ESA narrows down sites for Rosetta's comet landing
The European Space Agency has narrowed down to five the possible landing sites for the Rosetta spacecraft's lander Philae on Comet 67P/Churyumov-Gerasimenko.
The survey of potential land sites has only been possible since Rosetta closed in on the comet, giving detailed images of its surface.
The landing is expected to take place in mid-November when the comet is about 450 million km from the Sun. It is currently 522 million km from the Sun, which it takes 6.5 years to orbit.
At their closest approach on 13 August 2015, the comet and Rosetta will be 185 million km from the Sun, meaning an 800% increase in the light received from it.
As the ESA says on the Rosetta website, which also summarises the pros and cons of the different landing sites pictured above,
Choosing the right landing site is a complex process. That site 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 the navigation of the orbiter close to the comet mean that it is only possible to specify any given landing zone in terms of an ellipse – covering up to one square kilometre – within which Philae might land.
Below is a video animation of how the Philae is designed to land on the comet.