10 Feb. 2011

 

Stardust-NExT meets Tempel 1

 

There are 4 days and 3.8 million kilometers between the Stardust-NExT probe and its encounter with comet Temple 1. Both are veterans of previous historic encounters. Stardust, launched on 17th February 1999, visited comet Wild 2 in 2004, collecting particles from its coma and sending them back to Earth, where they arrived in January 2006. Still working perfectly, the probe was reprogrammed in 2007 for a rendezvous, on 14th February 2011, with Tempel 1, and with this the "NExT" was added to its name, standing for "New Exploration of Tempel".
Tempel 1 was visited by the Deep Impact probe in July 2005, with the prime objective of launching an impactor into the nucleus; this made a small crater and expelled a certain amount of volatile material. It was just this volatile material that actually denied Deep Impact the opportunity to photograph the new crater, and this will be the main aim of the Stardust-NExT flyby, that will happen during the night of the 14th February (04:37 GMT on the 15th).
The space craft should pass at a distance of only 200 km from the cometary nucleus (with a diameter of 6 km) and produce 72 high resolution images. Of these, some will image parts of the surface already photographed, while others will reveal regions never before seen. From the comparison of the old images from Deep Impact (that cover about 1/3 of the surface) and those that Stardust-NExT will take, it will be possible to determine how the surface has been modified by the cometary activity during the last 5.4 years. As the comet has an orbital period of 5.5 years, this is almost exactly one orbit.
According to Joe Veverka, astronomy professor and principal investigator of Stardust-NExT, it will be possible to understand how and where the surface has changed during the last perihelion passage. The study of the crater caused by Deep Impact will also allow the mechanical properties of the cometary surface to be determined, something that is important for future missions that plan to land on the surface of a comet.
Besides taking images, Stardust-NExT will also measure the composition, distribution and flux of volatile material emitted by Tempel 1. It will also be interesting to locate and analyse any layered terrain exposed by impacts, more or less remote, to identify material that has remained unchanged since the formation of the cometary nucleus, and therefore of the solar system.

 

by Michele Ferrara & Marcel Clemens

credit: NASA/JPL/Caltech/Cornell University