Somewhere on the other side of the sun, almost directly opposite to Earth, a 9-year-old NASA spacecraft, the STEREO-B, has drifted through the void of space since Oct. 1, 2014, unable to establish contact with our planet.
At least that was the depressing situation until Sunday night.
In a statement posted Monday, the space agency says it has finally contacted the STEREO-B solar observatory — an identical twin of another sun-monitoring robot, called STEREO-A — after nearly 2 years of effort.
The spacecraft was about 189 million miles from Earth when NASA finally made contact:
Each STEREO spacecraft — named "A" for "ahead" and "B" for "behind" — launched in 2006 and began circling the sun in slightly different yet Earth-like orbits.
That way, scientists could watch our backyard star (and its angry eruptions) from all angles.
This also allowed NASA to get amazing 3D views of solar flares, huge loops of plasma, coronal mass ejections, and more.
Though the $550 million mission was supposed to wrap up in 2008, it was a big success and NASA kept it going.
Trouble didn't hit until Oct. 1, 2014, when STEREO-B went into a hard reset and lost touch with Earth.
NASA tried to use the Deep Space Network to regain contact over the course of 22 months, and finally succeeded on Aug. 21, 2016.
But Joe Gurman, a STEREO project scientist, said everyone involved in the mission is sitting on the edges of their seats.
"The very hard and scary work is just beginning," Gurman told Business Insider. "This spacecraft was designed to be as autonomous as possible when it ran into trouble. If we turn on the computer, which is the only way we can get insight into what is wrong with the spacecraft ... what got us into this mess in the first place could turn back on again."
As NASA detailed in a December 2015 article about the recovery effort, the spacecraft doesn't know if it's rotating or how fast. That's a big problem for a robot that needs to aim its solar panels at the sun and continuously charge its batteries — meaning it has barely been charging itself since it reset, and could quickly drain what juice it has slowly built up.
"We have something like 2 minutes between when STEREO-B receives the command to boot up one of its computers and when it starts doing what we don't want it to do," Gurman said.
Making matters worse, it takes about 20 seconds to send commands to the spacecraft, and at a data rate that makes a dial-up modem seem lightning-fast.
As a result, Gurman said engineers are taking their time to hammer out a set of brief rescue instructions while they know the spacecraft is still responsive.
If their efforts to point STEREO-B's solar panels back toward the sun fail, he said they'll have another chance to send instructions in 6 months: when the spacecraft has partially charged up its batteries again by slowly orbiting the sun.
Here's the full statement from Karen C. Fox, a NASA spokesperson:
"On Aug. 21, 2016, contact was reestablished with one of NASA's Solar Terrestrial Relations Observatories, known as the STEREO-B spacecraft, after communications were lost on Oct. 1, 2014. Over 22 months, the STEREO team has worked to attempt contact with the spacecraft. Most recently, they have attempted a monthly recovery operation using NASA's Deep Space Network, or DSN, which tracks and communicates with missions throughout space.
"The DSN established a lock on the STEREO-B downlink carrier at 6:27 p.m. EDT. 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. The STEREO Missions Operations team plans further recovery processes to assess observatory health, re-establish attitude control, and evaluate all subsystems and instruments.
"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. The STEREO team was testing this function in preparation for something known as solar conjunction, when STEREO-B’s line of sight to Earth – and therefore all communication – was blocked by the sun.
"STEREO-A continues to work normally."
