Microwave remote sensing principles and applications
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Microwave Remote Sensing: Principles and Applications. Outline Introduction to RSL at the University of Kansas Introduction and History of Microwave Remote Sensing Active Microwave Sensors Radar Altimeter. Scatterometer. Imaging Radar. Applications of Active Sensors Sea ice. Glacial ice

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Microwave remote sensing principles and applications

Microwave Remote Sensing: Principles and Applications

  • Outline

    • Introduction to RSL at the University of Kansas

    • Introduction and History of Microwave Remote Sensing

    • Active Microwave Sensors

      • Radar Altimeter.

      • Scatterometer.

      • Imaging Radar.

    • Applications of Active Sensors

      • Sea ice.

      • Glacial ice

      • Ocean winds.

      • Soil Moisture.

      • Snow.

      • Vegetation.

      • Precipitation.

      • Solid Earth.

University of Kansas


Microwave remote sensing principles and applications1

Microwave Remote Sensing: Principles and Applications

  • Passive Microwave Sensors

    • Radiometers

      • Traditional

      • Interferometer

      • Polarimetric Radiometer

  • Application of Passive Microwave Sensors

    • Sea ice.

    • Glacial ice

    • Soil Moisture.

    • Atmospheric sounding

    • Snow.

    • Vegetation.

    • Precipitation

University of Kansas


Radar systems and remote sensing laboratory

Radar Systems and Remote Sensing Laboratory

Windvector Measurements over the Ocean

Radar at 14 GHz.

Concept developed at KU.

USA, Europe and Japan are planning to launch satellites to obtain data continuously.

University of Kansas


Radar systems and remote sensing laboratory1

Radar Systems and Remote Sensing Laboratory

Founded in 1964.

4 Faculty members, 20 Graduate students - Ph. D & M.S.

4-6 Undergraduate students, 2 Staff

Now satellites based on concepts developed at RSL are in operation.

NSCAT, QUICKSCAT- Radars to measure ocean surface winds.

ADEOS-2 (JAPAN), Europeans Met Office is planning to launch satellite to support operational applications.

ScanSAR-

Radarsat- Canadian satellite

Envisat - European

SRTM -Shuttle Radar Topography Mission.Radar Systems and Remote Sensing Laboratory

University of Kansas


Radar systems and remote sensing laboratory2

Radar Systems and Remote Sensing Laboratory

  • Shuttle Radar Topography Mission (SRTM)

    • to collect three-dimensional measurements of the Earth's surface.

    • Acquired data to obtain the most complete near-global mapping of our planet's topography to date.

    • This would not have been possible without ScanSAR operation--- concept developed at KU.

University of Kansas


Ittc information technology telecommunication center

ITTC– Information Technology & Telecommunication Center

  • Communications academic emphasis and research programs established in 1983.

  • Now RSL is a part of the Center

  • Graduated students

    • degrees in EE, CS, CoE, Math

  • 29 faculty, 15 staff researchers, 6 Center staff

  • Current student population ~ 130

    • ~ 13 Ph.D., ~81 M.S., ~37 B.S.

University of Kansas


Em spectrum

EM Spectrum

  • Microwave region

    • 300 MHz – 30 GHz.

      Millimeter wave

    • 30 GHz – 300 GHz.

      IEEE uses a different definition

    • 300 MHz – 100 GHz

University of Kansas


Microwave remote sensing principles and applications2

Microwave Remote Sensing: Principles and Applications.

  • Advantages

    • Day/night coverage.

    • All weather except during periods of heavy rain.

    • Complementary information to that in optical and IR regions.

  • Disadvantages

    • Data are difficult to interpret.

    • Coarse resolution except for SAR.

University of Kansas


Microwave remote sensing history

Microwave Remote Sensing— history

  • US has a long history in Microwave Remote Sensing.

    • Clutter Measurement program after the WW-II.

      • Ohio State University collected a large data base of clutter on variety of targets.

    • Earnest studies for the remote sensing of the earth can be considered to have began 1960s.

      • In 1960s NASA initiated studies to investigate the use of microwave technology to earth observation.

University of Kansas


Microwave remote sensing history1

Microwave Remote Sensing— history

  • The research NASA and other agencies initiated resulted in:

    • Development of ground-based and airborne sensors.

    • Measurement of emission and scattering characteristics of many natural targets.

    • Development of models to explain and understand measured data.

    • Space missions with microwave sensors.

      • NIMBUS

        • Radiometers.

      • SKYLAB

        • Radar and Radiometers

University of Kansas


Microwave remote sensing

Microwave Remote Sensing

  • Radar

    • Radio Detection and Ranging.

    • Texts:

      • Skolnik, M. I., Introduction to Radar Systems, McGraw Hill, 1981.

      • Stimson, G. W., Introduction to Airborne Radar, SciTech Publishing, 1998.

Applications

Civilian

Navigation and tracking

Search and surveillance

Imaging & Mapping

Weather

Sounding

Probing

Remote sensing

Military

Navigation and tracking

Search and surveillance

Imaging & Mapping

Weather

Proximity fuses

Counter measures

University of Kansas


Review em theory and antennas

Review – EM theory and Antennas

  • Propagation of EM waves is governed by Maxwell equations.

  • For time-harmonic variation we can write the above equations as

University of Kansas


Em theory

EM Theory

  • Helmholtz Equation

    • From the four Maxwell equations, we can derive vector Helmholtz equations

    • For each component of E and H field we can write a scalar equation

University of Kansas


Uniform plane wave

Uniform plane wave

Amplitude and phase are constant on planes perpendicular to the direction of propagation.

TEM case– no component in the direction of propagation.

For a TEM wave propagating in z direction Ez = 0 and Hz =0

Ex(z,t) = Eo e-αzCos(ωt-jβz)

University of Kansas


Em theory1

EM theory

  • α and β are determined by material properties.

  • Materials are classified as insulators and conductors

University of Kansas


Em theory2

EM Theory

  • Reflection and refraction

    • Whenever a wave impinges on a dielectric interface, part of the wave will be reflected and remaining will be transmitted into the lower medium.

θi

θr

θt

University of Kansas


Em theory scattering

EM Theory--Scattering

  • Microwave Scattering from a distributed target depends on

    • Dielectric constant.

    • Surface roughness.

    • Internal structure.

      • Homogeneous

      • Inhomogeneous

    • Wavelength or Frequency.

    • Polarization.

University of Kansas


Microwave scattering

θi

θr

Microwave Scattering

  • Surface scattering

    • A surface is classified as smooth or rough by comparing its surface height deviation with wavelength.

      • Smooth h < λ/32 cos(θ)

      • For example at 1.5 GHz and = 60 deg.,

      • h < 1.25 cm

Smooth surface

Moderately rough surface

Very rough surface

University of Kansas


Microwave scattering1

Microwave Scattering

  • Rough surface scattering

University of Kansas


Microwave scattering2

Microwave Scattering

  • Volume scattering

    • Material is inhomogeneous such as

      • Snow

      • Firn

      • Vegetation

      • Multiyear ice

University of Kansas


Microwave scattering3

Microwave Scattering

  • Surface scattering models

    • Geometric optics model

      • Surface height standard deviation is large compared to the wavelength.

    • Small perturbation model

      • Surface height standard deviation is small compared to the wavelength.

    • Two-scale model

      • Developed to compute scattering from the ocean

        • Small ripples riding on large waves.

University of Kansas


Antennas

Antennas

  • Antennas are used to couple electromagnetic waves into free space or capture electromagnetic waves from free space.

  • Type of antennas

    • Wire

      • Dipole

      • Loop antenna

    • Aperture

      • Parabolic dish

      • Horn

University of Kansas


Antennas1

Antennas

  • Antennas are characterized by their:

    • Directivity

      • It is the ratio of maximum radiated power to that radiated by an isotropic antenna.

    • Efficiency

      • Efficiency defines how much of the power is the total power radiated by the antenna to that delivered to the antenna.

    • Gain

      • It is the product of efficiency and directivity

    • Beamwidth

      • Width of the main lobe at 3-dB points.

dipole

University of Kansas


Antenna gain

Antenna gain

University of Kansas


Antennas2

Antennas

  • An array of antennas is used whenever higher than directivity is needed.

    • Can be used to electronic scanning.

    • Most of the SAR antennas are arrays.

University of Kansas


Antenna array

Antenna Array

  • Let us consider simple array consisting of isotropic radiators.

R1

Ro

d

q

P

University of Kansas


Radar principles

Radar Principles

  • Radar classified according to the trasmit waveform.

    • Continuous

      • Doppler

      • Altimeter

      • Scatterometer

    • Pulse

      • Wide range of applications

University of Kansas


Radar principles1

Radar Principles

  • Radar measures distance by measuring time delay between the transmit and received pulse.

    • 1 us = 150 m

    • 1 ns = 15 cm

Radar

University of Kansas


Radar principle

Radar— principle

  • Unambiguous range and Pulse Repetition Frequency (PRF)

    • PRF also determines the maximum doppler we can measure with a radar— SAR.

    • PRF > 2 fdmax

University of Kansas


Radar principle1

Radar equation

For a monostatic radar

GT = GR

Radar sensitivity is determined by the minimum detectable signal set by the receiver noise.

No = kTBF

F= noise figure

Signal-to-noise ratio

Radar—Principle

PT

GT

R

University of Kansas


Microwave remote sensing1

Microwave Remote Sensing

  • Radar cross section characterizes the size of the object as seen by the radar.

    Where

    Es = scattering field

    Ei = incident field

r

University of Kansas


Radar equation

Radar Equation

  • A distributed target contains many scattering centers within the illuminated area. It is characterized by radar cross section per unit area, which is refereed to as scattering coefficient

be

ba

qo

R

University of Kansas


Radar equation1

Radar Equation

For a distributed power received falls off as 1/R2

For a point target power received falls off as 1/R4

University of Kansas


Antenna array1

Antenna Array

  • Let us consider simple array consisting of isotropic radiators.

R1

Ro

d

q

P

University of Kansas


Antenna array2

Antenna Array

  • Let us consider simple array consisting of isotropic radiators.

R1

Ro

d

q

P

University of Kansas


Microwave remote sensing principles and applications history

Microwave Remote Sensing: Principles and Applications— History

  • Active Microwave sensing

    • Studies related to active sensing of the earth beagn in 1960s.

      • Clutter studies

      • SkYLab – radar altimeter and scatterometer in 1960s

      • SEASAT in 1978

      • ERS-1, JERS-1, ERS-2, RADARSAT, GEOSAT, Topex-Posoidon

University of Kansas


Active sensors radar altimeter

Active Sensors – Radar Altimeter

  • Radar altimeter is a short pulse radar used for accurate height measurements.

    • Ocean topography.

    • Glacial ice topography

    • Sea ice characteristics

      • Classification and ice edge

      • Vegetation

  • http://topex-www.jpl.nasa.gov/technology/images/P38232.jpg

University of Kansas


Radar altimeter

Missions

Radar Altimeter

University of Kansas


Radar altimeter waveform

Radar Altimeter— Waveform

  • Satellite altimeters operate in pulse-limited mode.

University of Kansas


Radar altimeter1

Radar Altimeter

  • A short pulse radar

    • Uses pulse compression to obtain fine range resolution or height measurement.

    • Range measurement uncertainty of a pulse radar.

University of Kansas


Radar altimeter2

Radar altimeter

  • Other sources of errors

    • Atmospheric delays

    • Troposheric delays.

    • EM bias

    • Pointing errors

    • Orbit errors

    • Accuracies of few cms are being achieved with new generation sensors.

      • Dual-frequency

      • Water vapor— radiometers

      • GPS – orbit determination

      • Calibration.

Resti et al, “The Envisat Altimeter System RA-2,”ESA Bulletin 98, June 1999

sigma=5.5 cm

University of Kansas


Radar altimeter typical system

Radar Altimeter—typical system

Resti et al, “The Envisat Altimeter System RA-2,”ESA Bulletin 98, June 1999

University of Kansas


Radar altimeter3

Radar Altimeter

  • Waveform analysis

    • Time delay is measured very accurately and converted into distance.

    • Spreading of the pulse is related to SWH.

    • Scattering coefficient can be obtained by determining the power.

Resti et al, “The Envisat Altimeter System RA-2,”ESA Bulletin 98, June 1999

University of Kansas


Radar altimeter typical system1

Radar Altimeter- typical system

  • Block diagram of Envisat RA

Resti et al, “The Envisat Altimeter System RA-2,”ESA Bulletin 98, June 1999

University of Kansas


Active sensors

Active sensors

  • Scatterometer

    • Scatter o Meter – A calibrated radar used to measure scattering coefficient.

    • They are used to measure radar backscatter as a function of incidence angle.

    • Ground and aircraft-based scatterometers are widely used.

      • Experimental data on variety of targets to support model and algorithm development activities.

        • Developing algorithms for extracting target characteristics from data.

        • Understanding the physics of scattering to develop empirical or theoretical models.

        • Developing target classification algorithms

University of Kansas


Active sensors scatterometers

Active sensors— Scatterometers

  • Wide range of applications

    • Wind vector measurements

    • Sea and glacial ice

    • Snow extent.

    • Vegetation mapping

    • Soil moisture

      • Semi-arid or dry areas.

University of Kansas


Microwave remote sensing atmosphere and precipitation

Microwave Remote Sensing— Atmosphere and Precipitation

  • Global precipitation mission

    • Will consist of a primary spacecraft and a constellation.

      • Primary Spacecraft

        • Dual-frequency radar.

          • 14 and 35 GHz.

        • Passive Microwave Radiometer

    • Constellation Spacecraft

      • Passive Microwave Radiometer

University of Kansas


Microwave remote sensing active sensors

Microwave Remote Sensing—Active Sensors

Imaging Radars


Imaging radars scatterometers

Imaging Radars & Scatterometers

  • Imaging Radars

    • Real Aperture Radar (RAR)

    • Synthetic Aperture Radar (SAR)

      • Widely used for military and civilian applications.

    • RAR

      • Thin long antenna mounted on the side of an aircraft.

University of Kansas


Imaging radars

RAR

Resolution is determined by antenna beamwidth in the along track direction

Pulse width in the cross-track direction

RAR geometry

Imaging radars

University of Kansas


Imaging radars1

Imaging radars

  • For a radar operating at f=10 GHz with a 3-m long antenna in the along track direction and 0.5 us pulse, resolution at 45 degree incidence and range of 10 km is given by

  • Assume k=0.8

University of Kansas


Imaging radars rar

Resolution

RARs were used until 1990s.

They are replaced by SARs.

Resolution should 1/20 about the dimensions of the target we want to recognize

Imaging Radars: RAR

MRS: vol. II, Ulaby, Moore and Fung

University of Kansas


Microwave remote sensing principles and applications

SAR

  • Synthetic Aperture Radar

    • Use the forward motion of an aircraft or a spacecraft to synthesize a long antenna.

    • Satellite SARs

      • ERS-1, ERS-2, RADARSAT, ENVISAT, JERS-1, SEASAT, SIR-A,B& C.

      • Applications

        • Ocean wave imaging

        • Oil slick monitoring

        • Sea ice classification and dynamics

        • Soil moisture

        • Vegetation

        • Glacial ice surface velocity

University of Kansas


Microwave remote sensing principles and applications

SAR

  • We can use a small physical antenna

  • For focused SAR resolution is independent of

    • Wavelength

    • Range

    • Best possible resolution is L/2

      • Where L= length of the physical antenna

University of Kansas


Rf spectrum

RF Spectrum

Microwave Radiometry covers a range of frequencies.

Soil

Moisture

1-3 GHz

Resolution /

aperture

Ocean Surface Wind

19, 22 GHz

Polarimetry

Atmospheric

Temperature

54, 118 GHz

Accuracy

Atmospheric

Water Vapor

22, 24, 92, 150,

183 GHz

Accuracy

Cloud Ice

325, 448, 643 GHz

High frequency

l

30 cm

3 cm

0.3 mm

3 mm

1000 GHz

100 GHz

10 GHz

1 GHz

Sea Surface Salinity

1-3 GHz

Receiver sensitivity/

stability

Sea Ice

37 GHz

Polar coverage

Precipitation

11, 31,37,89 GHz

Frequent global

coverage

Atmospheric

Chemistry

190, 240, 640,

2500 GHz

High frequency

Hartley, NASA

L band

S band

C band

X band

Ku/K/Ka band

Millimeter

Submillimeter

University of Kansas


Microwave radiometers theory

Microwave Radiometers— theory

  • Planck’s Law of radiation

  • Where S(λ,T) =Intensity of radiation in w/m2

  • T = temperature in Kelvins

  • h = Planck’s constant, 6.625 × 10-34 J·s

  • c = velocity of propagation m/s

  • k = Boltzmann constant, 1.380 × 10-23 J/K

  • λ = wavelength, m

University of Kansas


Microwave radiometer

Microwave Radiometer

  • At microwave frequencies radiation intensity is directly proportional to the temperature.

  • For gray bodies

    • Pa = kTb B

    • k =Boltzman constant, B = bandwidth, Hz.

    • Tb = Brightness temperature, K

    • Tb =e Tphy

    • e = Emissivity of the object or media

University of Kansas


Microwave radiometer1

Microwave Radiometer

Two basic types of radiometers

  • Total power radiometer

    • Highest sensitivity

  • Switching-type radiometers and its variants.

  • Typical total power radiometer

  • University of Kansas


    Microwave radiometer2

    Microwave Radiometer

    • Dicke or Switching-type radiometer

      • Any fluctuations in gain of the receiver will reduce radiometer sensitivity.

      • To eliminate system effects, Dicke developed switching type radiometer.

        • It consists of switch and a synchronous detector. The input is switched between the antenna and noise source. If the injected noise power is equal to input signal power, the effect of gain fluctuations is eliminated.

    University of Kansas


    Microwave radiometer3

    Microwave Radiometer

    • Typical Dicke-type radiometer

    University of Kansas


    Rf radiometry characteristics

    RF Radiometry Characteristics

    Moden Radiometer

    Digital processor

    To eliminate down conversion process

    Antenna

    Receiver

    multiplexer/

    spectrometer

    digital

    processor/

    correlator

    detector/

    digitizer

    low noise

    amplifier

    mixer

    LO

    Hartley, NASA

    scan

    University of Kansas


    Microwave remote sensing2

    Microwave Remote Sensing

    • Research and application of microwave technology to remote sensing of

      • Oceans and ice

      • Solid earth and Natural hazards..

      • Atmosphere and precipitation.

      • Vegetation and Soil moisture

    University of Kansas


    Microwave remote sensing ocean and ice

    Microwave Remote Sensing— Ocean and Ice

    • Winds

      • Scatterometer.

        • Quickscat, Seawinds

      • Polarimetric radiometer

    • Ocean topography

      • Radar altimeters

    • Ocean salinity

      • AQUARIUS

        • Radiometer and radar combination.

          • Radar to measure winds for correcting for the effect of surface roughness.

    University of Kansas


    Ocean vector winds scatterometers

    Ocean Vector Winds— Scatterometers

    QuikScat

    • Replacement mission for NSCAT, following loss of ADEOS

    • Launch date: June 19, 1999

      SeaWinds

    • EOS instrument flying on the Japanese ADEOS II Mission

    • Launch date: December 14, 2002 ????

      Instrument Characteristics of QuikScat and SeaWinds

    • Instrument with 120 W peak (30% duty) transmitter at 13.4 GHz, 1 m near-circular antenna with two beams at 46o and 54o incidence angles

    Scatterometers send microwave pulses to the

    Earth's surface, and measure the power scattered

    back. Backscattered power over the oceans

    depends on the surface roughness, which in turn

    depends on wind speed and direction.

    SeaWinds

    QuikScat

    Advanced sensors– larger aperture antennas.Passive polarimetric sensors.

    University of Kansas

    Courtesy: Yunjin Kim, JPL


    Ocean topography missions

    Ocean Topography Missions

    TOPEX/Poseidon and Jason-1

    • Joint NASA-CNES Program

      • TOPEX/Poseidon launched on August 10, 1992

      • Jason-1 launched on December 7, 2001

    • Instrument Characteristics

      • Ku-band, C-band dual frequency altimeter

      • Microwave radiometer to measure water vapor

      • GPS, DORIS, and laser reflector for precise orbit determination

    • Sea-level measurement accuracy is 4.2 cm

    • TOPEX/Poseidon & Jason-1 tandem mission for high resolution ocean topography measurements

    The most effective measurement of ocean currents

    from space is ocean topography, the height of the sea

    surface above a surface of uniform gravity, the geoid.

    The priority is to continue the measurement

    with TOPEX/Poseidon accuracy

    on a long-term basis for climate studies. 

    Courtesy: Yunjin Kim, JPL

    TOPEX/Poseidon Ocean topography of the Pacific Ocean during El Niño and La Niña.

    University of Kansas


    Microwave remote sensing principles and applications

    Ocean Surface Topography Mission An Experimental Wide-Swath Altimeter

    By adding an interferometric radar system to a conventional radar altimeter system, a swath of 200 km can be achieved, and eddies can be monitored over most of the oceans every 10 days. The design of such a system has progressed, funded by NASA’s Instrument Incubator Program. This experiment is proposed to the next mission, OSTM (Ocean Surface Topography Mission)

    South America

    Courtesy: Yunjin Kim, JPL

    University of Kansas


    Microwave remote sensing principles and applications

    1 week of salinity measurements from space

    100 yrs of salinity measurements by ship

    Global Ocean Salinity

    • Aquarius (JPL, GSFC, CONAE)

      • ESSP-3 mission in the risk mitigation phase

    • First instrument to measure global ocean salinity

      • Passive and active microwave instrument at L-band

      • Resolution

        • Baseline 100km, Minimum 200km

      • Global coverage in 8 days

      • Accuracy: 0.2 psu

      • Baseline mission life: 3 years

    University of Kansas

    Courtesy: Yunjin Kim, JPL


    Microwave remote sensing principles and applications

    SRTM (Shuttle Radar Topography Mission)

    • C-band single pass interferometric SAR for topographic measurements using a 60m mast

    • DEM of 80% of the Earth’s surface in a single 11 day shuttle flight

      • 60 degrees north and 56 degrees south latitude

      • 57 degrees inclination

    • 225 km swath

    • WGS84 ellipsoid datum

    • JPL/NASA will deliver all the processed data to NIMA by January 2003

    • Absolute accuracy requirements

      • 20 m horizontal

      • 16 m vertical

    • The current best estimate of the SRTM accuracy is

      • 10 m horizontal and 8 m vertical

    • Partnership between NASA and NIMA (National Imagery and Mapping Agency)

    • X-band from German and Italian space agencies

    Courtesy: Yunjin Kim, JPL

    University of Kansas


    Microwave remote sensing principles and applications

    L-band InSAR Technology

    • Interferometric Synthetic Aperture Radar (InSAR) can measure surface deformation (mm-cm scale) through repeated observations of an area

      • L-band is preferable due to longer correlation time due to longer wavelength (24cm)

    • Solid Earth Science Working Group recommended that

      • In the next 5 years, the new space mission of highest priority for solid-Earth science is a satellite dedicated to InSAR measurements of the land surface at L-band

    Surface deformation due to Hector Mine

    Earthquake using repeat-pass InSAR data

    InSAR velocity difference indicates a 10%

    increase in ice flow velocity from 1996 to

    2000 on Pine Island Glacier

    [Rignot et al., 2001]

    University of Kansas


    Microwave remote sensing soil moisture

    Microwave Remote Sensing— Soil Moisture.

    RadarPol: VV, HH & HV

    Res – 3 and 10 km

    Radiometer

    Pol: H, V

    Res =40 km,

    dT= 0.64º K

    SGP’97

    Courtesy: Tom Jackson, USDA

    • HRDROS

      • Back-up ESSP mission for global soil moisture.

        • L-band radiometer.

        • L-band radar.

    University of Kansas


    Microwave remote sensing principles and applications

    Microwave Remote Sensing— Atmosphere and Precipitation

    CloudSAT

    Salient Features

    NASA ESSP mission

    First 94 GHz radar space borne system

    Co-manifested with CALIPSO on Delta launch vehicle

    Flies Formation with the EOS Constellation

    Current launch date: April 2004

    Operational life: 2 years

    Partnership with DoD (on-orbit ops), DoE (validation) and CSA (radar development)

    Science

    Measure the vertical structure of clouds and quantify their ice and water content

    Improve weather prediction and clarify climatic processes.

    Improve cloud information from other satellite systems, in particular those of Aqua

    Investigate the way aerosols affect clouds and precipitation

    Investigate the utility of 94 GHz radar to observe and quantify precipitation, in the context of cloud properties, from space

    University of Kansas

    Courtesy: Yunjin Kim, JPL


    Earth science and rf radiometery

    Earth Science and RF Radiometery

    Atmospheric chemistry

    Precipitation

    Microwave Radiometry Applications.

    Sea surface temperature/

    Sea surface salinity

    Hartley, NASA

    Ocean surface wind

    Soil moisture

    Atmospheric temperature, humidity, and clouds

    University of Kansas


    Conclusions

    Conclusions

    • A brief overview of microwave remote sensing principles and applications.

    • Opportunities for research and education.

      • Science

      • Technology

    University of Kansas


    Sar principle

    SAR—Principle

    • SAR can explained using the concept of a matched filter or antenna array.

    Ro

    University of Kansas


    Sar principle1

    SAR— Principle

    • Unfocussed SAR

      • No phase corrections are made.

    Ro

    r

    University of Kansas


    Sar principle2

    SAR— Principle

    • Focussed SAR

    x

    Ro

    University of Kansas


    Sar principle3

    SAR— Principle

    • Resolution

    University of Kansas


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