Missions to Hubble

Five servicing missions extended Hubble's life and increased its capabilities. Hubble’s serviceable design and modular components enabled upgrades that took advantage of advancements in technology.

Quick Facts

NASA’s Hubble Space Telescope is the first space-based observatory specifically designed for servicing by astronauts while in orbit. The ability to make repairs and upgrade Hubble’s instruments while in orbit became even more important when in 1990, shortly after deployment, NASA discovered that the observatory's primary mirror had an aberration that affected the clarity of the telescope's early images. Astronauts corrected that aberration on their first servicing mission in December 1993. Some 30 years later, Hubble continues to capture our imaginations with its stunning imagery.  

Hubble servicing missions involved intensive coordination between NASA's Kennedy Space Center in Florida, Johnson Space Center in Texas, and Goddard Space Flight Center in Maryland. Preparations included astronaut training at all three centers; simulations of shuttle and telescope operations during the mission at Johnson and the Space Telescope Operations Control Center (STOCC) at Goddard; testing and preparing instruments and hardware for flight at Goddard; and preparing launch operations and the space shuttle for launch, flight, and landing at Kennedy.

During the missions, operations took place primarily at Johnson and in Goddard's STOCC. Johnson’s Mission Control Center monitored every aspect of the space shuttle and astronauts, including spacewalks, procedures and schedules, crew activities and health, and in-cabin and cargo bay systems and experiments. The STOCC ground crew handled telescope operations, sending commands to Hubble to place the instruments into "safe hold" (hibernation) or turning them off and on as needed, close the aperture door (which covers the precious optical components), and perform maneuvers to position the telescope for grappling by the shuttle’s robotic arm, operated by astronauts to bring Hubble into the shuttle’s payload bay. 

After the repair of existing instruments, installation of new instruments, and replacement of critical hardware, or science instruments, STOCC personnel performed tests to make sure each component had power and operated as it should. Many of these tests occurred during the astronauts' sleep cycles, when the STOCC team carried out detailed tests on the newly installed components to determine whether the astronauts needed to perform additional service. 

Once the astronauts completed all of the servicing tasks via a three- to five-day series of spacewalks, the STOCC controllers and Johnson Mission Control prepared the telescope for release. Often this also involved using the shuttle’s thrusters to carry Hubble into a slightly higher orbit, a step that prolonged Hubble's life by keeping it from naturally deorbiting due to atmospheric drag. 

The astronaut crew used the shuttle’s robotic arm to slowly raise Hubble from the payload bay and out into space, where controllers at the STOCC  opened  Hubble's  aperture door and made sure the telescope was functioning normally on its own. Returning Hubble to full science observations after a servicing mission usually took a few months.

Just as cars need maintenance on Earth, sometimes spacecraft need fixing, too. 🛠️ When astronauts work on spacecraft in orbit, it's called space servicing.

Servicing Missions Interactive Timeline

Hubble Servicing Missions

These videos tell the story of Hubble's five servicing missions: the challenges and successes.



April 24-29, 1990

When the Space Shuttle Discovery carried NASA’s Hubble Space Telescope into space, it took with it the hopes of generations of astronomers, including those of Lyman S. Spitzer, the astrophysicist who first outlined a proposal for a large space telescope in 1946.

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Image taken of the 1990 deployment of the Hubble Space Telescope. Hubble, bright and silver, reflects the Earth below, on either side of Hubble there are two golden solar arrays. At the bottom of the picture you can see the body of the Space Shuttle Discovery as well as the grapple arm letting go of Hubble.
Space shuttle Discovery’s robotic arm deploys Hubble on April 25, 1990.


Servicing Mission 1

Dec 2-13, 1993

The first opportunity to conduct planned maintenance on the telescope. Astronauts installed new instruments, including equipment that counteracted the flaw in Hubble's primary mirror.

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Image showing astronaut floating above the blue Earth, in the background you see Hubble with one of its solar arrays. The Shuttle is also visible at the bottom of the image.
SM1 Astronaut Kathryn Thornton during an EVA with Hubble in the background


Servicing Mission 2

Feb 11-21, 1997

The second servicing mission extended the range of wavelengths Hubble can see with the installation of two new instruments and increased the observatory's efficiency and performance.

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Image showing astronaut standing on the CANADARM (Coming from the right side of the image.) On the left there is Hubble, which the astronaut is touching as part of the repair.
Mark C. Lee (top with red stripe), payload commander, on the end of the Remote Manipulator System (RMS) arm, performs a patching task on the worn insulation material of the Hubble Space Telescope. This was the final extravehicular activity (EVA) of five performed by two teams of spacewalkers on the mission in 1997.


Servicing Mission 3A

Dec 19-27, 1999

What was originally conceived as a mission of preventive maintenance turned more urgent on Nov. 13, 1999, when the fourth of Hubble's six gyros failed. Hubble required at least three of its stabilizing gyros to conduct science at that time. Hubble entered a state of dormancy called safe mode while the telescope awaited repairs. To bring Hubble back into operation more quickly, NASA split the third servicing mission into two parts.

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Image showing astronaut holding the Pistol Grip Tool, which looks like an electric screwdriver. The astronaut's face is visible through his visor, he is smiling. He stands next to a large gold box with a bit of the Shuttle visible behind him.
Astronaut Claude Nicollier, mission specialist from the European Space Agency (ESA), works at a storage enclosure, using one of the Hubble powertools, during the second of three STS-103 extravehicular activities (EVA).


Servicing Mission 3B

Mar 1-12, 2002

During SM3B, astronauts replaced Hubble's solar panels and installed the Advanced Camera for Surveys, which took the place of Hubble's Faint Object Camera, the telescope's last original instrument.

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Image showing two astronauts working on Hubble while in space. One astronaut is on the left, holding on to the lower handrail of Hubble. The astronaut on the right is standing on top of the CANADARM, a long robotic arm, he works on the center bottom of Hubble. In the distance behind Hubble, the blue Earth is visible with wisps of white clouds.
John M. Grunsfeld, STS-109 payload commander, works in tandem with Richard M. Linnehan, mission specialist, as the two devote their attention to the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) on the giant Hubble Space Telescope (HST). Grunsfeld is in a foot restraint on the end of the Space Shuttle Columbia’s Remote Manipulator System (RMS). This was the fifth and final scheduled STS-109 (Servicing Mission 3B) spacewalk and the mission’s third extravehicular activity (EVA) for the team of Grunsfeld and Linnehan.


Servicing Mission 4

May 11-24, 2009

The Hubble Space Telescope was reborn with Servicing Mission 4 (SM4). The fifth and final serving mission left the observatory at the peak of its scientific capability, and prepared it for many years of further scientific discovery.

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Two Hubble astronauts working during Servicing Mission 4. One of the astronauts is carrying a large silver box, about the size of a telephone booth. He is standing on the long robotic CANADARM, to his left there is another astronaut, sideways and working inside Hubble, which has two giant bay doors open at the bottom.
STS-125 Mission Specialist 5 (MS5) Andrew Feustel, positioned on the Manipulator Foot Restraint (MFR), moves the Hubble Space Telescope (HST) Corrective Optics Space Telescope Axial Replacement (COSTAR) during the third session of extravehicular activity (EVA3). Mission Specialist John Grunsfeld is visible working behind the HST -V2 door on this, the final servicing mission to Hubble.

Meet the Hubble Astronauts

John Grunsfeld - Astronaut and Former Associate Administrator for the Science Mission Directorate

Mission Specialist

Photo of astronaut Scott Altman in his orange spacesuit. American flag is behind him.


Official astronaut portrait of Kathryn Thornton.

Mission Specialist

Photo of astronaut Megan McArthur in her orange spacesuit. American flag is behind her.

Mission Specialist

Official astronaut portrait of Claude Nicollier.

Mission Specialist

Hubble's Astronauts

This video celebrates the astronauts who helped the Hubble double its lifespan and reach its many ground-breaking discoveries that expanded our knowledge of the universe.