SECOR (1) (EGRS (1))

SECOR (1) [USAF]]

SECOR (Sequential Collation of Range), EGRS (Electronic & Geodetic Ranging Satellite) were small geodetic spacecraft used to precisely determine points on the earth. Geodetic SECOR (Sequential Collation of Range) was an all-weather geodetic survey system which was in operational use for several years, establishing a global survey network. It used the successive positions of artificial satellites in space to determine locations on the earth's surface with exactness over long distances. The system consisted of a satellite and 4 ground stations. 3 at geographical points where the co-ordinates had been surveyed accurately and the fourth at an unknown location. Radio waves were flashed from the ground stations to the satellite and returned. The position of the satellite at any time was fixed by the measured ranges from the 3 known stations. Using these precisely established satellite positions as a base, ranges from the satellite to the unknown station were used to compute the position of the unknown station. Geodetic SECOR allows continents and islands to be brought within the same geodetic global grid. Each ground station was entirely portable and contained 3 units: a radio frequency shelter, a data handling shelter and a storage shelter. Lighter weight, solid-state equipment was developed to replace the initial units.

Later SECOR satellites used a cubic structure instead of the Solrad type sphere.