08-ActiveMicrowave

08-ActiveMicrowave - Active and passive remote sensing...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
4/30/2008 ESM 266: Active microwave remote sensing 1 ESM 266: ESM 266: Active Active microwave microwave remote sensing 1 Jeff Dozier Active and passive remote sensing Passive: uses natural energy, either reflected sunlight or emitted thermal or microwave radiation • Active: sensor creates its own energy 2 Active: sensor creates its own energy – Transmitted toward Earth – Interacts with atmosphere and/or surface – Reflects back toward sensor (backscatter) Widely used active remote sensing systems Active microwave (radar) long-wavelength microwaves (1-100cm) recording the amount of energy back-scattered from the terrain Lidar 3 short-wavelength laser light (e.g., 0.90 μm) recording the light back-scattered from the terrain or atmosphere Sonar sound waves through a water column recording the amount of energy back-scattered from the water column or the bottom 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 = = 4 Typically measured in s –1 , called Hertz (Hz) Most often Gigahertz (GHz) = 10 9 Hz ( ) ( ) 8 -1 = Useful 3.00 tric 10 m s 30 GHz cm k ν λ × = 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 Unusual names are an artifact of the original secret work on radar remote sensing in World War II 5 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 Sending and receiving a pulse of microwave radiation transmitted pulse backscattered pulse antenna Transmitter Duplexer • sends and receives Pulse Generator CRT Display or Digital Recorder Receiver b. a. antenna
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon