The Space Shuttle Endeavor mission in 1993 successfully repaired the Hubble Space Telescope and corrected its visual defects, marking a historic achievement for NASA. The mission demonstrated the feasibility of complex space repairs and had a lasting impact on future space exploration.
Before dawn on December 2, 1993, the space shuttle Endeavor launched from the Kennedy Space Center in Florida to perform the important task of repairing NASA's Hubble Space Telescope.
Hubble is designed to be repaired in space, with parts sliding in and out by astronauts. But before the launch, no one thought that the first maintenance mission would be so urgent.
In the three years since its launch, Hubble has been the butt of late-night cartoons and editorial cartoons: a telescope that can't see clearly. Since its deployment in 1990, the telescope has been sending back blurry images to Earth, caused by a flaw in the shape of its primary mirror. Although the misalignment of the primary mirror was only one-fiftieth the width of a human hair, this error had devastating consequences: the light emitted by the primary mirror was not focused correctly. While the images are still better than those taken from Earth and science is still possible, the quality is not quite as good.
"The feeling at the time was that everyone viewed the maintenance and repair of the Hubble Space Telescope as a mission that would prove NASA's worth... There was tremendous concern and pressure for the success of this mission."
-Richard Covey, Maintenance Mission 1 astronaut
Service Mission No. 1 is the solution. The shuttle carries the Wide Field Planetary Camera 2 (WFPC2) and the Correcting Optics Space Telescope Axial Replacement (COSTAR), along with other key components for upgrading the telescope. Responsible for taking the telescope's visually striking images, WFPC2 has built-in corrective optics to compensate for mirror imperfections and will replace the Wide Field/Planetary Camera used during Hubble's launch. COSTAR is a refrigerator-sized component that contains an array of mirrors, some the size of a U.S. nickel, designed to correct and redirect light toward the telescope's other cameras and spectrograph.
The seven astronauts aboard the space shuttle realized they had on their shoulders not only the fate of Hubble, but also the public's perception of NASA and its space programs.
Hubble advocate and late astrophysicist John Bahcall, a member of the Hubble Science Working Group, told the New York Times in 1993: "If Hubble's repairs fail, we can give up on space science for the foreseeable future." "
On December 2, 2023, NASA will commemorate the 30th anniversary of Servicing Mission 1, which successfully turned the Hubble Telescope into one of NASA's greatest triumphs: a shining example of human ingenuity in the face of adversity.
In the most complex spacewalk mission in history, astronauts conducted five extravehicular activities, with a total duration of more than 35 hours. They removed the high-speed photometer instrument, added COSTAR, and replaced the original Wide Field/Planetary Camera with a Wide Field and Planetary Camera 2. They also installed other key components to upgrade the telescope.
At 1 a.m. on December 18, 1993, about a week after the mission ended, astronomers gathered around computers at the Space Telescope Science Institute in Baltimore and witnessed the telescope's first new image: a star shining clear and pure light in the image, without the haze caused by Hubble's defective mirror. The new images are so different that NASA released them ahead of schedule even though the telescope will need about 13 weeks of adjustments to reach its full functionality. Ed Weiler, Hubble's chief scientist during SM1, said at a press conference in January 1994: "It was restored successfully beyond our imagination."
"The look on people's faces when this picture came out - it was an old [cathode ray] picture tube type television. It took a while to develop, but it got clearer and clearer. Everybody started yelling."
-Ed Weiler, Hubble chief scientist during SM1
Maryland Senator Barbara Mikulski, who has been a vocal advocate for Hubble's development, was the first to show the new images to the public at a press conference on January 13. "I'm pleased to announce today that, after the 1990 launch and some previous disappointments, Hubble's troubles are behind us," she said.
Although Maintenance Mission 1 is best remembered for solving Hubble's blurry vision problems, it also completed many other tasks that helped transform Hubble into the astronomical powerhouse it is today.
When Maintenance Mission 1 was launched, the telescope's gyroscopes -- the precision equipment needed to steer and keep Hubble in position -- had malfunctioned. Three of Hubble's six gyroscopes malfunctioned. Three additional gyroscopes (usually used as backups) remain operational, the minimum number Hubble needs to continue collecting scientific data. Astronauts replaced four gyroscopes, a repair that will help the telescope run smoothly for several years.
Early in Hubble's orbit, NASA discovered that as the telescope moved in and out of sunlit space, the telescope's solar arrays expanded and contracted excessively in the alternating hot and cold spaces, causing them to vibrate. This forced engineers to use Hubble's computing power to compensate for "jitter," thereby reducing observation time. Astronauts replaced Hubble's solar array with a new one that reduced natural jitter to acceptable levels.
The astronauts also made an enhancement whose importance would become apparent a year later: upgrading Hubble's flight computer with a coprocessor and associated memory. Just weeks before the disintegrated comet Shoemaker-Levy 9 collided with Jupiter in 1994, Hubble entered a protective "safe mode" due to a problem with the main computer's memory unit. Engineers used the coprocessor's memory to solve the problem and captured stunning images of a gas giant planet being struck by comet debris.
Maintenance Mission 1's impact extends far beyond Hubble. The mission demonstrated what can be accomplished in space and proved that humans are capable of completing highly complex tasks in orbit. Lessons learned from Hubble's training and servicing work itself will be used on other astronaut missions, including four subsequent servicing visits to Hubble from 1997-2009. These additional missions to Hubble will make it possible to install new cutting-edge instruments, repair existing science instruments, and replace critical hardware, keeping Hubble at the forefront of astrophysics exploration.
Additionally, lessons learned from Maintenance Mission 1 have implications for work on the International Space Station as well as missions yet to be performed. "A lot of the knowledge developed there applies directly to the construction of the International Space Station and will apply to what we do in the future at [the future orbiting lunar space station] Gateway. That will apply to what we do on the moon and in deep space, including going to Mars and beyond. It's all connected," said Kenneth Bowersox, associate administrator of NASA's Space Operations Mission Directorate.
To celebrate the first servicing mission, NASA will release a series of videos over the next two weeks featuring key players -- astronauts, scientists, engineers and more -- looking back on the struggles and triumphs of the time, and the emotional and personal impact Hubble and SM1 had on their lives.