Microwave Remote Sensing
Table of Contents
What is Microwave Remote Sensing
Microwave Remote Sensing(RS) uses Electromagnetic radiation with a wavelength between 1 mm to 1 meter and frequency interval from 40,000 to 300 Hz. This covers the longest wavelengths used for remote sensing. Due to the greater wavelength compared to visible and infrared radiation, microwaves exhibit the important property of penetrating clouds, fog, and possible ash or powder coverages.
Inpotance of Microwave Remote Sensing
Microwave RS provides unique information on some aspect that can not be observed by visible and infrared sensors for instance, sea, wind, and wave direction, which are derived from frequency charcteristics, backscattering, polarization, doppler effect, etc.
Types of Microwave Remote Sensing
Microwave RS can be divided into two types:
- Active Microwave Sensor
- Passive Microwaves Sensor
Active Microwave Sensing
Active microwave sensor provide their own source of microwave radiation to illuminate the target. It is an observed scene and, therefore, can be used both at night and day, independently of the presence of the sun.
The sensor transmits a (radio) signal in the microwave bandwidth and records the part that is backscattered by the target towards the sensor itself. The power of the backscattered signal allows to discriminate between different targets within the scene, while the time between the sent and the received signal is used to measure the distance of the target. A system that operates is called Radar, and may allow to obtain a microwave image of the observed scene.
Passive Microwave Sensing
Passive microwave sensor are similar in concept to Thermal remote sensing. The Passive systems collect the radiation that is naturally emitted by the observed surface. The emitted energy is related to the temperature and moisture properties of the emitted object or surface within it is field of view.
Most passive microwave sensors are characterized by low spatial resolution.
Platform of Microwave
Microwave RS can be conducted from both platforms;
Active microwave is performed either from satellites or aeroplanes, but passive microwave generally perform only for satellite, because passive microwave used for earth’s atmosphere data collection.
Bands of Microwave
|P||30cm – 100cm|
|L||15cm – 30cm|
|S||7.5cm – 15cm|
|X||2.4cm – 3.75cm|
|K||0.75cm – 1.1cm|