The Sputnik 1 (PS-1) satellite is shown here on a rigging truck in the assembly shop in the fall of 1957 as a technician puts finishing touches on it. When the development of the first advanced scientific satellite, Object D, proved to be more difficult than expected, the Soviets decided to launch a simpler, smaller satellite. PS-1, or Sputnik 1, began development in November 1956. The pressurized sphere made of aluminum alloy had five primary scientific objectives: 1. Test the method of placing an artificial satellite into Earth orbit, 2. Provide information on the density of the atmosphere by calculating its lifetime in orbit, 3. Test radio and optical methods of orbital tracking, 4. Determine the effects of radio wave propagation though the atmosphere, and 5. Check principles of pressurization used on the satellites. On October 4, 1957, Sputnik 1 successfully launched and entered Earth's orbit. Sputnik shocked the world, giving the USSR the distinction of putting the first human-made object into space and putting the United States a step behind in the space race.