Page 29 - Intro to Space Sciences Spacecraft Applications

16 Introduction to Space Sciences and Spacecraft Applications

between the sun and the earth. Pioneer and Voyager spacecraft, sent to visit
the planets, also sampled the interplanetary environment. These satellites
are now on their way out of our solar system, but scientists continue to
monitor their signals in hopes of gaining information on interstellar space.
The sun has the greatest effect on the near-earth space environment,
and a series of Orbiting Solar Observatory (OSO) spacecraft launched
between 1962 and 1975 were used to study solar flares and temperature
differences on the sun’s surface. The Solar Maximum Mission (SMM or
SolarMax) was launched in 1980 to observe the sun during the maximum
phase of its 11-year cycle. This spacecraft was the objective of a Space
Shuttle rendezvous and EVA repair mission in 1984. UZysses, a joint
U.S ./European Space Agency spacecraft deployed from the Space Shuttle
in October 1990, used a gravity assist from Jupiter to send it into a solar-
polar orbit to allow mapping the solar environment in this previously
unexplored region of our solar system.
Long-term effects of the space environment on spacecraft has been inves-
tigated with the Long Duration Exposure Facility (LDEF). Released from the

Figure 1-1 1. The SolarMax sun-observing satellite was the object of a Space
Shuttle repair mission in 1984.