PAGEOS

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Passive Geodetic Earth Orbiting Satellite (PAGEOS)
PAGEOS Satellite - GPN-2000-001896.jpg
Test inflation of PAGEOS, 5 August 1965
NamesPAGEOS-A
Operator NASA Office of Space Applications
COSPAR ID 1966-056A OOjs UI icon edit-ltr-progressive.svg
SATCAT no. 02253
Spacecraft properties
Launch mass56.7 kg (125 lb)
Dimensions30.48 m (100.0 ft) diameter [1]
Start of mission
Launch date00:14:00,June 24, 1966(UTC) (1966-06-24T00:14:00Z)
RocketThrust augmented Thor-Agena D
Launch site Vandenberg AFB
End of mission
Destroyedpartially disintegrated July 1975 (1975-07)
Orbital parameters
Reference system Geocentric [2]
Eccentricity 0.00301
Perigee altitude 4,207 km (2,614 mi)
Apogee altitude 4,271 km (2,654 mi)
Inclination 87.14°
Period 181.43 min
Epoch 24 June 1966
 

PAGEOS (PAssive Geodetic Earth Orbiting Satellite) was a balloon satellite which was launched by NASA in June 1966. [1] It was the first satellite specifically for use in geodetic surveying, [3] or measuring the shape of the earth, by serving as a reflective and photographic tracking target. At the time, it improved on terrestrial triangulations of the globe by about an order of magnitude. [4] The satellite, which carried no instrumentation, broke up between 1975 and 1976. [5] One of the largest fragments of the satellite finally deorbited in 2016. [6]

Contents

PAGEOS was part of a larger program of inflatable satellites that grew from the original concept by William J. O'Sullivan of a 30-inch diameter inflatable satellite in 1956 to measure air drag at high altitudes, called the Sub-Satellite. [7] While the Sub-Satellite failed, the idea of a visible US satellite became very attractive after Sputnik launched in the Cold War, resulting in a program of similar, larger satellites. [7] These included satellites Echo 1 and Echo 2 under Project Echo, which were also used for experiments in geodetic surveying; [3] the Explorer satellites; and eventually PAGEOS. [7]

Design

PAGEOS had a diameter of exactly 100 feet (30.48 m), consisted of a 0.5 mils (12.7  μm ) thick mylar plastic film coated with vapour deposited aluminum enclosing a volume of about 524,000 cubic feet (14,800 m3) [8] [9] The metal coating both reflected sunlight and protected the satellite from damaging ultraviolet waves. The satellite was launched in a canister, which explosively separated as it was ejected from the rocket. Then, the balloon was inflated by benzoic acid and anthraquinone placed inside, which turned to gas when the satellite was exposed to the heat of the sun, as well as some residual air left inside. [9] The satellite carried no instrumentation. [9] The study and construction of PAGEOS was done by the Schjeldahl company, which also made Echo 1. [10]

Usage

PAGEOS was placed into a polar orbit, about 200 nautical miles above the earth, so that the U.S. Coastal and Geodetic Survey could practically apply triangulation techniques developed from experiments with Echo 1. Over five years, 12 mobile tracking stations tracked the satellite during good weather in a few minutes of twilight each evening, resulting in the fixing of the precise locations of 38 different points around the world. This could be used to help determine the precise locations of the continents relative to each other, and to help determine the precise shape and size of the earth. Some unclassified data was used by scientists studying continental drift, and more classified data was used by US military planners studying intercontinental ballistic missiles. [7] Observations took place by 16 groups at 45 globally distributed stations, between 1966 and 1970. [11] The observations were done with BC4 cameras, and could last more than a year at each station before satisfactory results were obtained. [11] The stations were around 3000-4000km apart from each other. [11] The network reached an accuracy about an order of magnitude better than terrestrial triangulations at the time. [4] This project was the first time that a scientific determination had been made with accuracy of a complete global polyhedron. [11]

Orbit

Thor-SLV2A Agena-D launching PAGEOS Thor-SLV2A Agena-D (Thor 473) with PAGEOS.jpg
Thor-SLV2A Agena-D launching PAGEOS

The PAGEOS spacecraft was launched by a Thor-SLV2A Agena-D (Thor 473) on 24 June 1966, [12] [ better source needed ] and placed into a polar orbit (inclination 85–86°) with an initial height of 4200km, [6] which had gradually lowered during its 9 years of operation.[ citation needed ] The satellite partly disintegrated in July 1975, which was followed by a second break-up that occurred in January 1976 resulting in the release of a large number of fragments. Most of these re-entered during the following decade. [5] [ better source needed ] In 2016, one of the largest fragments of PAGEOS de-orbited. [6]

The satellite's orbital period was approximately three hours. [2] It was about as bright as Polaris, and appeared as a slow-moving star. [10] Thanks to its high orbit and its polar inclination, it did not pass through the Earth's shadow and was visible any time of night, unlike lower-orbit satellites which had to be viewed exclusively just before sunrise and after sunset. [10]

See also

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References

  1. 1 2 "PAGEOS 1". National Aeronautics and Space Administration. Retrieved March 16, 2017.
  2. 1 2 "NSSDCA – PAGEOS 1 – Trajectory Details". nssdc.gsfc.nasa.gov. NASA . Retrieved June 22, 2016.
  3. 1 2 "Modern Surveying". Encyclopaedia Britannica. Retrieved March 24, 2024.
  4. 1 2 Kleusberg, Alfred (2003). "Satelliten im Dienst der Geodäsie und Geoinformatik" (PDF). University of Stuttgart. Archived from the original (PDF) on May 23, 2006.
  5. 1 2 "PAGEOS 1". Gunter's Space Page. Retrieved March 16, 2017.
  6. 1 2 3 J.-C. Liou (February 1, 2017). "USA Space Debris Environment, Operations, and Research Updates" (PDF). 54th Session of the Scientific and Technical Subcommittee, Committee on the Peaceful Uses of Outer Space, United Nations, 30 January – 10 February 2017, Vienna. Retrieved February 5, 2017.
  7. 1 2 3 4 Hansen, James (March 12, 2013). Spaceflight Revolution: NASA Langley Research Center from Sputnik to Apollo. Cia Publishing.
  8. ↑ Teichman, L. A. (June 1, 1968). "The fabrication and testing of Pageos 1". NASA Technical Reports Server
  9. 1 2 3 "Pageos Satellite to Girdle Globe for Earth Mapping". NASA Technical Reports Server. June 19, 1966.
  10. 1 2 3 Dicati, Renato (January 10, 2017). Stamping the Earth from Space. Springer. ISBN   978-3-319-20756-8.
  11. 1 2 3 4 Seeber, Günter (August 22, 2008). Satellite Geodesy: Foundations, Methods, and Applications. Walter de Gruyter. ISBN   978-3-11-020008-9.
  12. ↑ "Thor-SLV2A Agena-D". Gunter's Space Page. Retrieved May 9, 2024.
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