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29 Cards in this Set
- Front
- Back
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Rayleigh Scattering |
Scattering that occurs when diameter of matter is many smaller than the wavelength of incident microwave radiation Scattering of blue light |
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Mie Scattering |
Takes place when diameter is equal to the wavelength Visible: smog/pollution Microwave: snow grains |
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Non-Selective Scattering |
Scattering that occurs when diameter of matter is several xlarger than wavelength Visible: snow |
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Blackbody |
Emits a continuos spectrum of radiation across the electromagnetic spectrum proportional to its physical temperature Wavelength emitted at peak spectral existence Hotter objects emit peak spectral existence at shorter wavelengths sun 6000K=0.43 Earth 300K=10 |
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Grey Body |
Object that emits a fraction of the radiation of a blackbody Emissivity <1 |
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Emissivity |
The ratio of radiant energy of an object compared to that of a blackbody at the same temperature Blackbody = 1 Grey Body <1 |
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Selective Radiator |
Emits radiation at varying intensities at different wavelengths depending on the objects emisivitty |
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Microwave Radiometry - Emissivity |
Emissivity is the ratio between the radiant flux exiting a real work selective radiating body (Fr) and a blackbody at the same temperature (Fb) |
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Brightness Temperature |
Passive microwave sensors observe brightness temperature (Tb) defined as the products emissivity and physical temperature (Tsurf) |
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Thermal Capacity |
the ability of a material to store heat - water has highest |
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Thermal Conductivity |
rate that heat will pass through the material |
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Thermal Inertia |
measurements of thermal response of material to temperature - how long does it take for an object to heat up/cool down? Rocks/water = high thermal inertia Sand = low thermal inertia |
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Relative Permittivity |
Describes how electromagnetic energy propagates through a medium Real Part E' - describes what happens when electric field interacts with objects boundary Imaginary Part E" - Dielectric loss - describes ability of material to dissipate penetrated energy (absorption), if material absorbs, loss factor is high |
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Atmospheric Windows |
Regions of the EMS where wavelengths of incoming solar radiation or emitted radiation from ground are not absorbed by molecules in the atmosphere Caused by energy of same freq as resonant is absorbed producing excited state Energy transformed into heat motion and reradiated at longer wavelengths |
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Radiant Flux |
rate of flow of energy onto, off of, or through a surface |
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Radiance |
radiant flux per unit solid angle leaving an extended source is given direction per unit projected source area |
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Reflectance |
re-radiation of photons in unison by atoms or molecules in layer one-half the wavelength depth Surface types: Specular - smooth Diffused - rough Perfectly Diffused - lambertian surface |
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Refraction |
measure of optical density of a substance |
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Absorption |
process by radiant energy is absorbed and converted into other forms of energy - occurs when energy of same freq. as resonant is absorbed |
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Transmission |
inversly related to extinction coefficient times thickness of layer |
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Extinction Coefficient |
amount of radiation that does not get through the medium |
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Stefan Boltzmann Law |
Total spectral radiant flux existance Black body is proportional to 4power temp TIR - area under curve |
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Wein's Displacement Law |
Relationship b/w true temp of blackbody in degrees Kelvin and peak spectral existence TIR - where peak of curve is |
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Thermal IR
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kinetic heat converted to radiant energy electromagnetic radiation exiting is radiant flux concentration of radiant flux is the Trad positive correlation with kinetic temp Emitted from all objects that have temp of greater than 0 |
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Active Microwave (RADAR) |
sensor payload carries its own source of EMR 1) Transmits energy towards target 2) EMR interactive with a target producing backscatter 3) EMR returned to sensor is measured |
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Passive Microwave |
Records EMR reflected or emitted from external source - low spatial resolutions |
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Advantages & Disadvantages of Passive Microwave |
Adv. - penetrates cloud - low freq allows soil moisture content calc - independent of solar radiation Dis. - larger field = lower spatial resolution - polar orbiting - discontinuous temporal coverage of equatorial regions |
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Viewing Geometry |
Foreshortening Layover Shadowing |
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Polarization |
Pulses of Energy is filtered so that electrical wave vibrations only in a single plane perpendicular to direction of travel VV - send vertical, received vertical HH - send horizontal, received horizontal HV - send horizontal, receive vertical VH - send vertical, receive horizontal |
