Monica was a range-only

tail warning radar A tail warning radar, sometimes TW for short, was a short-lived class of aircraft-mounted radar systems used to provide warning of another aircraft approaching from the rear. They were mostly used on World War II bombers, starting with the Moni ...

for

bombers A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped from an aircraf ...

, introduced by the

RAF The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...

in June 1942. Officially known as ARI 5664, it operated at

frequencies Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

of around 300

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

(on the boundary between

VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...

and

UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...

). The system was also used by the

US Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

, under the name AN/APS-13, and the nickname Archie.

History

Monica was developed at the

Bomber Support Development Unit A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped from an aircr ...

(BSDU) in

Worcestershire Worcestershire ( , ; written abbreviation: Worcs) is a county in the West Midlands of England. The area that is now Worcestershire was absorbed into the unified Kingdom of England in 927, at which time it was constituted as a county (see His ...

. After the ''

Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht'' before and during World War II. Germany's military air arms during World War I, the ''Luftstreitkräfte'' of the Imperial Army and the '' Marine-Fliegerabtei ...

'' became aware of Monica from a crashed bomber, German scientists developed a passive radar receiver, named Flensburg (FuG 227). From early 1944, FuG 227 was used by

nightfighter A night fighter (also known as all-weather fighter or all-weather interceptor for a period of time after the Second World War) is a fighter aircraft adapted for use at night or in other times of bad visibility. Night fighters began to be used i ...

crews to home in on Allied bombers using Monica. However, on the morning of 13 July 1944, a 7.''Staffel''/

NJG 2 ''Nachtjagdgeschwader'' 2 (NJG 2) was a German Luftwaffe night fighter and night intruder wing during World War II. Background Night fighter operations did form part of Wehrmacht war games during 1935 and 1936. Luftwaffe Service Regulation No. 1 ...

-flown

Junkers Ju 88 The Junkers Ju 88 is a German World War II ''Luftwaffe'' twin-engined multirole combat aircraft. Junkers Aircraft and Motor Works (JFM) designed the plane in the mid-1930s as a so-called ''Schnellbomber'' ("fast bomber") that would be too fast ...

G-1 nightfighter equipped with Flensburg mistakenly landed at

RAF Woodbridge Royal Air Force Woodbridge or RAF Woodbridge, is a former Royal Air Force station located east of Woodbridge in the county of Suffolk, England. Constructed in 1943 as a Royal Air Force (RAF) military airfield during the Second World War to ass ...

. After examining the Flensburg equipment, the RAF ordered Monica withdrawn from all

Bomber Command Bomber Command is an organisational military unit, generally subordinate to the air force of a country. The best known were in Britain and the United States. A Bomber Command is generally used for strategic bombing (although at times, e.g. during t ...

aircraft.Price, p. 154. An AN/APS-13 was used as a

radar altimeter A radar altimeter (RA), also called a radio altimeter (RALT), electronic altimeter, reflection altimeter, or low-range radio altimeter (LRRA), measures altitude above the terrain presently beneath an aircraft or spacecraft by timing how long it t ...

during the

Atomic bombings of Hiroshima and Nagasaki The United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August 1945, respectively. The two bombings killed between 129,000 and 226,000 people, most of whom were civilians, and remain the onl ...

by the

509th Composite Group The 509th Composite Group (509 CG) was a unit of the United States Army Air Forces created during World War II and tasked with the operational deployment of nuclear weapons. It conducted the atomic bombings of Hiroshima and Nagasaki, Japan, in ...

, USAAF.

References

External links

Oral History of Defence Electronics

History

See also

References

External links

Further reading