NASA has announced that a solar probe thought lost in space has been recovered and is now communicating with mission control. After 22 months of silence, the Deep Space Network (DSN) re-established contact with the unmanned Solar TErrestrial RElations Observatory B (STEREO-B) on August 21 at 6:27 pm EDT. According to the space agency, the spacecraft is operational and recovery efforts are continuing.
STEREO-B was launched on October 26, 2006 from Space Launch Complex 17B at Cape Canaveral Air Force Station, Florida atop a Delta II rocket along with its sister probe STEREO-A. Using a slingshot trajectory past the Moon, the two spacecraft went into a four-year solar orbit that placed them on opposite sides of the Sun, so each could observe a different hemisphere and send back detailed stereoscopic images. This was important not only for pure research, but also as a way to monitor solar weather and warn against potentially damaging or deadly solar flares.
On October 1, 2014, mission control was carrying out a routine precautionary test of STEREO-B. The probe was testing its command loss timer, which executes a hard reset of the spacecraft’s systems if it loses communications with Earth for 72 hours. This is necessary because the orbit of the STEREO spacecraft occasionally sends them behind the Sun in what is called solar conjunction, when the Sun’s massive energy can drown out radio links between Earth and spacecraft.
During the test, communications with mission control were lost and STEREO-B’s antenna was no longer properly aligned with Earth, so the link couldn’t be reestablished. For the past 22 months, NASA has been carrying out monthly attempts to regain control of the craft using the DSN.
After Sunday’s successful recovery, mission control monitored the downlink for several hours before ordering the spacecraft to power down its transmitter to conserve battery power. NASA says that it will assesses STEREO-B’s health and work towards re-establishing attitude controls to ensure that it continues to point at the Earth, as well as testing its instruments and subsystems.