SECOR (Sequential Collation of Range)
Small United States Army geodetic satellites launched in the 1960s to determine
the precise location of points on the Earth's surface (notably islands in
the Pacific). Each SECOR satellite was linked to four ground stations –
three at geographical points where the coordinates had been accurately surveyed
and a fourth at the location whose coordinates were to be to be pinpointed.
Radio waves were sent from the ground stations to the satellite and returned
by a transponder. The position of the
satellite at any time was fixed by the measured ranges from the three known
stations. Using these precisely established positions as a base, ranges
from the satellite to the unknown station were used to compute the position
of the unknown station. SECOR allowed continents and islands to be brought
within the same geodetic global grid. It was a predecessor to navigational
satellite systems such as Timation and,
more recently, the Navstar-GPS (Global Positioning
System).
Related category
• SATELLITES
AND SPACE PROBES
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