The interdepartmental Atomic Trials Executive in London, chaired by Lieutenant General Sir Frederick Morgan, assumed responsibility for both Operation Mosaic and Operation Buffalo, sitting as the Mosaic Executive (Mosex) or Buffalo Executive (Buffalex) as appropriate. Sir William Penney was appointed scientific director for Operation Buffalo, with Roy Pilgrim, the head of Aldermaston's Trials Division, as his deputy. Group Captain Cecil (Ginger) Weir was appointed Task Force Commander. Planning was completed by June 1956. Except for the air drop, all tests were scheduled for 07:00 Central Standard Time. About 1,350 personnel would be present, including 200 scientists from Aldermaston and Harwell, 70 from other UK departments, 50 Canadians and 30 Australians. There would be 500 RAF and RAAF personnel, and 250 Australian Army servicemen to run the camp. Observers would include politicians, journalists, and six American officials, including Major General Leland S. Stranathan from the Armed Forces Special Weapons Project, Alvin C. Graves from the Los Alamos Scientific Laboratory, Frank H. Shelton from Sandia Laboratories and Brigadier General John G. Shinkle from the White Sands Missile Range.