Japan's space agency said Thursday that a quarter-of-a-billion-dollar satellite sent to study mysterious black holes has failed, concluding a month-long effort to salvage the ambitious project closely watched across the globe.

The ultra-high-tech satellite "Hitomi" -- or eye -- was launched in February to observe X-rays emanating from black holes and galaxy clusters.

But the device -- developed in collaboration between the Japan Aerospace Exploration Agency (JAXA), NASA and other groups -- stopped responding to ground crews around the end of last month, apparently due to a lack of battery power.

Technicians scrambled to find out what had happened to Hitomi and recover its functions.

"We concluded that the satellite is in a state in which its functions are not expected to recover," Saku Tsuneta, director general of JAXA's Institute of Space and Astronautical Science, told a press conference on Thursday.

"I deeply apologise for abandoning operation" of the satellite, he said.

JAXA officials said it is highly likely that solar panels, which power the satellite's battery, became separated from the device.

They had said earlier this month that the satellite could still function if half of the six solar panels were intact.

Black holes have never been directly observed, but scientists believe they are huge collapsed stars whose enormous gravitational pull is so strong that nothing can escape.

The announcement in February that gravitational waves had been detected for the first time added to evidence of their existence after scientists found the waves had been caused by two enormous black holes colliding.

The next launch of a similar satellite is scheduled in 2028 by the European Space Agency.

Tsuneta said the loss of the device, which cost 31 billion yen ($273 million), including the cost of launching it, was not only a disappointment for Japan but for overseas astronomers as well who held out high hopes for its success.

"We're sorry we cannot respond to the expectations," he said.

The satellite was launched by the country's mainstay H-IIA rocket from the Tanegashima Space Center in southern Japan.

Japan has a massive space programme and has achieved successes in both scientific and commercial satellite launches while also sending astronauts on space shuttle and International Space Station missions.