NASA’s launch of the Kepler space observatory in March of 2009 was intended to move mankind closer to solving one of the great mysteries of science — are we alone in the Universe? The 15-foot long, 2,300-pound spacecraft, built by Ball Aerospace & Technologies, is equipped with a telescope and computer systems sufficiently sensitive to detect minute changes in the brightness of stars thousands of light years away.

Such fluctuations are a tipoff to the presence of planets, since orbiting planets will intermittently dim some of a star’s intensity. A marvel of technology, Kepler has found proof of more than 2,300 planets outside our solar system, giving scientists a reason to suspect there may be an abundance of rocky, Earth-sized planets — perhaps billions of them — in habitable zones just within our own galaxy.

Yet Kepler’s sophisticated technology has been difficult to keep working. Two of its four “reaction wheels” — flywheels that are essential to fixing the telescope’s aim at its targets — failed unexpectedly in 2012 and 2013, forcing engineers to revamp the planet-hunting mission so thoroughly they re-christened it K2. In April, mission operators had to scramble again as Kepler’s main computer shut down. The task of solving those daunting problems fell mainly to a few dozen specialists led by Marcie Smith, Kepler’s Mission Director and 35-year veteran at NASA’s Ames Research Center. She spoke with BREAKGROUND about Kepler and its challenges.

BREAKGROUND: What’s been your single most thrilling moment as a Mission Director?

Marcie Smith: It’s hard to say. Initial acquisition, when you first get data from the spacecraft and know that it survived launch, is incredibly satisfying. But overcoming challenges is when you really learn how things work and recovering from anomalies, be they big or small, is very rewarding too.


BG: Tell us about the loss of the two reaction wheels. That sounds like a crippling situation.

MS: It was. That had us very worried. We use the reaction wheels to point the line of sight of the telescope. We have the pressure of the sun to deal with. The telescope has most of its weight at the bottom. The center of mass is really toward the bottom where the electronics is. If you imagine the solar wind as being a wind, and you’re sitting there with the telescope pointing straight up, it’s going to tilt away from the wind. It’s a very light force, but there’s nothing else [in space] so the spacecraft responds to it.


BG: How did you get it to fly right?

MS: We spent almost a year testing how to use a new concept that one of the engineers at Ball Aerospace came up with. He figured out how to [keep Kepler oriented] so that it’s always lying in the plane of its orbit. The sun moves up and down the spacecraft, but it’s always moving along a line of symmetry so there’s not that tilting effect around the line of sight. The two remaining reaction wheels keep the line of sight of the telescope pointed at the observing field.


BG: What effect did that have on the mission itself?

MS: It saved it, but it changed it. Originally, we were looking for a long time at a certain field [in the sky]. Now, because the sun does move [in relation to the spacecraft], we’re limited to about 80 days of looking at a particular field. We stare at a different field every 80 days. We can still do planet finding, but we can only find shorter-period planets.

Image courtesy of NASA

BG: How personally stressful is it trying to deal with a crisis in space?

MS: A real crisis is stressful because it’s a combination of not having all the data you need, slow response time due to the distance of the spacecraft, and having to make decisions where you don’t understand the fine details but your team does. Add to that a lack of sleep mixed with lots of coffee and junk food and you find you are physically stressed as well as mentally challenged.


BG: Kepler is described as being in an Earth-trailing orbit. How far away is it?

MS: About 120 million kilometers [74 million miles], or about 8/10th of an astronomical unit, which is the distance from the sun to the Earth. It’s slowly getting farther away. Even if we tried to talk to it all the time, the round-trip light time is 13 minutes. We check on it about twice a week.


BG: A few months ago, you encountered another problem. What happened then?

MS: We were checking on the spacecraft, and we were pretty excited because we were expecting to confirm the state of a new observing campaign. Unexpectedly, we found that it was not in science mode. In fact, it was in what we call emergency mode — a mode the [onboard] computers can put it in when things have gone wrong. The people at the Mission Ops Center learned first — at Boulder — and they called Ball and Ball called us. We gathered here at my office at Ames to try to see what to do.


BG: What was the anomaly?

MS: We didn’t know for quite a while. We have a main computer that runs the spacecraft most of the time. It’s always checking for sun angles and battery voltages — all the engineering parameters to know if the spacecraft is healthy. The flight computer started seeing problems throughout the spacecraft. The computer said, ‘This is too hot, this is too cold — I’d better turn it off.’ A lot of things shut down, more than we wanted. The problem seems to be something that generated a lot of bad data, and it only lasted about 12 seconds.


BG: What difficulties did you encounter trying to fix something so far away?

MS: In emergency mode, the back-up computer said, ’I’m taking over,’ and it did so successfully. But when we’re in emergency mode we can’t get very much data out. The back-up computer is limited. Kepler is not only far away, but we were in a limited-data mode with limited windows of communication. We’re sending commands while the spacecraft is rotating. We’d get a little bit of data for 30 minutes every two hours.

BG: Sounds very nerve-wracking.

MS: It’s a combination of nerve-wracking and frustrating, because it’s hard to do anything even once you know how to do it. We’d say, “This is what we’re going to do on the next revolution.” There is no automatic recovery from emergency mode.


BG: Kepler is now functioning again. How well has the spacecraft fulfilled its objectives so far?

MS: The original mission was very successful. We wanted to operate for 3½ years; we were able to operate almost four. It’s not just about finding planets. What we need to do is come up with what we call the occurrence rate. How common are planets? How common are small planets? The final results are still in the works.


BG: What answers lie ahead?

MS: My interpretation is that [planets] seem to be pretty common. Whether we can say that Earth-size planets in the habitable zone are common or not, I don’t know. Now we can start looking for planets around nearby stars. None of that will help us get to those planets, but it might help us figure out where we want to go.


BG: How does it feel personally to be involved in such an historic project?

MS: Working for NASA, in general, is a real thrill. Working on something that makes such a profound change — it’s an extension of the idea that we’re not the center of the Universe. It’s pretty amazing to be a part of that discovery.

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