ASV Mark I, the First Airborne Maritime Surveillance Radar

ASV (Air to Surface Vessel) Mk. I was the first operational airborne maritime surveillance radar. It entered service with the Royal Air Force (RAF) in January 1940, in response to urgent operational requirements at the start of WWII. This system was quite experimental, it was unreliable, and its performance was relatively modest. By the start of 1941, it was already obsolete, replaced by ASV Mk. II. Nevertheless, it represented a pioneering engineering endeavor that laid the foundations for the systems that would be developed in the U.K. and USA and which would ultimately play a decisive role in the battle against the U-boats. This paper describes the equipment that was developed, its installations in Lockheed Hudson and Short Sunderland aircraft of RAF Coastal Command, its operation, and performance.