The lander re-established contact at 2122 GMT Sunday, nearly a day after a solar battery recharge roused it from hibernation, they said.
"We had another contact overnight. It wasn't very long, about five minutes," European Space Agency (ESA) senior science advisor Mark McCaughrean told AFP.
The connection was "pretty short and pretty faint," he said, but "we got some data down."
Philae landed on Comet 67P/Churyumov-Gerasimenko on November 12 after an epic 10-year trek piggybacking on its mothership Rosetta.
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It had enough stored battery power for about 60 hours of experiments, enabling it to send home reams of data before going into standby mode.
The hope was that better light as the comet approaches the Sun would recharge Philae's batteries enough for it to reboot, make contact and ultimately resume scientific work.
The first word came on Saturday night -- a two-minute connection with Earth via Rosetta during which Philae sent home about 40 seconds worth of data -- some 300 of an estimated 8,000 data packets on board.
McCaughrean explained that as the comet rotates every 12.5 hours, scientists had hoped for two contacts in the 24 hours after the first, but had only one.
"We missed one, then you begin to worry... Was it just a random event?" he said.
When the signal finally came it was "a bit like when you have a very bad mobile signal and you see you have a signal on your phone but you're really not able to load any webpages, for example," the scientist said.
Comet "67P" is now 215 million kilometres from the Sun and 305 million km from Earth, racing at a speed of 31.24 km a second.