How Fixing the Hubble Spacecraft Works

Hubble telescope over the Bahamas
A view of the Hubble spacecraft as it orbits the Earth. See more Hubble Space Telescope pictures.
Courtesy NASA

The Hubble Spacecraft, also known as the Hubble Space Telescope or just the Hubble, launched in 1990 and has been sending us amazing pictures of distant galaxies ever since. But the Hubble's journey hasn't been a smooth one. In fact, there were problems with the Hubble from the very beginning. As a result, part of the Hubble's history is a series of NASA missions designed to repair the telescope. The latest repair mis­sion will also be the Hubble's last -- NASA plans to replace the Hubble with a new space telescope in 2013.

Hubble Space Telescope Image Gallery

Why use a space telescope in the first place when we have massive telescopes here on Earth? Space telescopes can focus on objects that are fainter and further away than terrestrial telescopes. It all has to do with the Earth's atmosphere. Particles in the air absorb, refract and reflect light. Warm air rises and cold air falls, which can also distort light. In space, there's no interference because there's no atmosphere. Telescopes in space are able to collect much sharper images than the ones we have here on the ground.


But a space telescope is more accurate than Earthly telescopes only if it's designed properly. About a month after NASA launched the Hubble, the organization discovered that the telescope they had been working on for eight years had a fundamental flaw. A mirror designed to reflect light into the telescope's sensors wasn't the right shape. The mirror's manufacturer had made a mistake when building it. As a result, the images the Hubble sent to NASA were out of focus and blurry.

NASA soon scheduled a repair mission, which launched in 1993. NASA sent up astronauts in the space shuttle Endeavour to manually repair the telescope. Five space walks later, the astronauts completed the repairs. They installed a device containing 10 small mirrors that intercepted the light from the primary mirror and corrected the pathway to the sensors. Afterwards, the Hubble began to take some of the most astounding images of space we've seen so far.

Exploding stars
Courtesy STScI and NASA

But the Hubble once again needs repairs. Unlike the problem with the mirror, these repairs involve multiple systems and are much more complicated. For a while, NASA considered abandoning the Hubble completely rather than invest in another repair mission. Ultimately the organization changed its course, and now it has scheduled another repair mission. We'll take a look at what exactly happened to the Hubble to necessitate repairs, why NASA almost decided to give up on the telescope and what the future has in store for this device.

So what exactly is wrong with the Hubble? We'll focus on the problem in the next section.


What's Wrong with the Hubble?

A picture of the planet Jupiter taken by the Hubble telescope
A shot of Jupiter taken by the Hubble telescope
Courtesy STScI and NASA

Like all devices, the Hubble telescope is vulnerable to wear and tear. Sometimes a minor system fails, or a battery dies. At other times, a more critical system begins to wear out. Because the Hubble is both a telescope and a spacecraft, it has several complicated systems that could cripple the telescope's functionality if they failed.

With that in mind, NASA has scheduled regular maintenance and repair missions to keep the Hubble in working order since its launch. Besides the mission in 1993 to install the correctional device to address the mirror problem, NASA scheduled three more missions to upgrade and maintain the telescope. Those missions took place in 1997, 1999 and 2002 [source: NASA].


On Feb. 1, 2003, the space shuttle Columbia broke apart upon reentry. All seven members of the shuttle's crew died in the accident. NASA became the subject of tremendous pressure and scrutiny. The agency decided to ground the space shuttle program and conduct a full investigation to determine if manned space flight was worth the risks involved. As a result, NASA canceled a planned Hubble maintenance mission.

In 2004, the Hubble's Space Telescope Imaging Spectrograph (STIS) malfunctioned when its power supply failed. Spectrographs separate light into its component wavelengths, which we perceive as colors. By analyzing the different wavelengths of light, astronomers can learn a lot about the cosmic bodies they're observing. Just by studying light wavelengths, scientists can determine an object's chemical composition, temperature and density, among other traits. The Hubble's STIS was instrumental in detecting black holes, and is a critical component of the Hubble. Currently, the STIS is in "safe mode," which means it isn't turned on, but it's still capable of functioning if NASA replaces the power supply.

Crab Nebula
The Hubble telescope has taken many incredible pictures, including this photo of the Crab Nebula generated from optical and x-ray images.
Courtesy STScI and NASA


In 2007, the Hubble's Advanced Camera for Surveys (ACS) suffered a partial failure. The ACS has three cameras and has taken some of the most impressive images of objects in deep space. An electrical short circuit disabled two of the three cameras. Each camera fulfills a different function. The solar blind camera takes images of objects that emit ultraviolet wavelengths. It's the only camera in the ACS that still functions. The two defunct cameras include a wide field camera and a high-resolution camera.

While NASA resumed the space shuttle program in the summer of 2005, there were no plans to repair or upgrade the Hubble. As systems began to experience problems, NASA debated the merits of a repair mission. Would the benefits of fixing the Hubble outweigh the risk and cost of a manned mission? Was there some other way to repair the telescope without subjecting humans to danger? Did it make more sense to let the Hubble deteriorate and eventually fall out of orbit?

These aren't easy questions to answer. The demand for the kind of information and images the Hubble could gather extends far beyond NASA's doors. Scientific laboratories around the world depend on that data.

What options did NASA have? Keep reading to find out.


What Were NASA's Options?

Deployed Hubble space telescope
Courtesy STScI and NASA

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.

Bubble Nebula
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.


The Repair Mission

Eagle Nebula
Courtesy STScI and NASA

In 2004, NASA began to look into the possibility of using a robot to repair the Hubble. NASA would launch the robot using a rocket similar to the ones used in the Apollo missions. Although such a mission wouldn't endanger the lives of humans, there were other considerations that made it a difficult decision. For one thing, engineers designed the Hubble so that humans could make repairs and upgrades, so the robot would have to mimic a human's range of motion in space. For another, such a program would be extremely expensive, making it a challenge to raise the proper funding.

NASA looked at several companies and research facilities when considering a robotic solution to the Hubble problem. Among the candidates was the Canadian Space Agency (CSA). The CSA developed a robot they called Dextre. The robot featured two long, multi-jointed arms that were capable of performing several basic tasks. Early research was promising. But NASA eventually decided against using the robot. Why? Partly because skeptics believed the job of repairing the Hubble was too delicate for a robot. Another big factor was the price -- estimates on the cost of a mission using Dextre ranged between $1 and $2 billion. NASA didn't have enough money in the budget to fund such an operation.


It looked as if NASA was going to let the Hubble die after all. But when Mike Griffin became the NASA Administrator in 2005, he decided to take another look at repairing the Hubble. After some consideration, Griffin announced on Oct. 31, 2006, that a new manned mission would travel to the Hubble to install upgrades and repair the telescope. The proposed changes would extend Hubble's life to 2013. By then, the James Webb Space Telescope should be online and in orbit.

Supergiant star Monoceritus
Courtesy STScI and NASA

Griffin's announcement meant that NASA again had to take a close look at the space shuttle program. NASA scheduled the repair mission for the summer of 2008. That was first pushed back to the fall of 2008 due to a delay in space shuttle fuel tank production [source: New Scientist]. Further problems delayed the launch until May 11, 2009. Now the space shuttle Atlantis is carrying a crew of astronauts to the Hubble. Standing by is a second space shuttle, the Endeavour. It's the crew of the Endeavour's job to serve as a rescue team if something should go wrong with the Atlantis.

Once at the Hubble, the astronauts will switch out the gyroscopes and batteries, effectively giving the telescope at least five more years of operational power and guidance. They'll also repair some thermal shielding on the telescope designed to protect the Hubble's electronics from the hazards of space. They'll replace the two defective ACS cameras and the STIS, and they'll also install new equipment that gives the Hubble even more capabilities. NASA expects the entire mission will require at least five spacewalks [source: HubbleSite]. All the repairs and upgrades will be done by hand.

Once the Hubble is repaired, what happens then? Find out in the next section.


The Future for Hubble

Whirlpool Galaxy
The exotic Whirlpool Galaxy, as seen through the Hubble telescope
Courtesy STScI and NASA

The 2009 repair mission will be the final Hubble upgrade and repair project. Once the crew of the Atlantis finishes working on the Hubble, the telescope will continue to collect data and transfer the information back down to NASA. With its new equipment, the Hubble will be able to look further into the universe and collect more information about celestial bodies.

The Hubble's upgrades will include a Wide Field Camera 3 (WFC3) and a Cosmic Origins Spectrograph (COS). The WFC3 can capture images using light across a wide spectrum, from infrared to ultraviolet. It will be the most powerful camera installed on the Hubble to date. The COS will gather data in a way similar to the STIS. So not only will NASA receive information from the Hubble's repaired systems, but also information from new, more powerful components.


Information from the Hubble can tell us a lot about the universe. Scientists plan to use the Hubble to continue research on everything from black holes to dark matter. With the Hubble, we might be able to detect more planets that are similar to our own. Without it, we'd have to wait several years before its replacement could take over the job.

Assuming all the Hubble's bits and pieces work as they're supposed to, the telescope should be able to continue functioning until 2013. That's just an estimate -- in reality, the telescope might function longer than that. Part of the repair mission involves attaching a device to Hubble that will assist NASA when it comes time to deorbit the telescope. That's space talk for making the telescope crash on Earth. Even if the repair mission is a complete success, the Hubble's days are numbered.

Crab Nebula
Courtesy STScI and NASA

But NASA is working on another space telescope. It's called the James Webb Space Telescope, developed by Northrop Grumman Space Technology. The new telescope will include multiple cameras that are more powerful than the ones currently on the Hubble.

The Hubble has provided invaluable information to scientists since its launch. Hopefully after this final repair mission, it will continue to do so for several more years.

To learn more about the Hubble Space Telescope and other subjects, take a closer look at the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Gitlin, Jonathan M. "Hubble shuts down." Ars technica. Jan 30, 2007. Retrieved May 6, 2008.
  • Halverson, Todd. "Canadian Robot Top Choice for Hubble Service Mission." Florida Today via Aug. 11, 2004.
  • "Hubble." NASA. Retrieved May 6, 2008.
  • "Hubble repair mission delayed." New Scientist Space and Reuters. May 2, 2008. Retrieved May 5, 2008.
  • HubbleSite
  • Hubble Space Telescope. (2008). Encyclopedia Britannica. Retrieved May 06, 2008, from Encyclopedia Britannica Online:
  • Malik, Tariq. "Spacewalkers Add Tool Kit, Cameras to Station's New Robot." March 18, 2008. Retrieved May 5, 2008.
  • NASA.