PAGEOS


PAGEOS was a balloon satellite which was launched by NASA in June 1966.

Design

PAGEOS had a diameter of exactly, consisted of a thick mylar plastic film coated with vapour deposited aluminium enclosing a volume of and was used for the Weltnetz der Satellitentriangulation – a global cooperation organized by Hellmut Schmid 1969-1973.
Finished in 1974, the network connected 46 stations of all continents with an accuracy of 3-5 m.

Orbit

The PAGEOS spacecraft was placed into a polar orbit 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 has been tracked 11 times.
PAGEOS' predecessors in satellite triangulation were the balloons Echo 1 and Echo 2 which were also used for passive telecommunication. Their apparent magnitude was 1 mag, that of Pageos 2 mag 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. 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. In the early 1970s PAGEOS varied from 2nd apparent magnitude to beyond visibility over a period of a few minutes.
In 2016, one of the largest fragments of PAGEOS de-orbited.