Two spacewalkers outside space shuttle Atlantis have begun repairing and upgrading the Hubble Space Telescope as part of the fifth and final Hubble servicing mission. The first of five spacewalks planned for the mission began at 8:52 A.M. today (Eastern Daylight Time) and was expected to take six and a half hours.

Top on the agenda was removing Hubble's Wide Field Planetary Camera 2 (WFPC2), a workhorse with more than 15 years of service. Astronauts Drew Feustel and John Grunsfeld replaced WFPC2 with the new Wide Field Camera 3 (WFC3), which will cover a broader range of the electromagnetic spectrum.

A stuck bolt initially hindered WFPC2's removal, and Feustel and Grunsfeld then encountered some resistance in stowing the decommissioned camera in the shuttle's payload bay. But around 12:30 P.M. the old camera was secured and Hubble's controllers were getting signals that WFC3 was connected and properly drawing power.

The astronauts then replaced a critical data handler on Hubble that failed in September and had been running on backup components. Grunsfeld also installed a soft capture mechanism to facilitate the telescope's future deorbiting. In the coming decades a mission will pluck Hubble from its orbit and guide it safely into the ocean.

The final remaining task, now under way, is to install kits that will permit easier opening and closing of the telescope's access doors in the mission's later spacewalks.

Photo of Atlantis crewmembers removing Hubble's Wide Field Planetary Camera 2, in use since 1993, for replacement with Wide Field Camera 3: NASA TV