Spaceflight Insider

Era ends as Kepler planet hunting satellite runs out of fuel

Artist's concept of NASA's Kepler Space Telescope on its K2 mission

This artist’s concept shows NASA’s Kepler Space Telescope on its K2 mission. Image Credit: NASA/JPL-Caltech

With fuel tanks low and no gas gauge, the Kepler spacecraft is in the final months of operations. The planet hunting satellite was launched in March 2009 atop a United Launch Alliance (ULA) Delta II rocket from Cape Canaveral Air Station in Florida. The planned mission duration was 3.5 years but the spacecraft has exceeded all expectations and continues to function.

Kepler uses three reaction wheels to position the spacecraft as it points it’s sensors skyward looking for exoplanets and relays that data to scientists on Earth. Two of those reaction wheels have failed, the last one in 2013 ending the primary mission. Engineers on the mission team considered the problem and devised a new way to orient the spacecraft.

By using the pressure of the solar wind and the ship’s onboard thrusters they were able to extend the life of Kepler. The new mission, dubbed K2, continued the search. However, since that time Kepler has relied on it’s chemical thrusters to steer the satellite to send data back to Earth.

“Without a gas gauge, we have been monitoring the spacecraft for warning signs of low fuel—such as a drop in the fuel tank’s pressure and changes in the performance of the thrusters. But in the end, we only have an estimate—not precise knowledge. Taking these measurements helps us decide how long we can comfortably keep collecting scientific data.” said Charlie Sobeck, a system engineer for the Kepler space telescope mission, in a press release. “It’s like trying to decide when to gas up your car. Do you stop now? Or try to make it to the next station? In our case, there is no next station, so we want to stop collecting data while we’re still comfortable that we can aim the spacecraft to [send data] back to Earth.”

Current estimates are that Kepler’s tanks will run dry within several months, according to NASA. During that time the Kepler team plans to continue flight operations and collect as much data as possible. The hope is to complete the work and beam the data back to Earth before the fuel runs out.

The Kepler mission has been ongoing for over nine years under some of the hardest conditions possible. Extreme temperatures, cosmic rays, and solar winds have taken a toll on the vehicle but it still continues to perform even as it runs out of fuel. According to the NASA Exoplanet Archive, the number of confirmed planets found by the spacecraft exceeds 2,600. Of those, 30 have been confirmed to be less than twice Earth-size and in their parent star’s habitable zone.

Despite the upcoming loss of the Kepler spacecraft, the search exoplanets will continue. This April, NASA will launch the Transiting Exoplanet Survey Satellite (TESS) from Cape Canaveral, Florida. This new spacecraft will look for exoplanets orbiting the brightest stars within a 300-light-year radius from Earth.

Video courtesy of NASA’s Ames Research Center





Joe Latrell is a life-long avid space enthusiast having created his own rocket company in Roswell, NM in addition to other consumer space endeavors. He continues to design, build and launch his own rockets and has a passion to see the next generation excited about the opportunities of space exploration. Joe lends his experiences from the corporate and small business arenas to organizations such as Teachers In Space, Inc. He is also actively engaged in his church investing his many skills to assist this and other non-profit endeavors.

Reader Comments

It seems to me that ion motors would make a longer lasting and more reliable attitude control mechanism. But I havent seen them used in this way. What am I missing?

Would this be a good candidate for attaching a fuel tug to act as a replacement propulsion system?

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