NASA’s Kepler spacecraft has delivered groundbreaking data to the science community during its remarkable nine-year journey. Its hunt for Earth-like planets in habitable zones of stars has not only assisted in the search for extraterrestrial life, but also provided crucial clues to the formation of our universe. Sadly, though, the exoplanet-hunting telescope isn’t exempt from the cheesy “all good things must come to an end” expression. After almost a decade in space, Kepler is expected to run out of fuel within the next few months. Although its expiration is inevitable, its legacy will burn indefinitely.
Without a fuel gauge, Kepler’s demise is simply estimation, and it hasn’t shown signs of slowing down just yet. NASA is continually monitoring the craft for signs of low fuel, like changes in thruster performance and fuel tank pressure, but no warnings have arisen so far. Kepler will continue to carry out research campaigns and send scientific data back to Earth until its thrusters, which are needed to aim the spacecraft and transmit data, begin to show signs of fuel depletion.
Spacecraft typically have to reserve fuel for a final finish, like Cassini’s final descent into Saturn’s atmosphere, so they don’t collide with other satellites, contaminate extraterrestrial environments, or come crashing down to Earth. Kepler, however, is in an isolated area 94 million miles (151 million kilometers) from Earth, so its last bit of fuel can be used to continue observing and collecting data.
Kepler, which launched from Florida’s Cape Canaveral Air Force Station on March 6, 2009, had a specific assignment —survey our area of the Milky Way for Earth-size planets within habitable zones of stars. Its mission was to keep a continuous eye on a specific galactic zone that houses roughly 150,000 Sun-like stars and search for the faint dimming that occurs when a planet orbits its host star. Unfortunately, this mission was cut short in May 2013, when Kepler’s second of four reaction wheels, which stabilize the craft, broke. At that point, the orbiting observatory had confirmed the existence of 2,342 exoplanets.