Next Hubble Servicing Mission

Hubble Servicing Mission 4 (SM4)

Preparations for the final Hubble servicing mission are well underway. It will be the last and most complex of them all.

Astronauts will race against the clock to complete all of the assigned task which include replacement and repair of existing components and the installation of completely new pieces of equipment. This will extend the life of Hubble and increase its capabilities.

STS-125 is currently scheduled for an October 8 launch.A recap of earlier missions is provided below.

Previous Servicing Missions

Servicing Mission 3B, March 2002: Astronauts aboard space shuttle Columbia (STS-109) installed several new instruments on Hubble that vastly improved the observatory's capability. Astronauts performed five spacewalks. Their principal task was to install the Advanced Camera for Surveys (ACS). With its wide field of view, sharp image quality and enhanced sensitivity, ACS could collect data ten times faster than the Wide Field and Planetary Camera 2, the telescope's earlier surveying instrument. The ACS brought the nearly 12-year-old telescope into the 21st century. The ACS was quickly used to capture the most distant image of the universe, called the Hubble Ultra Deep Field. The 8-year-old solar array panels were replaced with smaller rigid ones that produce 30 percent more power. Astronauts also replaced the outdated Power Control Unit, which distributes electricity from the solar arrays and batteries to other parts of the telescope; and they replaced one of the four reaction wheel assemblies that make up Hubble's pointing control system. Another key upgrade was the installation of a new cooling system for the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), down since 1999 after depleting its refrigerant. Hubble's infrared vision was finally back.
Visit SM3B Site.

Servicing Mission 3A, December 1999: NASA decided to split the Third Servicing Mission into two parts, SM3A and SM3B, after the third of Hubble's six gyroscopes failed. Hubble needs three gyroscopes to observe a target. Astronauts aboard space shuttle Discovery (STS-103) replaced all six gyroscopes, as well as one of Hubble's three fine guidance sensors, used to keep Hubble steady while viewing objects. The astronauts also installed a transmitter, an advanced central computer, a digital data recorder, an electronics enhancement kit, battery improvement kits, and new outer layers of thermal protection. On November 13 before this mission, Hubble was placed into "safe-mode" after a fourth gyroscope failed unexpectedly. In safe-mode Hubble is in a sort of protective hibernation and cannot observe objects. Luckily the servicing mission had been planned by this point, so Hubble wasn't out of action for long. After servicing, Hubble was as good as new.
Visit SM3A Site.

Servicing Mission 2, February 1997: During this 10-day mission (STS-82) astronauts aboard the space shuttle Discovery installed two technologically advanced instruments. The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) enabled Hubble to observe infrared wavelengths, crucial for viewing very distant "optical" sources that have lost energy traveling across most of the visible universe and now radiate in the infrared band. The second instrument, the Space Telescope Imaging Spectrograph (STIS), could take detailed pictures of celestial objects and hunt for black holes. Both instruments featured technology that wasn't available when scientists designed and built the original Hubble instruments in the late 1970s. Astronauts also installed a refurbished Fine Guidance Sensor, one of three essential instruments used to keep Hubble steady while viewing objects and to calculate celestial distances; a Solid State Recorder to replace one of Hubble's data recorders; and a refurbished, spare Reaction Wheel Assembly, part of the Pointing Control Subsystem.
Visit SM2 Site.

Servicing Mission 1, December 1993: The primary goal of Servicing Mission 1 was to restore Hubble's vision. Because Hubble's primary mirror was incorrectly shaped, the telescope could not focus all the light from an object to a single sharp point. Instead, it saw a fuzzy halo around objects it observed. Astronauts on the space shuttle Endeavor (STS-61) spent five days tuning it up. They installed two new devices---the Wide Field and Planetary Camera 2 and the Corrective Optics Space Telescope Axial Replacement---to compensate for the primary mirror's incorrect shape. Astronauts also installed new solar arrays, to reduce the "jitter" caused by excessive flexing of the solar panels during the telescope's orbital transition from cold darkness into warm daylight, and new gyroscopes to help point and track the telescope, along with fuse plugs and electronic units.
Visit SM1 Site.

See also the Hubble Story

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