NASA's Kepler telescope lost two of the four wheels it used to aim at stars — engineers gave it a second mission by balancing the spacecraft against the pressure of sunlight

NASA's Kepler telescope lost two of the four wheels it used to aim at stars — engineers gave it a second mission by balancing the spacecraft against the pressure of sunlight

When Kepler lost a second reaction wheel, engineers balanced it against sunlight and turned it into K2. Here's how the trick worked, what it cost, and the software that made its shaky data usable.