An astronaut using the International Space Station's robot arm successfully plucks a commercial cargo ship out of open space to complete a dramatic rendezvous.

Gotcha! The robotic arm of the International Space Station captures the Dragon capsule.

In a moment of high drama on the high frontier, flight engineer Donald Pettit, operating the International Space Station's robot arm, this morning reached out and locked onto SpaceX's Dragon capsule.

That capture of the commercial cargo ship came after a complex rendezvous, a final sequence of approach-and-retreat test maneuvers and quick work to adjust critical sensors that were getting fooled by reflections from a Japanese research module.

The last-minute hiccups were just that, relatively minor adjustments to correct for the real-world performance of complex laser and infrared imagers used to compute the Dragon cargo ship's velocity and distance from the station.

The SpaceX Dragon cargo ship as seen from the International Space Station Friday, poised just below the lab complex awaiting capture by the station's robot arm.

But like everything in the world of manned spaceflight, where the stakes are high and the margins for error small, flight controllers in Houston and at SpaceX's Hawthorne, Calif., control center took their time, inserting additional checks to make sure everything was working properly.

Now running well behind schedule, flight controllers left it up to Pettit as to whether he felt comfortable grappling the spacecraft in orbital darkness or would prefer delaying to the next daylight pass depending on lighting conditions. When all was said and done, the crew was about two hours behind schedule when the Dragon completed its approach, halting at a designated capture point 30 feet directly below the lab complex.

As the huge space station and the diminutive cargo craft flew in tandem at 5 miles per second, Pettit, working inside the lab's multi-window cupola module, decided to press ahead in orbital darkness, guiding the arm's latching end effector onto a grapple fixture on the side of the cargo ship at 9:56 a.m. EDT (GMT-4). Internal snares were tightened to secure the spacecraft to the arm, completing a rendezvous that began with Dragon's launch Tuesday from the Cape Canaveral Air Force Station.

Like a bird swooping to its perch, the Dragon cargo ship moves into position for capture at the International Space Station.

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Success! Space station snags SpaceX Dragon capsule