PAGEOS (PAssive Geodetic Earth Orbiting Satellite) was a
balloon satellite
A balloon satellite is inflated with gas after it has been put into orbit. It is also occasionally referred to as a "satelloon", which is a trademarked name owned by Gilmore Schjeldahl's G.T. Schjeldahl Company.
List of balloon satellites
abbr ...
which was launched by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeedin ...
in June 1966.
Design
PAGEOS had a diameter of exactly , consisted of a thick
mylar
BoPET (biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and a ...
plastic film coated with vapour deposited aluminium enclosing a volume of and was used for the Weltnetz der Satellitentriangulation (Worldwide Satellite
Triangulation
In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points.
Applications
In surveying
Specifically in surveying, triangulation involves only angle me ...
Network) – a global cooperation organized by
Hellmut Schmid
Hellmut H. Schmid (12 September 1914 – 27 April 1998) was Professor of geodesy and photogrammetry on the ETH Zürich (Switzerland), where he emerited in 1985. In the 1950s, he worked on research projects of space exploration in the United State ...
(Switzerland & USA) 1969-1973.
Finished in 1974, the network connected 46 stations (3000–5000 km distance) of all continents with an accuracy of 3–5 m (approx. 20 times better than terrestrial triangulations at that time).
Orbit
The PAGEOS spacecraft was placed into a
polar orbit
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about ...
(
inclination
Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object.
For a satellite orbiting the Ea ...
85–86°) with a height of approx. 4000 km, which had gradually lowered during its 9 years of operation. 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. PAGEOS data have been released in 11 data sets.
PAGEOS' predecessors in
satellite triangulation
Stellar triangulation is a method of geodesy and of its subdiscipline space geodesy used to measure Earth's geometric shape. Stars were first used for this purpose by the Finnish astronomer Yrjö Väisälä in 1959, who made astrometric photograph ...
were the balloons
Echo 1 (1960, 30 m) and Echo 2 (1964, 40 m) which were also used for passive
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that ...
. Their
apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...
(brightness) was 1 mag, that of Pageos 2 mag (like
Polaris
Polaris is a star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris ( Latinized to ''Alpha Ursae Minoris'') and is commonly called the North Star or Pole Star. With an apparent magnitude th ...
) due to its higher orbit. Pageos could therefore be observed simultaneously e.g. from the ground in places such as Europe and North America. PAGEOS appeared as a slow-moving star (at first glance it would appear to be stationary). Its orbital period was approximately three hours. Because of its high orbit and polar inclination it would avoid the Earth's shadow and be observed any time of the night (low-orbit satellites are only observable shortly after sunset and before sunrise). In the early 1970s PAGEOS varied from 2nd
apparent magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...
to beyond visibility over a period of a few minutes.
In 2016, one of the largest fragments of PAGEOS de-orbited.
See also
*
List of passive satellites
List of passive satellites is a listing of inert or mostly inert satellites, mainly of the Earth. This includes various reflector type satellites typically used for geodesy and atmospheric measurements.
Passive satellites
*Calsphere
**Calsph ...
*
Reference ellipsoid
An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth's form, used as a reference frame for computations in geodesy, astronomy, and the geosciences. Various different ellipsoids have been used as approximations ...
*
World Geodetic System
The World Geodetic System (WGS) is a standard used in cartography, geodesy, and satellite navigation including GPS. The current version, WGS 84, defines an Earth-centered, Earth-fixed coordinate system and a geodetic datum, and also descr ...
(WGS84)
References
External links
NASA technical note: The fabrication and testing of PAGEOS I
Geodesy
Satellites formerly orbiting Earth
Passive satellites
Spacecraft launched in 1966
Balloon satellites
{{US-spacecraft-stub