America's First Satellite
Better Late Than Never
After the launches of Sputnik and Sputnik II,
the first American satellite needed to demonstrate its significance in order to
compete with its Soviet rivals. That significance was scientific discovery.
I, while small, contained two key scientific instruments: A
micrometeoroid impact detector and a cosmic ray detector. These were installed
on top of the Juno I rocket in a tub that rotated at 720 rotations per minute.
The spinning kept the satellite stable after it separated from the rest of the
rocket. This was essential because the satellite could not carry fuel or
engines to stabilize itself. The Explorer I satellite confirmed the existence
of bands of radiation around the Earth, now known as the Van Allen Radiation
Belts, and recorded 145 impacts of cosmic dust over 12 days.