Within the context of Earth Observation, sensors are part of a platform: a vehicle, such as a satellite or aircraft.
Sensors used in Earth Observation can be operated at altitudes ranging from just a few centimetres above the ground—using field equipment—to those far beyond the atmosphere. Very often the sensor is mounted on a moving vehicle—which we call the platform—such as an aircraft or a satellite. Occasionally, static platforms are used. For example, we could mount a spectrometer on a pole to measure the changing reflectance of a specific crop during the day or over a whole season.
Various platforms such as aircraft, space shuttles, space stations and satellites are used to carry one or more sensors for Earth Observation.