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| Fifth spacewalk energises Hubble | Fifth spacewalk energises Hubble |
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| Space shuttle astronauts have embarked on the fifth and final spacewalk to repair the Hubble Space Telescope. | Space shuttle astronauts have embarked on the fifth and final spacewalk to repair the Hubble Space Telescope. |
| Mission specialists John Grunsfeld and Andrew Feustel have replaced three batteries, so that Hubble now has a brand new complement. | Mission specialists John Grunsfeld and Andrew Feustel have replaced three batteries, so that Hubble now has a brand new complement. |
| They have also replaced one of the telescope's three fine-guidance sensors which keep the telescope's gaze precisely fixed for observations. | They have also replaced one of the telescope's three fine-guidance sensors which keep the telescope's gaze precisely fixed for observations. |
| Space shuttle Atlantis is scheduled to return to Earth on Friday. | Space shuttle Atlantis is scheduled to return to Earth on Friday. |
| Hubble will be released from the orbiter's cargo bay on Tuesday, with the repairs and upgrades that the mission has accomplished promising at least five more years of observations. | Hubble will be released from the orbiter's cargo bay on Tuesday, with the repairs and upgrades that the mission has accomplished promising at least five more years of observations. |
| HUBBLE SPACE TELESCOPE Named after the great US astronomer Edwin HubbleLaunched in 1990 into a 600km-high circular orbit Equipped with a 2.4m primary mirror and five instrumentsLength: 15.9m; diameter: 4.2m; Mass: 11,110kg In pictures: The best of Hubble | HUBBLE SPACE TELESCOPE Named after the great US astronomer Edwin HubbleLaunched in 1990 into a 600km-high circular orbit Equipped with a 2.4m primary mirror and five instrumentsLength: 15.9m; diameter: 4.2m; Mass: 11,110kg In pictures: The best of Hubble |
| Among the final tasks is to replace one of the telescope's Fine Guidance Sensors, which allow the extraordinary precision and steadiness of Hubble's pointing. | Among the final tasks is to replace one of the telescope's Fine Guidance Sensors, which allow the extraordinary precision and steadiness of Hubble's pointing. |
| According to Nasa, that precision is equivalent to keeping a laser beam focused on a US dime coin at a distance of 320km. | According to Nasa, that precision is equivalent to keeping a laser beam focused on a US dime coin at a distance of 320km. |
| The servicing mission has been largely successful but not without its problems. | The servicing mission has been largely successful but not without its problems. |
| During Friday's spacewalk, one of the three brand-new sets of gyroscopes brought up to replace the existing units would not fit into its assigned slot. A old, refurbished set had to be installed instead. | During Friday's spacewalk, one of the three brand-new sets of gyroscopes brought up to replace the existing units would not fit into its assigned slot. A old, refurbished set had to be installed instead. |
| Saturday's walk successfully installed the Cosmic Origins Spectrograph, filling the instrument bay previously occupied by a corrective optics unit which has acted as Hubble's "spectacles" for 15 years, compensating for the manufacturing flaw in its main mirror. | Saturday's walk successfully installed the Cosmic Origins Spectrograph, filling the instrument bay previously occupied by a corrective optics unit which has acted as Hubble's "spectacles" for 15 years, compensating for the manufacturing flaw in its main mirror. |
| But the spacewalk failed to repair the high-resolution channel of the Advanced Camera for Surveys (ACS), Hubble's most versatile and well-used camera before its failure in 2007 due to a short-circuit. Two other channels on the ACS are working, though. | But the spacewalk failed to repair the high-resolution channel of the Advanced Camera for Surveys (ACS), Hubble's most versatile and well-used camera before its failure in 2007 due to a short-circuit. Two other channels on the ACS are working, though. |
| On Sunday, a handrail initially hindered the mission objective of replacing the Space Telescope Imaging Spectrograph. | On Sunday, a handrail initially hindered the mission objective of replacing the Space Telescope Imaging Spectrograph. |
| Mission specialists Mike Massimino and Michael Good removed - and captured - more than 100 screws to access the spectrograph. Their spacewalk lasted 8 hours, two minutes, making it the the sixth longest spacewalk in US history. | Mission specialists Mike Massimino and Michael Good removed - and captured - more than 100 screws to access the spectrograph. Their spacewalk lasted 8 hours, two minutes, making it the the sixth longest spacewalk in US history. |
| The final task of Monday's spacewalk will be to remove and replace thermal blankets protecting Hubble's electronics. | The final task of Monday's spacewalk will be to remove and replace thermal blankets protecting Hubble's electronics. |