Astronauts have ventured out on a spacewalk to prepare the International Space Station for a new parking spot.
Nasa's Shane Kimbrough and France's Thomas Pesquet emerged from the orbiting complex and went their separate ways to accomplish as much as possible 250 miles up.
"We are ready to get to work," Mission Control informed them.
Their main job involves disconnecting an old docking port, which needs to be moved to make room for a docking device compatible with future commercial crew capsules, and provide more clearance.
The new docking device - the second of two - will fly up late this year or early next and hook on to this port.
If all goes well, flight controllers in Houston will relocate the old docking port on Sunday, using the station's robotic arm. The crew will conduct another spacewalk next Thursday to secure the unit.
SpaceX and Boeing are developing capsules capable of flying astronauts to and from the space station. Until the SpaceX Crew Dragon and Boeing Starliner come on line - possibly next year - US astronauts will have to keep riding Russian rockets to orbit.
Before working on the docking port, Mr Kimbrough replaced a computer-relay box with an upgraded version.
Mr Pesquet looked for signs of a small ammonia coolant leak in outdoor plumbing. He patted and tugged at hoses, but did not spot any frozen flakes of ammonia. A GoPro camera caught his every move for playback later.
"No flakes. All good," he reported.
The pair also aim to replace a pair of cameras and grease latching mechanisms on the end of the robot arm.
Nasa wants to cram in two and possibly three spacewalks before Mr Kimbrough, the station's commander, returns to Earth on April 10.
Before a third spacewalk, Orbital ATK needs to launch a cargo ship to the space station with replacement parts. That shipment was supposed to be there by now, but has been delayed repeatedly because of rocket concerns.
It is unclear when the Atlas V rocket will be ready to soar from Cape Canaveral, Florida.
Nasa has been contracting out cargo deliveries since the end of the space shuttle programme in 2011. The space agency is counting on private companies to do the same with astronauts.