SpaceX's robotic Dragon capsule was released from the International Space Station on Tuesday to begin a five-hour trip back down to Earth, carrying more than a ton of cargo.
NASA astronaut Tom Marshburn and Canada's Chris Hadfield released the Dragon from the grip of the space station's robotic arm just before 7 a.m. ET.
"It looks both beautiful and nominal from here," Hadfield reported as the station flew 256 miles (411 kilometers) above the Pacific.
Marshburn said he was "sad to see the Dragon go. ... She performed her job beautifully, now heading back to her lair."
The Dragon is now going through a sequence of thruster burns that will send it down to a 12:34 p.m. ET splashdown in the Pacific Ocean, 214 miles (344 kilometers) west of Baja California.
This marks the third time that SpaceX's commercial cargo craft has made a round trip to the space station. The first visit, in May 2012, showed NASA that the California-based company could deliver payloads safely. Last October, another Dragon took on the first of 12 cargo runs under the terms of a $1.6 billion contract with the space agency. The current mission launched on March 1, carrying 1,200 pounds (544 kilograms) of supplies and equipment.
Dragon's arrival at the station was delayed by a day, due to a glitch with Dragon's thruster system, but the mission has gone swimmingly since then. Astronauts quickly unloaded the cargo, then packed 2,600 pounds (1,180 kilograms) of gear into the room-sized compartment - including biological samples, station hardware and trash.
Also among the items being returned to Earth are 13 sets of Lego toy blocks that were flown up to the station two years ago aboard the shuttle Endeavour. The models were used by the astronauts in educational videos to demonstrate how machines work in weightlessness. One of the kits, a 3-foot-long (meter-long) scale model of the space station, was so bulky that it would have collapsed under its own weight in Earth's gravity.
Dragon's return was originally scheduled for Monday, but "fairly aggressive" seas at the intended splashdown zone forced a one-day postponement, NASA spokesman Josh Byerly said. The weather was better on Tuesday, and the splashdown was set to take place a couple of hundred miles nearer to shore. "It makes for a bit of a shorter trip to get all this NASA and international-parner science back to port," Byerly said.
A recovery ship is ready to pick up the Dragon and make the 30-hour voyage back to port. The scientific samples will be offloaded there, and then the Dragon and its remaining cargo will be shipped to Houston.
The next SpaceX cargo run is scheduled for September. Another company, Virginia-based Orbital Sciences Corp., is working on a second commercial delivery system that's due for its first test launch next month. But only the Dragon is capable of bringing significant amounts of cargo back to Earth.
NASA selected SpaceX and Orbital to help fill the gap left by the retirement of the space shuttle fleet in 2011. Russian, European and Japanese cargo craft also service the space station. For now, Russia's Soyuz capsules are the only spacecraft that transport people to and from the station, but NASA intends to have U.S.-built commercial spaceships - perhaps including an upgraded version of the Dragon - carrying astronauts within five years.