But after a troubled landing and 60 hours of operation, there has largely been radio silence from Philae.
The German Aerospace Center (DLR), which led the consortium behind Philae, said the lander is probably now covered in dust and too cold to function.
“Unfortunately, the probability of Philae re-establishing contact with our team at the DLR Lander Control Center is almost zero, and we will no longer be sending any commands,” said Stephan Ulamec, the lander’s project manager at DLR.
The probe’s historic landing famously happened several times in succession – with its first bounce looping nearly 1km back from the comet’s surface and lasting a remarkable 110 minutes.
When it finally settled, its precise location was unknown but images and other data suggested it was sitting at an awkward angle, in the shade.
That meant Philae’s scientific activities were limited to a single charge of its solar-powered batteries.
On several occasions, attempts to contact Philae – via the Rosetta spacecraft, still orbiting Comet 67P – did receive a response.
But the last such contact was on July 9 2015 and the comet is now hurtling into the much colder part of its orbit, plunging to temperatures below -180C at which the lander was never designed to operate.
“It would be very surprising if we received a signal now,” Dr Ulamec said.
The Rosetta mothership may have a chance to take some final pictures of Philae in the summer, during a series of close fly-bys.
Rosetta itself will end its mission when it falls onto the comet in September.
“It’s a sad day, of course. Philae certainly captured the imagination around the world back in 2014.
“But all good things come to an end. In fact, if it had landed properly on the surface in the first place, it all would have been over last March because Philae would have overheated.”
Prof McCaughrean emphasised that the Rosetta orbiter was “still out there doing fantastic science”.