01-Introduction

01-Introduction - Remote Sensing The Major Source for...

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Remote Sensing: Remote Sensing: The Major Source for Large- The Major Source for Large- Scale Environmental Information Scale Environmental Information Jeff Dozier Emphasis: understand the principles of acquiring and interpreting data from satellite-based remote sensing systems Basic physics Available sensors and products Environmental applications through image analysis
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Observations from space Observations from space Sun-synchronous polar orbits Global coverage, fixed crossing, repeat sampling Typical altitude 500-1,500 km Low-inclination, non-Sun-synchronous orbits Tropics, mid-latitudes, varying sampling Typical altitude 200-2,000 km Geostationary orbits Regional views of full Earth disk, continuous coverage Over Equator only, altitude 35,000 km
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Observations from aircraft and ground Observations from aircraft and ground Aircraft Regional and local, any sampling times Repeat sampling In situ atmospheric chemistry, clouds and aerosols, heat and vapor fluxes Sparse coverage Ground Repeat or continuous sampling Sparse coverage
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Radiation Radiation A body radiates energy when electrons in its atoms receive or generate so much energy that they release a small packet of energy (photon) If the atoms are receiving or generating a lot of energy (i.e. they are hot) they emit photons in large numbers and frequently. Thus, both the intensity (energy per unit time) and the frequency of emission are high. Since energy ( E ) travels through a vacuum at a constant speed ( c, the speed of light), if the frequency ( ν ) of particle (wave) emission is high, the wavelength ( λ ) is short: Planck’s law: energy per photon λ ν c = h h = = h is Planck’s constant 4
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There is a  There is a  spectrum spectrum  (range) of wavelengths of   (range) of wavelengths of  electromagnetic radiation electromagnetic radiation Wavelength ( λ ) For remote sensing, we usually use µm (micrometer, 10 –6 m) or nm (nanometer, 10 –9 m) to measure wavelength, except in microwave. http://www.yorku.ca/eye/spectrum.gif 5
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Two rules describing radiation were derived  Two rules describing radiation were derived  from this simple postulate from this simple postulate Planck’s equation At a given temperature a body emits a spectrum of wavelengths and the intensity of radiation varies with the wavelength ( 29 2 5 2 , where 1 x hc hc L x k T e λ = = - 0.0 E +0 0 4 0 wavelength energy Peak radiation for hotter object is higher and at shorter wavelength Hotter object radiates more at all wavelengths c = speed of light = 3.0 x 10 8 ms –1 h = Planck’s constant = 6.63 x 10 –34 Js k = Boltzmann’s constant = 1.38 x 10 –23 JK –1 6
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So, total energy at Sun = 4 πR 2 Watts That same amount of energy spreads out over the surface of a sphere at a distance of Earth’s radius (4 πP 2 ) So, energy at Earth is
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This note was uploaded on 08/06/2008 for the course ESM 266 taught by Professor Dozier during the Spring '08 term at UCSB.

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01-Introduction - Remote Sensing The Major Source for...

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