Charlie Sobeck AIR & SPACE INTERVIEW
Engineer, NASA Ames Research Center, California
Air & Space: What are the advantages of Kepler’s simple design?
What we’re basically looking for is the shadow of planets as they circle their stars. As the planets orbit their host star, if the alignment between the star, planet, and telescope is correct, we will see that planet transit right in front of the star, and we can measure a dimming in the brightness of the star. Conceptually, this is a very simple principle to understand.
Are there any disadvantages to such a streamlined design?
No one telescope is going to do all things. For what Kepler was designed to do—find these planets and characterize them—we were able to do that job really well with what we had. The next thing that we would like to do in understanding exoplanets is to understand whether there are atmospheres and if there are, what might be in those atmospheres. To do that, you would need to be able to take a spectrum: be able to separate the light coming from a star into different wavelengths. Kepler does not have that ability.
Kepler has exceeded its original lifespan of three and a half years. Do you know how much longer it will return data?
The spacecraft itself is still capable of working quite well, and what’s going to limit its operation right now is fuel. We do burn fuel slowly, and we have a limited amount, but we believe that we have enough fuel to last another maybe three years.
It’s not operating for the Kepler Mission because it can no longer point at the Kepler field of view [an approximate 100-square-degree section of sky between the constellations Cygnus and Lyra]. We’ve lost two of our four reaction wheels [which point the spacecraft and control its attitude]. But we’ve been able to repurpose the spacecraft and the instrument and look at other parts of the sky. And we call that mission “K2.”
How many Earth-size planets has Kepler detected to date?
I’m guessing a few hundred Earth-size planets. Not necessarily in the right orbit to be Earth-like at all. Many of them are going to be very close to their stars, so they’re going to be very hot planets. What we’re really interested in is in the Earthsize planets in the habitable zone around stars that are like our sun. And we’re only now starting to uncover that within the data. So we don’t have any confirmed planets in that category. We do have now six candidates, and we have to follow up on those to confirm if they are real planets. That would be the ultimate prize: to find that kind of a planet—one that resembles the Earth.
SOBECK IS PROJECT MANAGER for the Kepler Mission. Launched in 2009, the Kepler space observatory, now in a heliocentric orbit, was designed to look for Earth-size planets around other stars. The Kepler team received this year’s National Air and Space Museum Trophy for Current Achievement.