Almost a decade since its launch, and 2,245 exoplanet discoveries later, Nasa’s plucky Kepler telescope is said to be on its last legs.
System engineer Charlie Sobeck has announced that Kepler’s fuel tank “will run dry within several months” as the agency gears up to cease flight operations and awaits the dreaded fuel-low warning.
Kepler is an observatory dedicated to finding planets outside our solar system. Since its 2009 launch, the Kepler Space Telescope has helped astonomers discover 2,245 exoplanets, with a further 2,342 yet to be confirmed. At least 30 of these are exoplanets that are less than twice the size of Earth and which sit in the habitable zones of their stars. This increases the chances of finding life on such exoplanets. Many of these exoplanets were spotted in a small region of the constellation Cygnus, at which Kepler was pointed for the first four years of its mission.
In addition, K2, the second part of Kepler’s mission, has found 479 exoplanets, with 307 still to be confirmed.
“Our current estimates are that Kepler’s tank will run dry within several months—but we’ve been surprised by its performance before,” said Sobeck. “So, while we anticipate flight operations ending soon, we are prepared to continue as long as the fuel allows.”
The “surprise” Sobeck refers to an incident in 2013 when a mechanical failure almost knocked Kepler out of action.
Before Kepler’s death, Sobeck and his team plan to collect as much data as possible before the loss of the fuel-powered thrusters stops them from being able to aim the spacecraft in the way they previously have. Sobeck added that the team even has plans to take final calibration data with the last bit of fuel, “if the opportunity presents itself.”
“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,” continued Sobeck. “But in the end, we only have an estimate – not precise knowledge.
“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 bring it back to Earth. We will continue to provide updates on the science and the spacecraft, which has yet to show warning signs.”
Kepler: What is it?
You’ll hear the term “telescope” to describe Kepler, although that’s only half of the story. Kepler is in fact a space observatory, launched by Nasa in March 2009 to discover Earth-sized planets orbiting stars.
The spacecraft is named after German astronomer Johannes Kepler (1571-1630), esteemed contemporary of Galileo, and the man responsible for ameliorating the refracting telescope.
Kepler: What does it do?
Kepler is kitted out with a photometer, an instrument that monitors the brightness of more than 145,000 main sequence stars – stars which fuse hydrogen atoms to form helium atoms in their cores, making up about 90% of stars in the universe.
The data picked up by Kepler’s photometer is transmitted to Earth, where it’s analysed – with the help of Google’s AI – to discern periodic dimming. These lapses in brilliance (of the stars, that is, not Nasa’s engineers) are caused by exoplanets in orbit, obscuring their host star.
Its official scientific objective is “to explore the structure and diversity of planetary systems”, which includes determining the sizes and shapes of such planets, estimating how many planets there are in multiple-star systems, studying orbit sizes and planet reflectivities, sizes, masses and densities of giant planets and more.
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