Van Allen Probes

Part of NASA’s Living With a Star program, Van Allen Probes was the first mission to use two spacecraft in tandem to study Earth’s radiation belts. By having two spacecraft with identical instruments, with one followed by the other along nearly the same path, researchers could measure changes that occur in Earth’s radiation belts over time and through space, providing insights into the physical dynamics of the radiation belts and changes that occur in this critical region of space.

The probes measured the particles, waves, magnetic fields, and electric fields that fill geospace, the region around Earth that includes its upper atmosphere, ionosphere, and magnetosphere. Each probe was deactivated when it ran out of fuel—Van Allen Probe B on July 19, 2019, and Van Allen Probe A on October 19, 2019—bringing the mission to a close.

Van Allen Probe A re-entered Earth’s atmosphere in March 2026. Analysis when the mission ended in 2019 found that the spacecraft would re-enter Earth’s atmosphere in 2034. However, those calculations were made before a solar cycle that has proven far more active than expected. These conditions increased atmospheric drag on the spacecraft beyond initial estimates, resulting in an earlier-than-expected re-entry. Van Allen Probe B is not expected to re-enter before 2030.

Built, managed, and operated at APL, the Van Allen Probes were designed to operate entirely within the radiation belts, enduring years of harsh radiation and continuous operation under conditions that would force other spacecraft to shut down. Each spacecraft was equipped with a suite of five instruments, including particle detectors to characterize the various ions and electrons in the radiation belts, an instrument to study the electric fields created by the motion of charged particles in near-Earth space, and an instrument to investigate the role of magnetic fields and plasma waves in accelerating the particles to extremely high energies.
 

The Van Allen Probes enabled the discovery of the processes that accelerate and transport electrons and charged atoms called ions in the radiation belts, and what conditions lead to that transport. They helped scientists understand and quantify the loss of electrons from the radiation belts and determined the balance between competing processes that accelerate those particles or cause them to be lost to space. The probes also provided a deeper understanding of how the radiation belts change during geomagnetic storms.

More than 700 studies have used data collected by the Van Allen Probes.