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SECOR 5 (SEquential COllation of Range) was a US Army geodetic satellite launched by a Scout B launch vehicle from Wallops Island on 10 August 1965 at 18:00:00 UT into an initial 1135 x 2427 km altitude orbit with an inclination of 69.24 degrees and a period of 122.2 minutes. The apogee was about 550 km higher than planned. It was a Type I SECOR satellite used to precisely determine points on the Earth. Signals ceased on 3 March 1966 for unknown reasons.

The Type I SECOR satellites were basically modified versions of Vanguard II, spherical in shape and about 20 inches (50.8 cm) in diameter with a mass of approximately 37 pounds (16.8 kg). The surface was polished aluminum with a thin layer of silicon monoxide to help regulate temperatures. Power was supplied by six solar array disks, each about 8 inches (20.3 cm) in diameter containing 160 P/N-type solar cells. They were mounted equidistantly on the spherical surface, three in the upper hemisphere and three in the lower.

SECOR 5 used a Cubic TR-27 transponder. Eight antenna protruded from the equator, four 449 MHZ and four 224.5 MHz, alternatively spaced around the diameter. A 136-MHz antenna protruded from the top of the satellite. The antennas were half-inch (1.3 cm) diameter rods that were spring loaded and collapsed aroiund the satellite until deployment. A cylindrical opening from the bottom to top of the satellite held the voltage regulator and battery pack, comprising 22 hermetically sealed nickle-cadmium cells. Magnetic despin rods were located throughout the outer part of the probe. A 0.5 x 3 inch (1.3 x 7.7 cm) bar magnet and two damping rods, 0.065 inch (0.165 cm) in diameter, were used for stabilization.

Experiments with these led to Timation, and finally to the GPS Navstar system.

Image credit: U.S. Army Corps of Engineers Digital Library

Alternate Names

  • EGRS 5
  • 01506
  • SECOR5

Facts in Brief

Launch Date: 1965-08-10
Launch Vehicle: Scout
Launch Site: Wallops Island, United States
Mass: 24 kg

Funding Agency

  • Department of Defense-Department of the Army (United States)


  • Navigation/Global Positioning

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



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