India joined the fray in the 1990s. Some of the imagery from this series is commercially available, including 23.5 meter color and 5.8 meter black and white imagery. Surrey Satellite Technology Ltd from the United Kingdom commercializes small, lightweight, inexpensive microsatellites weighing between 10 and 100 kilograms that are capable of remote sensing. Optical remote sensing can be used to acquire spaceborne imagery. However, numerous studies have demonstrated that optical sensing does not work for most terrestrial biomass densities, because there is a saturation effect at very low levels of biomass.
Radar is an acronym for radio detection and ranging.
A synthetic aperture radar transmits pulses of microwave energy towards Earth and measures the strength and time delay of the energy that is scattered back to the antenna. Sensors on board of the SARs provide unique information about the Earth's surface through most weather conditions and even darkness. SAR data provide unique information about the health of the planet and its biodiversity. Applications We have seen of late significant growth in research focused on developing approaches for using synthetic aperture radar to study Planet Earth. Space-borne remote sensing is an extremely important field covering a wide range of applications.