Description of the radar set, tactical-technical characteristics
Figure 1: AN/APQ-181
(© 2012 Raytheon)
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AN/APQ-181 is operating in the Ku-Band multimode radar system with GPS aided targeting system. The radar features 21 separate modes for terrain-following and terrain-avoidance, navigation system updates, target search, location, identification and acquisition and weapon delivery. It is a completely redundant modular system which employs two separate radar sets and two liquid cooled active phased array antennas. The APQ-181 is designed for the Northrop Grumman B-2 Spirit stealth bomber.
The radar uses sophisticated software modes and advanced >Low Probability of Intercept (LPI) techniques that match the aircraft’s overall stealth qualities. The conformal antennas are below the leading wing edges and are covered by furtive dielectric panels preventing the antennas from reflecting enemy radar waves while allowing a normal operation. The radar transmitter is of amplifier-type using a liquid-cooled, high-power gridded traveling wave tube.
The radar was developed by Hughes Aircraft (now Raytheon) in the early 1980s. The prototype radar first flew in 1987. During the early 1990s the first radar sets have been delivered. In November 2002, Raytheon was awarded a contract to develop a new active antenna for the B-2 radar to avoid interference with commercial satellite systems after 2007. Flight tests with new radar began in October 2007 and continued until 2008. Installation of the new antenna on the B-2 fleet was completed in 2014.