Space station junk burns up over ocean

NASA astronaut Clayton Anderson, an Expedition 15 flight engineer, tosses a hefty unneeded ammonia tank the size of a refrigerator overboard from the international space station during a spacewalk on July 23, 2007. NASA said the tank broke up Sunday during atmospheric re-entry.

A piece of space trash the size of a refrigerator plunged into Earth's atmosphere late Sunday to burn up over the southern Pacific Ocean, more than a year after an astronaut tossed it off the international space station, NASA officials said Monday.

Space station program manager Mike Suffredini told reporters that the orbital trash, a 1,400-pound (635-kilogram) tank of toxic ammonia coolant, slammed into Earth's atmosphere and broke up at an altitude of about 50 miles (80 kilometers) as it flew above the ocean just south of Tasmania.

"What debris may have been still together after re-entry, it fell into the ocean between Australia and New Zealand," Suffredini said during a NASA briefing. "I know a lot of folks were wondering what the end result of that was."

NASA expected up to 15 pieces of the tank to survive the fiery plunge, ranging in size from about 1.4 ounces (40 grams) to nearly 40 pounds (17.5 kilograms). The largest pieces, if they survived, may have hit the ocean at speeds of up to 100 mph (164 kilometers per hour).

The U.S. Space Surveillance Network kept a close watch on the ammonia tank for NASA as part of its effort to monitor the thousands of pieces of orbital debris circling Earth.

Known as an Early Ammonia Servicer, the coolant tank was the largest piece of trash ever disposed of by hand from the space station. NASA astronaut Clayton Anderson junked the tank while wearing a spacesuit and standing at the tip of the station's Canadian-built robotic arm during a July 23, 2007, spacewalk.

"We're really fortunate to be able to track objects to a fairly small size," Suffredini told Space.com before the ammonia tank re-entered, adding that the ammonia tank was rather large and easy to track.

NASA takes great care to ensure that any trash tossed overboard from the space station does not endanger other spacecraft or people on Earth, he added.

The obsolete tank had served as a spare reservoir of ammonia coolant for the space station in case of leaks since 2001, but was no longer required after astronauts activated the outpost's main cooling system in early 2007. Because the tank was so old, engineers were worried that its structural integrity wouldn't hold during a return to Earth aboard a NASA shuttle.

Instead they asked Anderson to toss it during a spacewalk dedicated to discarding old equipment. He also jettisoned a 212-pound (96-kilogram) video camera stand. That item burned up in Earth's atmosphere earlier this year.

"I just like it when they've re-entered and it's not a problem," Suffredini said. "One of the big concerns for any orbiting pressurized spacecraft is orbital debris."