The European Space Agency's Rosetta mission has chosen five candidate landing sites on comet 67P/Churyumov-Gerasimenko for its Philae lander.
Philae's descent to the comet's nucleus, scheduled for this November, will be the first such landing ever attempted.
“This is the first time landing sites on a comet have been considered,” said Stephan Ulamec, Philae Lander Manager at the German Aerospace Center, Cologne, Germany. “The candidate sites that we want to follow up for further analysis are thought to be technically feasible on the basis of a preliminary analysis of flight dynamics and other key issues – for example, they all provide at least six hours of daylight per comet rotation and offer some flat terrain. Of course, every site has the potential for unique scientific discoveries.”
For each possible zone, important questions must be asked: Will the lander be able to maintain regular communications with Rosetta? How common are surface hazards such as large boulders, deep crevasses or steep slopes? Is there sufficient illumination for scientific operations and enough sunlight to recharge the lander’s batteries beyond its initial 64-hour lifetime without causing overheating?
The potential landing sites were assigned a letter from an original pre-selection of 10 possible sites, which does not signify any ranking. Three sites (B, I and J) are located on the smaller of the two lobes of the comet and two sites (A and C) are located on the larger lobe.
“The process of selecting a landing site is extremely complex and dynamic; as we get closer to the comet, we will see more and more details, which will influence the final decision on where and when we can land,” said Fred Jansen, Rosetta's mission manager from the European Space Agency's Science and Technology Centre in Noordwijk, The Netherlands. “We had to complete our preliminary analysis on candidate sites very quickly after arriving at the comet, and now we have just a few more weeks to determine the primary site. The clock is ticking and we now have to meet the challenge to pick the best possible landing site.”
The next step in preparation for landing operations is a comprehensive analysis of each of the candidate sites, to determine possible orbital and operational strategies that could be used for Rosetta to deliver the lander to any of them.
At the same time, Rosetta will move to within 31 miles (50 kilometers) of the comet, allowing a more detailed study of the proposed landing sites. By September 14, the five candidate sites will have been assessed and ranked, leading to the selection of a primary landing site.
A fully detailed strategy for the landing operations at the selected site will be developed, along with a backup.
The landing of Philae is expected to take place in mid-November when the comet is about 280 million miles (450 million kilometers) from the sun.
This will be before activity on the comet reaches levels that might jeopardize the safe and accurate deployment of Philae to the comet’s surface, and before surface material is modified by this cometary activity.
Rosetta is an international mission spearheaded by the European Space Agency with support and instruments provided by NASA.
For more information on the U.S. instruments aboard Rosetta, visit: http://rosetta.jpl.nasa.gov . The ESA's Rosetta home page is at http://www.esa.int/rosetta .
Dr. Tony Phillips works for the National Aeronautics and Space Administration.
Space News: Candidate comet landing sites identified
- Dr. Tony Phillips
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