By DPA,
Washington : US astronauts Friday completed a delicate spacewalk to replace three pairs of gyroscopes aboard the Hubble Space Telescope.
In the second of five planned spacewalks during the mission, astronauts Mike Massimino and Michael Good removed and replaced the gyroscopes that keep the telescope aligned and pointed toward celestial bodies being examined by astronomers.
The duo had trouble installing a box containing a pair of gyroscopes, which would not sit properly in the space designed for it. After multiple attempts to get the unit to fit on Hubble, the crew instead decided to use a spare set of gyroscopes.
The replacement gyroscopes had previously been on Hubble and were removed in an earlier mission. The refurbished devices were loaded on Atlantis as part of a contingency plan.
NASA officials described Friday’s work as the most delicate of all the planned spacewalks, with Massimino required to crawl inside the telescope to reach the work site, while being careful not to disturb its instruments. Good rode on the shuttle’s robotic arm.
The delay in installing the gyroscopes caused ground control to extend the spacewalk beyond its planned six-and-a-half hours. The seven-hour, 56-minute spacewalk was the eighth longest in NASA history.
The astronauts changed one of the huge battery units that power the telescope. The 209-kg battery unit holds three batteries.
On Thursday, spacewalkers John Grunsfeld and Andrew Feustel replaced Hubble’s camera with a more advanced model.
A third spacewalk is set for Saturday, when Grunsfeld and Feustel are scheduled to install a new instrument known as the Cosmic Origins Spectrograph.
The Wide Field Planetary Camera 3 will allow astronomers to see deeper into space and to take images in the three regions of the light spectrum – ultraviolet, visible and near infrared.