Astrobiology Top 10: Humankind’s Robotic Footprint on a Comet
As 2014 comes to a close, Astrobiology Magazine is counting down the ‘Top 10’ stories of the past year. At number 2 is a story that captured the world’s imagination. After more than a decade en route, the European Space Agency’s Rosetta mission delivered the Philae lander to the surface of a comet.
Watch Live: Historic Rosetta Comet Landing was originally published on November 12, 2014.
Contact with Philae Re-established was originally published on November 13, 2014.
Pioneering Philae Completes Main Mission before Hibernation originally ran on November 16, 2014.
Watch Live: Historic Rosetta Comet Landing
By Johnny Bontemps – Nov 12, 2014
Today is the day!
After a 10-year and 4-billion-mile journey, the European Space Agency’s Rosetta spacecraft will finally land a robotic probe on a comet.
The event can also be followed here with NASA commentary starting at 6 a.m. PST (9 a.m. EST).
The Rosetta spacecraft was launched in March 2004 and reached comet 67P/Churyumov-Gerasimenko last August, becoming the first spacecraft to orbit a comet. For the last couple months, Rosetta has been capturing images and surveying the surface of 67P/C-G.
The satellite will release its 220-pound lander Philae at 11:35 p.m. PST (2:35 a.m. EST). After floating from a height of 13 miles, the small probe is expected to touch down today at 7:35 a.m. PST (10:35 a.m. EST).
In keeping with the mission’s Egyptian theme, the landing site (formerly dubbed “J”) has been named Agilkia after an island on the Nile River. The ancient Egyptian temple complex of Philae was moved to Agilkia when the building of the Aswan dams last century threatened to flood the site. The Rosetta spacecraft was named after the Rosetta Stone.
After fixing itself onto the comet using harpoons and drills, the Philae lander will use its 16 instruments to study the composition of 67P/C-G.
As the comet gets closer to the Sun and heats up, it will also release gas and particles that have been trapped since the formation of our Solar System. The mission could provide answers about the origins of Earth’s water and life.
The Rosetta spacecraft will continue to study 67P/CG from orbit. The comet will make its closest pass to the Sun in August 2015.
This video from the Open University includes five common questions answered about the Rosetta landing:
Contact with Philae Reestablished
By Aaron L. Gronstal – Nov 13, 2014
Update: Nov 17, 2014: Philae lander’s battery power has dropped too low to safely maintain operations, and the lander is now in standby mode. ESA reports that the lander may be in standby mode for quite some time: http://blogs.esa.int/rosetta/2014/11/15/our-landers-asleep/
Update: 13:40 GMT, Nov 13, 2014: In ESA’s media brief, the mission team explained that, after bouncing, the Philae lander may be positioned in a permanent shadow on the comet 67P/Churyumov–Gerasimenko. This could affect the amount of sunlight that reaches the lander, potentially limiting the energy produced by its solar panels. As of now, there’s no telling how long Philae will last. Rosetta itself has another 20 months of exploring the comet in its primary mission.
Yesterday, the European Space Agency’s (ESA) Rosetta mission performed the first soft landing on a comet. The landing didn’t go entirely according to plan, but contact has been reestablished and the Philae lander appears to be safely on the comet.
Bouncing Down to a Comet
When Philae touched down on the comet 67P/Churyumov–Gerasimenko, it was supposed to fire anchoring harpoons that would keep it safely attached to the comet’s surface. However, the harpoons did not fire. Instead of being safely anchored, the lander relied on the comet’s low gravity to stay in position.
During ESA’s live coverage of events, Dr. Stephan Ulamec, Head Rosetta Lander at the German Aerospace Center (DLR), suggested that Philae had “landed twice,” and may have bounced up and turned slightly after first contact with the comet.
The sequence of events during the landing was a bit harrowing for all who were watching, and it now appears that the craft bounced twice. Philae made it to the surface of the comet and sunk about four centimeters into soft dust and debris. But then the small craft bounced off as its harpoons failed to fire.
Gravity on 67P/Churyumov–Gerasimenko has been estimated (based on simulations) to be only one ten-thousandth of what we experience here on Earth.
This low gravity meant that Philae’s first bounce after landing took it about a kilometer from the surface before falling back down toward the comet two hours later. When it hit the comet a second time, Philae bounced again – but this time it only lifted a short way and fell back to the comet after 10 minutes.
Now, it appears that Philae is safely in position.
In Position for Science
Philae is currently sending a steady signal, and data is pouring back to Earth. Using its Comet nucleus Infrared and Visible Analyzer (CIVA), Philae has sent back images to confirm that it is safely at the comet’s surface.
Before the lander begins its primary mission, the mission team will work to determine exactly where Philae has come to rest on the comet.
The Philae lander was released from the Rosetta spacecraft after a nearly decade-long journey through space. The small craft spent seven hours descending toward the surface of Comet 67P/Churyumov–Gerasimenko. At 16:03 GMT, a signal was received that Philae had become the first robotic mission to perform a soft landing on a comet.
When Philae bounced up from the comet, the comet continued turning while the lander was ‘airborne’ for two hours. When the lander finally came to rest, it ended up in a position slightly different than the intended landing site.
Philae‘s original landing site was carefully selected for scientific value, and also for optimum exposure to the sunlight that will keep the lander charged.
It is now important to determine the lander’s exact location so that the mission team can determine how effectively its solar panels can power the spacecraft, and the nature of the surface where the probe will be drilling.
The Rosetta mission will return valuable data about Comet 67P/Churyumov–Gerasimenko that will help astrobiologists understand the formation of our solar system and the potential role of comets in delivering materials for the origin of life on the early Earth.
For more details about the mission and its goals:
Recent Images from the Rosetta Mission
After a ten-year journey, Rosetta and Philae had finally reached their destination, Comet 67P/Churyumov–Gerasimenko. Rosetta spent many weeks studying the comet, sending lots of information back to Earth. But where was Philae going to land?Credit: European Space Agency, ESA (YouTube)
Pioneering Philae Completes Main Mission before Hibernation
Rosetta’s lander has completed its primary science mission after nearly 57 hours on Comet 67P/Churyumov–Gerasimenko.
After being out of communication visibility with the lander since 09:58 GMT / 10:58 CET on Friday, Rosetta regained contact with Philae at 22:19 GMT /23:19 CET last night. The signal was initially intermittent, but quickly stabilised and remained very good until 00:36 GMT / 01:36 CET this morning.
In that time, the lander returned all of its housekeeping data, as well as science data from the targeted instruments, including ROLIS, COSAC, Ptolemy, SD2 and CONSERT. This completed the measurements planned for the final block of experiments on the surface.
In addition, the lander’s body was lifted by about 4 cm and rotated about 35° in an attempt to receive more solar energy. But as the last science data fed back to Earth, Philae’s power rapidly depleted.
“It has been a huge success, the whole team is delighted,” said Stephan Ulamec, lander manager at the DLR German Aerospace Agency, who monitored Philae’s progress from ESA’s Space Operations Centre in Darmstadt, Germany, this week.
“Despite the unplanned series of three touchdowns, all of our instruments could be operated and now it’s time to see what we’ve got.”
Against the odds – with no downwards thruster and with the automated harpoon system not having worked – Philae bounced twice after its first touchdown on the comet, coming to rest in the shadow of a cliff on Wednesday 12 November at 17:32 GMT (comet time – it takes over 28 minutes for the signal to reach Earth, via Rosetta).
The search for Philae’s final landing site continues, with high-resolution images from the orbiter being closely scrutinised. Meanwhile, the lander has returned unprecedented images of its surroundings.
While descent images show that the surface of the comet is covered by dust and debris ranging from millimetre to metre sizes, panoramic images show layered walls of harder-looking material. The science teams are now studying their data to see if they have sampled any of this material with Philae’s drill
“We still hope that at a later stage of the mission, perhaps when we are nearer to the Sun, that we might have enough solar illumination to wake up the lander and re-establish communication, ” added Stephan.
From now on, no contact will be possible unless sufficient sunlight falls on the solar panels to generate enough power to wake it up. The possibility that this may happen later in the mission was boosted when mission controllers sent commands to rotate the lander’s main body with its fixed solar panels. This should have exposed more panel area to sunlight.
The next possible communication slot begins on 15 November at about 10:00 GMT / 11:00 CET. The orbiter will listen for a signal, and will continue doing so each time its orbit brings it into line-of-sight visibility with Philae. However, given the low recharge current coming from the solar panels at this time, it is unlikely that contact will be re-established with the lander in the near future.
Meanwhile, the Rosetta orbiter has been moving back into a 30 km orbit around the comet.
It will return to a 20 km orbit on 6 December and continue its mission to study the body in great detail as the comet becomes more active, en route to its closest encounter with the Sun on 13 August next year.
Over the coming months, Rosetta will start to fly in more distant ‘unbound’ orbits, while performing a series of daring flybys past the comet, some within just 8 km of its centre.
Data collected by the orbiter will allow scientists to watch the short- and long-term changes that take place on the comet, helping to answer some of the biggest and most important questions regarding the history of our Solar System. How did it form and evolve? How do comets work? What role did comets play in the evolution of the planets, of water on the Earth, and perhaps even of life on our home world.
“The data collected by Philae and Rosetta is set to make this mission a game-changer in cometary science,” says Matt Taylor, ESA’s Rosetta project scientist.
Fred Jansen, ESA’s Rosetta mission manager, says, “At the end of this amazing rollercoaster week, we look back on a successful first-ever soft-landing on a comet. This was a truly historic moment for ESA and its partners. We now look forward to many more months of exciting Rosetta science and possibly a return of Philae from hibernation at some point in time.”