Oboe was a British bomb aiming system developed to allow their aircraft to bomb targets accurately in any type of weather, day or night. Oboe coupled radar tracking with radio transponder technology.[1] The guidance system used two well-separated radar stations to track the aircraft. Two circles were created before the mission, one around each station, such that they intersected at the bomb drop point. The operators used the radars, aided by transponders on the aircraft, to guide the bomber along one of the two circles and drop the bombs when they reached the intersection.
The system was developed in 1942 by the Telecommunications Research Establishment at Malvern in Worcestershire, working in close association with 109 Squadron.[2] By December 1942 a working system had been developed. The first major use of Oboe was in March 1943 when the system was used to mark the Krupp Works in an attack against Essen. Over the course of the month the system was used with great success to mark targets for the Main Force against the German industrial center of the Ruhr and for attacks against Cologne. Through November 1943 Oboe was used with good success against targets within its 250 mile range.
In December 1943 Bomber Command entered what was hoped to be a war winning campaign with the Battle of Berlin. Berlin was over the horizon for even the highest flying RAF aircraft, and thus beyond the range of Oboe. The campaign had to depend upon straight navigation and H2S. Bomber Command's efforts against Berlin over the next four months were unsuccessful. At the end of March Bomber Command was directed to serve under SHAEF to make preparations for the invasion of occupied Europe. These missions to northern France allowed Oboe to again demonstrate its value in the precision delivery of markers or bombs, regardless of weather or the visibility of the target.
Neither H2S nor Gee-H could provide the accuracy of Oboe. By guidance direction of individual aircraft, Oboe was used both to guide marker aircraft for the Main Force and for bombing aircraft making precision bombings of high value targets. It was by far the most accurate bombing system used during the war.[3][4]
In order to accurately determine your location relative to objects on the ground you need two data points; two angles (as in triangulation), two distances (trilateration), or an angle and a distance (VOR/DME). Using radio to provide some or all of these measurements was an area of continual development leading up to the start of the war. The Germans pioneered this approach with operational systems like Lorenz beam and X-Gerät that used two narrow beam-like signals that crossed at a point in the sky to indicate a target using triangulation. Later, during The Blitz, the Germans introduced Y-Gerät, which combined a single Lorenz beam with a transponder-based distance measurement to fix locations. The problem with all of these systems was that they produced no information except within their narrow beams, and were not useful for general purpose navigation.
A more useful system was introduced in the RAF's Gee system, which used two timed signals that allowed the navigator on the bomber to determine their location using trilateration. It could be used anywhere within line-of-sight of the transmitter stations in the UK, and generally provided a reasonable signal up to about 500 kilometres (310 mi), depending on the aircraft's altitude. Gee was read on an oscilloscope display about 3 inches (76 mm) across, which limited the accuracy of the timing measurements. As a result, Gee was accurate on the order of kilometers, which was extremely useful for navigation and area bombing, but did not provide the accuracy needed for pinpoint bombing.