Abandoned by NASA at the end of its mission in 1997, ISEE-3 has slumbered in heliocentric orbit ever since, since whenever budget forces NASA to abandon a working probe, they generally prefer to put them into hibernation than to actually deactivate them. A private team calling itself ISEE-3 Project Reboot obtained permission from NASA to attempt to make contact with and reactivate the probe ahead of its upcoming Earth flyby. ISEE-3 has had a long and complicated history, starting out in 1978 as a solar wind monitoring probe at the Sun-Earth L1 point, and then redirected in the 80s to become the first spacecraft to encounter a comet (Comet Giacobini-Zinner) after which it went on to visit Comet Halley, with the new designation ICE. It drifted further out into deep space after that, and by 1997, was too distant for communications to continue.
Now it’s coming back.
Nobody knew if the probe would respond to communications; they were able to pick up a carrier signal, but that was it, and NASA no longer was equipped for its antiquated communication protocol. The ISEE-3 Project Reboot team managed to build a system to talk to it, and last week, using the Arecibo Observatory in Puerto Rico, easily the world’s largest and most powerful communications device, gained control of the spacecraft. So far, they’re taking baby steps, requesting and receiving telemetry, but they hope to be able to start doing actual science with the probe soon.