Landing site on comet chosen for Philae spacecraft

Spacecraft to land at Site J

Photos courtesy of the European Space Agency
Photos courtesy of the European Space Agency

The Rosetta spacecraft's lander, Philae, will land on Comet 67P/Churyumov–Gerasimenko at "Site J," which offers unique scientific potential, with hints of activity nearby, and minimum risk to the lander compared to the other candidate sites.

Site J (identified by the cross on the photo) is on the head of the comet, an irregular shaped world that is just over 2-3 miles across at its widest point. The decision to select Site J as the primary site was unanimous:  it offers the minimum risk to the lander in comparison to other candidate sites. At Site J, the majority of slopes are less than 30 degrees, reducing the chances of Philae toppling over during touchdown. Site J also appears to have relatively few boulders and receives sufficient daily illumination to recharge Philae and continue science operations on the surface beyond the initial battery-powered phase. 

Philae is scheduled to reach the comet's surface on Nov.11th, where it will perform in-depth measurements to characterize the nucleus in a totally unprecedented way.  But choosing a suitable landing site was not an easy task.

"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 Stephan Ulamec, Philae lander manager at the DLR German Aerospace Center. "None of the candidate landing sites met all of the operational criteria at the 100 percent level, but Site J is clearly the best solution."

"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 analyze pristine material, characterize the properties of the nucleus, and study the processes that drive its activity."

Below is a closer image of Philae's primary landing site:


The race to find the landing site couldn't begin until Rosetta arrived at the comet on Aug. 6, when the comet was seen close-up for the first time. By Aug. 24, using data collected when Rosetta was still about 67 miles from the comet, five candidate regions had been identified for further analysis.

Since then, the spacecraft has moved to within 20 miles of the comet, affording more detailed scientific measurements of the candidate sites.  Coincident with this, the operations and flight dynamics teams have been exploring options for delivering the lander to all five candidate landing sites.

This past weekend, the Landing Site Selection Group of engineers and scientists met to consider the available data and to choose the primary and backup sites, and they announced the selection of Site J this morning.

So why are comets important?  Because they represent pristine, unaltered material from the time our solar system formed.  By learning more about comets, we learn more about the history of our planet.  But wait…there's more!  Comets contain a lot of water ice, and it is believed that a massive comet bombardment early in Earth's history brought the water we have here.  And finally, many scientists speculate that comets may have also brought the fundamental building blocks that led to the development of life here on Earth.

I have always considered comets the Holy Grail of space research.  Aside from actually finding life on another planet (which is unlikely), comets represent that best chance we have of answering some of the most vexing questions about Earth's distant past.

I've been following this mission since it was just a "drawing board" idea…I can't wait for November, and will certainly keep you updated here on ClickOnDetroit.com and on Twitter (@PaulGrossLocal4).

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