About the SA Blog Network



Opinion, arguments & analyses from the editors of Scientific American
Observations HomeAboutContact

NASA’s Kepler Mission Endangered by Hardware Failure

The views expressed are those of the author and are not necessarily those of Scientific American.

Email   PrintPrint

NASA's Kepler telescope

Kepler artist's conception. Courtesy NASA

The prolific planet-hunting spacecraft that has already discovered some of the most intriguing exoplanets known has abruptly lost the capacity to carry out its mission, NASA officials announced May 15.

NASA’s Kepler spacecraft, which launched in 2009, relies on an array of flywheels, or reaction-wheel assemblies, to stabilize the pointing of its telescope toward a field of stars in the Milky Way. Kepler needs three of its four reaction wheels in working order to carry out its exoplanetary mission, and the spacecraft had already lost one wheel in July 2012. Now a second wheel appears to have failed, and unless it can be revived the spacecraft’s search for extrasolar worlds may be over.

“Basically we need three wheels in service to give us the pointing precision we need to find planets,” Kepler principal investigator Bill Borucki of the NASA Ames Research Center said in a teleconference with reporters. “Without three wheels it’s unclear whether we could do anything of that order.”

One of the remaining reaction wheels, which had been giving indications of trouble for some time, was discovered to have failed yesterday. The spacecraft is programmed to go into a protective safe mode when it loses its ability to orient its telescope. “Yesterday we turned on the antennas on the ground and we found the spacecraft was in safe mode,” said Charles Sobeck, deputy project manager for Kepler at NASA Ames, adding that mission controllers then attempted to fire up the reaction wheels. “We did that and we initially saw some movement of the wheels, but wheel four went back to zero speed.” He said the plan now was to put Kepler into a parking mode that will preserve its fuel while mission planners decide what to do next.

Kepler has already identified more than 100 confirmed exoplanets, including nearly all of the worlds discovered to date that are comparable in size to Earth. But mission scientists have yet to deliver the prize that astronomers have been waiting for: an Earth-size planet orbiting in the habitable zone of a sunlike star—in other words, the first planet that might pass for our own. Even more important, it is hoped that Kepler will reveal how common such planets are, thereby providing an indication of how many potentially habitable locales exist in the galaxy.

But Borucki said that “we’re well on our way” to determining the prevalence of roughly Earth-size planets in the habitable zone, noting that the spacecraft has already collected roughly two years of data “that has not been fully searched for planets.” Added John Grunsfeld, associate administrator for NASA’s Science Mission Directorate, “We’re not ready to call the mission over, but by any measure this has been a very successful mission.”

About the Author: John Matson is an associate editor at Scientific American focusing on space, physics and mathematics. Follow on Twitter @jmtsn.

The views expressed are those of the author and are not necessarily those of Scientific American.

Rights & Permissions

Comments 8 Comments

Add Comment
  1. 1. N a g n o s t i c 6:57 pm 05/15/2013

    Guess we’ll have to get the Chinese to fix it.

    Link to this
  2. 2. N a g n o s t i c 7:00 pm 05/15/2013

    What’s the point of finding other planets anyway, when we have so much work left to do here on Earth making life safe for the unproductive.

    Link to this
  3. 3. Owl905 11:39 pm 05/15/2013

    Kepler’s 3 1/2 year mission was completed last November. This is bonus-round territory. The alignment wheels are failing due to friction. They nursed it for a few weeks, thinking the lubricant might spread, but it didn’t respond. Hopefully, in the crackerjack box of data waiting to be analyzed is ‘the prize’.

    Link to this
  4. 4. syhprum1 12:13 am 05/16/2013

    Why do the flywheels have bearings that require lubrication ? are there not magnetic suspension systems available such as are used in power storage flywheel.

    Link to this
  5. 5. YangHui 7:14 am 05/16/2013

    @syprum1- I’m not familiar enough with Kepler’s design to say for sure, but I would guess that the magnets in more sophisticated flywheels might disturb Kepler’s sensitive telescope.

    Link to this
  6. 6. sault 10:27 am 05/16/2013


    Magnetic bearings would have to survive launch and function on-orbit for the entire lifetime of the spacecraft just like physical bearings. Maybe designig a system that could satisfy these requirements would make the bearings too heavy / bulky or unable to satisfy the lifetime requirements. In addition, satellite builders are notoriously conservative in their designs (for good reason) and magnetic bearings might not be “space qualified” for this specific application yet. Since flywheel failures lead to mission failures, the risk tolerance for their design is increadibly low.

    Link to this
  7. 7. cbsimkins 5:14 pm 05/16/2013

    I was reading about the Kepler mission and thought about the telescope. Now I really like engineering and love the pictures we get of astronomical stuff; really beautiful and thought provoking. But I think about the Kepler mission, search for exoplanets, and then wonder how important this is at this time. The thing is that even if you found a planet, exactly like earth with a star exactly like our sun, then what does that mean? Well, the experts will tell you that it is possible, even likely, that there will be sentinent beings, and we might be able to communicate with them. So, is this really, really, important in the larger scheme of things? After all, we are here for one among many reasons, because the huge dinosaurs were all killed off, apparently by a large asteroid. And if that hadn’t happened, we would not likely be here today. So maybe we need to think about whether or not it is a great idea to try to fix the gyroscopes, reaction wheels, on the Kepler, at least any time soon.
    Maybe it would be just as interesting to hold a raffle with a buy in price of 100 million dollars, and requiring at least 100 entrants. Then the winner could go on a flight to repair the Kepler, and have their name affixed to the name of the telescope; like Kepler-Charlie.

    Link to this
  8. 8. david123 9:16 am 05/18/2013

    Kepler completed its mission and essentially died on schedule. There is still 2 years of unprocessed Kepler data in the pipeline to keep plenty of astronomers plenty busy. In the meantime, Kepler’s scheduled replacements are pretty much right on schedule. And the technology of these devices (Kepler, strictly speaking, is not a telescope) both on the ground and in orbit, just keeps getting better and better all the time.

    We are going to find at least a few true-earth candidates in the next 10 years. I am quite confident about that. And the prospect, in my opinion, is extremely exciting, even if there’s nothing we can actually DO about it.

    Link to this

Add a Comment
You must sign in or register as a member to submit a comment.

More from Scientific American

Email this Article