Nasa re-establishes contact with lost sun spacecraft after nearly 2 years of radio silence

Nasa has successfully re-established contact with one of its solar observatory spaceships after nearly two years of radio silence. The spacecraft, Stereo-B, was one of two solar spaceships that were launched by Nasa in 2006, aimed at better understanding the sun.

Nasa lost contact with Stereo-B in 2014, just as it was about to commence orbiting the other side of the sun. However, contact was re-established on 21 August after the Solar Terrestrial Relations Observatories mission team used Nasa's Deep Space Network (DSN), which tracks and communicates with missions in space, to effectively end the 22-month-long radio silence with the spacecraft.

"The DSN established a lock on the Stereo-B downlink carrier at 6.27 pm EDT. The downlink signal was monitored by the Mission Operations team over several hours to characterise the attitude of the spacecraft and then transmitter high voltage was powered down to save battery power. The Stereo Missions Operations team plans further recovery processes to assess observatory health, re-establish attitude control, and evaluate all subsystems and instruments," said Nasa spokesperson Karen C Fox.

Stereo-B's twin Stereo-A, "continues to function normally", Fox added. The two spacecraft were designed originally to complete a two-year mission, which was supposed to have ended in 2008. However, the spacecraft outlasted the mission and are now 10 years old. According to Nasa, after being launched into space, the twin Stereos steadily drifted away from Earth as they orbited the sun, such that they were aligned one behind and one ahead of Earth. This alignment provided scientists with "constantly-improving" views of the sun's other side, which in turn allowed scientists to view the sun as a whole for the first time.

According to Nasa, the communications may have been blocked due to the sun's interference. "Communications with Stereo-B were lost during a test of the spacecraft's command loss timer, a hard reset that is triggered after the spacecraft goes without communications from Earth for 72 hours," said Fox. It was while the Stereo team was testing this function that the Stereo-B's "line of sight to Earth" and correspondingly, all communications were blocked out by the sun.