Astronauts at the orbiting International Space Station on Tuesday installed a permanent Italian-built storage module, while Russia nixed plans to fly around and take pictures of the crowded lab.
The flyabout by Russia's Soyuz capsule would have provided new camera angles on the ISS as well as an unusual group photo of all the five participating nations' vehicles and equipment together for the first time.
Japan's HTV craft, the European ATV supply ship, Russia's Soyuz and Progress space capsules and the American space shuttle Discovery are all docked at the ISS, and Canada's Dextre robot is up and running there, too.
"It was kind of a late proposal that we do this," largely because the US shuttle was delayed from its initial November launch plan due to technical problems, said NASA spokesman John Ira Petty.
"The Soyuz that is attached to the station that would have been used is a new type of Soyuz and they (the Russians) were reluctant to add this extra activity," said Petty.
"The risk of failure would have seen three new crew members going home earlier than scheduled," he said, adding that NASA understood and backed the Russians' decision.
Meanwhile, NASA decided to extend the shuttle's mission to the ISS by one day, with a return to Earth now set for March 8, and astronauts completed the installation of the Permanent Multipurpose Module on the underside of the lab.
The new module is actually the Leonardo module, which has flown up and back to the space station multiple times over the past 12 years as a multipurpose logistics carrier.
The module underwent some revamping to ensure it can stay in space for another decade, including an "improved micrometeoroid debris protective shield design," NASA said.
Leonardo will provide astronauts with 21 by 15 feet (6.5 by 4.5 meters) of extra room for storage and experiments.
NASA said it will use the extra day in space to empty the Permanent Multipurpose Module and move supplies from the US shuttle to the space station.
The Discovery shuttle's mission now will last 12 days.
A second spacewalk by two of the six-member US crew that arrived aboard Discovery is set for 10:18 am Eastern time (1518 GMT) Wednesday, but could start 30-45 minutes ahead of schedule, NASA spokesman Michael Curie said.
The first spacewalk to install preparations for the storage module was completed Monday.
The same two US astronauts, Steve Bowen and Alvin Drew, will step out on Wednesday's spacewalk. This time, their mission will be to finish up work on a failed ammonia pump and to install spare parts on the Canadian robot Dextre.
Monday was the Drew's first spacewalk and marked the sixth for Bowen, who replaced US astronaut Tim Kopra after a bicycle accident in January.
The shuttle blasted off from Kennedy Space Center on February 24, on its final mission into orbit before entering retirement. Discovery is the first of three US shuttles set to become museum pieces later this year.
Endeavour is to lift off on April 19 followed by Atlantis on June 28, marking the official end of the US space shuttle program after 30 years.
Explore further: NASA extends Discovery shuttle mission by a day