After lengthy hiatus, NASA’s Kepler has found another planet – a ‘super Earth’

Make a list of every groundbreaking mission NASA has attempted, and the Kepler spacecraft will sit very near the top of the heap. Its ability to detect planets on the other side of the galaxy has revamped our understanding of how solar systems form, which types of stars tend to pair with which types of planets, and shed light on the early dynamics of solar system formation. Unfortunately, problems with its gyroscopic stabilization system appeared to force an early end to its groundbreaking mission. A year ago NASA said it might have a way to bring the satellite back online, and now we know that the method has worked  — Kepler has found another super Earth.
The new method of balancing Kepler on just two reaction wheels relies on pressure from photons from the sun. Photons have no mass, but they do have energy and momentum — that’s why solar sails work. Solar radiation is sufficiently powerful that mission planners have to account for it — and that means it provides an additional source of balance for Kepler to push against.

NASA’s K2 balancing act

It wasn’t clear if the method proposed with K2 would offer sufficient resolution to find a planet, but we now know it will. Lead researcher Andrew Vanderburg reviewed data gathered by Kepler during its initial test of K2 earlier this year. The data revealed evidence of a planet, HIP 116454b. This newly discovered exoplanet is about 2.5 times larger than Earth, with a mass that’s 12 times that of Earth — it’s a super-Earth, in other words. The planet is very close to its parent star, completing an orbit every 9.1 days (as opposed to our Earth’s 365 days) — and because it’s too close, the planet is probably too hot to support life.

The new method of stabilizing Kepler isn’t perfect — Kepler’s reduced accuracy does hurt its ability to accurately pick out exoplanets — and the K2 method, while it allows the spacecraft to continue operating, isn’t quite as good as conventional research. The problem here is that while we can push back against solar radiation, Kepler is still attempting to balance on two wheels and a static force as opposed to having three maneuvering wheels to manipulate. That’s intrinsically more difficult for a spacecraft that needs to maintain an absolute position to make its measurements.

Kepler’s measured data in blue, with the corrected, filtered data below it

Fortunately, Vanderberg’s team was able to develop a software filtering algorithm that can adjust for the reduced stability of the probe while preserving the hints of planetary presence that Kepler’s mission requires it to detect.

Kepler, reborn

With a new successful detection under its belt, Kepler can be officially deemed back on active duty. Of course that declaration is somewhat delayed — the spacecraft has actually been making observations for quite some time since it was initially reactivated with the K2 parameters.
There have always been aspects of NASA that deserved crticism; a scathing story in the Washington Post this week detailed how Congressional pork projects and NASA administrative failures led to the building of a truly impressive rocket test center that was immediately mothballed post-construction due to a total lack of usefulness. When it comes to the program’s unmanned efforts, however, I’ve been consistently impressed by what the program pulls off on a shoestring budget. From Kepler to Curiosity, all the way back to the Galileo and Voyager probes, NASA has pushed back our understanding of the heavens, often inventing new ways of pushing old equipment past its original design lifetime and capabilities in the process.

Welcome back, Kepler — it’s a great Christmas present to have you back with us.