After Sputnik stunned the world in October 1957 and the first Vanguard rocket blew up on its launch pad that December, the U.S. Navy's program badly needed a win. On March 17, 1958, a three-stage Vanguard rocket put a small aluminum sphere into orbit, making it America's second satellite. Solar cells powered one of its radio transmitters, a first for any spacecraft. Its orbit was far higher than expected, so it never came back down, and it is still up there nearly seven decades later.
Vanguard 1 was tiny: a polished sphere about 16.5 centimetres across that weighed roughly 1.5 kilograms, with six short antennas sticking out of it. Nikita Khrushchev sneered at it as a "grapefruit" satellite. The Naval Research Laboratory's engineers, though, had packed it with ideas that would last. Its solar cells kept a transmitter going for years, long after chemical batteries would have run down, and it helped make solar power the standard way to run spacecraft.
The satellite also changed how scientists saw the planet. By tracking tiny shifts in its orbit, researchers found that Earth is not a perfect sphere but very slightly pear-shaped, with a small bulge in the southern hemisphere. Vanguard 1 went silent in 1964, but it did not come down. Its orbit reaches from roughly 650 kilometres at its lowest to almost 4,000 kilometres at its highest, which keeps it clear of most atmospheric drag. The grapefruit Khrushchev laughed at has outlasted Sputnik, the Soviet Union and Khrushchev himself, and it is expected to stay in orbit for centuries.