Dead in the water
What happened: Kepler loses its second reaction wheel When it happened: March 2013
Disaster struck the Kepler mission in May 2013 when the telescope lost its second of four reaction wheels. These wheels are essentially gyroscopes which spin to move the telescope and point it towards distant stars.
The telescope needed three of these wheels to work, and after one was lost in July 2012, the worst happened in May 2013 when another failed.
After months of testing, scientists confirmed the telescope would not be able to return to its previous full operation. However, hope was not lost. Scientists came up with an ingenious solution to solve the issue, using the pressure of the Sun’s radiation to act as a makeshift third reaction wheel.
Thinking this would only be useful to observe supernovae and other larger phenomena, scientists were surprised in 2014 to find an exoplanet hiding in the latest batch of Kepler data following this repurposing. Two years later a new mission for the telescope had been approved, dubbed K2 or ‘second light’, and the discovery of exoplanets could continue.
The K2 mission meant Kepler could stay in use