Radar image. Polarization in Remote Sensing

L band radars operate on a wavelength of 15-30 cm and a frequency of 1-2 GHz. L band radars are mostly used for clear air turbulence studies. S band radars operate on a wavelength of 8-15 cm and a frequency of 2-4 GHz. Because of the wavelength and frequency, S band radars are not easily attenuated.

.

Polarization refers to the direction of travel of an electromagnetic wave vector's tip:

vertical (up and down),

horizontal (left to right), or 

circular (rotating in a constant plane left or right).

.

a synthetic aperture radar (SAR) for high-resolution imaging.

a radar altimeter, to measure the ocean topography.

echo amplitude

a wind scatterometer to measure wind speed and direction.

Other types of radars have been flown for Earth observation missions: precipitation radars such as the 

Tropical Rainfall Measuring Mission,

or

cloud radars like the one used on Cloudsat.

.

RISAT-1 (SAR, ISRO India, 2012)

RORSAT (SAR, Soviet Union, 1967-1988)

Seasat (SAR, altimeter, scatterometer, US, 1978)

.

ERS-1 & ERS-2 (European Remote-Sensing Satellite) (altimeter, combined SAR/scatterometer)

.

TOPEX/Poseidon (altimeter)

.

Tropical Rainfall Measuring Mission (Precipitation Radar)

Cloudsat (cloud radar)

Metop (scatterometer)

QuickScat (scatterometer)

Polarization in radar imaging refers to the orientation of the electric field of the radar waves that are used to illuminate the target. There are two main types of polarization: linear and circular. Linear polarization has the electric field oscillating in one plane, while circular polarization has the electric field oscillating in a circular pattern. The type of polarization used can affect the radar image, as different types of targets will reflect the radar waves differently based on the polarization. For example, linear polarization is better for detecting targets with smooth surfaces, while circular polarization is better for detecting targets with rougher surfaces. Additionally, using different types of polarization can help to reduce the effects of interference from other sources.

HH, HV, and VV are types of polarization that are used in radar imaging.

HH stands for horizontally polarized transmitted signal and horizontally polarized received signal. This type of polarization is useful for detecting targets with smooth surfaces, as the horizontally polarized radar waves will be reflected more efficiently by these types of targets.

HV stands for horizontally polarized transmitted signal and vertically polarized received signal. This type of polarization is useful for detecting targets with rougher surfaces, as the horizontally polarized radar waves will be scattered in many directions by these types of targets, resulting in a stronger return signal.

VV stands for vertically polarized transmitted signal and vertically polarized received signal. This type of polarization is useful for detecting targets with rougher surfaces, as the vertically polarized radar waves will be scattered in many directions by these types of targets, resulting in a stronger return signal.

Using these different types of polarization can help to enhance the contrast and details in radar images, and also it can be used to extract information about the targets, such as their shape, size, and surface roughness.