In the next couple weeks, NASA will try a last-ditch revival of a satellite called Kepler. Over the past four years, Kepler has been discovering planets outside our solar system at an amazing rate.
A couple months ago, the satellite had a gyroscope lockup, so we can no longer rotate the telescope accurately. The success and tragedy of this satellite are good reminders that ambitious science is still worth it, but we should always prepare ourselves for things going wrong.
But first, the success: Until the mid-1990s, we had no idea how many planets exist around other stars. We knew quite a bit about the eight planets around our sun, but we didnt know whether other planets were common or a one-in-a-million event.
Starting in the 1990s, we started discovering other planets by observing their effect on their parent stars. Some planets make their parent star wobble back and forth, which we measured. Other planets blocked out some of their parent stars light, which we could also measure.
It was a long process, because we didnt have a great idea of which stars to look at or when to look at them, so there was a lot of needle-in-a-haystack-style searching. It paid off, though. We discovered hundreds of planets (remember, there are 100 billion stars in our galaxy, so these are still small numbers).
Enter Kepler. Some bold astronomers at NASA decided it was time to launch a satellite to find more planets. Getting above the atmosphere makes things a lot easier, but it is expensive and you cant fix any serious technical problems when the satellite is orbiting the sun.
In 2010, after about a year of observing, Kepler scientists started publishing results that were astounding. We were finding planets everywhere. It appears that about half of the coolest stars have Earth-sized planets. Most of those planets are closer to their star than Earth, and thus not habitable by our standards. However, one in six such stars probably has an Earth-sized planet at the right distance to potentially have life.
Wow. That number is higher than most astronomers were hoping for. It means there might be planets like Earth very close to us.
This didnt have to be true. If planets were uncommon, Kepler would have found almost nothing, and the mission would probably have been labeled a failure. They took a real risk with this mission, and it paid off.
But then we got the news a couple months ago about the mechanical problem. Kepler, like all telescopes in space, uses gyroscopes to move itself. It has four. Two of them broke. Without them, the telescope cannot point at the stars to take its data. In the next couple weeks, NASA engineers will try to revive the gyroscopes. When something like this breaks, however, we typically dont have a lot of ways of fixing it, and the tricks well try are probably not going to work.
Kepler was scheduled for a three-year mission, so in that limited sense it was a success. However, everyone I know was hoping it would discover planets for many years to come. Overall, the news has been a bit of a punch to the gut to the astronomy community.
In the current political environment, such an end might be seen as a failure. However, thats not how we should think about it. This was a high-risk, high-reward project. That means we had the opportunity to really discover something new, and we did that. However, high risk means things can go wrong. They did, and the mission is over sooner than anyone would like.
In science, we dont come across guaranteed-to-work projects often. If we want spectacular results, we have to prepare ourselves for the risks. I, for one, am glad Kepler was funded, and I eagerly look forward to the next mission.