Azimuth Matched Filtering Output

SAR Focusing – Point Target azimuth range original After migration After range compression After azimuth compression

Synthetic Aperture Radar – Systems and Signal Processing Southeast Cost of Spain ERS-2 (13 km x 13 km) Descending, Right Looking

Synthetic Aperture Radar – Systems and Signal Processing Geometric Distortion Terrain Imaging Geometry Layover Foreshortening Shadow

Synthetic Aperture Radar – Systems and Signal Processing Scattering Mechanisms

Synthetic Aperture Radar – Systems and Signal Processing Rule of Thumb in SAR images • Backscattering Coefficient • Smooth – Black • Rough surface – white • Calm water surface – black • Water in windy day – white • Hills and other large-scale surface variations tend to appear bright on one side and dim on the other. • Human-made objects - bright spots (corner reflector) • Strong corner reflector- Bright spotty cross (strong sidelobes)

Synthetic Aperture Radar – Systems and Signal Processing 청주공항 (ERS-2)

Synthetic Aperture Radar – Systems and Signal Processing Aleutian Volcanic Islands (ERS-1)

Synthetic Aperture Radar – Systems and Signal Processing Ship Wakes over the Bering Sea The Calving of Iceberg A-38 (ERS-1 46 km x 28 km)

Synthetic Aperture Radar – Systems and Signal Processing 대청호 ERS-1/2 SAR Calm Water Rough Water

Synthetic Aperture Radar – Systems and Signal Processing Ronne Ice Shelf, Antarctica The Calving of Iceberg A-38 (Radarsat Scan. SAR 150 km x 150 km)

4 -inch SAR onboard UAV

Synthetic Aperture Radar – Systems and Signal Processing SAR Advanced Techniques Radarclinometry: DEM from Shape-from-shading (experimental) Radargrammetry: DEM from stereo SAR image matching (m) In. SAR: n n Interferogram: DEM (cm) Coherence: statistical measurement of temporal and spatial decorrelation (cm) DIn. SAR: surface displacement, penetration depth (mm). Pol-SAR: Classification, segmentation Pol-In. SAR: measurement of scattering structure SAR Tomography: 3 D target distribution

Synthetic Aperture Radar – Systems and Signal Processing In. SAR – Digital Elevation Model ERS-1/2 Tandem Interferogram

In. SAR Coherence Imagery Random Change Detection In. SAR Coherence Image Optical Image

In. SAR Coherence Imagery Seismic Survey Lines

Differential In. SAR Earthquake

DIn. SAR Volcano

DIn. SAR Glacier Velocity

DIn. SAR Land Subsidence

Planetary SAR Magellan to Venus

Planetary SAR Cassini to Titan

Synthetic Aperture Radar – Systems and Signal Processing SAR Applications for Peace reconnaissance, survelliance and targetting target detection and recognition moving target detection navigation and guidence - Sandia National Lab. 4 -inch SAR

Synthetic Aperture Radar – Systems and Signal Processing SAR Peaceful Applications Cartography – DEM, DTM Geology – Geological Mapping Seismology – Co-seismic displacement field Volcanology – Prediction of volcano eruption Forestry – Forest classification, deforest monitoring Soil Science – Soil moisture Glaciology – Glacier motion Oceanography – Ocean wave, wind, circulation, bathymetry Agriculture – Crop monitoring Hydrology – Wetland assessment Environment – Oil spill, hazard monitoring Archaeology – Sub-surface mapping

Synthetic Aperture Radar – Systems and Signal Processing Korean SAR