Courtesy STScI and NASA
What Were NASA's Options?
NASA's first option was to not do anything at all. The Hubble maintains its orientation using a complex navigational system. This system in turn relies on six gyroscopes, which help the Hubble maintain its orientation in relation to the Earth. Without proper maintenance, the gyroscopes could fail. After such a failure, NASA would be unable to direct Hubble in the right direction to gather data and images.
The Hubble's batteries are also starting to die. If they aren't replaced, the Hubble will lose power and stop functioning. If NASA chose not to act, the Hubble would likely fail before 2009. NASA would be unable to gather the kind of information and images the Hubble was designed to collect until a replacement telescope could launch -- something that isn't scheduled to happen until 2013.
Eventually, the dead telescope would suffer orbit decay. That means the Earth's gravity would gradually pull the telescope closer to the planet. Left alone, the telescope would reenter the Earth's atmosphere and crash to Earth. NASA probably wouldn't let that happen on its own -- it would be too dangerous without knowing where the telescope would land. Instead, NASA would likely send up a mission, either manned or unmanned, to retrieve the telescope safely or crash it into an unpopulated area, such as an ocean. NASA considered just letting the Hubble die, but an enthusiastic outcry from the scientific community caused NASA officials to reconsider.
The next option was to send up a manned space mission and use astronauts to manually replace, upgrade and repair the Hubble's systems. After the Columbia disaster, NASA was reluctant to risk the lives of astronauts on Hubble repair jobs. Even when the space shuttle program started up again in 2005, astronauts were sent only to the International Space Station. That's because the astronauts could take shelter in the station if something went wrong with the shuttle. There they could await rescue.
The Hubble telescope doesn't have the facilities or equipment required to keep a shuttle crew alive and safe. The telescope is also too far away from the space station for a shuttle to travel to the telescope, then maneuver to the space station. If something went wrong, the astronauts on the mission would be placed in severe danger. For a few years, NASA was unwilling to support a manned mission to repair the telescope.
Courtesy STScI and NASA
The third option was to send up a robot to the Hubble telescope to make repairs. NASA began to look into this option in 2004. A robot would allow NASA to make repairs and upgrades without placing human life in danger. But there was also a downside to using a robot. Robots are extremely expensive to design, develop and produce. NASA had to weigh the costs of developing a robot with the benefits of having the Hubble back online.
NASA had a tough decision to make. The scientific community pleaded on the telescope's behalf. But the risk to human life would always be a factor. With that in mind, NASA set out on a specific course of action. Where they ended up was a completely different story.
What did NASA decide to do, and how did the organization's plans change over time? Find out in the next section.