August 25, 2014
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. Rosetta is an international mission spearheaded by the European Space Agency with support and instruments provided by NASA.
Choosing the right landing site is a complex process. It must balance the technical needs of the orbiter and lander during all phases of the separation, descent and landing, and during operations on the surface, with the scientific requirements of the 10 instruments on board Philae. A key issue is that uncertainties in navigating the orbiter close to the comet mean that it is possible to specify any given landing zone only in terms of an ellipse – covering up to six-tenths of a square mile (one square kilometer) – within which Philae might land.
“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?
Image credit: ESA