In 1956, the UK aircraft company A.V.Roe (“Avro”), based at Woodford, south of Manchester, was awarded the contract for developing an airborne astronavigation equipment to be capable of installation in British V-bombers (Valiant, Victor, Vulcan) - notably the Avro Vulcan, last of the line. This was to enable the aircaft to carry and launch the US air-launched ICBM (intercontinental ballistic missile) named Skybolt, then under development, but to be purchased for British use. I was recruited by Avro for the small research facility they were setting up for this secret purpose in Chertsey, Surrey, starting there in mid-1957.
The Skybolt guidance system was to be by inertial navigation, ‘astro-crutched’ by signals from within the carrying aircraft up to the moment of the missile’s release. Those signals were to be derived from the astronavigation system we were to design. The aircraft/weapon system was to be able to operate in ‘daylight’ at launch heights of 18,000-35,000 ft altitude, so sky brightness and brightness gradient were going to be important factors, in that the 2 stars needed had to be searched for and located faster than the drift rate of the aircraft’s inertial platform enlarged their patches of uncertainty on the sky, during the interval between precise-data input, just before takeoff from the ground, and attaining operating altitude. Thereafter, positional accuracy was to be maintained for a potentially long period of stand-off, pending any instruction to fire the missile. Spatially, the third dimension was the flight altitude, independently known.
The two principal design responsibilities of the Chertsey establishment were (a) a telescope small enough to be alt-azimuth mounted on a small existing gyro-stabilized inertial platform, with star-search, detection and any other related facilities, (b) a navigation computer and related mathematics for instructing the telescope where to look and search for the pair of navigation stars selected as suitable at that moment from a prescribed list.