The European Space Agency (ESA) made history last fall with the long-awaited arrival of their Rosetta mission to comet 67P, a decade-long trip intended to establish orbit around a cold and ancient time capsule from the darkest depths of the outer Solar System. But not only that, Rosetta brought along Philae, a lander. Humanity had never landed on a comet until 2014 with the arrival of Philae.
Rosetta’s arrival and establishment in its science orbit alone was incredible, but a successful landing and real science on the comet’s surface was always the big payoff. Now Philae, the lander that infamously went into hibernation after completing its science mission on Nov. 14, 2014, is awake again after seven months of silence.
ESA announced that on June 13, signals from the intrepid lander were received at the European Space Operations Centre in Darmstadt at 22:28 CEST. On social media, the reaction was a mix of disbelief and elation. Philae’s first tweets on its “return” read in part: “Hello Earth! Can you hear me?… Hello @ESA_Rosetta! I’m awake! How long have I been asleep?”
ESA added, “More than 300 data packets have been [analyzed] by the teams at the Lander Control Center at the German Aerospace Center (DLR).” ESA revealed that they await the next contact from the lander, and that 8,000 data packets in its mass memory will be analyzed. This will aid researchers in further discovering what life on a live comet is like.
It appears Philae, despite having been “asleep” on the craggy face of a comet for the better half of a year, is in good shape. DLR’s Philae project manager, Dr. Stephan Ulamec, confirmed this bit of news: “Philae is doing very well: It has an operating temperature of -35ºC and has 24 watts [of power] available. The lander is ready for operations.”
It was also revealed by ESA that Philae “spoke” to ground controllers for 85 seconds, its first communication since November 2014, and data reveals that the lander has been awake for some time. Dr. Ulamec continued, “We have also received historical data – so far, however, the lander had not been able to contact us earlier.”
In March, ground controllers began looking out for signals from the lander. A previous AmericaSpace article published on March 12 underscored the conditions that needed to be met in order for Philae to once again “wake up” from its sleep: “DLR stated that in order for Philae to get back to work, several conditions must first be met. The interior of the lander must be ‘warmed up’ to a temperature of -45 degrees Celsius. In addition, Philae must be able to generate at least 5.5 watts from its solar panels. According to DLR, ‘As soon as Philae realises that it is receiving more than 5.5 watts of power and its internal temperature is above –45ºC, it will turn on, heat up further and attempt to charge its battery.’ A common household light bulb, by comparison, is rated at 60 watts. Philae was designed in part to withstand low-power operations.”
DLR pointed out at the time that its engineers had started engaging in “blind commanding” to optimize Philae’s heating, and to conserve power. While Philae may have not been able to respond to those commands at that time, it would have still been able to receive them.
An issue contributing to Philae not waking up earlier is the location of the lander on the face of the comet. The landing site, called “Abydos,” appears to be heavily shaded in photos obtained, and Philae seems to be surrounded by craggy, rocky cliff-like formations, inhibiting exposure to the Sun. However, in the last few months, Comet 67P/Churyumov-Gerasimenko’s orbit has taken it closer to the Sun, which may have aided in Philae’s “wake up” on this day. According to recent images from the Rosetta spacecraft still orbiting the comet, increasing activity has been detected.
Philae, which separated from Rosetta to make its historic landing on Nov. 12, 2014, had an arduous journey when it reached Comet 67P/Churyumov-Gerasimenko’s surface. It landed three times due to its landing harpoons not deploying as expected, but soon settled into its landing site, completing and transmitting its full science package before falling asleep due to lack of power. More recently, the Rosetta orbiter in conjunction with its ground team has been working to pinpoint the location on Philae on the comet’s nucleus.
What a long, strange trip it has been. But now, with Philae’s re-awakening, it appears the “trip” has been extended. It is hoped that Philae may return more scientific data from the face of one of the most “alien” worlds known, in hopes that we may not just understand its origins, but also our origins.
Stay tuned to AmericaSpace for more updates on Philae’s re-awakening. This article was authored by Emily Carney and Mike Killian.
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