After another gyroscope failure, the Hubble Space Telescope went into a "safe mode" this weekend. Only 2 of the Hubble's 6 onboard gyroscopes are working now, and it needs at least 3 to function properly. While operators on the ground saw this kind of failure coming and planned for it, the lost gyros will limit the Hubble's future capabilities. The Hubble's successor, the James Webb Space Telescope, isn't expected to launch until 2021 at the earliest. On the question of switching to one gyro, she added: "The plan has always been to drop to 1-gyro mode when two remain. There isn't much difference between 2- and 1, and it buys lots of extra observing time. Which the Astro community wants desperately." Prof Nial Tanvir, from Leicester University, UK, told BBC News: "You can in principle, with relatively little impact, continue to observe with one gyro. It may place some limitations on which part of the sky you can look at at any one time, and take a little longer to move from one target to another." He explained: "In that sense, it's not a catastrophe. However, if it's indicating another component on the telescope has died now, it does lead you to believe that the clock is ticking away on the overall lifetime… it would be a very great shame."