Enabling Science through New Technologies
Launched in 1990, the Hubble Space Telescope was designed for periodic servicing to keep it running smoothly and extend its life. Between 1993 and 2009, astronauts visited Hubble five times to replace limited-life items such as batteries, gyroscopes and electronic boxes, and to install state-of-the-art science instruments. Each time astronauts visited Hubble, they left it a more capable, more productive observatory.
Because Hubble was designed to be serviced, the items astronauts replaced were easily accessible. Ranging in size from a shoebox to a telephone booth, most of these items could be removed or installed using special wrenches and power tools.
On-orbit servicing has ensured Hubble’s health and productivity well into the 21st century, allowing this unique scientific resource to continue making exciting discoveries as it explores the universe.
December 2-13, 1993
SPACE SHUTTLE: Endeavour
Crew: Commander Richard O. Covey, Pilot Kenneth D. Bowersox, Payload Commander F. Story Musgrave, and Mission Specialists Kathryn C. Thornton, Claude Nicollier, Jeffrey A. Hoffman and Tom Akers
As the first in a series of planned visits to the orbiting Hubble Space Telescope, this mission’s most important objective was to install two devices to fix Hubble’s vision problem. 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.
Once astronauts from the space shuttle Endeavour caught up with the orbiting telescope, they hauled it into the shuttle's cargo bay and spent five days tuning it up. They installed two new devices — the Wide Field and Planetary Camera 2 (WFPC2) and the Corrective Optics Space Telescope Axial Replacement (COSTAR). Both WFPC2 and the COSTAR apparatus were designed to compensate for the primary mirror’s incorrect shape.
Also installed during Servicing Mission 1 were 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. Spacewalkers also installed new gyroscopes to help point and track the telescope, along with fuse plugs and electronic units.
This successful mission not only improved Hubble's vision — which led to a string of remarkable discoveries in a very short time — but it also validated the effectiveness of on-orbit servicing.
- COSTAR, Corrective Optics Space Telescope Axial Replacement installed, replacing High Speed Photometer (HSP)
- Wide Field Planetary Camera 2 (WFPC2) replaced Wide Field Planetary Camera (WFPC)
- Solar Arrays replaced with Solar Arrays 2 (SA2)
- Replacement of #1 Solar Array Drive Electronics (SADE)
- Replace the #2 and #3 Rate Sensor Unit (two gyros each)
- Replacement of two Gyro Electronic Control Units, which direct the RSUs
- Replacement of eight electrical fuses
- Installation of two new magnetometers
- Installation of Goddard High Resolution Spectrograph Redundancy (GHRS) kit
- Installation of two protective covers over original magnetometers
February 11-21, 1997
SPACE SHUTTLE: Discovery
Crew: Commander Kenneth D. Bowersox, Pilot Scott J. Horowitz, Payload Commander Mark C. Lee, Mission Specialists Steven A.Hawley, Gregory J. Harbaugh, Steven L. Smith and Joseph R. Tanner
Hubble’s first generation cameras gave us remarkable views of very distant galaxies. However, the light from the most distant galaxies is shifted to infrared wavelengths by the expanding universe. To see these galaxies, Hubble needed to be fitted with an instrument that could observe infrared light.
During a 10-day mission, seven astronauts aboard the space shuttle Discovery installed two technologically advanced instruments. The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) would be able to observe the universe in the infrared wavelengths. The second instrument — the versatile Space Telescope Imaging Spectrograph (STIS) — would be used to take detailed pictures of celestial objects and hunt for black holes.
Both instruments had optics that corrected for the flawed primary mirror. In addition, they featured technology that wasn’t available when scientists designed and built the original Hubble instruments in the late 1970s — and opened up a broader viewing window for Hubble.
The new instruments replaced the Goddard High Resolution Spectrograph and the Faint Object Spectrograph.
Also installed during Servicing Mission 2 were:
- A refurbished Fine Guidance Sensor — one of three essential instruments used to provide pointing information for the spacecraft, to keep it pointing on target, and to calculate celestial distances
- A Solid State Recorder (SSR) to replace one of Hubble’s data recorders (an SSR is more flexible and can store 10 times more data)
- A refurbished, spare Reaction Wheel Assembly — part of the Pointing Control Subsystem
- Space Telescope Imaging Spectrograph (STIS) replaced Faint Object Spectrometer (FOS)
- Near Infrared Camera/Multi-Object Spectrometer (NICMOS) replaced Goddard High Resolution Spectrograph (GHRS)
- Replacement of Fine Guidance Sensor #1 with modified spare with added capability for ground-controlled alignment corrections
- Addition of an Optical Control Electronics Enhancement Kit (OCE-EK)
- Replacement of #1 Engineering Science Tape Recorder (ESTR) with digital Solid State Recorder (SSR) and replacement of #2 ESTR with a spare ESTR unit
- Replacement #1 of 4 Reaction Wheel Assemblies (RWA), with refurbished spare
- Replacement of Data Interface Unit (DIU) #2 with modified and upgraded spare unit
- Replacement of #2 Solar Array Drive Electronics (SADE) with refurbished unit
- Replacement of more durable covers on Magnetic Sensing System (MSS)
December 19-27, 1999
SPACE SHUTTLE: Discovery
Crew: Commander Curtis L. Brown, Pilot Scott J. Kelly, Payload Commander Steven L. Smith, Mission Specialists C. Michael Foale, John M. Grunsfield, Claude Nicollier and Jean-Francois Clervoy
NASA decided to split the Servicing Mission 3 (SM3) into two parts, SM3A and SM3B, after the third of Hubble’s six gyroscopes failed. (At that time, Hubble needed three gyroscopes to observe a celestial target.) The second part of the mission, SM3B, took place March 1–12, 2002.
On November 13, 1999, the Hubble Space Telescope was placed into safe mode after the failure of a fourth gyroscope. In safe mode Hubble could not observe targets, but its safety was preserved. This protective mode allows ground control of the telescope, but with only two gyros working, Hubble cannot be aimed with the precision necessary for scientific observations of the sky. Controllers closed the aperture door to protect the optics and aligned the spacecraft to ensure that Hubble’s solar panels would receive adequate power from the Sun.
In the first of the two-part mission, the most pressing task was the replacement of the gyroscopes. The crew, two of whom were Hubble repair veterans, replaced all six gyroscopes — as well as one of Hubble’s three Fine Guidance Sensors, which allow fine pointing and keep Hubble stable during observations, and a transmitter.
The astronauts also installed an advanced central computer, a digital data recorder, an electronics enhancement kit, battery improvement kits, and new outer layers of thermal protection. Hubble was as good as new.
- Replacement of all three Rate Sensing Units (RSUs), each of which contains two gyroscopes
- Installation of new computer, 20 times faster with six times more memory than its predecessor
- Replacement of original reel-to-reel data recorder with digital Solid State Recorder (SSR) which is faster, more reliable and can store 10 times as much data
- Replacement of #2 of 3 Fine Guidance Sensors (FGS) with refurbished unit
- Replacement of failed #2 of 2 S-Band Single Access Transmitter (SSAT) used to relay data to the ground
- Installation six Voltage/Temperature Improvement Kits (VIKs) on wiring between Solar Arrays and each battery to control charging of Hubble's batteries
- Installation of Shell/Shield Replacement Fabric (SSRF) over the original Multi-Layer Insulation on Hubble’s forward shell and light shield to add thermal protection
- Installation of Handrail Covers around the handrails above the Fine Guidance Sensor bay to prevent possible contamination to the Aft Shroud area from flaking handrail paint
- Fit New Outer Blanket Layers (NOBLs) on equipment Bay 1
March 1-12, 2002
SPACE SHUTTLE: Columbia
Crew: Commander Scott D. Altman, Pilot Duane G. Carey, Payload Commander John M. Grunsfeld, Mission Specialists Nancy J. Currie, James H. Newman, Richard M. Linnehan and Michael J. Massimino
Servicing Mission 3B was the fourth visit to Hubble. NASA split the original Servicing Mission 3 into two parts and conducted the first part — Servicing Mission 3A — in December 1999.
The astronauts’ principal task was to install a new science instrument called the Advanced Camera for Surveys (ACS). The first new instrument to be installed in Hubble since 1997, ACS brought the nearly 12-year-old telescope into the 21st century. With its wide field of view, sharp image quality, and enhanced sensitivity, ACS doubled Hubble's field of view and collects data 10 times faster than the Wide Field and Planetary Camera 2 (WFPC2), the telescope's earlier surveying instrument.
Spacewalking astronauts replaced the large, flexible, eight-year-old Solar Array Panels with smaller, rigid ones that produce 30 percent more power. They also replaced the outdated Power Control Unit, which distributes electricity from the solar arrays and batteries to other parts of the telescope. Replacing the original unit, which has been on the job for nearly 12 years, required the telescope to be completely powered down for the first time since its launch in 1990.
Astronauts also installed a new cooling system for the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), which became inactive in 1999 when it depleted the 230-pound block of nitrogen ice that had cooled it since 1997. The new cryocooler extended the life of Hubble’s infrared camera.
Spacewalkers also replaced one of the four Reaction Wheel Assemblies that make up Hubble’s Pointing Control System. Flight software commands the reaction wheels to steer the telescope by spinning in one direction, which causes Hubble to spin in the other direction.
- Installation of Advanced Camera for Surveys (ACS), replacing the Faint Object Camera (FOC)
- Installation of NICMOS Cooling System (NCS) comprised of two components, the NICMOS Cryogenic Cooler (NCC) and the NCS radiator, to revive the NICMOS instrument
- Replace Solar Arrays 2 (SA2) with smaller, more efficient Solar Arrays 3 (SA3)
- Replace the #2 of three Rate Sensor Units (each RSU contains two gyros)
- Replace #1 of four Reaction Wheel Assemblies (RWA), part of Hubble’s pointing control system, with a refurbished unit
- Replace Power Control Unit (PCU) to take full advantage of additional power generated by the new solar arrays
- Fit New Outer Blanket Layers (NOBLs) on Bays 1, 9 and 10
STS-109 Shuttle Mission Photos
May 11-24, 2009
SPACE SHUTTLE: Atlantis
Crew: Commander Scott D. Altman, Pilot Gregory C. Johnson, Payload Commander John M. Grunsfeld, Mission Specialists Michael J. Massimino, Andrew J. Feustel, Michael T. Good and K. Megan McArthur
Servicing Mission 4 (SM4) was the culmination of a long effort to provide the telescope with one, final servicing mission. Originally scheduled for 2004, SM4 was postponed and then cancelled after the loss of the Space Shuttle Columbia. Following the successful recovery of the shuttle program and a re-examination of SM4 risks, NASA approved another mission. This was perhaps Hubble’s most challenging and intense servicing mission, with a multitude of tasks to be completed over the course of five spacewalks.
Astronauts installed two new instruments on Hubble during SM4: Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS). These instruments made the observatory 100 times more powerful than when it was launched.
WFC3 sees three different kinds of light: near-ultraviolet, visible and near-infrared, though not simultaneously. The camera’s resolution and field of view is much greater than that of previous instruments. Astronauts removed Hubble’s Wide Field and Planetary Camera 2 (WFPC2) to make room for WFC3.
COS, a spectrograph that breaks light into its component colors, revealing information about the object emitting the light, sees exclusively in ultraviolet light. COS improves Hubble’s ultraviolet sensitivity at least 10 times, and up to 70 times when observing extremely faint objects.
COS took the place of the device installed in Hubble during the first servicing mission to correct Hubble’s flawed mirror, the Corrective Optics Space Telescope Axial Replacement (COSTAR). Since the first servicing mission, all of Hubble’s replacement instruments have had technology built into them to correct Hubble’s flawed vision, making COSTAR no longer necessary.
In late September 2008, only two weeks before the mission was to launch, a malfunction occurred in one of the systems that commands the science instruments and directs the flow of data within the telescope. The problem was fixed by switching to a backup system, but NASA was unwilling to leave the telescope without a spare. The mission was delayed until May while engineers and scientists tested and prepared an existing and nearly identical system. Astronauts were able to install the spare Science Instrument Command and Data Handling unit in addition to all previously scheduled tasks.
During SM4, astronauts accomplished a feat never envisioned by the telescope creators: On-site repairs for two instruments, the Advanced Camera for Surveys (ACS) and the Space Telescope Imaging Spectrograph (STIS). Both had stopped working; ACS after an electrical short in 2007, and STIS after a power failure in 2004. To perform the repairs, astronauts had to access the interior of the instruments, switch out components and reroute power. The successful completion of this task, along with the addition of the two new instruments, gave Hubble a full complement of five functioning instruments for future observations.
One of the goals of SM4 was to reinforce and reinvigorate the telescope’s basic spaceflight systems. Astronauts replaced all of Hubble’s batteries, which were 18 years old, with new, improved ones. Astronauts installed six new gyroscopes, which are used to point the telescope, and a Fine Guidance Sensor, which locks onto stars as part of the pointing system. They covered key Hubble equipment bays with insulating panels called New Outer Blanket Layers, to replace protective blankets that had broken down over the course of their long exposure to the harsh conditions of space. They also installed a new device, the Soft Capture Mechanism, to allow a robotic spacecraft to attach itself to Hubble someday, once the telescope is at the end of its life, and guide its descent to Earth or boost it to a higher orbit.
- Replace Wide Field Planetary Camera 2 (WFPC2) with Wide Field Camera 3 (WFC3)
- Remove the Corrective Optics Space Telescope Axial Replacement (COSTAR) and install the Cosmic Origins Spectrograph (COS) in its place
- Repair the Space Telescope Imaging Spectrograph (STIS)
- Repair the Advanced Camera for Surveys (ACS)
- Replace gyroscopes
- Replace one Fine Guidance Sensor (FGS)
- Replace batteries
- Install New Outer Blanket Layers (NOBL) on bays 5, 7 and 8
- Install Soft Capture Mechanism (SCM)
- Replace Science Instrument Control and Data Handling (SIC&DH) unit
STS-125 Shuttle Mission Photos