NASA's Swift satellite telescope, which spent two decades studying the most powerful known blasts of energy in the cosmos, tumbled out of orbit as expected on Wednesday and burned up in Earth's atmosphere over Indonesia, the space agency reported.

The fiery demise of the Neil Gehrels Swift Observatory, weighing roughly 3,200 pounds (1,452kg), came less than three months after a rescue spacecraft failed its mission to boost the satellite to higher orbit and extend its life.

The US Space Force confirmed that Swift's re-entry occurred at 7:39am EST (1239 GMT), as the satellite streaked into the upper atmosphere at about 22 times the speed of sound over Indonesia's North Sumatra province, roughly 200 miles (322km) north of the equator, according to NASA.

NASA said it expected the frictional heat of re-entry would incinerate most of the satellite well above Earth's surface, with some fragments surviving the plunge, though the US space agency reported no damage or injuries on the ground from falling debris.

It was not immediately clear how close the telescope's re-entry point was to North Sumatra's capital and largest city, Medan, home to about 2.5 million people. The population of the province as a whole totals around 16 million.

The Space Force had earlier calculated the risk posed to populated areas as very low, putting the odds of harm coming to anyone on Earth at one chance in 2,100.

Dean Sladen, an aerospace engineer for Britain-based industrial parts supplier Accu Components, said prior to re-entry that only a “handful of small, scorched fragments are expected to make it down, nothing recognisable as a telescope”.

"Satellites this size re-enter the atmosphere regularly, and in nearly 70 years of spaceflight no one has ever been killed by falling debris," Sladen said in an email.

The risk of a re-entry accident grows over the longer term, "which is why designing satellites to come down safely matters more and more," he added.

NASA's prized $500 million Swift satellite was primarily designed to study gamma-ray bursts - the most intense blasts of energy in the universe - using its multi-wavelength array of three telescopes.

Since its launch in 2004, Swift had also studied hundreds of supernova explosions, star-shredding black holes, stellar X-ray flares, asteroids and comets, contributing to some 7,000 published scientific papers. It ceased operations on Oct 20.

The observatory, which lacked its own propulsion system, had long outlasted its two-year design life and had been drifting toward orbital instability for months.

In July, NASA and Arizona-based startup Katalyst launched a specially built rescue vehicle called LINK on a mission to rendezvous with Swift, latch onto the satellite and tug it into a higher, more sustainable orbit.

But the LINK spacecraft itself began spinning uncontrollably soon after reaching space, and by mid-August, mission managers abandoned the effort, resigned to letting Swift fall back to Earth.