After nearly two years of silence, NASA has finally picked up a signal from its wayward STEREO-B probe designed to study the sun. The contact was lost on Oct. 1, 2014, during a test of the spacecraft’s command loss timer, when the probe was on the other side of the sun.
NASA revealed that its Deep Space Network (DSN), which tracks and communicates with spacecraft in space, established a lock on the STEREO-B downlink carrier at 6:27 p.m. EDT on Aug. 21, restoring the contact with the orbiter.
“The downlink signal was monitored by the Mission Operations team over several hours to characterize the attitude of the spacecraft and then transmitter high voltage was powered down to save battery power,” NASA said in a statement.
However, the agency noted that the recovery process is not over yet as the mission controllers still need to determine if the spacecraft is safe and sound and capable of continuing its science operations after the long period of silence.
“The STEREO Missions Operations team plans further recovery processes to assess observatory health, re-establish attitude control, and evaluate all subsystems and instruments,” NASA said.
STEREO-B (Solar Terrestrial Relations Observatory) is one of the two identical spacecraft, launched in October 2006 and placed in a highly eccentric orbit around the sun with the aim to provide the first-ever stereoscopic measurements of the sun and solar phenomena. STEREO-B flies behind Earth in its orbit, while STEREO-A is ahead of our planet, what provides a unique and revolutionary view of the sun-Earth system.
While STEREO-A continues its science operations uninterrupted, contact with STEREO-B was lost during a test of a command loss timer - an automatic reset button restarting the spacecraft after 72 hours without contact. NASA was testing this feature to prepare the probe for solar conjunction, when STEREO-B’s line of sight to Earth is blocked by the sun, disabling any communications.
Based on a weak signal received from the probe after the failed test, the STEREO team concluded last year, that the spacecraft’s instrument designed to send data on how the spacecraft is oriented and moving through space, has suffered a failure.
“The only concrete information we have is that the Inertial Measurement Unit was feeding bad information to the guidance and control system. From there, we made educated guesses about what the spacecraft would do,” Dan Ossing, STEREO mission operations manager at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said in December 2015.
NASA hopes that maintaining the current reestablished signal with STEREO-B would get easier over time due to the fact that the probe gets closer to Earth every day.