European scientists have revised their plans for the comet lander Philae and are now focussing on getting images and drill samples if communications are restored.

After coming to rest in the shadows when it landed on a comet in November, Philae woke up in June, delighting scientists from the European Space Agency, who came up with plans for several experiments they wanted to run before working up to the most risky one - drilling into the surface.

But with the 100kg washing-machine size lander having been silent for over a month now, those plans have been revised.

"The problem is not power, but communications," Aurelie Moussi from space agency CNES said. "We have to find something to do in a shorter duration."

She said the priorities were now to get pictures from the surface and also to drill into the surface, which Philae was notable to do when it first landed in November.

Scientists hope that samples from the surface of the comet67P/Churyumov-Gerasimenko will help show how planets and life are created as the rock and ice that make up comets preserve organic molecules like a time capsule.

The Rosetta spacecraft, which is orbiting the comet and through which communications with Philae are relayed to Earth, has spent two weeks at a different part of the comet.

But since 11 August it has been back in an area where it should be able to communicate with Philae.

No contact has been established though and the data from the last communications shows one of the lander's transmitters is broken.

Its two receivers are also not working as they should, Barbara Cozzoni, Philae operations engineer said.

The comet yesterday passed the closest point to the sun on its orbit, about 185 million kilometres from the sun.   

The comet's activity levels have been increasing as it approaches the sun and it is now shedding up to 1,000kg of dust and enough water to fill two bathtubs every second.

When Rosetta first approached the comet last year, the comet was giving off only about two small glasses of water per second.

Scientists have also observed powerful gas jets, though Ms Cozzoni said it was unlikely that Philae could be pushed off into space by a jet.