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Vanguard 1 (ID: 1958-Beta 2[3]) (March 17, 1958) is an American satellite that was the fourth artificial Earth orbital satellite to be successfully launched (following Sputnik 1, Sputnik 2, and Explorer 1). Vanguard 1 was the first satellite to have solar electric power.[4] Although communication with the satellite was lost in 1964, it remains the oldest human-made object still in orbit, together with the upper stage of its launch vehicle.

Vanguard 1 was designed to test the launch capabilities of a three-stage launch vehicle as a part of Project Vanguard, and the effects of the space environment on a satellite and its systems in Earth orbit. It also was used to obtain geodetic measurements through orbit analysis. Vanguard 1 was described by the Soviet Premier, Nikita Khrushchev, as "the grapefruit satellite".[5]

Vanguard 1 satellite sketch

After its scientific mission ended in 1964, Vanguard 1 became a Naval Research Laboratory (NRL) proposals for the project included conical satellite bodies; this eliminated the need for a separate fairing and ejection mechanisms, and their associated weight and failure modes. Radio-tracking would gather data and establish a position. Early in the program, optical tracking (with a Baker-Nunn camera network and human spotters) was added. A panel of scientists proposed changing the design to spheres, at least twenty inches in diameter and hopefully thirty. A sphere would have a constant optical reflection, and constant coefficient of drag, based on size alone, while a cone would have properties that varied with its orientation. James Van Allen of the University of Iowa proposed a cylindrical satellite based on his work with rockoons, which became Explorer 1, the first American satellite. The Naval Research Laboratory finally accepted a sphere with a 16 cm (6.4-inch) diameter as a "test vehicle", with a diameter of twenty inches set for the follow-on satellites. The weight savings, from reduced size as well as decreased instrumentation in the early satellites, was considered to be acceptable.

Since three of the Vanguard satellites are still orbiting with their drag properties essentially unchanged, they form a baseline data set on the atmosphere of Earth that is over 60 years old and continuing.[13][14][15]

After its scientific mission ended in 1964, Vanguard 1 became a derelict object—just like the upper stage of the rocket used to launch the satellite had after it finished the delta-v maneuver to place Vanguard 1 in orbit in 1958. Until otherwise noted, both objects remain in orbit.[13][16]

50th anniversary

The Vanguard 1 satellite and upper launch stage hold the record for being in space longer than any other human-made object,[17][18] and as such have traveled farther over the Earth's surface than any other human-made object.[19]

A small group of former NRL and NASA workers had been in communication with one another, and a number of government agencies

The Vanguard 1 satellite and upper launch stage hold the record for being in space longer than any other human-made object,[17][18] and as such have traveled farther over the Earth's surface than any other human-made object.[19]

A small group of former NRL and NASA workers had been in communication with one another, and a number of government agencies were asked to commemorate the event. The Naval Research Laboratory commemorated the event with a day-long meeting at NRL on 17 March 2008.NASA workers had been in communication with one another, and a number of government agencies were asked to commemorate the event. The Naval Research Laboratory commemorated the event with a day-long meeting at NRL on 17 March 2008.[20] The meeting concluded with a simulation of the satellite's track as it passed into the orbital area visible from Washington, D.C., (where it is visible from the Earth's surface). The National Academy of Sciences scheduled seminars to mark the 50th anniversary of the International Geophysical Year, which were the only official observances known.[21]