Communication with a newly-launched, innovative Japanese satellite with X-ray telescopes meant to study black holes and other space mysteries has failed.
Japan Aerospace Exploration Agency spokeswoman Izumi Yoshizaki said efforts to restore communication links since the problem began on Saturday afternoon had been unsuccessful and it was investigating what might have happened to the Hitomi satellite, which was launched on February 17.
"We are really doing our best," she said.
She said the agency was looking into a statement from the Joint Space Operations Centre, (JSpOC), the US military organisation that tracks and identifies objects in space, that Hitomi may have splintered into several pieces.
Whether that had happened or not is unclear, Ms Yoshizaki said.
Jonathan McDowell, an astronomer at the Harvard-Smithsonian Centre for Astrophysics, said he suspected the satellite had suffered an "energetic event", possibly a gas leak or a battery explosion, that sent it tumbling end-over-end.
That would mean its antenna was not pointing where it needed to, which is why the satellite cannot communicate with the space agency, he said.
The danger is that in that state, the satellite may not be able to draw the solar energy it needs to its panels and its battery will run down before the space agency can reconnect with the satellite and try to fix it.
"Everyone's just gutted," said Mr McDowell, who works with another high-tech space X-ray telescope, Chandra.
"To hear that they've run into this piece of bad luck, it's so very sad. I know enough about how the sausage was made to know that this could have easily have happened to us. Space is very unforgiving."