By the Numbers: Explorer 1

A model of Explorer 1 is held high by (from left) Jet Propulsion Laboratory Director William Pickering, physicist James Van Allen, and Wernher von Braun at a late-night news conference announcing the launch of Explorer 1, held at the National Academy of Sciences in Washington, DC, on Jan. 31, 1958. Photo by NASA/JPL-Caltech.

On Jan. 31, 1958, Explorer 1 became the first successful spacecraft launched by the United States, almost four months after the Soviet Union shocked the world with the launch of Sputnik (on Oct. 4, 1957). Its signal ended when the batteries ran out on May 23, 1958.

4

The number of scientific instruments aboard, including a cosmic ray detector, micrometeorite detector, satellite drag atmospheric density and temperature sensor. It detected for the first time trapped radiation that became known as the Van Allen Radiation Belt, named after University of Iowa physicist James Van Allen, the principal cosmic ray investigator on the project.

6.25

Explorer 1’s diameter in inches.

12

The number of years Explorer 1 existed before re-entering Earth’s atmosphere and burning up on March 31, 1970.

31

The weight in pounds of Explorer 1. Eighteen of those pounds were the instruments.

80.75

The length in inches of Explorer 1.

114.8

The number of minutes it took for Explorer 1 to orbit Earth, or 12.54 orbits per day.

22

The closest in miles the satellite got to Earth during an orbit.

1,563

The farthest away from Earth in miles the satellite traveled.

58,000

The number of orbits Explorer 1 made in its 12-year life.

Source:  nasa.gov, space.com