عنوان مقاله [English]
Satellite sensors provide the opportunity for continuous multi-time measurements of a vast area over a period of several days to several decades. Sensor coverage and distance repetition are determined by the height of the shooting platform (satellite), angular acceleration, orbital inclination in proper relation to the equator, and determining the position in proper relation to spring equinox (Elachi, 1987).
Many optic sensors have been deployed in near-polar solar synchronous orbits so that global coverage and geometry of continuous light can be achieved. The distance repetition between sensors is different because it depends on the elevation and acceleration of sensors.
Other sensors have been placed in the Earth's synchronous orbit so that a high coverage frequency can be obtained from that area. (For example, GEOS meteorological satellites)
The ability to detect changes in the surface area photographed over time depends on the recording of spatial geometry and spatial resolution, spectral width and spectral band location, and the radiometric and temporal properties of the sensor imagery frequency. Comparison of received images by a sensor in different dates with any variations in deviation of measuring device and the difference in atmospheric characteristics, is particularly complicated in the secondary pixel cloud coverage.
Detection change is considerably more complicated when more than a sensor system is used due to differences between IFOV and PSF sensors, and in bandwidth and spectral response properties.