\<COLOUR 1> SIZE: \<COLOUR 0> Box-shaped, 1.73 metres by 74 cm by 74 cm
\<COLOUR 1> WEIGHT: \<COLOUR 0> 515 kg
\<COLOUR 1> COUNTRY: \<COLOUR 0> USA
\<COLOUR 1> COMMENTS: \<COLOUR 0> Third (out of six) and first successful orbiting geophysical observatory; studies Earth's magnetosphere, Van Allen belts, solar wind.