Page 26 - Curriculum Visions Dynamic Book

The Vanguard series was launched in an effort to find out about the Earth’s magnetic field and to test the working of solar cells (at that time quite revolutionary).
After the launch of the Sputniks 1, 2, and 3 the Soviet Union did not officially send up any more satellites (although its military program actually put up many satellites). Instead, its public efforts went into manned spaceflight. By contrast, the United States launched satellite after satellite in its attempts to master rocket and satellite technology.
Discoverer
The first of the Discoverer satellites was launched on February 28, 1959. Discoverer 13 contained a capsule with a heat shield, making it the first item to be returned safely to the Earth’s surface. It landed by parachute in the sea. As people found out later, the Discoverer program was probably also the very first military spy satellite series, each containing high-resolution cameras.
 The Vanguard satellite launched on March 17, 1958, was the first to carry an alternative power source to batteries. It had solar cells. The solar cells were used to power the transmitter. Vanguard I had such a high orbit that it still has not reentered the Earth’s atmosphere and is the oldest object left in space.
 Discoverer 13 was the first space vehicle to be recovered from Earth orbit.
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