Launched from Earth nearly two decades ago, the Cassini spacecraft is in its final stage of operations on its mission around Saturn. The spacecraft is about to commence the first of a total of five ultra-close passes around the ringed gas giant, giving the scientists back home valuable data regarding the planet's atmosphere.
The dying battery life of the spacecraft and the fear of its crashing and contaminating one of Saturn's moon Titan and Enceladus has forced the NASA scientists to destroy Cassini by crashing it inside Saturn eventually.
The probe's current trajectory puts it between the rings of the planet and its harsh atmosphere. Cassini will travelling around 1,600 km above the gaseous clouds of Saturn, allowing it to take direct sample of the gases present in the extended atmosphere while it spirals down to its doom. It hopes to collect data on the chemical composition of Saturn.
Saturn is mostly composed of hydrogen (75 percent) and has traces helium and other gases as explained by European Space Agency scientist Nicolas Altobelli in an interview with BBC.
He also said in the interview that, "It's expected that the heavier helium is sinking down. Saturn radiates more energy than it's absorbing from the Sun, meaning there's gravitational energy which is being lost. And so getting a precise measure of the hydrogen and helium in the upper layers sets a constraint on the overall distribution of the material in the interior."
To maintain its orbit during the dives grazing the atmosphere, Cassini will have to fire its thrusters. The previous close flybys of Saturn's moon Titan with its hazy atmosphere have prepared the Cassini team for executing the close flybys on Saturn.
Cassini bid farewell to Titan one last time before initiating the set of grand finale orbits.
If the thrusters have to be fired too hard to maintain the orbit, the scientists will know that the upper atmosphere of Saturn is denser than models suggest. In this case, the altitude of the spacecraft will be slightly raised in the subsequent orbits, an approach known as the pop-up maneuver. If the atmosphere is less dense, then the altitude of the spacecraft will be lowered further, known as the pop-down maneuver.
A joint venture between the US, European and Italian space agencies, Cassini is bound to take the final plunge to its eventual destruction on 15 September, 2017.