The first solar-powered satellite, Vanguard I was the second artificial satellite successfully placed in earth orbit by the United States. (Vanguard predecessors, Sputniks I and II and Explorer I have long since fallen out of orbit.) Just six inches in diameter and weighing just 3 pounds, Vanguard was described by then-Soviet Premier Nikita Khrushchev as "the grapefruit satellite."

As part of the scientific program for the International Geophysical Year (1957-58), NRL was officially delegated the responsibility of placing an artificial satellite with a scientific experiment into orbit around the earth. Designated Project Vanguard, the program was placed under Navy management and DoD monitorship.

NRL was responsible for developing the launch vehicles; developing and installing the satellite tracking system; and designing, constructing and testing the satellites.

The tracking system was called Minitrack. The Minitrack stations, designed, built and initially operated by NRL, were along a North-South line running along the east coast of North America and the west coast of South America. Minitrack was the forerunner of another NRL-developed system called NAVSPASUR, which is operational today and a major producer of spacecraft tracking data.

In late 1958, responsibility for Project Vanguard was transferred to NASA, forming the nucleus of the Goddard Space Flight Center. After the transfer, NRL rebuilt their spacecraft technology capability and have developed some 87 satellites over the past 40 years for the Navy, DoD and NASA. NRL's relationship with NASA is still very active; for example, NRL is currently developing the Interim Control Module for NASA's International Space Station.

Vanguard met 100 percent of its scientific objectives, providing a wealth of information on the size and shape of the earth, air density, temperature ranges and micrometeorite impact. It proved that the earth is pear-shaped, not round; corrected ideas about the atmosphere's density at high altitudes and improved the accuracy of world maps.

NRL space scientists say that the Vanguard I program introduced much of the technology that has since been applied in later U.S. satellite programs, from rocket launching to satellite tracking. For example, it proved that solar cells could be used for several years to power radio transmitters. Vanguard's solar cells operated for about seven years, while conventional batteries used to power another onboard transmitter lasted only 20 days.

Although Vanguard's solar-powered "voice" became silent in 1964, it continues to serve the scientific community.

Ground-based tracking of the satellite provides data concerning the effects of the sun, moon and atmosphere on satellite orbits.

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