2 years ago the Kepler probe was dealt a critical blow. Out of 4 reaction wheels, the devices which keep the telescope pointed in the right direction, only 2 remained functioning. This meant that the telescope was no longer able to maintain the level of precision required to continue its planet hunting mission. However there was a bold plan to continue Kepler’s mission, albeit in rather different capacity. Kepler could use the solar pressure exerted by our sun as a third reaction wheel, allowing it to continue imaging the sky and looking for planets. It wouldn’t be able to look at the same piece of sky for the entire time however and would be limited to viewing periods of approximately 80 days each.
Whilst this was a significant downgrade in Kepler’s abilities it was a far better option than just retiring the spacecraft completely. In its previous incarnation Kepler was able to track hundreds of thousands of stars continuously, allowing us to detect numerous planets orbiting their parent stars. In its current incarnation Kepler will only be able to detect planets with shorter orbits which are unlikely to be the Earth-like ones we’re all hoping for. Still even in that reduced capacity Kepler has been able to identify no less than 100 new exoplanets with over 200 additional candidates awaiting confirmation by other methods. For a telescope that may have been written off that’s an amazing accomplishment, but it doesn’t just stop there.
As the above diagram shows Kepler has to reorient itself every so often so that light from the sun doesn’t enter the telescope (this would damage its sensors). Not all of these orientations are good for looking for exoplanets however and so Kepler has been put to other uses. Several of the viewing periods have been dedicated to looking at planets within our own solar system, giving us insights into their behaviour like we didn’t have before. It recently spent 70 days observing the weather on Neptune and the motion of its moons, the longest observation of the planet to date. Additionally another observation period is being dedicated to doing a similar investigation on Uranus.
Like I’ve said before second chances with space missions are rare and it’s incredibly heartening to see Kepler producing these kinds of results 2 years after its reaction wheels failed. Whilst these might not be the exact results we’re after they’re still invaluable pieces of data that will help broaden our understanding of both our universe and galactic backyard. I’m sure that we’ll continue to see great things from Kepler and, hopefully, many more exoplanets.