[4] Although communications with the satellite were lost in 1964, it remains the oldest human-made object still in orbit, together with the upper stage of its launch vehicle.

[6] The spacecraft is a 1.46 kg (3.2 lb) aluminum sphere six inches (150 mm) in diameter, with antennae spanning three feet (0.91 m).

The transmitters were used primarily for engineering and tracking data, but were also used to determine the total electron content between the satellite and the ground stations.

[1] A backup version of Vanguard 1 is on display at the Smithsonian National Air and Space Museum, Steven F. Udvar-Hazy Center in Chantilly, Virginia.

Original estimates had the orbit lasting for 2,000 years, but it was discovered that solar radiation pressure and atmospheric drag during high levels of solar activity produced significant perturbations in the perigee height of the satellite, which caused a significant decrease in its expected lifetime to about 240 years.

[10] Because of its symmetrical shape, Vanguard 1 was used by experimenters for determining upper atmospheric densities as a function of altitude, latitude, season, and solar activity.

By measuring the rate and timing of orbital shifts, together with the body's drag properties, the relevant atmosphere's parameters could be back-calculated.

Initial 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.

[15] 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.