This
NASA JPL Mission, will be launched this November, and is scheduled to impact
July 4, 2005. It is, simply put, a mission to use a 1020 pound, explosive laden vehicle make a really large
explosion in the side of a comet to study the comet's interior. The
comet chosen is called Tempel 1, after it's discoverer, Ernst Wilhelm Leberecht Tempel, in 1867. It is roughly 6km in diameter, and is slightly elongated. The
impact crater will be between 2 to 14 stories deep, and will be the result of 19 Gigajoules (that's 4.8 tons of
TNT) of
kinetic energy, delivered by the 817 pound impactor at an impact
velocity of more them 10 km/s.
The probe consists of two pieces, the impactor and the flyby craft, which will launch the impactor, then pass close by and record and receive data, which will be transmitted to a large number of stations around the globe. The main goals of the mission are to discover what is in the inner layers of the comet, below the outer shell, and to understand their tensile strength base on their composition.This will be accomplished using several imaging packages, including a spectrascope, and two visual telescopes.
The impact will occur at a range visible to better amateur telescopes, and information is availible as to when and where in the night sky it will occur.
Also see:
http://deepimpact.jpl.nasa.gov/mission/wwws.html (A pair of vidoes showing the projected impact.)