NASA has shut down the first of the two Van Allen Probes in anticipation of their controlled burn up in the Earth's atmosphere in about 15 years. On July 19, 2019, at 1:27 pm EDT, mission control at Johns Hopkins University Applied Physics Lab in Laurel, Maryland sent the signal ordering Van Allen Probe B to close down its systems after running out of propellant.
Launched on August 23, 2012 atop an Atlas V rocket from Cape Canaveral Air Force Station, Florida, the Van Allen Probes A and B began a planned two-year mission studying the famous Van Allen radiation belts that encircle the Earth and protect us from cosmic radiation. After subsequent extensions that stretched the study out to seven years, both unmanned orbiters were still fully functional, but lacked sufficient propellant to make needed course corrections and keep their solar panels angled toward the Sun.
As a result, in February 2019 NASA engineers ordered the probes to go into a circular orbit that will slowly decay over the next 15 years and see them reenter the atmosphere and prevent the craft from becoming space junk. However, Probe B has now exhausted its propellant and cannot maintain its attitude, so the space agency has shut down its electronics to prevent its radio from accidentally blinding other spacecraft or ground stations.
According to the agency, Probe A is still operating, but is expected to run dry in early September when it, too, will be deactivated.
"Seven years is a very long time," says Sasha Ukhorskiy, Van Allen Probes project scientist. "People who came onto this mission as students and postdocs are now well into their careers. We've raised a new generation of scientists. It's a great legacy for the Van Allen Probes."
Source: NASA
