Radar surveillance is used to measure the electromagnetic waves reflected from a space object. This technology measures the shape of the space object based on the distance, altitude, direction and speed.
Various types of radar technology are used in space surveillance. Passive radar can be used to measure a number of meteoroids coming through the ionosphere without utilizing the independent transmission function. However, the more general space surveillance radar is used to monitor space objects located outside the atmosphere.
Radar used for space surveillance should be equipped with a powerful transmitter to send signals over long distances. There are two main types of radar, that each use different types of antennas.
- Parabola type: The antenna uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. A plate-shaped antenna may also change the direction of the radio waves by using a drive unit in order to narrowly focus the beam, and to keep track of a moving object or scan a large area.
- Phased Array Radar: A phased array antenna is composed of lots of radiating elements each with a phase shifter. Beams are formed by shifting the phase of the signal emitted from each radiating element, to provide constructive/destructive interference and steer the beams in the desired direction. This type of radar can monitor a very large area at a rapid rate without moving the unit.