The team leading the European Space Agency’s (ESA) Rosetta mission has chosen Nov. 12 as the date to deploy the piggybacked Philae lander for mankind’s history-making first attempt to touchdown on the surface of a comet.
The “head” of the bizarre comet 67P/Churyumov-Gerasimenko had already been selected as the primary landing site for Philae, at a target known as “Site J,” which is located on the smaller of the two “lobes.” See location in image above.
The backup landing target, known as “Site C,” is located on the comet’s “body,” which is the larger of the two lobes.
Both landing sites were originally unveiled at a media briefing held at ESA headquarters on Sept.15. But the exact date and timing had not yet been determined—until now.
The landing sites were announced Sept. 15 by Stephan Ulamec, Philae Lander Manager at the DLR German Aerospace Center, barely six weeks after Rosetta’s Aug. 6 rendezvous with comet 67P, following a decade-long chase of over 6.4 billion kilometers (4 billion miles).
Since arriving, the team ’s primary task has been to utilize Rosetta’s 11 science instruments to conduct an unprecedented scientific analysis of the comet to gather as much data as possible to maximize the chances of success for the Philae lander to safely soft land on comet 67P and study it for as long as possible.
“All of Rosetta instruments are supporting the landing site selection,” said Holger Sierks, principal investigator for Rosetta’s OSIRIS camera from the Max Planck Institute for Solar System Research in Gottingen, Germany.
The team has been in a race against time to first select a suitable landing zone quickly and then develop the complex landing sequences, since the comet warms up and the surface becomes ever more active as it swings in closer to the Sun and makes the landing ever more hazardous beyond November.
Philae’s landing will be entirely automatic with no intervention from Earth. The 100-kg lander is equipped with 10 science instruments.
Since the descent to the comet is passive, it is only possible to predict that the landing point will take place within a “landing ellipse” typically a few hundred meters (or yards) in size.
Therefore, for both sites J and C an area encompassing about one square kilometer (four-tenths of a square mile) was assessed.
Although Site J was chosen unanimously as the primary landing site, nothing was straightforward.
“As we have seen from recent close-up images, the comet is a beautiful but dramatic world—it is scientifically exciting, but its shape makes it operationally challenging,” says Ulamec.
“This was not an easy task. Site J is a mix of flat areas and rough terrain. It’s not a perfectly flat area. There is still risk with high slope areas.”
“Site J is just 500-600 meters away from some pits and an area of comet outgassing activity. They will become more active as we get closer to the Sun,” explained Sierks.
But Site J won out because “the majority of terrain has slopes of less than 30 degrees relative to the local vertical and because there are relatively few large boulders. The area also receives sufficient daily illumination to recharge Philae and continue surface science operations beyond the initial 64-hour battery-powered phase,” according to an ESA statement.
Since the landing sites were selected, the flight dynamics and operations teams at ESA have been pouring over all the data for both the primary and backup landing sites in order to develop detailed “flight trajectories and timings for Rosetta to deliver the lander … for separation and landing on Nov. 12.”
Here are the detailed landing sequences from ESA:
Primary Site J:
“For the primary landing scenario, targeting Site J, Rosetta will release Philae at 3:35 a.m. EST (9:35 a.m. Central European Time) at a distance of 14 miles (22.5 kilometers) from the center of the comet, landing about seven hours later. The one-way signal travel time between Rosetta and Earth on Nov. 12 will be 28 minutes and 20 seconds, meaning that confirmation of the landing will arrive at Earth ground stations at around 11 a.m. EST (5 p.m. CET).”
Backup Site C:
“If a decision is made to use the backup site, Site C, separation will occur at 8:04 a.m. EST (2:04 p.m. CET) at a distance of 7.8 miles (12.5 kilometers) from the center of the comet. Landing will occur about four hours later, with confirmation on Earth at around 12:30 p.m. EST (6:30 p.m. CET). The timings are subject to uncertainties of several minutes.”
The three-legged Philae lander will fire two harpoons and use ice screws to anchor itself to the four-kilometer-wide (2.5-mile) comet’s surface. Philae will collect stereo and panoramic images and also drill 20 to 30 centimeters into comet 67P and sample its incredibly varied surface.
“We will make the first ever in situ analysis of a comet at this site, giving us an unparalleled insight into the composition, structure and evolution of a comet,” says Jean-Pierre Bibring, a lead lander scientist and principal investigator of the CIVA instrument at the IAS in Orsay, France.
“Site J in particular offers us the chance to analyse pristine material, characterise the properties of the nucleus, and study the processes that drive its activity.
“It’s amazing how much we have learned so far.
“We are in a true revolution of how we think planets form and evolve,” Bibring elaborated at the briefing.
“We will make many types of scientific measurements of the comet from the surface. We will get a complete panoramic view of the comet on the macroscopic and microscopic scale.”
Final confirmation of the primary landing site and its landing scenario will be made Oct. 14 after a formal Lander Operations Readiness Review of the most up-to-date, high-resolution imagery and spectra obtained, according to ESA.
“No one has ever attempted to land on a comet before, so it is a real challenge,” says Fred Jansen, ESA Rosetta mission manager.
ESA also announced that they will hold a public competition to name the primary landing site. Details will be forthcoming.
Stay tuned here for continuing developments.
Want to keep up-to-date with all things space? Be sure to “Like” AmericaSpace on Facebook and follow us on Twitter: @AmericaSpaceMissions » Rosetta »