The actual operational satellite that was to be launched by the Vanguard launcher. The only successful one operated for 18 days; satellite wobble degraded data.

Typical orbit: 557 km x 3049 km at 33 degrees inclination. Mass: 10 kg (22 lb).

• 1952 May 16 - International Geophysical Year Committee established. -
  The Special Committee for the International Polar Year (later designated the International Geophysical Year), was established.

• 1955 March 19 - Plan for a United States satellite in the International Geophysical Year - Launch Vehicle: Vanguard.
  Dr. Alan T. Waterman of the National Science Foundation presented President Dwight Eisenhower with a plan to implement the United States' portion of the International Geophysical Year satellite experiment.

• 1955 July 29 - Eisenhower approves earth satellites for IGY - Launch Vehicle: Vanguard.
  President Eisenhower endorsed the IGY proposal for the launching of small earth-circling satellites.

• 1955 September 9 - Project Vanguard began operations. - Launch Vehicle: Vanguard.
  The Department of Defense's Stewart Committee reviewed the alternatives for an IGY satellite program: wait for the development of an Atlas launcher, use a modified Redstone, or develop a rocket derived from the Viking missile. The committee voted seven to two in favor of abandoning Project Orbiter (Redstone) and developing Vanguard (Viking derivative with and Aerobee-Hi upper stage). Secretary Donald Quarles ruled with the committee majority in the Department of Defense Policy Committee, which approved the decision. The Department of Defense wrote a letter to the Department of Navy authorizing the Navy Research Laboratory to proceed with the Vanguard proposal. The responsibility for carrying out the program was placed with the Office of Naval Research. Objectives of Project Vanguard were: to develop and procure a satellite-launching vehicle; to place at least one satellite in orbit around the earth during IGY; to accomplish one scientific experiment; and to track flight to demonstrate the satellite actually attained orbit.

• 1958 May 28 - Vanguard 2B - Program: Vanguard. Launch Site: Cape Canaveral. Launch Complex: LC18A. Launch Vehicle: Vanguard. FAILURE: Improper third stage trajectory - unknown cause. Mass: 10 kg (22 lb). Apogee: 3,500 km (2,100 mi).
  

• 1958 June 26 - Vanguard 2C - Program: Vanguard. Launch Site: Cape Canaveral. Launch Complex: LC18A. Launch Vehicle: Vanguard. FAILURE: Premature second stage cutoff. Unknown cause. Mass: 10 kg (22 lb). Apogee: 165 km (102 mi).
  

• 1958 September 26 - Vanguard 2D - Program: Vanguard. Launch Site: Cape Canaveral. Launch Complex: LC18A. Launch Vehicle: Vanguard. FAILURE: Insufficient 2nd stage thrust - unknown cause. Mass: 10 kg (22 lb). Apogee: 426 km (264 mi).
  

• 1959 February 17 - Vanguard 2 - Program: Vanguard. Launch Site: Cape Canaveral. Launch Complex: LC18A. Launch Vehicle: Vanguard. Mass: 10 kg (22 lb). Perigee: 557 km (346 mi). Apogee: 3,049 km (1,894 mi). Inclination: 32.90 deg. Period: 122.80 min.
  Operated for 18 days; satellite wobble degraded data.