H2X radar ("Mickey set", AN/APS-15) was an American development
of the British H2S radar, the first ground mapping radar to be
used in combat. It was used by the USAAF during World War II as
a navigation system for daylight overcast and nighttime
operations. It used a shorter 3 cm wavelength (10 GHz frequency)
than the H2S, giving a sharper picture (H2S subsequently adopted
3 cm in the Mark III version entering operational service on
November 18, 1943, for “Battle of Berlin”) and not known to have
ever been spotted by the German Naxos radar detector, due to
that receiving device's specific purpose being to spot the
original British H2S equipment's lower frequency, 3 GHz
emissions. The first H2X-equipped B-17s arrived in England in
early February 1944, and were first used in combat later that
month. Those missions where bombing was done by H2X were called
"Pathfinder missions" and the crews were called "Pathfinder
crews". The hemispherical radome for the H2X's rotating dish
antenna replaced the ball turret of