Radar Remote Sensing
use synthetic aperture principle

SEASAT SAR 1978
        - designed to observe ocean waves, sea ice, and coastlines
        - 800km orbit, 25m range and azimuth resolutions,
          l=23.5cm, HH, 20-26^o look angle
        - the fine resolution required high transmission rate
        - data were only acquired when satellite was in the sight of
            the ground station

Shuttle Image Radar-A (SIR-A) 1981
        - a synthetic aperture radar carried by the Shuttle
            Transportation System
        - designed to observe land information
        - 260km altitude, 40m range and azimuth resolutions,
          l=23.5cm, HH, fixed large look angle (47-53)

Shuttle Image Radar-B (SIR-B) 1984
        - l=23.5cm, HH, 25m azimuth resolution, 15-45m range resolution
        - varied look angle 15-60o to acquire stereo images
        - obtain roughness and moisture info at different look angles

Shuttle Image Radar-C (SIR-C) 1994
        - multiple radar bands l=23.5, 5.8, 3.1cm, color composite
        - varied look angle 15-60^o, HH, HV, VV, and VH
          25m azimuth resolution, 15-45m range resolution

        - ocean: waves, wind motion, current motion, and sea ice,
            ecosystems: land use, vegetation, fire effects, flood,
                                and clear cutting
            hydrology: water, wetland, soil moisture, snow and glacier
            geology: geologic structures, soil erosion, transportation,
                                and deposition, active volcanoes
            rain and clouds

ALMAZ-1 1991
        Soviet Union satellite radar system
        - 300km orbit, l=10cm, HH, varied look angle 20-70^o,
          10-30m range and azimuth resolutions

ERS-1, ERS-2,
        European Space Agency, 1991, 1995
        - sun-synchronous orbit, 785km
        - 16 ~ 18 days temporal resolution
        - three sensor systems including a C-band active microwave
            instrumentation with 30m resolution, VV, 23^o look angle

ENVISAT-1
        European Space Agency, 2002
        - Advanced Synthetic Aperture Radar (ASAR)
        - 30m resolution, 14-45^o look angle

JERS-1
        National Development Agency of Japan, 1992
        - sun-synchronous orbit, 568km
        - a four-band optical sensor
        - 23cm L band SAR, HH, 18m resolution, 35^o look angle

ALOS
        National Development Agency of Japan
        Advanced land Observing Satellite (ALOS)
        - a Phased Array L-band Synthetic Aperture Radar system
        - varied look angle and multi-polarization

RADARSAT
        Canadian Space Agency, 1995
        - designed to observe sea ice, coastal line, land cover,
            agriculture, and forest
        - 798km orbit, 1-3days, l=5.6cm, HH
        - various spatial resolutions and look angles
 

Interferometric Radar
        - based on the phase difference of radar signals received by
            antennas located at different positions in space
        - with a known interferometric baseline, the phase difference
            is used to calculate elevation
        - single-pass interferometry: two antennas on a single
            aircraft
        - repeat-pass interferometry: single antenna with multiple
            passes

        Shuttle Radar Topography Mission (SRTM)
        - single-pass interferometry
        - covers 60^oN-56^oS, 30m resolution DEM, C and X bands
 

LIDAR
        LIght Detection And Ranging
        uses pulses of laser light directed toward the ground and measured
        return time to measure distances
        - rapid pulsing
        - can record up to five returns per pulse, thus
            discriminating multiple surfaces per pulse
        - equipped with GPS, recorded data are georeferenced
        - large quantity of data
        - used for generating DEMs, contours, and feature extraction

        Ice, Cloud, and Land Elevation Satellite (ICESat) 2003

        Vegetation Canopy Lidar (VCL), the first mission of NASAs Earth
                System Science Pathfinder (ESSP) program
        - measure ground surface and canopy-top elevation, vertical
            distribution of canopy elements
        - no longer actively developed

Reading; chpt 8
 
 
 
 
 
 
 

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