Two astronauts have taken part in a spacewalk to hang micrometeorite shields and a grapple hook on the international space station.
It was the first of three spacewalks planned during shuttle Endeavour'sweek long visit to the space station.
Endeavour astronauts Mr Franklin Chang-Diaz and Mr Philippe Perrin's first job involved attaching a hook for the space station's robot arm on a piece of framework that must be moved on a later assembly flight.
Then they had to remove a set of six protective panels from Endeavourand hang them on the exterior of the space station.
The panels are needed to strengthen the hull of the Russian-built living quarters.
NASA officials said the six shields will result in only a 1 per cent decrease in the odds of a piece of space junk penetrating the module's hull over the next decade.
"This is the first step," said Mr Bill Gerstenmaier, deputy space station program manager.
Mr Chang-Diaz, a NASA astronaut who was born in Costa Rica, is making a record seventh space flight. Mr Perrin, a French astronaut, is making his first.
Their next two spacewalks, on Tuesday and Thursday, will focus on the space station's robot arm, which needs a new wrist joint.
PA