NASA’s Kepler space telescope has been in orbit about 94 million miles from Earth for nine years. The mission has been a success and has survived some mechanical failures to keep operating. The mission for Kepler is coming to an end because it is almost out of fuel. NASA expects the fuel to run out within several months.
The biggest challenge during Kepler’s mission came in 2013 when its primary mission ended when a second reaction wheel broke. That left the space telescope unable to hold its gaze steady. NASA was able to salvage the telescope by using the pressure of sunlight on the spacecraft to maintain its position and rebranded the mission as K2.
NASA originally expected that Kepler could conduct 10 campaigns consisting of fuel burns to change its gaze every three months. As it turns out NASA was too conservative, and this month Kepler entered its 17th campaign. While fuel is running out, NASA plans to continue its mission as long as possible.
Kepler has no fuel gauge, NASA is monitoring for signs that fuel is running low. These signs include a drop in the fuel tank pressure and changes to thruster performance. NASA plans to capture as much data as possible from the telescope before fuel runs out.
The fuel is needed to aim the telescope at the Earth for data transfer. NASA wants to stop collecting data while it is confident it can still aim the spacecraft at the Earth to transfer the data. Taking over for Kepler will be the Transiting Exoplanet Survey Satellite known as TESS set to launch April 16.