After recovering from thruster problems and flying a near-perfect rendezvous, a SpaceX cargo ship pulled up to the International Space Station early Sunday and stood by while commander Kevin Ford, wielding the lab's robot arm, locked onto a grapple fixture to secure the spacecraft for berthing.
Operating the Canadian-built arm from a robotics work station in the multi-window Cupola compartment, Ford grappled the Dragon cargo ship at 5:31 a.m. EST (GMT-5), an hour earlier than expected, as the two spacecraft passed 253 miles above northern Ukraine.
Flight controllers at the Johnson Space Center in Houston congratulated the crew for "a brilliant capture."
"Let me just say congratulations to the SpaceX and Dragon team in Houston and in California," Ford replied. "As they say, it's not where you start but where you finish that counts, and you guys really finished this one on the mark. You're aboard, and we've got a lot of science to bring aboard and get done."
Capture came a day later than originally planned because of problems pressurizing rocket thruster propellant tanks shortly after the ship reached orbit Friday.
But SpaceX flight controllers at company headquarters in Hawthorne, Calif., were able to coax the system into normal operation. While the root cause of the problem is not yet known, the thrusters worked normally throughout the replanned rendezvous and the approach and capture went off without a hitch.
"Great job this morning, guys," spacecraft communicator Kathy Bolt radioed from mission control in Houston. "Always nice to see something that plays back exactly the way you trained."
"I remember exactly where I was the very first time I ever heard of this scheme ... when I was a young astronaut," Ford recalled. "And I said, 'We're going to do what?' That was when it was an idea, and now it's starting to become routine. So great job to everybody who dreamed it up and who made it all work. It's really something to see."
Making the company's third space station visit -- the second fully operational flight under a $1.6 billion commercial contract with NASA -- the Dragon capsule is loaded with some 2,300 pounds of supplies, spare parts and science gear.
The manifest includes 178 pounds of crew provisions, including food and clothing; 300 pounds of space station hardware, including replacement components for the lab's carbon dioxide removal system; and more than 700 pounds of science gear, including a pair of Glacier freezers and experiment components.
During the first two dockings of Dragon capsules last May and October, the station crew attached the cargo ship to the station, manually operating the arm to maneuver the spacecraft to the Earth-facing port of the forward Harmony module.
But this time around, ground controllers at the Johnson Space Center took over, sending commands to remotely operate the arm through berthing to demonstrate their ability to carry out complex arm procedures and to give the astronauts a bit of a break during a busy day.
The process was executed slowly but surely and Ford reported the Dragon was safely locked to its docking port at 8:56 a.m.
The same procedures will be used later in the week when ground controllers use the arm to pull a spacewalk equipment handling fixture from the Dragon's unpressurized trunk section. The fixture will be mounted on the station's exterior for use during a future spacewalk.
The Dragon is the only space station cargo craft now in operation that can bring equipment and experiment samples back to Earth, a critical capability that was lost when NASA's space shuttle fleet was retired in 2011.
As the crew unpacks the capsule's pressurized compartment, they will re-load the spacecraft with about 1.5 tons of no-longer needed gear, components that need refurbishment or failure analysis and experiment samples that are needed by scientists back on Earth.
If all goes well, the astronauts will use the robot arm to detach the capsule March 25, setting the stage for a fiery re-entry and splashdown in the Pacific Ocean southwest of Los Angeles.