The JPL Project that is getting the most attention this week is Cassini, mostly because this week it began it’s long goodbye.  Cassini is a deep space mission sent to investigate Saturn, it’s moons, and it’s rings.  Arguably, what it has accomplished is some of the great discoveries of another planet we have had since we started looking at Mars.    Like all good things, it has to come to an end, so a farewell is set for September (barring an at this point acceptable catastrophe) in one final fiery exit.

Cassini was launched way back on October 15, 1997.  It took nearly seven years for it to arrive in orbit around Saturn, stopping off to do fly-bys of Venus, Earth again, and Jupiter on it’s 2.2 billion mile trip.  While the original mission was to hang there for about four years, the mission was extended twice and now has been in orbit around Saturn for almost 13 years.  While the distance and time is amazing in it’s own way, the full breadth of what this missions means comes in different numbers:

• Over 600 GB of Raw Technical Data has been transfer from Cassini to Earth
• Nearly 400,000 images were taken
• 10 New Moons were Discovered around Saturn
• Over 3600 scientific papers have been authored based on Cassini data

Cassini found liquid on moons shooting off into space.  Found possible new means of life habitation.  It landed the Huygens probe on Titan, the first such probe to land on a moon other than our own.  Cassini made us rethink the way the universe could exist outside of our solar system.

On September 15, Cassini’s trajectory will be so it runs deep into the Saturn Atmosphere, which should cause the entire 2-1/2 ton probe to disintegrate in less than a minute.  Cassini’s fuel is depleting, and if kept alive for a few more months will be uncontrollable.  The fear at that point is that any possible remnants of Earth microbes or material could fall on something in orbit around Saturn and ruin a possible system there (like if there happened to be life on a moon, and we kill it because there just happened to be a flu bug stowed in a hole somewhere).  Before it does, Cassini will attempt to make 22 orbits dipping into the space between it’s rings and the atmosphere.  This is the most dangerous part of the mission because there could be loads of rock and debris from moon break-ups that create the rings.  Cassini doesn’t have eyes capable to duck around that stuff … and wouldn’t have the fuel to do it anyway.  So it will rely on luck, until the choice to rely on luck runs out.  The last pass, Cassini will dip to within 1,000 miles of it’s clouds traveling at over 70,000 miles an hour.

Last night, The Grand Finale began when signals came through that it made it’s first past between the rings and the atmosphere.  For the next few monts, we will keep the Deep Space Network pointed its way to make sure things are still going as plan.  If they do, on September 15 at 10:45a Pacific, Cassini will send it’s last signal as it burns up.  Thirteen and a half hours later, we will see that signal come across our screens, and then there will be nothing else.

Until then, we have our long goodbye.