麻豆传媒

Spacewalking astronauts outfitted the Hubble Space Telescope with new batteries and gyroscopes on Friday. The gyroscopes were the shuttle servicing mission鈥檚 top priority, as they help the telescope orient itself in space. But one of the three new gyro units did not fit properly, and astronauts had to install a spare instead.

The installation of the gyros took longer than planned, but astronauts Mike Massimino and Michael Good decided to plough ahead with the rest of the day鈥檚 spacewalk plans to replace three of Hubble鈥檚 six batteries. To accommodate the extra work, the astronauts鈥� sleep schedule will be pushed forward by one hour.

The space shuttle Atlantis is currently orbiting Earth on an 11-day mission to refurbish the telescope and extend its life until at least 2014 (see Pimp my scope: Revamping Hubble).

Hubble was designed to use three gyroscopes to hold it steady, and was sent into orbit with a set of six. But the telescope鈥檚 gyros have been degrading. Before this mission, the telescope had just three working gyros left. Since 2007, Hubble had been operating with just two gyros, keeping the third offline as a backup.

Spare unit

Massimino, who also flew on the previous servicing mission to Hubble in 2002, spent several hours wedged inside the telescope on Friday replacing three Rate Sensor Units, each of which holds a pair of gyros.

While the spacewalkers were able to install two new RSU鈥檚, a third did not fit properly, and the team eventually installed a spare unit. The spare does not contain any new silver-coated electrical leads, which are designed to reduce corrosion.

After the units鈥� installation, ground controllers announced that all three sets of gyros had passed their first electrical tests, intended to make sure the equipment is properly connected and receiving power.

鈥楬old your breath鈥�

A challenging spacewalk is on tap for Saturday, when astronauts John Grunsfeld and Andrew Feustel will attempt to revive the telescope鈥檚 Advanced Camera for Surveys, which has been hobbled by an electrical short since 2007.

Grunsfeld will have to remove 32 screws to open up the camera, which is partially obstructed by a strut and was not designed to be repaired in orbit. In a briefing on Thursday, Hubble senior scientist David Leckrone anticipated Saturday鈥檚 spacewalk would be 鈥渉old-your-breath time for most of the day鈥�.

Before beginning the repair job, the team will install a new instrument called the . It can measure the light spectrum of objects at ultraviolet wavelengths, revealing more about the diffuse gas that floats between galaxies and the web-like distribution of matter in the universe.