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.
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.