Hubble Space Telescope Goes into Safe Mode: Beginning of the End?

The venerable Hubble Space Telescope has been put into safe mode by mission managers. One gyro has failed and another is malfunctioning. Only two directional gyros remain.

Published on 9th Oct, 2018

Hello Space Fans and welcome to another edition of Space Fan News. Bad news I’m afraid for the venerable Hubble Space Telescope. Project Scientists tweeted earlier today that Hubble has been placed in safe mode as two of it’s critical gyros used for pointing have failed. As sad as it is, it appears that the clock is ticking on this 28 year old masterpiece. Long time subscribers to this channel know very well just how important the Hubble Space Telescope is to us here at Deep Astronomy. We were founded on one of the most important images ever taken with with it: the Hubble Ultra Deep Field. Well this weekend, HST was placed into safe mode as they try to figure out what when wrong when one of them failed on Friday. Then, when they tried to switch on one of the backups, it turned on, but was acting strangely and appeared to be malfunctioning. This leaves Hubble with only two fully functioning gyros. The thing is, it needs three to work optimally. Hubble has six gyroscopes that when spinning always point in the same direction. They are used as a reference point that enables Hubble to look at specific points in the sky very accurately. It needs this accuracy because the field of view of Hubble is so small that it is less than the width of a grain of sand held out at arms length. So it needs to know exactly where it is pointing at all times and the gyroscopes tell it that…. And it need at least three to work properly, one gyroscope for each axis of rotation. These types of gryos are called Control Moment Gyros and are used in lots of spacecraft, and they degrade over time. As you can imagine, having something always spinning for years at a time can wear out, even when you make them to space qualified standards, so gyroscopes are always a mission limiting component. Let’s remember that the only reason Hubble’s been up there for 28 years taking data is that it’s been serviced five times since its launch in 1990. So what are they doing right now to fix Hubble? Operators are now trying to revive the gyroscope that went screwy when the last one failed. If they can’t get that one to work right, then the observatory may have to operate on just one. This would conserve the remaining gyro but at a cost of reduced pointing ability. Hubble mission managers had always planned on dropping to one gyro if they ever got down to two because there isn’t much difference between using two versus using one. It also buys a lot more observing time by keeping one gryo on reserve. They state that, 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 but it can be done for quite a while. As you can imagine, Hubble is in great demand among astronomers and no one wants to see it die, and with JWST being delayed until 2021, at the earliest, then we’d have some dark ages (literally) in store if there’s a gap between when HST dies and JWST finally gets up there. Even with JWST though, there’s some things only Hubble can do. For example, if you’’re interested in hot, young stars and galaxies that are bright in the ultraviolet, there is no other telescope in orbit or being built that can see this wavelength range. The possible mission of LUVOIR and other future telescopes may have UV capability, but there isn’t anything yet. Gyroscopes have always been problematic for Hubble, they degrade over time and have had problems. There are two kinds on Hubble, three of an older type and three newere gyros that were expected to last five times longer. The one which failed on Friday was the older kind, and when one of the newer gyros was switched on, it misbehaved, but at least as of today, mission team members are hopeful they can bring it back, giving us three gyros again. So this is sad news Space Fans, it appears the clock is ticking on our venerable old friend. Since the 1990’s nothing has changed our perception of our view of our place in the universe quite like Hubble. Here’s hoping we can squeeze every possible photon from the universe that we can get from this amazing spacecraft. I promise I will keep you posted. That’s it for this episode Space Fans, SFN is made possible by these amazing people, Deep Astronomy Patreon Patrons who want to make sure we keep producing content that provides perspective on our place in the universe. Thank you all so much. Thank you for watching and as always, Keep Looking Up!