The Hubble Space Telescope is creeping ever closer to 30 years old, and nothing lasts forever. Scientists are acutely aware of that today after placing the orbiting observatory into safe mode following the failure of another gyroscope. The team is currently working to bring another gyro online, but Hubble may be limited in what it can do going forward.
NASA originally designed Hubble with six internal gyroscopes, but these components have a limited lifespan. Each one spins at 19,200 rpm inside a sealed chamber of high viscosity fluid. Gyroscopes use the principle of angular momentum to track movements, which allows the satellite to ensure it’s pointed in the right direction. These are not to be confused with reaction wheels, which actually move the telescope.
To operate optimally, Hubble needs three operational gyroscopes. The failure over the weekend took the telescope down to just two. Scientists are working to bring another sleeping gyro online to restore full functionality, but it’s not working. With two gyroscopes, Hubble would be limited in the objects it could observe. NASA replaced all six of Hubble’s gyroscopes in the final 2009 servicing mission. Three of the gyroscopes were the same type already installed at the time, and three of them were a new design intended to last longer. The newly failed gyro is the last of that old design, and it lasted about six months longer than expected.
There are two possible outcomes here. First, the team could get that backup gyroscope online and working correctly. That would restore Hubble to full working order until another of those gyroscopes fail — there would no longer be any backups. If the backup gyroscope doesn’t start working again, Hubble will never be quite the same. With only two working gyroscopes, Hubble will go down to single-gyro mode. According to Deputy Hubble Mission Head Rachel Osten, the single-gyro mode is not much worse than two gyros. That way, Hubble has a longer total lifespan.
Extending Hubble’s life is key right now. NASA’s next-generation James Webb Space Telescope has suffered from repeated delays. Primary construction has finished, but engineers are going over the design in order to address some anomalies that popped up during vibration testing. The telescope is not expected to launch until around 2021. When it does, it will be able to observe objects at greater distances with sensitive infrared scanners. It could help astronomers learn more about the origins of the universe, as well as nearby exoplanets.