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SECOR 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13 (EGRS 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13)


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 four ground stations. Three 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 three 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 three 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. The satellite had a mass of 18 kg and contained a transponder, a telemetry system to monitor temperature and operating voltages, and a power unit comprised of solar panels and batteries.

There were two types of SECOR satellites: the spherical Type I SECOR and the cubic Type II SECOR version.

The size of the Type II SECOR satellite was much more compact measuring 25.2 × 29.8 × 34.9 cm and weighing approximately 17.6 kg. The satellite was almost covered with solar cells on all surfaces. The number of antennas was the same as for the Type I, but, rather than being "collapsible," they were made of flexible steel tape.

The prime reason for inception of the Type II was to provide a satellite which was extremely adaptable as a secondary payload. Launch vehicles that were funded by primary payloads frequently had additional space available for secondary payloads of low weight and suitable compactness. Since the Type II met these requirements, the Army avoided the high costs of launch vehicles.

The satellite also provided flexibility in accepting transponders of several different designs. Because the Type II's construction was compact and ruggedized, it was easier to handle.

Better provisions were made for external evaluation of the satellite's performance during acceptance and pre-launch test phases. Covers and panels did not have to be removed; therefore, monitoring the internal parameters of the system was more realistic.

The Type II satellite was constructed primarily of aluminum and was assembled around four structural subassemblies: baseplate assembly, center support assembly, solar panel support assembly, and wraparound assembly. The baseplate assembly provided mounting surfaces for the transponder and the center support and solar panel support assemblies. The center support assembly provided compartments for the storage of batteries as well as mounting surfaces for the telemetry and power system components. This assembly also supported the telemetry antenna. The solar panel support assembly provided surfaces to support the strings of solar cells. The wrap around assembly supported the solar panel assembly and the transponder ranging antennas.

Nation: USA
Type / Application: Geodesy
Operator: US Army
Contractors: Cubic Corporation
Equipment: TR-27 SECOR transponder (#1, 2, 3); C-101 SECOR transponder (#4); TR-30A SECOR transponder (#6, 7, 8, 9); MAT SECOR transponder (#10, 12); TR-30A SECOR transponder (#11, 13);
Configuration: cube
Propulsion: ?
Power: Solar cells, batteries
Mass: 18 kg
Satellite COSPAR Date LS Launch Vehicle Remarks
SECOR 1 (EGRS 1) 1964-001C 11.01.1964 Va 75-3-5 Thor-SLV2A Agena-D with Poppy 3A (Solrad 7A), Poppy 3B, Poppy 3C (GGSE 1), Hayloft
SECOR 2 (EGRS 2) 1965-017B 11.03.1965 Va 75-1-1 P Thor-DSV2A Able-Star with Transit-O 3
SECOR 3 (EGRS 3) 1965-016E 09.03.1965 Va 75-1-2 Thor-DM21 Agena-D with Poppy 4A (Solrad 7B), Poppy 4B, Poppy 4C (GGSE 2), Poppy 4D (GGSE 3), Dodecapole 1, Surcal 4, OSCAR 3
SECOR 4 (EGRS 4) 1965-027B 03.04.1965 Va PALC-2-4 Atlas-SLV3 Agena-D with Snapshot
SECOR 6 (EGRS 6) 1966-051B 09.06.1966 Va PALC-1-2 Atlas-SLV3 Agena-D with RTS-1 1, ORS 2
SECOR 7 (EGRS 7) 1966-077B 19.08.1966 Va SLC-3E Atlas-SLV3 Agena-D with RTS-1 2, ORS 1
SECOR 8 (EGRS 8) 1966-089B 05.10.1966 Va SLC-3E Atlas-SLV3 Agena-D with RTS-1 3
SECOR 9 (EGRS 9, P67-1) 1967-065A 29.06.1967 Va LE-6 Thor-LV2D Burner-2 Star-13A with Aurora
SECOR 10 (EGRS 10, S68-2) 1968-F04 18.05.1968 Va SLC-2E F Thorad-SLV2G Agena-D with Nimbus B
SECOR 11 (EGRS 11, P68-1) 1968-F08 16.08.1968 Va SLC-3E F Atlas-SLV3 Burner-2 (unk + Star-13A) with Orbiscal 1, OV5 8, Gridsphere 1, Gridsphere 2, Mylar Balloon, Rigidsphere, LCS 3, LIDOS, RM 18 & UVR, Radcat, SECOR 12
SECOR 12 (EGRS 12, P68-1) 1968-F08 16.08.1968 Va SLC-3E F Atlas-SLV3 Burner-2 (unk + Star-13A) with Orbiscal 1, OV5 8, Gridsphere 1, Gridsphere 2, Mylar Balloon, Rigidsphere, LCS 3, LIDOS, RM 18 & UVR, Radcat, SECOR 11
SECOR 13 (EGRS 13, S69-2) 1969-037B 14.04.1969 Va SLC-2E Thorad-SLV2G Agena-D with Nimbus 3


  • Robert H. Nichols: Geodetic SECOR Satellite, Army Engineer Topographic Laboratories, Fort Belvoir, Virginia, June 1974
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