Comet lander makes second contact
The Philae spacecraft has been in touch with Earth from a comet for the second time since waking up - though it delivered less data than on its first contact.
Sylvain Lodiot, spacecraft operations manager for Philae's mothership Rosetta, said Philae had sent back five packets of data on Sunday night, a day after it broke its seven-month silence.
Philae became the first spacecraft to settle on a comet when it touched down on icy 67P/Churyumov-Gerasimenko in November, but only managed to send data to Earth for about 60 hours before its batteries ran out.
Scientists' hopes that the probe would wake up as the comet approached the sun, enabling Philae's solar panels to absorb enough light to charge its main battery, were fulfilled over the weekend.
Philae broke its silence on Saturday by sending a signal back to Earth via Rosetta, which is between 124 and 150 miles away from the comet.
Philae then got in touch again on Sunday night, sending back five packets of data, Mr Lodiot said.
It is not clear why the connection was less stable, but scientists suspect a slight increase in the lander's distance from Rosetta may have been a factor.
"Now we have the green light from all the scientists and from the mission manager to optimise everything we can do for Philae contact," Mr Lodiot added.
On Wednesday, scientists plan a manoeuvre to bring Rosetta closer, reducing the distance to Philae as little as 112 miles, something they had planned to do regardless of Philae's status, he said.
For the time being, the washing machine-size lander is only sending back what controllers describe as housekeeping and systems data. To be able to get more, scientists will need to improve communications and send new commands.
"It's going to take a few days," Mr Lodiot said.
Scientists hope that Philae's restart will allow them to clear up the mystery of where exactly on the two-and-a-half-mile-wide comet the probe has landed.