XSTAR is the most developed of the STAR Dynamics Advanced Program radars. It is a mobile X-band CW instrumentation radar designed to provide precision tracking of multiple airborne or ground-mobile targets. The system incorporates a sophisticated, complex proprietary digital processing subsystem to beamform digitally so that the multiple targets can be tracked simultaneously. The system supports skin and transponder tracking; the latter using frequency shifting transponders designed by STAR Dynamics. The full XSTAR system is designed to track a one square meter (0 dBsm) target to ranges of more than 300 km, and a reduced range version – XSTAR-Pilot – with somewhat less capability and reduced cost.