spaceSpace and Physics

NASA's Planet-Hunting Kepler Telescope Is Running Out Of Fuel


Jonathan O'Callaghan

Senior Staff Writer


NASA has announced that its groundbreaking Kepler telescope, which has discovered thousands of planets outside our Solar System, is nearing its end.

In an update from the system engineer for the mission, Charlie Sobeck, it was revealed that the telescope is running out of fuel. The team expect it to run out of fuel completely, and thus be unusable, within several months.


“While we anticipate flight operations ending soon, we are prepared to continue as long as the fuel allows,” Sobeck said. “The Kepler team is planning to collect as much science data as possible in its remaining time and beam it back to Earth.”

Kepler doesn’t have a fuel meter on board, but by monitoring the fuel tank’s pressure and the performance of its thrusters, the team has been able to work out how long it has left.

It needs its thrusters to point itself at distant stars and hunt for planets, but also to point its antenna to Earth and send its data to us. Without fuel this is impossible, and positioned 151 million kilometers (94 million miles) from Earth we can't refuel it, so the mission will come to an end when the fuel runs out. When this happens, it will simply be left where it currently is.

Before then the team is continuing to gather data. The spacecraft is currently on its second mission, called K2, which started in 2014. During this mission it has exceeded expectations and is currently in its 17th observing campaign – seven more than expected.

Kepler-186f was the first Earth-sized exoplanet to be found in a habitable zone. NASA Ames/JPL-Caltech/T. Pyle

The Kepler telescope, launched in 2009, has just a single instrument on board – a photometer, used to watch the light from distant stars. By doing this, it can detect planets as they transit in front. Once a planet is seen transiting three times, it can be confirmed.

This has proved wildly successful. Prior to Kepler’s launch, we knew of less than 100 planets outside the Solar System. Kepler has confirmed more than 2,500 planets so far, with a further 2,800 candidates at least awaiting verification.

Most of these have been large planets like hot Jupiters, gas giants that orbit extremely close to their star. It has also, however, found a number of tantalizing Earth-sized worlds in habitable zones.

All hope is not lost without Kepler. On April 16 NASA is launching a new planet-hunting telescope, the Transiting Exoplanet Survey Satellite (TESS) on a SpaceX Falcon 9 rocket, to take over the reigns.


But it’ll be a sad day when Kepler finally comes to an end. Its legacy, though, will live long into the future. And who knows, maybe one of the worlds it has found will be one just like our own, a habitable place for us to explore far in the future.


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