Dr Ian Griffin: Final hours for Saturn's space probe

This graphic shows Cassini's final plunge toward Saturn with tick marks representing time intervals of 2 minutes leading to the spacecraft's entry into the atmosphere

The 22ft robot craft will break into fragments and burn up as it ploughs into the ringed planet's cloud tops, ending a 20-year mission that cost £2.9 billion.

The same might be true for Cassini's place in pop culture.

After four decades of planning and execution, NASA's awe-inspiring Cassini spacecraft will plunge to its death in the next 24 hours.

Its demise will be the end of a space mission that has yielded an unprecedented amount of knowledge about a mysterious planet.

The spacecraft's Grand Finale orbits have brought it closer to the gas giant than any spacecraft has traveled, traversing the gap between the planet and its rings and diving into the unknown to learn as much as possible about the planet.

Its final mission was a gravity assist around Saturn's largest moon, Titan, to set it on a collision course with Saturn's main body. This probe explored Saturn's moon Titan, which is larger than Mercury and is the only moon in the solar system with a dense atmosphere.

Cassini's last five orbits will take it through Saturn's uppermost atmosphere, before a final plunge directly into the planet on September 15. Not knowing that its death has been carefully scripted, Cassini may try to alert mission control that something has gone horribly wrong. "Cassini will be followed up by future missions, I am nearly sure". Hence, on 1997 NASA launched its robotic spacecraft, Cassini for an ambitious mission to Saturn. "Cassini's final weak radio signals will have travelled 1.5 billion km at the speed of light to reach Canberra". "The haze has cleared remarkably as the summer solstice has approached", Cassini Project Scientist Linda Spilker said in a news conference September 13.

In 2004, Cassini became a "Cool Kids Combo" meal toy offered by Hardee's and Carl's Jr. fast food restaurants.

"Goodbye, Cassini! Your mission's fini". "You're racing against the clock at that point", he said. Cassini's sacrifice will be remembered for ever. The live telecast shall be followed by a post-mission briefing from JPL at 9:30 a.m. EDT (13:30 UTC) which shall also air on NASA TV.

Why crash Cassini into Saturn?

This is another reason the mission scientists decided on Cassini's particular end-game. But after Cassini revealed so many ocean worlds close at hand, that assumption has to be revised. "I find great comfort in the fact that Cassini will continue teaching us up to the very last second". "I have seen a lot of visual artists take images from Saturn, primarily the rings, and use those as motifs, backgrounds or design elements in their art". Data from the spacecraft indicate Saturn's rings - which consist of icy bits ranging in size from dust to mountains - may be on the less massive side.

If you're a Cassini fan-and the mission has picked up quite a few, including adorable six-year-olds-that's always going to be little sad.

Why are scientists crashing the probe into Saturn?

What are scientists and space aficionados saying about this finale?

"We study the stars because they tell us where we came from, and inspire us to imagine just how far we might go. We did it.' Cassini was so profoundly, scientifically successful", said planetary scientist Carolyn Porco at the University of California, Berkeley.

First there was the sheer distance involved. "If in 1990, someone had stepped forward and said we needed an instrument specifically built to sample Enceladus' plumes, they would have been laughed out of the room as a kook", Neiber says. Over the mission, the northern hemisphere shifted from a bluish hue to the more familiar golden tones as the shadows cast by Saturn's rings moved south.



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