Radars are basically systems that use radio waves to detect objects. They emit radio waves in order to determine whether an object is in the sky.
Helmet mounted display and sight (HMD/S) systems are an increasingly common addition to the cockpits of modern fighter aircraft.
It has been a rocky road for the U.S Air Force (USAF) and U.S Army’s current Boeing 707-based E-8 Joint Surveillance Target Attack Radar System (JSTARS) ‘replacement’ program, and it will likely remain so for the foreseeable future.