Kepler Space Telescope Is Almost Out of Fuel
Source: Popular Mechanics
After an extraordinarily durable run, NASA's Kepler space telescope is finally running out of gas. The agency expects Kepler to burn the last of its fuel within the next several months, ending nine years of incredible science searching for planets beyond the solar system. Trailing behind the Earth as it orbits the sun, the space telescope has located more than 2,500 confirmed exoplanets.
Launched in 2009, Kepler is designed to scan the skies for planets by detecting the dip in brightness of their host stars as the planets pass in front. The space telescope's primary mission was only to last three and a half years, but after "outstanding success," its mission was extended through 2016.
However, mechanical problems began to plague the space telescope in 2012 and 2013. Two of its reaction wheels failed, which are used to point the telescope at target stars and their orbiting planets. The telescope still works, but the craft carrying it could not stabilize the optical components, threatening to end the mission. But then NASA found a fix.
"Using the sun and the two remaining reaction wheels, engineers have devised an innovative technique to stabilize and control the spacecraft in all three directions of motion," NASA explained at the time. "To achieve the necessary stability, the orientation of the spacecraft must be nearly parallel to its orbital path around the sun."
Read more: https://www.popularmechanics.com/space/telescopes/a19444952/kepler-space-telescope-is-almost-out-of-fuel/
It's a good thing the TESS is set to launch next month. Kepler will be sorely missed.
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Now it will just have to wait for help from a passerby. 
