SCIENTISTS are already in mourning as the Cassini spacecraft, which was launched on October 15, 1997, will expire in the clouds of Saturn on September 15, 2017, twenty years and a month later.
Although the Pioneer and Voyager missions took just three years to get as far as Saturn (approximately 1.2 billion kilometres at its closest point), Cassini took seven; because of it weighing in at six-tonnes it could not accelerate as quickly, and had to thus take a very circuitous route to the ringed gas giant.
Remember, everything is moving around the sun, so you cannot simply aim at a planet and fire because your target won’t be in the same place as when you sent it. In fact, the Earth takes a smidgen over a year to orbit the sun (365.25 days hence, every four years a leap year), but Saturn takes almost 29 and a half years for a complete orbit. Imagine how accurately you have to calculate both planets’ orbits to precisely reach Saturn from Earth. Also take into account that when we look at Saturn, the light has taken just over an hour to reach us, so we are not looking at where the planet is, but where it was an hour before.
Cassini has made a number of amazing discoveries since it reached Saturn in 2004 and has been in operation a full eight years longer than was intended. It has visited Saturn’s moon Titan and discovered the only other planet in the solar system (that we currently know of) that has a thick prominently nitrogen atmosphere like Earth, as well as liquid flowing on its surface. However, the liquid on Titan is methane, ethane and other hydrocarbons, not water. But this does not necessarily dismiss the chances that life is present on the moon. Titan is considerably larger than our own moon, and Cassini has photographed rivers, mountain ranges and dunes similar to Earth geological features.
When Cassini visited another moon, Enceladus which is much smaller than our moon, it detected salt water plumes emanating through the solid ice that forms the moon’s surface.
The Cassini mission has revealed many more secrets of our solar system and broadened our knowledge considerably. Now, however, the spacecraft has run out of fuel, so its final mission is to plunge into Saturn’s atmosphere and probably be crushed or burn up on entry. Either way, on September 15 we shall say our final goodbyes, and that is why space scientists are sad.
Of course Space Scientists are sad! Who wouldn’t be after the incredible roller coaster ride delivered by Cassini after the spacecraft’s arrival at the Saturn system.
Having orbited Saturn nearly 300 times over a full 13 year mission the spacecraft made some amazing discoveries. Such as, liquid methane seas of Saturn’s giant moon Titan and Enceladus’s subsurface oceans which incidentally , it is hoped will be further investigated in a proposed future mission to the Saturn system.
Launched in 1997 and equipped with a dozen scientific instruments, the 2.5-tonne probe, Cassini-Huygens, entered Saturn’s orbit in 2004 and successfully landing an ESA probe ‘Huygens’ on Titan in December of that year.
Cassini’s last five orbits will take it through Saturn’s uppermost atmosphere, before a final plunge directly into the planet tomorrow, September 15. By disposing of the spacecraft in Saturn’s atmosphere , it is hoped that by doing so there will be no contamination of any of Saturn’s 60 odd moons!
Cassini is expected to lose communications with Earth one or two minutes into its final dive, but 10 of its 12 scientific instruments will be working right up until the last moment to analyse Saturn’s atmospheric composition. At 1031 GMT, ( 1131 SA time) the spacecraft is due to enter Saturn’s atmosphere with its antennas pointed toward Earth and its motors running full blast in order to hold its trajectory.
Just a minute later, at some 1,510 kilometres above Saturn’s clouds, the probe’s communications will stop before Cassini begins to disintegrate moments later, according to NASA .
RIP Cassini what a fascinating, rewarding and data filled mission you have completed!.
Now we look forward to soon hearing more news about New Horizons the spacecraft that overflew the ice planet Pluto. New Horizons is now deep into Kuyper belt region at the outermost reaches of our suns inter-Stella medium.