Radar Cross-section

Radar Cross-section

Radar cross section (RCS) is a measure of how detectable an object is with a radar. A larger RCS indicates that an object is more easily detected.

An object reflects a limited amount of radar energy. A number of different factors determine how much electromagnetic energy returns to the source such as:

• material of which the target is made;
• absolute size of the target;
• relative size of the target (in relation to the wavelength of the illuminating radar);
• the incident angle (angle at which the radar beam hits a particular portion of target which depends upon shape of target and its orientation to the radar source);
• reflected angle (angle at which the reflected beam leaves the part of the target hit, it depends upon incident angle);
• the polarization of transmitted and the received radiation in respect to the orientation of the target

While important in detecting targets, strength of emitter and distance are not factors that affect the calculation of a RCS because the RCS is a property of the target reflectivity.

Radar cross section is used to detect planes in a wide variation of ranges. For example, a stealth aircraft (which is designed to have low detectability) will have design features that give it a low RCS (such as absorbent paint, smooth surfaces, surfaces specifically angled to reflect signal somewhere other than towards the source), as opposed to a passenger airliner that will have a high RCS (bare metal, rounded surfaces effectively guaranteed to reflect some signal back to the source, lots of bumps like the engines, antennae, etc.). RCS is integral to the development of radar stealth technology, particularly in applications involving aircraft and ballistic missiles. RCS data for current military aircraft is most highly classified.