07-PassiveMicrowave

07-PassiveMicrowave - 4/28/2008 Frequency...

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4/28/2008 ESM 266: Passive microwave remote sensing 1 ESM 266: Passive microwave remote sensing 1 Jeff Dozier Frequency wavelength relation • Generally in the microwave part of the spectrum we use frequency instead of wavelength Frequency where speed of light c c ν λ = = 2 • Typically measured in s –1 , called Hertz (Hz) – Most often Gigahertz (GHz) = 10 9 Hz 8- 1 =3.00 10 m s × Microwave band codes Band Wavelength, cm Frequency, GHz Mid-IR (3-5) × 10 –4 100,000-60,000 Thermal IR (8-15) × 10 –4 37,500-20,000 K a 0.75-1.18 40.0-26.5 K 1.19-1.67 26.5-18.0 3 K u 1.67-2.4 18.0-12.5 X 2.4-3.8 12.5-8.0 C 3.9-7.5 8.0-4.0 S 7.5-15.0 4.0-2.0 L 15.0-30.0 2.0-1.0 P 30.0-100 1.0-0.3 Advantages of passive microwave remote sensing • Sees through clouds at lower frequencies • Long heritage, various instruments since 1978 • Emissivity sensitive to state of surface, particularly moisture 4 – Soil moisture – Snow-water equivalent – (water is ~80× as absorptive as ice at these frequencies, whereas in visible through infrared, water and ice have similar absorption coefficients) • But, because of small amount of energy emitted, pixel size must be large Characteristics of major passive microwave instruments Footprint (km) Frequency (GHz) SSM/R 1978-85 SSM/I 1987-pres AMSE-E 2002-pres AMSR 2002-pres 6.6-6.9 148 × 95 75 × 43 70 × 40 10.7-10.9 91 × 59 51 × 29 46 × 27 18.7-19.4 55 × 41 69 × 43 27 × 16 25 × 14 22-23.8 46 × 30 60 × 40* 32 × 18 29 × 17 36-37 27 × 18 37 × 29 14 × 81 4 × 8 50.3/52.8 10 × 6* 85-89 15 × 13 6 × 46 × 3 *V-polarization only Planck equation Planck equation – frequency form frequency form () 3 2 1 21 1 2 , where 1 W/s units Wm Hz sr x hh Lx kT ce −− == = 6 2 units ms r c speed of light 3.00 × 10 8 ms –1 h Planck’s constant 6.63 × 10 –34 Js k Boltzmann’s constant 1.38 × 10 –23 JK –1
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4/28/2008 ESM 266: Passive microwave remote sensing 2 Planck equation = f( Planck equation = f(frequency,Temperature
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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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07-PassiveMicrowave - 4/28/2008 Frequency...

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