What Is The Oldest Manmade Object In Earth Orbit?
Answer: Vanguard 1
Vanguard 1 can’t claim to be the first artificial satellite in Earth orbit—that distinction belongs to Soviet launched Sputnik 1. Vanguard 1 is actually the fourth artificial satellite—after Sputnik 1 (USSR), Sputnik 2 (USSR), and Explorer 1 (USA). Despite being the fourth artificial satellite launched into Earth orbit, Vanguard can lay claim to several titles, however.
The most notable of the titles it can claim is: the artificial satellite that has been in Earth orbit the longest. Launched on March 17, 1958, Vanguard 1 has been in orbit for over 60 years and has orbited the Earth over 235,000 times (it completes a full elliptical orbit every 134.2 minutes). Unlike the three satellites launched prior to it, Vanguard 1 has not succumbed to orbital decay and burned up in the atmosphere.
Vanguard 1 was originally launched as part of a two-part program. The primary function of Vanguard 1 was to serve as a test platform for the 3-stage satellite launch rockets used for Project Vanguard. Since getting something into Earth orbit is neither a small nor inexpensive task, the satellite was configured to perform tests and observations once it was in orbit. Among the various tests undertaken by Vanguard 1 were studying the effects of space on a satellite and its systems in Earth orbit and obtaining geodetic measurements through orbit analysis.
The effect of atmospheric drag and rate of orbital decay at high altitudes were two of the more useful contributions made by the satellite. Although it was only operational until May of 1964, the data transmitted was invaluable for future satellite launches. Scientists had predicted, for example, that Vanguard 1 would have an orbital decay of 2,000 years. It turns out that, due to various variables and effects that had been excluded from their calculations, the orbital decay of Vanguard 1 is more like 240 years—Earth’s longest-lived artificial satellite will burn up in the atmosphere around 2198, not 3958.
In addition to being the longest-lived artificial satellite, Vanguard 1 also has the distinction of being the first satellite to have solar electric power (via solar cells mounted on the body of the satellite). Finally, although none of the satellites from the Vanguard program are operational today, they still serve an important function. Three of the satellites are still in orbit with their orbital properties essentially unchanged—the three satellites are used as a baseline reference for continued study and calculations.
Image courtesy of National Air and Space Museum, Smithsonian Institution.