The earth-science satellite Vanguard 1 was launched by the Department of Defense/U.S. Navy, with assistance from the U.S. Naval Research Laboratory, to study the effects of a space environment on a satellite and its systems while in orbit about the Earth.
The 3.2-pound (1.47-kilogram) satellite was launched at 12:15:41 UTC, on March 17, 1958, while onboard a three-stage Vanguard launch vehicle.
It was launched from Launch Pad LC 18A at Cape Canaveral, Florida as part of the scientific program Project Vanguard for the International Geophysical Year (1957-1958)
The spherical-shaped Vanguard 1 (NSSDC ID: 1958-002B, also called Vanguard TV4), at 5.9 inches (fifteen centimeters) in diameter, was called by Soviet premier Nikita Khrushchev, upon its launch: “the grapefruit satellite.” (NSSDC stands for National Space Science Data Center.)
Vanguard 1 orbits about the Earth with an apogee of 2,466 miles (3,969 kilometers) and a perigee of 406 miles (654 kilometers). Its orbital period is approximately 134.2 minutes.
Vanguard 1’s original mission was designed to last 2,200 days. The probe was composed of a 10-milliwatt, 108-megahertz mercury-battery powered transmitter and a 5-milliwatt, 108.03 megahertz transmitter, which was powered by six square solar cells. Six aerial antennas protruded from its surface. It also carried two thermistors, which measured interior temperature of the probe.
In the early days of U.S. space exploration, the United States was just trying to get its launch vehicles to work. The country was inexperienced in space exploration. However, Vanguard 1 proved the fledgling space explorer could be a master in space travel. Please read more about the accomplishments of Vanguard 1.
The mission of Vanguard 1 was considered a complete success, providing much information on the shape and size of the Earth, along with atmosphere information such as high-altitude air density and temperature ranges.
In fact, the grapefruit-shaped satellite proved that the Earth is pear-shaped (technically, an oblate sphereoid).
Vanguard 1, the first solar powered artificial satellite, was the second artificial satellite successfully launched into Earth orbit by the United States.
Sputnik I and II were sent into orbit earlier by the Soviet Union, and Explorer 1 was the first satellite to be placed in orbit by the United States. All three satellites have since lost their orbits and have been destroyed while falling back into Earth’s atmosphere.
Small events are planned on March 17, 2008 to commemorate the mission of Vanguard 1.
The Naval Research Laboratory is planning a celebration, while the National Academy of Sciences has scheduled various seminars to mark the fiftieth anniversaries of the International Geophysical Year (1958) and Vanguard 1.
The pioneering efforts of Vanguard 1 showed that solar powered satellites are operable in space. Although communications with Vanguard 1 ended in May 1964, it continues to be optically tracked by astronomers and other scientists. Its position in space helps to determine positional data on the Sun and Moon, along with other positional data.
The U.S. Navy’s website “Vanguard I--the World's Oldest Satellite Still in Orbit” provides additional information on Vanguard 1.
NASA’s Goddard Space Flight Center website “Vanguard 1” also provides information on the satellite.
The launch of Vanguard 1 is shown, several times, at YouTube’s 4:36-minute video “Launch of Vanguard 1 (TV-4)” .