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| Human World | Space on May 16, 2013

Planet-hunting Kepler spacecraft in trouble

It went into safe mode on Tuesday, May 14 after the #4 reaction wheel, needed to orient the spacecraft, would not spin.

NASA’s $600 million Kepler space observatory – launched in 2009 with the goal of discovering Earth-like planets in distant solar systems – is in trouble. NASA reported the problem yesterday (May 15, 2013): a malfunction in the part of the spacecraft that enables it to aim precisely toward distant stars, in the planet search. Spacecraft controllers learned on Tuesday that Kepler had gone into a safe mode. The reason was that the #4 reaction wheel needed to orient the spacecraft would not spin, despite repeated attempts from Earth to prompt it to continue spinning, according to Associate NASA Administrator John Grunsfeld.

He told reporters at a press conference yesterday that NASA engineers are trying to figure out whether they can get the balky part back into service or whether they can resume control by another method, adding,

We’re not ready to call the mission over, [but at roughly 40 million miles from Earth], Kepler is not in a place where I can go up and rescue it.

In July of last year, Kepler’s #2 reaction wheel also failed. Kepler engineers say the spacecraft needs at least three reaction wheels to be able to point precisely enough to hunt for planets orbiting distant stars.

So is the mission over? It’s too early to say. NASA engineers said at the press conference yesterday that, if the wheel doesn’t start back up, they think they can use the spacecraft’s on-board thrusters to help point it. Not exactly an elegant solution, and possibly not as precise as using the original system with reaction wheels. So the fate of the planet-hunting spacecraft still isn’t known.

Kepler, planet-hunter.  Image via NASA

Kepler, planet-hunter. Image via NASA

Kepler completed its primary mission some time ago. The mission was extended in 2012. If Kepler’s controllers have to call it quits now, the mission still has been unbelievably successful. Do you notice how many of the known exoplanets – planets orbiting other stars – carry the name Kepler? That’s because this spacecraft has discovered a significant fraction of all known exoplanets, with 888 confirmed planets known as of today (May 16, 2013). Plus Kepler found hundreds more planet candidates, now waiting to be confirmed.

In recent years, astronomers have begun to say that many if not most of the billions of stars in our Milky Way galaxy may have their own planetary systems. Whatever Kepler’s fate in the coming days and weeks, astronomers will surely continue striving to discover and analyze these distant worlds.

Bottom line: NASA’s planet-hunting Kepler spacecraft went into a safe mode on Tuesday, May 14 after the #4 reaction wheel needed to orient the spacecraft would not spin. NASA engineers are still trying to prompt the wheel to do its job.

Read more from Phil Plait on Slate: Kepler planet-finding mission in jeapardy