Pioneer A to E (Pioneer 6 to 9 after launch) were a series of five solar-orbiting, spin-stabilized, solar-cell and battery-powered satellites designed to obtain measurements of interplanetary phenomena from widely separated points in space on a continuing basis.
Heliocentric N/AATS-5, the last spacecraft in the Hughes/NASA ATS program, was launched August 12, 1969, in a near-perfect trajectory for insertion into synchronous orbit. Although injected successfully into orbit, the spacecraft's reverse spin (counterclockwise) prevented successful deployment of the 124 foot gravity gradient booms for the stabilization experiment. However nine of the other 13 experiments aboard the spacecraft returned useful data.
Geosynchronous Orbit