Ground controllers bid a final farewell to robot lab Philae, cutting communications after a year-long silence with the tiny probe hurtling through space on the surface of a comet.

"Today communication with Philae was stopped," Andreas Schuetz of German space agency DLR told AFP from ground control in Cologne.

"This is the end of a... fascinating and successful mission for the public and for science."

The decision to cut the link was taken to save energy on mothership Rosetta, orbiting around comet 67P/Churyumov-Gerasimenko, for the final weeks of its own historic mission.

Its batteries depleted, Philae's last successful communication with Earth was on 9 July last year.

The lines had been left open on the very small chance of it coming back to life.

On the eve of the break, Philae tweeted:

The washing machine-sized probe has been on 67P's surface since 12 November 2014, an exciting part of the ESA's groundbreaking Rosetta mission to probe a comet for clues to the origins of life on Earth.

Rosetta remains in 67P's orbit, but as the comet moves further and further away from the Sun with its battery-boosting rays, the spacecraft needs to save all the energy it can.

"We need to maximise the power available to Rosetta's scientific instruments, and thus had no choice but to turn off the ESS," ESA senior science advisor Mark McCaughrean told AFP.

ESS stands for the Electrical Support System Processor Unit on board of Rosetta, which was used for Philae to send home the results of its science experiments and intermittent status reports.

Rosetta's own mission will come to an end on 30 September, when it makes a crash landing to join stranded Philae on the comet surface.