CAPE CANAVERAL: A spacewalk by two astronauts is still on for Thursday evening even though a large piece of space junk is headed their way.

Part of an old European rocket is expected to pass within two miles of space shuttle Discovery and the international space station late Friday morning. NASA officials say that should be a safe distance and they do not expect the linked spacecraft to change course. But if the projections change, the astronauts would complete the spacewalk before steering out of the way.

The debris is believed to have an area surface of 200 square feet.

Astronauts Danny Olivas and Christer Fuglesang will install a new ammonia tank outside the space station. It will be the second spacewalk of the mission.