An exclusive look inside the comet lander control room

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Bearing Witness: 2014 — The Globe and Mail looks back on the cataclysmic news events of 2014 through the eyes of the people who were there – be they bystanders, participants or journalists. Their accounts shaped our perceptions, while their witnessing the events changed their lives.

There were plenty of theories about what would happen when a European spacecraft became the first to land on the surface of a comet.

Some said the lander would vanish into a deep layer of comet dust; others, that it would miss the comet altogether. Instead, the lander surprised everyone by setting down right on target – and then bouncing off again when it failed to anchor itself to the comet's surface.

"That's definitely not what I was expecting," says Valentina Lommatsch, an operations engineer at the German Aerospace Centre near Cologne. "I knew immediately that the lander had left the surface, because I was watching the solar array data the whole time and I could see the lander was still turning. So I knew we were flying."

An American by birth, Ms. Lommatsch came to Germany to do a master's degree, which serendipitously led to her joining the comet mission two year ago. On Nov. 12, the day of the landing, she was one of the handful of mission operators monitoring the lander's vital signs during its fateful descent.

For the next two hours after its big bounce, the lander followed an arcing trajectory over the comet's craggy landscape. It ricocheted off something hard, then slammed into the surface again, possibly against a cliff, like a hockey player hitting the boards.

Miraculously, when the lander finally came to rest it was still alive and communicating. Scientists hadn't the faintest clue where it was – and still don't – but it was sending back data all the same.

Based on the power coming from the lander's solar arrays, Ms. Lommatsch could tell it was in a partly shadowed location that received only 90 minutes of sunlight during each 12-hour rotation of the comet. That would not be enough to recharge the lander's batteries. Mission controllers soon realized they were in a race against the clock to squeeze as much science out of the little lander as possible before it fell silent.

"Since we didn't know what the situation is we had to completely change plans," Ms. Lommatsch says. "It was the most exciting thing that I probably have ever done in my life,"

For the next 2 1/2 days, a carefully choreographed sequence of operations that had been prepared years in advance was thrown out the window and rebuilt on the fly. Schedules went out the window, too, as the entire control room shifted to a 20-hour work day.

Each time a communication window closed, engineers had no idea if the lander would be alive when the next window opened. By the fourth window, the team was astonished that the intrepid spacecraft was still talking to them and struggling to carry out their final block of commands.

"That was the most critical block because we redesigned an entire sequence without testing it, so we're really lucky that everything worked fine and we got all the way to the end," Ms. Lommatsch says. "We were sitting there watching the voltage go down, just cheering it on and hoping it would finish that last sequence. We actually saw the lander die and come back three times. The battery was able to recover a little bit and find bit more charge and go on again and go off."

Once the communication link was broken for good, the team broke out the champagne. It was not the landing they had expected or trained for, but they had still managed to return science data from the surface of a comet – a first in the history of spaceflight.

Come May or June, the angle at which the sun is hitting the comet will shift enough for the lander to possibly start up again and resume its adventure. In the meantime, Ms. Lommatsch – who, at 28, is still early in her career as an aerospace engineer – says she knows she's lived through the experience of a lifetime.

"It was really interesting – extremely unexpected, but a lot of fun."

Ivan Semeniuk is The Globe's science reporter.