Overview
Vanguard 1 was the fourth artificial satellite to orbit Earth, following Sputnik 1, Sputnik 2, and Explorer 1. Launched by the US Naval Research Laboratory as part of the International Geophysical Year, it was the first satellite to use solar cell power. Soviet Premier Nikita Khrushchev famously dismissed it as "the grapefruit satellite" — it is just 16.5 cm in diameter and weighs 1.47 kg.
Key Facts
| NORAD ID | 00005 |
| Launch | 17 March 1958 |
| Last Signal | May 1964 (solar-powered transmitter) |
| Orbit | 660 × 3,820 km, 134 min period, 34.25° inclination |
| Diameter | 16.5 cm (6.5 inches) |
| Estimated Orbital Lifetime | ~240 years (revised from original 2,000-year estimate) |
Why Is It Still In Orbit?
Its highly elliptical orbit (perigee ~660 km, apogee ~3,820 km) keeps it well above the densest parts of Earth's atmosphere for most of each orbit. While Sputnik 1 re-entered within 3 months and Explorer 1 lasted 12 years, Vanguard 1's high apogee ensures it will orbit for roughly 240 more years — making it a permanent monument to the dawn of the Space Age.
Scientific Legacy
By tracking Vanguard 1's orbital deviations, scientists made the first discovery that Earth is not a perfect sphere but slightly pear-shaped (with a bulge in the southern hemisphere). This geodetic discovery fundamentally improved models of Earth's gravitational field. A proposal to retrieve Vanguard 1 for study has been presented by a team of aerospace engineers — it would be the oldest spacecraft ever returned to Earth.