Vanguard 3 (Harvard designation: 1959 Eta 1) is a scientific satellite that was launched into Earth orbit by the Vanguard SLV-7 on 18 September 1959, the third successful Vanguard launch out of eleven attempts. Vanguard rocket: Vanguard Satellite Launch Vehicle-7 (SLV-7) was an unused Vanguard TV-4BU (TV-4BU=Test Vehicle-Four BackUp) rocket, updated to the final production Satellite Launch Vehicle (SLV).Project Vanguard was a program managed by the United States Naval Research Laboratory (NRL), and designed and built by the Glenn L. Martin Company (now Lockheed-Martin), which intended to launch the first artificial satellite into Earth orbit using a Vanguard rocket. as the launch vehicle from Cape Canaveral, Florida. Vanguard 3 was an important part of the Space Race between the U.S. and the Soviet Union.