NASA is reporting that one of the Solar Terrestrial Relations Observatories, known as the STEREO-B spacecraft, has made contact after two years of silence.

Launched in 2006, STEREO-B and its sister spacecraft, STEREO-A entered an orbit around the sun just ahead of and just behind the Earth, allowing them to observe solar phenomena such as coronal mass ejections from multiple angles.

STEREO-B went silent in October 2014, just after mission control tested its “command loss timer,” a hard reset that would be automatically triggered if STEREO-B ever stopped communicating with Earth for 72 hours.

For some reason – the team still isn’t sure exactly why – the spacecraft reacted poorly to the hard reset that its sister probe breezed right through. STEREO-B let out a single weak signal, then went quiet.

The STEREO team spent months sending signals meant to correct STEREO-B’s position in the hopes of catching it with enough power to respond.

Now, 22 months after the silent treatment began, STEREO-B is back in communication with the Deep Space Network, the antennae system that NASA uses to pick up signals from its missions.

After periodic check-ins from the team ever since December, the Deep Space Network finally locked on to STEREO-B’s signal at 6:27 p.m. EDT on Sunday.

Further communications will be required to determine the health of the spacecraft and whether it’s capable of resuming its scientific duties with STEREO-A, which continues to function normally.

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