Encyclopedia Astronautica
GEOS



geosa.jpg
GEOS-A
Credit: NASA
American solar satellite. 3 launches, 1965.11.06 (Explorer 29) to 1975.04.09 (Geos 3). The GEOS spacecraft were gravity-gradient-stabilized, solar-cell powered satellites designed exclusively for geodetic studies.

They were flown as part of the National Geodetic Satellite Program.

Instrumentation varied by mission, with the objectives of locating observation points (geodetic control stations) in a three dimensional earth center-of-mass coordinate system within 10 m of accuracy, to determine the structure of the Earth's gravity field to 5 parts in 10 million, of defining the structure of the earth's irregular gravitational field and refining the locations and magnitudes of the large gravity anomalies, and of comparing results of the various systems onboard the spacecraft to determine the most accurate and reliable system. Acquisition and recording of data were the responsibility of the GSFC Space Tracking and Data Acquisitions Network (STADAN). Ten major observing networks were used.

GEOS-A was a 175 kg, 1.32 m diameter, top-shaped satellite. It had an array of 5 geodetic systems: flashing light beacons, radio Doppler transmitters, a radio range system, a combined range and range rate system, and a laser reflector. Primary power for the instrumentation was obtained from solar cells that covered most of the exterior of the satellite.

The program was directed by NASA's Goddard Space Flight Center. Prime Contractor was The Johns Hopkins University Applied Physics Laboratory.

Gross mass: 341 kg (751 lb).
First Launch: 1965.11.06.
Last Launch: 1975.04.09.
Number: 3 .

More... - Chronology...


Associated Countries
See also
  • Delta The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Development began in 1955 and it continued in service in the 21st Century despite numerous candidate replacements. More...

Associated Launch Vehicles
  • Delta American orbital launch vehicle. The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Delta began as Thor, a crash December 1955 program to produce an intermediate range ballistic missile using existing components, which flew thirteen months after go-ahead. Fifteen months after that, a space launch version flew, using an existing upper stage. The addition of solid rocket boosters allowed the Thor core and Able/Delta upper stages to be stretched. Costs were kept down by using first and second-stage rocket engines surplus to the Apollo program in the 1970's. Continuous introduction of new 'existing' technology over the years resulted in an incredible evolution - the payload into a geosynchronous transfer orbit increasing from 68 kg in 1962 to 3810 kg by 2002. Delta survived innumerable attempts to kill the program and replace it with 'more rationale' alternatives. By 2008 nearly 1,000 boosters had flown over a fifty-year career, and cancellation was again announced. More...
  • Delta E American orbital launch vehicle. Thor augmented with 3 x Castor 2 motors with Delta E and Altair 2 upper stage. More...
  • Delta E1 American orbital launch vehicle. Four stage vehicle consisting of 3 x Castor + 1 x Thor DSV-2C + 1 x Delta E + 1 x FW4D More...
  • Delta 1410 American orbital launch vehicle. Three stage vehicle consisting of 4 x Castor 2 + 1 x ELT Thor/MB-3 + 1 x Delta P /TR-201 More...
  • Delta 1000 American orbital launch vehicle. The Delta 1000 series used Castor 2 strap-ons and the Extended Long Tank core with MB-3 engine. More...

Associated Manufacturers and Agencies
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • APL American manufacturer of rockets and spacecraft. Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, Laurel, Maryland, USA. More...

Associated Programs
  • Explorer Series of satellites launched by Jet Propulsion Laboratory for the exploration of the space environment (micrometeoroids, charged particles, radiation, etc) from both earth orbital and heliocentric orbital locations. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: here.
  • Aerospace Yearbook, 1966,
  • NASA Report, Geos A Readiness Test Evaluation Report, Web Address when accessed: here.
  • NASA Report, Reliability Assessment of The Geos A Spacecraft, Web Address when accessed: here.
  • NASA Report, Intercomparison of GEOS-A observation systems, Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Vandenberg Vandenberg Air Force Base is located on the Central Coast of California about 240 km northwest of Los Angeles. It is used for launches of unmanned government and commercial satellites into polar orbit and intercontinental ballistic missile test launches toward the Kwajalein Atoll. More...
  • Vandenberg SLC2E Delta launch complex. Originally a Thor 75 SMS launch pad. Upgraded to a space launch complex in 1966. More...
  • Vandenberg SLC2W Delta launch complex. Originally a Thor 75 SMS launch pad. Upgraded to a space launch complex in 1966. More...
  • Cape Canaveral LC17A Delta launch complex. Part of a dual launch pad complex built for the Thor ballistic missile program in 1956. Pad 17A supported Thor, Delta, and Delta II launches into the 21st Century. More...

GEOS Chronology


1965 November 6 - . 18:38 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Delta E. LV Configuration: Thor Delta E 457/D34.
  • Explorer 29 - . Payload: GEOS A. Mass: 175 kg (385 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: GEOS. USAF Sat Cat: 1726 . COSPAR: 1965-089A. Apogee: 2,269 km (1,409 mi). Perigee: 1,120 km (690 mi). Inclination: 59.4000 deg. Period: 120.30 min. The primary objective of GEOS-A was to provide global geodetic measurements for determining the positions of fiducial control points on the Earth to an accuracy of 10 meters in an Earth centre of mass co-ordinate system, and to determine the structure of the Earth's gravity field to 5 parts in 10 million. Instrumentation included (1) four optical beacons, (2) laser reflectors, (3) a radio range transponder, (4) Doppler beacons, and (5) a range and range rate transponder. These were designed to operate simultaneously to fulfil the objectives of locating observation points (geodetic control stations) in a three dimensional earth centre-of-mass co-ordinate system within 10 m of accuracy, of defining the structure of the earth's irregular gravitational field and refining the locations and magnitudes of the large gravity anomalies, and of comparing results of the various systems onboard the spacecraft to determine the most accurate and reliable system. In January 1967, a failure in the satellite's command system rendered several geodetic systems inoperable. Radio doppler measurements and the passive laser reflector experiment could continue indefinitely, however. Additional Details: here....

1968 January 11 - . 16:16 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2E. LV Family: Delta. Launch Vehicle: Delta E1. LV Configuration: Thor Delta E1 454/D56.
  • Explorer 36 - . Payload: GEOS B. Mass: 209 kg (460 lb). Nation: USA. Agency: NASA Greenbelt. Program: Explorer. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: GEOS. USAF Sat Cat: 3093 . COSPAR: 1968-002A. Apogee: 1,574 km (978 mi). Perigee: 1,081 km (671 mi). Inclination: 105.8000 deg. Period: 112.20 min. The geodetic instrumentation systems included (1) four optical beacons, (2) two C-band radar transponders, (3) a passive radar reflector, (4) a sequential collation of range radio range transponder, (5) a Goddard range and range rate transponder, (6) laser reflectors, and (7) Doppler beacons. Non-geodetic systems included a laser detector and a Minitrack interferometer beacon. The objectives of the spacecraft were to optimise optical station visibility periods and to provide complementary data for inclination-dependent terms established by the Explorer 29 (GEOS 1) gravimetric studies. The spacecraft was placed into a retrograde orbit to accomplish these objectives. Operational problems occurred in the main power system, optical beacon flash system, and the spacecraft clock, and adjustments in scheduling resulted in nominal operations.

1975 April 9 - . 23:58 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC2W. LV Family: Delta. Launch Vehicle: Delta 1410. LV Configuration: Delta 1410 584/D109.
  • Geos 3 - . Payload: GEOS C. Mass: 341 kg (751 lb). Nation: USA. Agency: NASA Wallops. Class: Astronomy. Type: Solar astronomy satellite. Spacecraft: Geos. USAF Sat Cat: 7734 . COSPAR: 1975-027A. Apogee: 848 km (526 mi). Perigee: 817 km (507 mi). Inclination: 115.0000 deg. Period: 101.60 min. Geodynamics Experimental Ocean Satellite. The mission of GEOS 3 (Geodynamics Experimental Ocean Satellite) was to provide the stepping stone between the National Geodetic Satellite Program (NGSP) and the Earth and Ocean Physics Application Program. It provided data to refine the geodetic and geophysical results of the NGSP and served as a test for new systems. A major achievment was the flight of a radar altimeter. Further mission objectives: intercomparison of tracking systems, investigation of solid-earth dynamic phenomena through precision laser tracking, refinement of orbit determination techniques, determination of interdatum ties and gravity models, and support of the calibration and position determination of NASA Spaceflight Tracking and Data Network (STDN) S-band tracking stations.

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