Scientists are trying to recover a massive NASA balloon and several tonnes of equipment that drifted into outback Queensland over the weekend.

The 300-metre balloon was launched recently from Alice Springs in the Northern Territory to gather data about the universe.

The balloon is the size of the Melbourne Cricket Ground and carries two tonnes of equipment used to study outer space phenomena.

Launch director Associate Professor Ravi Sood says it landed without incident near Longreach in central western Queensland on Sunday afternoon.

"About 70 kilometres south of Longreach very close to a farm track, so we should have our recovery people there some time this morning," he said.

"The balloon landed separately - the balloon landed about 20 kilometres west of where the instrument and the parachute impacted."

Associate Professor Sood says overall the exercise was a success, considering its magnitude.

"The equipment was just about two tonnes - then there was about a tonne of ballast and the balloon weighed about two tonnes - we had a gross lift of about four or five tonnes," he said.

"It was spectacularly successful ... the whole flight was flawless and that's a great credit to the team that comes out from the Columbia Scientific Balloon Facility in Texas."

He says some residents may have thought the balloon was a UFO.