17-04-2009, 06:39 PM
Microwave Remote Sensing
(MRS)
What is microwave remote sensing?
A special application of microwave communications technologies for the purpose of collecting geophysical information about targets (objects and media) without making physical contact.
Microwave reflections or emissions from earth materials bear no direct relationship to their counterparts in the visible portions of the spectrum.
How does Microwave Remote Sensing work?
There is an interaction between the EM waves and matter.
The target imposes a modulation on the EM wave which becomes its identifying characteristics.
Sensors use microwave communications technologies.
Active (radar) and passive (microwave radiometry) measurements.
Active and Passive Microwave Sensors
Passive: uses natural energy, either reflected sunlight or emitted thermal or microwave radiation
Active: sensor creates its own energy
Transmitted toward Earth
Interacts with atmosphere and/or surface
Reflects back toward sensor (backscatter)
Microwave Radiometry
In the microwave region of the EM spectrum, the
power collected by a microwave antenna is:
P blackbody = k Tb * bandwidth
Microwave Brightness Temperature, Tb, of a
media is the product of the media emissivity and its physical temperature.
For blackbodies, e = 1.0
Tb = e * T phys
Radiative Transfer Theory
The TB measured by spaceborne radiometer is the linear sum of individual contributions from the atmosphere and surface
Defense Meteorological Support Program (DMSP)
What is a Microwave Scatterometer?
A special purpose radar sensor that measures scattering from the earth's surface i.e., a scatter-meter
If the objects are having smaller wavelengths,then scattering occurs
Scatterometer Applications
Ocean Wind Vector (wind speed & direction)
Hurricanes & Typhoons
Sea Ice Imaging
Land Imaging
Synthetic Aperture Radar
Generally refers to the case of a moving radar and a stationary target- usually an extended scene, such as the surface of the Earth.
ISAR refers to the case in which the radar is relatively stationary and a rotating target provides all(or most) of the motion to create the synthetic aperture.
REFERENCES
[1] Lillesand Thomas M. and Ralph W. Kiefer,"Remote Sensing and Image Interpretation", fourth edition, chapter 8,pp. 616-692
[2] Sullivan Roger J., "Radar Foundations for Imaging and Advanced Concepts", Chapter 7, pp.191-194
[3] http://engr.ucf.edu/centers/cfrsl/
[4] http://trmm.gsfc.nasa.gov/
