Explorer 10, also known as Explorer X or P-14, was launched from Cape Canaveral aboard a Thor-Delta rocket to investigate Earth's magnetic field and the surrounding solar-wind plasma. Placed into a highly elliptical orbit extending more than 112,000 miles from Earth, the spacecraft traveled deep into the magnetosphere and provided the first direct observations of the boundary where Earth's magnetic field interacts with the solar wind.
 |
| An Explorer 10 launch cover, postmarked at Patrick Air Force Base with a machine cancel on March 25, 1961, signed by Dr. James Van Allen, the University of Iowa space scientist whose pioneering research established the existence of Earth's radiation belts. |
Despite transmitting useful data for only about 52 hours, Explorer 10 revealed the complex structure of Earth's magnetosphere, including its elongated magnetotail on the side facing away from the Sun. The mission was an important early step in the development of magnetospheric physics and in understanding the space environment that future astronauts would encounter.
(Reference from
Explorer 10)
