Among the services that satellites can provide for disaster risk management and emergency response are weather forecasting, remote sensing, geo-positioning, navigation, television and telecommunication. Instruments onboard satellites circling the Earth are designed to cover specific wavelength ranges of the electromagnetic spectrum in order to capture images, atmospheric sounding, satellite communication, geo-positioning and navigation.
Satellites are circling Earth in different orbits depending on the type of application or instrument onboard:
A satellite in a geostationary orbit circles the Earth above the equator (0° latitude) synchronously to the Earth's rotation. Its apparently fixed position above a point on the equator at an altitude of more than 36,000 km makes it suitable for communications and regional climate observation of that specific area, with high temporal but low spatial resolution.
Earth observation satellites and satellites for meteorological purposes are located in low Earth orbit at an altitude of typically about 500-800 km and near polar inclination. Due to their orbit, these satellites provide global coverage with comparatively lower temporal, but medium to very high spatial resolution. Due to the high costs of space transportation, constellations of communication or navigation satellites are also placed in Low Earth Orbit.
Earth Observation satellites use either optical or radar sensors to capture images of Earth:
Optical sensors for Earth observation are designed to deliver images in either panchromatic spectral format or multispectral format. Panchromatic refers to images in black and white that are reflected from Earth's surface exposed to all visible light. Multispectral images usually include four bands of the electromagnetic spectrum: blue, green, red and near-infrared.
Radar sensors for Earth observation are designed to operate in the microwave range.