The Philae comet lander spoke to Earth again late Friday night, a welcome development for mission scientists eager to download as much data as possible before the lander's batteries run down and it can no longer transmit signals.
Shortly before midnight local time, mission controllers at the European Space Operations Centre in Darmstadt, Germany, confirmed that communications have been re-established with the lander. In addition to acquiring data, the flight team also sent instructions to the lander to try to tilt its solar panels into a more favourable position.
The lander has been feeding back data in spurts from its location on Comet 67P/Churyumov-Gerasimenko as it runs through a series of experiments – the first ever conducted on the surface of a comet.
Data can only be received when the Rosetta spacecraft, which is in orbit around the comet, has a clear line of sight to the lander and can relay the lander's signal to Earth.
When the lander's signal cut out Friday morning at the expected time, it was in the process of attempting to drill into the comet's surface to extract samples for analysis by a suite of instruments on board. Data from this attempt is thought to be part of what came down from the lander during its Friday night call, but the results are not yet known.
Scientists have already received some data from the Alpha Particle X-ray Spectrometer, which measures the chemical elements in the comet's surface material.
Philae touched down on Wednesday, but bounced after is first contact with the comet and came to rest on its side in the shadow of a cliff with its solar panels starved for light.
With limited time and battery power available before the lander dies, scientists are anxious for the lander to return at least one set of measurements that may reveal for the first time what comets are made of and their role in the formation of the solar system.
"We're on the cutting edge of science," said Matt Taylor, project scientist with the Rosetta mission. "It's beyond words."
During a science briefing Friday morning, Dr. Taylor held back tears as he apologized for "upsetting a lot of people." The apology was in reference to a shirt bearing images of women in skimpy attire, which Dr. Taylor was seen wearing throughout the widely televised landing. The shirt triggered a storm of criticism on social media sites.