Originally a simple nose cone was to be carried but in July of 1957 it was decided that a small 1.47 kilogram (3.25 pound) test satellite would be used instead to exercise the tracking stations. This test satellite would consist of a simple 16 centimeter (6.4 inch) polished aluminum alloy sphere equipped with two transmitters operating at frequencies around 108 MHz.

The successes of Vanguard I set the pattern for a multitude of other space ventures in this country and abroad. Vanguard also served as a springboard for scientists to launch several series of space probes to study various aspects of radiation phenomena.

Vanguard I introduced much of the technology that has been applied in other U.S. satellite programs. For example, it proved that solar cells could be used for several years to power radio transmitters. Vanguard's solar cells operated for about seven years, while conventional batteries used to power another onboard transmitter lasted only 20 days.

Now the oldest man-made satellite in orbit, Vanguard I has been 100 percent successful in meeting its scientific objectives.

There were three operational satelites built but Bell Laboratories built many more copies--they furnished the transistors and invented the solar cells.
The total cost was about $125,000 in 1957-dollars for all three units.
Although the Vanguard 1 satellite must be looked at as a test satellite its technical and scientific results is impressive.
Technically its purpose was to test and evaluate solar cells,satellite terminal design and on board instrumentation. All this test objectives met. The solar cells worked so well that its transmitters was active i 7 years.(interfering the 108 MHz frequency) Well beyond expected lifetime.
The scientific results was also a success.
As Soviet authorities and even some in the West scoffed at the diminutive size of Vanguard 1 and its lack of sophisticated instrumentation, it was proving to be a very useful tool.
Maintained an orbit so stable that cartographers were able to more accurately redrawn maps of islands in the Pacific Ocean.
Analysis of the motion of Vanguard 1 established the fact that the earth is not spherical but has a bulge,disclosed unsuspected stress deep within the earth. These measurements indicated that there was large scale convection taking place inside the Earth which supported the then-new theories of continental drift and sea floor spreading. Analysis of the drag exerted by the atmosphere on Vanguard 1 proved the atmosphere to be far more extensive and variable in extent than believed before. Perturbations in Vanguard 1:s orbit also led to a more refined estimate of the Earths oblateness.