Hubble's Servicing Missions

Hubble was designed to be one of the greatest telescopes. It operates in space, where there are no clouds, atmosphere or anything else to get in its way to take great pictures.

But, immediately after deployment, a problem became clear. The main mirror was flawed, suffering from spherical aberration, or simply imperfection! So a servicing mission, in December 1993, was sent out to fix this flaw (Servicing Mission 1, see picture at left). Spending five days to work on this, the astronauts installed two devices, Wide Field and Planetary Camera 2 and the Corrective Optics Space Telescope Axial Replacement.

For Servicing Mission 2, in February 1997, the humongous telescope was outfitted with the Near Infrared Camera and Multi-Object Spectrometer, in order to see our universe in infrared wavelength. Astronauts also installed the Space Telescope Imaging Spectrograph.

For Servicing Mission 3A, the telescope received a major hardware update. Among the new items added were gyroscopes and a replacement of one of the three Fine Guidance Sensors (you can see this in the picture at left). This improvement for the Hubble made it like new again. The telescope was deployed back into space on December 25, 1999.

In Servicing Mission 3B (NASA split Servicing Mission 3 into two parts, that's why there's 3A and 3B), in March of 2002, the seven member crew of Columbia installed the Advanced Camera for Surveys, or ACS, (see picture at right) with a wide field of view and better image quality than the previous surveying instrument, the Wide Field and Planetary Camera 2. The solar panels were replaced as well, with four new large and flexible panels. These panels produce 30 percent more power than the old ones. Along with this change, the original Power Control Unit was changed, too. This change required the telescope to power down for the first time after its launch in 1990. A new cooling system was added on to the Near Infrared Camera and Multi-Object Spectrometer, because the previous one had used up its nitrogen ice, and new steering equipment was added on as well.

Originally, NASA was planning not to conduct any further service missions, due to concerns about safety of the space shuttle. But now, a future servicing mission is planned as well, called Service Mission 4. The mission will work on replacing outdated and old equipment, like the Fine Guidance Sensor, on the telescope and make sure the telescope is in top shape. Right now, this mission is planned for September 2008.

For more information, visit:

• HubbleSite (Servicing Missions, Servicing Mission 4)
• SPACE.com