Sic Transit

"It's working like a Swiss watch right now." That, last week, was the judgment of a top member of the team that developed the Navy's navigation satellite Transit IVA. Following three earlier Transits that suffered from minor but decisive bugs (e.g., a burst battery), Transit IVA, launched last fortnight, is doing its electronic job better than anyone had hoped. Though planned as an experimental model, it will become a regular part of the navigation-satellite system if it continues to work well.

Transit's intricate workings [TIME, July 7] depend on an electronic system that ground stations can "inject" with information enabling the satellite to tell where it is on its orbit. Ships with proper equipment (a precision receiver and a computer) can pinpoint the moment when the satellite comes closest to them, how far away it is, and in what direction. From this information, the computer can quickly deduce the ship's position.

Transit is being injected with information on schedule, has proved its efficiency by giving land stations their already known positions. So far, it has not told any ships where they are on the ocean, but only because no ship at sea has the proper receiving equipment. Probably the first to get such equipment will be the nuclear submarines. When they poke a whip antenna above the surface to listen to Transit they will be able to tell where they are within 600 ft. A navigator who shoots the sun or stars with a sextant in good weather does an excellent job if he gets a fix that is accurate within one and a half miles.

Since a single navigation satellite cannot cover the whole earth, the Navy plans to have four of them in operation by October 1962. Revolving on polar orbits, they will divide the earth into quadrants. By that time authorized ships will be equipped to use them as guides across the world's oceans.

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