INTRODUCTION TO MICROWAVE REMOTE SENSINGece.uprm.edu/~pol/pdf/Ch1Iintro.pdf · Dr. Sandra L. Cruz Pol INEL 6069 Microwave Remote Sensing, Dr. Sandra Cruz-PolRemote Sensing of Ocean-Atmosphere

Dr. Sandra L. Cruz Pol

INEL 6069 Microwave Remote Sensing, Dr. Sandra Cruz-PolRemote Sensing of Ocean-Atmosphere 1

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Dr. Sandra Cruz Pol Microwave Remote Sensing INEL 6669/8695 Dept. of Electrical & Computer Engineering, UPRM, Mayagüez, PR

INTRODUCTION TO MICROWAVE REMOTE SENSING

INEL 8695/6669

OUTLINE

•  Importance of Microwaves •  Sensor types: passive/active

•  Radiometers •  RADARS

•  Electromagnetic Spectrum •  Atmospheric windows

•  Brief history •  Applications

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WHY MICROWAVES?

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•  Capability to penetrate clouds and, to some extent, rain.

•  Independence of the sun as a source of illumination.

•  Provides info about geometry and bulk-dielectric properties.(e.g. salinity)

3 stages of El Niño www.cencoos.org/sections/news/LaNina_2010.shtml 4

WHY MICROWAVES?

•  Penetrate more deeply into vegetation than optical waves.

•  Penetrate into ground (more into dry than wet soil).

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30 GHz 300 MHz PENETRATION DEPTH VS. SOIL MOISTURE

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•  Visible and IR sensors can sometimes be used to complement this information



IR (TOP) VERSUS MICROWAVES (BOTTOM)

7 http://www2.hawaii.edu/~jmaurer/sst/ 8

ELECTROMAGNETIC SPECTRUM

http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html

WAVE PENETRATION DEPENDS ON FREQUENCY

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SOIL PENETRATION [WWW.UNI.EDU/STORM/RS/2001/VH7.HTML]

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Aplicaciones: mapas zonas propensas a fuegos.

SNOW – MICROWAVE PENETRATION

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Aplicación: mapas de barcos icebreakers, estudios climáticos.

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•  Affect Earth’s radiation budget •  Improve global climate models (GCM) •  Improve reliability of forecasts

Why study Clouds?…

Absorbed (blue area)

Transmitted (white)

W Ka Atmospheric Windows X



MICROWAVE REMOTE SENSING SENSORS

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1. Passive– Uses of radiometers to study the Earth Passive sensors are called microwave radiometers, which

receive and detect the radiation emitted from various objects on the earth

2. Active– Uses RADAR (RAdio Detection And Ranging) to study Earth

Active microwave remote sensor illuminates the ground with microwave radiation and then receives the back-scattered energy from the object. Some of the active microwave remote sensors are :

•  Radars: CW, Pulse, Doppler, FM, Side looking airborne radar (SLAR) , Synthetic aperture radar (SAR)

•  Wind scatterometer •  Altimeter •  Polarimeter

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WHAT IS RADIOMETRY?

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•  All objects radiate EM energy. •  Radiometry measures of

natural EM radiation from objects; earth, ice, plants...

WHERE DOES ENERGY GOES?

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•  Energy (EM waves) received at the Earth from the Sun is •  absorbed (atmosphere, clouds, earth, ocean…) •  scattered •  transmitted

•  Absorbed energy is transformed •  into thermal energy.

•  Thermodynamic balance •  through emission, absorption,… is called

RT=Radiative Transfer

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Microwave Radiometer (~70% of the time)

(Arecibo Observatory works as radar too!)

Microwave Radar

(Tropical Rainfall Measuring Mission (TRMM) satellite)

Global Precipitation Measurement (GPM)



HISTORY OF RADARS •  Henry Hertz, 1886 1st radio experiment, reflections detected

@200MHz, confirmed experimentally that an electric spark propagates electromagnetic waves into space.

•  1890, Tesla illuminated a vacuum tube wirelessly—having transmitted energy through the air using a Tesla coil to change 60Hz into hi-freq.

•  1895 Marconi patent for radio, 1986 in England, using 17 patents from Tesla.

•  1925- Pulse radars to measure height of ionosphere. •  1930- unintentional detection of airplanes •  1943 the Supreme Court overturned Marconi's patent in favor of Tesla. •  WWII- detecting ships and aircraft. Used PPI displays. •  MIT- developed magnetron – hi-power Tx and klystron –Lo-power

source •  1938 Altimeter – airborne FM radars at 400MHz to measure altitude. •  1950 – SLAR – finer resolution cause antennas length up to 15 m fixed

|| to fuselage. Airplane motion produced a scan.

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HISTORY OF RADARS

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Side Looking Aperture Radar (SLAR) Range resolution =>pulse width Azimuth resolution=> antenna size

www.csr.utexas.edu/projects/rs/whatissar/rar.html PPI= Plan position indicator

Sea Ice and Iceberg Detection By SLAR (Side Looking Airborne Radar)

•  Light blue- sea ice •  Green -open water

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http://www.etl.noaa.gov/technology/instruments/rads/ice.html

HISTORY OF RADARS •  1952- 54 SAR –”fine resolution

Doppler”, •  pixel dimension in the along track

direction independent of distance from radar,

•  antenna could be much smaller. [Complex processing to produce an image.]

•  Scatterometer – radar that measures scattering coefficient, σ. (In ocean, scatter is proportional to wind speed.)

•  1950s 1st U.S. weather radars•  1970 – Doppler becomes major

technique for meteorology. NEXRAD

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RADARSAT is a Synthetic Aperture Radar (SAR) at C-band. Used for oceanic oil spill and ice sheet monitoring.A target's position along the flight path determines the Doppler frequency of its echoes: Targets ahead of the aircraft produce a positive Doppler offset; targets behind the aircraft produce a negative offset. As the aircraft flies a distance (the synthetic aperture), echoes are resolved into a number of Doppler frequencies. The target's Doppler frequency determines its azimuth position.

http://www.met.ed.ac.uk/~chris/RS1Web/sar2-2000/ppframe.htm

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Seasat-1 Antenna pattern for each of its microwave sensors



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SCATTEROMETERS

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Global View Radar Backscatter by SeaWinds Scatterometer

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ALTIMETERS

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EARTH GEOID

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The geoid is the shape that the surface of the oceans would take under the influence of Earth gravity and rotation alone, in the absence of other influences such as winds and tides

HISTORY OF MICROWAVE RADIOMETERS P=kTB only at µλ frequencies

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•  1930s- First radiometers used for radio-astronomy (RAS)

•  1950s- First radiometers used for terrestrial observations

•  Earth Exploration Satellite Service (EESS)



RADIOMETERS

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WATER ABSORPTION MEASUREMENTS

circa 1945 •  A Radiation Laboratory roof-

top crew use microwave radiometer equipment pointed at the sun to measure water absorption by the atmosphere.

•  Atop Building 20 (from left): Edward R. Beringer, Bob L. Kyhl, Arthur B. Vane, and Bob H. Dicke (Photo from Five Years at the Radiation Laboratory)

32 http://rleweb.mit.edu/groups/g-radhst.HTM

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WHY MONITOR WV?

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•  Water vapor is one of the most significant constituents of the atmosphere since it is the means by which moisture and latent heat are transported to cause "weather".

•  Water vapor is also a greenhouse gas that plays a critical role in the global climate system. This role is not restricted to absorbing and radiating energy from the sun, but includes the effect it has on the formation of clouds and aerosols and the chemistry of the lower atmosphere.

•  Despite its importance to atmospheric processes over a wide range of spatial and temporal scales, it is one of the least understood and poorly described components of the Earth's atmosphere.



ELECTROMAGNETIC SPECTRUM

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IEEE MICROWAVE RADAR BANDS BAND Designation

Nominal Frequency Range

SPECIFIC Bands

HF 3-30 MHz0

VHF 30-300 MHz 138-144 MHz 216-225

UHF 300-1000MHz 420-450 MHz 890-942

L 1-2 GHz 1.215-1.4 GHz

S 2-4 GHz 2.3-2.5 GHz 2.7-3.7>

C 4-8 GHz 5.25-5.925 GHz

X 8-12 GHz 8.5-10.68 GHz

Ku 12-18 GHz 13.4-14.0 GHz 15.7-17.7

K 18-27 GHz 24.05-24.25 GHz

Ka 27-40 GHz 33.4-36.0 GHz

V 40-75 GHz 59-64 GHz

W 75-110 GHz 76-81 GHz 92-100

millimeter 110-300 GHz 40

www.serve.com/mahood/RCS/bands.htm

(millimeter)

Airport Millimeter Wave scanners use 24.25GHz-30GHz frequency range (wavelength

10-12mm)

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RADARS

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SLAR

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SAR Resolution

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SOUNDERS = TEMPERATURE PROFILES

1965 •  On location at the National Center

for Atmospheric Research (NCAR) in Texas. A launch crew prepares a 60-GHz atmospheric sensing receiver. Once lofted airborne by balloon, the receiver remotely sensed the temperature profile at different altitudes.

•  These experiments evolved into the Nimbus series of NASA satellites, which later became part of the National Oceanic and Atmospheric Administration's (NOAA) satellite weather forecasting system, also used by NASA.

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MICROWAVE TEMPERATURE PROFILER

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is a microwave radiometer that measures thermal emission from oxygen molecules along a line of sight that is scanned in elevation angle.

•  Knowledge gained in developing this radiometers are useful in developing radiometers for unstart-prevention systems in high-speed (up to mach 2.4) civil-transport aircrafts.

ATMOSPHERIC IMAGERS

1977 •  Checking an instrument

that is the direct forerunner of today's operational satellite microwave atmospheric imagers used by NOAA

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MODERN MICROWAVE WATER RADIOMETER (MWR)

•  Provides time-series measurements of column-integrated amounts of water vapor and liquid water.

The instrument itself is essentially a sensitive microwave receiver.

That is, it is tuned to measure the microwave emissions of the vapor and liquid water molecules in the atmosphere at specific frequencies. (~22 GHz) 55

TRUCK MOUNTED RADIOMETER

This truck-mounted microwave radiometer system measures surface soil moisture at

L, S and C bands.

56 http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/SGP97/slmr.html#100

EL NIÑO (ENSO) FROM SPACE

57 3 stages of El Niño www.cencoos.org/sections/news/LaNina_2010.shtml 58

59 Launched in 2006 60

GPM follows TRMM- launch Feb 2014



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http://www.epa.gov/climatechange/science/future.html#

Future Climate Change MEDICAL APPLICATIONS

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•  Microwave Radiometry can be used for the detection of different diseases. •  Madison, WI- tumor-detection system exploits

the large dielectric contrast between normal tissues and malignant tumors at microwave frequencies.

•  Clinical trials at Moscow oncological centers, conducted in over 1000 patients have shown that breast cancer detective ability of microwave radiometry is ~90%.

•  Microwave Radiation used for treatment. •  The microwave procedure used a finely focused

beam which heats up and kills tumour cells. The trial is being organised at two centres in the US, in Palm Beach, Florida, and the Harbor UCLA Medical Centre in California. www.resltd.ru/eng/company/r_history.php

www.whitaker.org/abstracts/jun99/hagness.html

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NASA TOPEX/POSEIDON AND JASON(S)

�  One of the contributions to the altimetric delay is the wet path delay caused by tropospheric water vapor in the altimetric signal path.

�  The wet path delay is the additional time that it takes for the signal to pass through the water vapor.

�  If this contribution is not subtracted from the measured altimetric delay, this additional time will introduce error to the measured sea surface height.

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Altimeter on board measures sea levels with accuracy to better than 5 cm!

NASA JASON 1-3

•  Downward-looking water vapor radiometer onboard the altimeter satellite measures microwave radiation at several different frequencies, 18 GHz, 21 GHz, and 37 GHz.

•  These frequencies were chosen because radiances at these frequencies are sensitive to atmospheric water vapor and liquid water.

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EL NIÑO AS MEASURED BY T/P

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WEATHER APPLICATIONS: RADAR

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COLLABORATIVE ADAPTIVE SENSING OF THE ATMOSPHERE (CASA)

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Earth curvature effects prevent 72% of the troposphere below 1 km from being observed

10,000 ft

tornado

wind

earth surface

snow

3.05 k

m

0 40 80 120 160 200 240 RANGE (km)

Horz. Scale: 1” = 50 km Vert. Scale: 1” -=- 2 km

5.4 km

1 km

2 km

4 km

gap

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http://weather.uprm.edu

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CASA NSF-ERC

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•  DCAS - Distributed Collaborative Adaptive (Weahter Radar) System

TROPINET @ UPRM

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Documents

INTRODUCTION TO MICROWAVE REMOTE SENSINGece.uprm.edu/~pol/pdf/Ch1Iintro.pdf · Dr. Sandra L. Cruz Pol INEL 6069 Microwave Remote Sensing, Dr. Sandra Cruz-PolRemote Sensing of Ocean-Atmosphere