in Huntingdon. When new aircraft, such as the de Havilland Mosquito became available, the PFF got the first examples, and then equipped them with ever more sophisticated electronic equipment, such as Oboe, the radio navigation and bombing aid. By January the pace of Bomber Command missions had dramatically increased, with major raids being carried out almost every night. On 11/12 February 1943 against Wilhelmshaven, the PFF used their H2S radar for the first time, dropping parachute flares above the heavy cloud cover in a technique known as "sky marking". The follow-up force observed an incredible event, a huge explosion seen through the complete cloud cover that lingered for 10 minutes. It was later learned this was the explosion of the naval ammunition depot at Mariensiel, which destroyed . Mission size continued to grow throughout, and although many missions continued to mark the wrong targets or fail for other reasons, the damage being caused continued to increase. On one particularly successful raid against Essen on 5/6 March 1943, 160 acres of land were destroyed with 53 separate buildings within the Krupp factories hit by bombs. Master bomber On the night of 20/21 June 1943 another change in technique was tested by 60 Lancasters (mostly from 5 Group) against Zeppelin works at Friedrichshafen which were believed to be making radar. In this raid one of the Lancasters was equipped with new high-frequency radio equipment that allowed them to communicate with the other bombers in the attack force. The follow-up force consisted of several groups, including PFF aircraft, who marked the target based on radio instructions from what would become known as "the Master Bomber". Another group of aircraft were to attempt a new technique, bombing at a specific time after passing a ground feature, in this case the shores of Lake Constance. Nearly 10% of the bombs hit the factory in what was considered a great success. A combination of these techniques was first used on a large raid to great success on the night of 17/18 August 1943 in Operation Hydra against German rocket research at Peenemünde. 596 aircraft were led by a Master Bomber to a series of target indicators dropped at several different locations around the target area. By dropping different colours of indicators and calling aircraft to attack each one in turn, the entire area was heavily bombed. The aircraft from No.5 Group used their time-from-landmark technique again.