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Lesson 7: Remote Sensing. Dr Andrew Ketsdever MAE 5595. Outline. Electromagnetic Radiation Blackbody Radiation Atmospheric Windows Instrument Parameters Remote Sensing Architectures. EM Radiation. Photon wavelength, frequency and energy. h = 6.626 x 10 -34 J sec. EM Radiation.
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Lesson 7: Remote Sensing Dr Andrew Ketsdever MAE 5595
Outline • Electromagnetic Radiation • Blackbody Radiation • Atmospheric Windows • Instrument Parameters • Remote Sensing Architectures
EM Radiation • Photon wavelength, frequency and energy h = 6.626 x 10-34 J sec
EM Radiation • Communications • Microwaves: 1 mm to 1 m wavelength. The microwaves are further divided into different frequency (wavelength) bands: (1 GHz = 109 Hz) • P band: 0.3 - 1 GHz (30 - 100 cm) • L band: 1 - 2 GHz (15 - 30 cm) • S band: 2 - 4 GHz (7.5 - 15 cm) • C band: 4 - 8 GHz (3.8 - 7.5 cm) • X band: 8 - 12.5 GHz (2.4 - 3.8 cm) • Ku band: 12.5 - 18 GHz (1.7 - 2.4 cm) • K band: 18 - 26.5 GHz (1.1 - 1.7 cm) • Ka band: 26.5 - 40 GHz (0.75 - 1.1 cm) • V band: 50 – 75 GHz • W band: 75 – 111 GHz
EM Radiation • Heat energy is the KE of random motion of the particles in matter • Temperature is the measure of heat energy concentrated in a substance • Random motion results in COLLISIONS • COLLISIONS cause changes in the internal energy of the molecules • Internal energy modes relax to ground state by giving off photons (EM Radiation)
Blackbody Radiation • An ideal thermal emitter • Transforms heat energy into radiant energy at the maximum rate allowed (Thermodynamics) • Any real material at the same temperature can not emit at a rate in excess of a blackbody • An ideal thermal absorber • Planck’s formula C1 = 3.74 x 10-16 Wm2 = 2phc2 C2 = 1.44 x 10-2 mK = hc/k
Blackbody Radiation • Wien’s Displacement Law • Defines wavelength in a blackbody at which the maximum energy is emitted
Blackbody Radiation • Stefan-Boltzmann Law • Relates the power emitted by a body to that body’s temperature s = 5.669 x 10-8 Wm-2K-4
Other Than Blackbody Radiation • Emissivity • Ratio of the spectral energy radiated by a material to that of a blackbody at the same temperature • Can depend on • Wavelength • Temperature • Phase (solid/liquid)
Atmospheric Window M13 Observations Rotational Transitions in CO
Window Transmission Glass Quartz Sapphire
Instrument Parameters Telescopes: Microwave, Radio, IR, Vis, UV, XRay, Gamma Ray
Instrument Parameters f – focal length h – altitude rd – radius of detector array Rg – ½ Swath Width
Instrument Parameters • Focal Length Refractive System Reflective System
Instrument Parameters • F-Stop or F-Number D - Aperture
Instrument Parameters • A telescope's spatial (or angular) resolution refers to how well it can distinguish between two objects in space which are separated by a small angular distance. • The closer two objects can be while still seen as two separate objects, the higher the spatial resolution of the telescope. • The spatial resolution of a telescope affects how well details can be seen in an image. • A telescope with higher spatial resolution creates clearer and more detailed images.
Instrument Parameters • Diffraction Limited Resolution • Rayleigh diffraction criteria • Angular distance from maximum brightness at the center of the image to the first dark interference ring h can be replaced by slant range for off Nadir obs.
Instrument Parameters Aberration Stigmatism Coma
Instrument Parameters • Silicon Imager Spectral Response
Instrument Parameters • IR Detectors
Remote Sensing Architectures Global Ocean Temperatures
Remote Sensing Architectures Passive Active Mie scattering (small particles) Rayleigh Scattering (large particles)
Remote Sensing Architectures What is the driver for the remote sensing architecture? Cosmic Background Explorer SPOT Mars Reconnaissance Orbiter
Remote Sensing Architectures • Landsat 7 • a panchromatic band with 15m spatial resolution • on-board, full aperture, 5% absolute radiometric calibration • a thermal IR channel with 60m spatial resolution • an on-board data recorder
Remote Sensing Architectures Baghdad Chicago
Diffuse – Rough Surface Specular – Smooth Surface Maxwell Model
Remote Sensing Architectures • Space Radar • Mauna Loa Volcano • Rift Zones (Orange) • Smooth Lava Flows (Red) • Pahoehoe Flows • Rough Lava Flows (Yellow/White) • A’a Flows • Obtained by sensing different Radar bands
Remote Sensing Architectures • LIDAR • Light Detection and Ranging