results were "immediately staggering", with the displays showing high-quality images of individual buildings, roads, railways and even small streams. Similar experiments with the smaller 3-foot scanner were not so successful in this role. At a meeting on 16 December, it was decided to move ahead with Lancasters with 6-foot scanners and Mosquitos with 3-foot scanners. This meant the K-band equipment originally planned to be installed on the Pathfinder Force would be used on these aircraft instead. Pathfinder Force received the Mark IIIF X-band equipment instead. Ultimately, only the Mosquitoes were ready before the war ended, and carried out a total of three target marking operations for the Pathfinder Force. When the war ended and the Lend-Lease program ended with it, the availability of the K-band magnetrons disappeared. Additionally, in high-altitude tests, it was noticed that the signal disappeared in clouds, an observation that would later give rise to weather radar systems, but in the meantime made the system less than useful. The Director of Radar in the Air Ministry decided to embargo all work on the K-band systems for security reasons. H2D Looking to further improve the navigational aspects of the system, some work was carried out on a system known as H2D, the D for "Doppler". The idea was that the Doppler shift of the signals due to the motion over the ground could be used to determine the ground speed. In still air, the maximum Doppler shift would be seen dead ahead, but in the presence of any winds aloft, the sideways component would cause the maximum point to shift to an angle, while the head or tail component would make the measured Doppler speed differ from the airspeed indicator. By comparing these measurements to the aircraft's airspeed and heading, the wind speed and direction could be accurately calculated. Testing began at RAF Defford on Wellington NB822 in early 1944. It became apparent that the sensitivity of the unit was enough that ground traffic like trucks and trains became visible on the display. This is the first example of what is today known as moving target indication, which would theoretically allow an aircraft to scan for targets across a wide area. A second aircraft, NB823, joined the effort in June 1944, and then a third (unknown ID). More rigorous testing demonstrated that the experimental set was only really useful when the aircraft was flying under and had a