Cassini mission prepares for 'grand finale' at Saturn

April 4, 2017
This illustration shows Cassini above Saturn's northern hemisphere prior to one of its 22 Grand Finale dives. Credit: NASA/JPL-Caltech

NASA's Cassini spacecraft, in orbit around Saturn since 2004, is about to begin the final chapter of its remarkable story. On Wednesday, April 26, the spacecraft will make the first in a series of dives through the 1,500-mile-wide (2,400-kilometer) gap between Saturn and its rings as part of the mission's grand finale.

"No spacecraft has ever gone through the unique region that we'll attempt to boldly cross 22 times," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "What we learn from Cassini's daring final orbits will further our understanding of how giant planets, and planetary systems everywhere, form and evolve. This is truly discovery in action to the very end."

During its time at Saturn, Cassini has made numerous dramatic discoveries, including a global ocean that showed indications of hydrothermal activity within the icy moon Enceladus, and liquid methane seas on its moon Titan.

Now 20 years since launching from Earth, and after 13 years orbiting the ringed planet, Cassini is running low on fuel. In 2010, NASA decided to end the mission with a purposeful plunge into Saturn this year in order to protect and preserve the planet's moons for future exploration—especially the potentially habitable Enceladus.

But the beginning of the end for Cassini is, in many ways, like a whole new mission. Using expertise gained over the mission's many years, Cassini engineers designed a flight plan that will maximize the scientific value of sending the spacecraft toward its fateful plunge into the planet on Sept. 15. As it ticks off its terminal orbits during the next five months, the mission will rack up an impressive list of scientific achievements.

"This planned conclusion for Cassini's journey was far and away the preferred choice for the mission's scientists," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "Cassini will make some of its most extraordinary observations at the end of its long life."

The mission team hopes to gain powerful insights into the planet's internal structure and the origins of the rings, obtain the first-ever sampling of Saturn's atmosphere and particles coming from the main rings, and capture the closest-ever views of Saturn's clouds and inner rings. The team currently is making final checks on the list of commands the robotic probe will follow to carry out its science observations, called a sequence, as it begins the finale. That sequence is scheduled to be uploaded to the spacecraft on Tuesday, April 11.

Cassini will transition to its grand finale orbits, with a last close flyby of Saturn's giant moon Titan, on Saturday, April 22. As it has many times over the course of the mission, Titan's gravity will bend Cassini's flight path. Cassini's orbit then will shrink so that instead of making its closest approach to Saturn just outside the rings, it will begin passing between the planet and the inner edge of its rings.

"Based on our best models, we expect the gap to be clear of particles large enough to damage the spacecraft. But we're also being cautious by using our large antenna as a shield on the first pass, as we determine whether it's safe to expose the science instruments to that environment on future passes," said Earl Maize, Cassini project manager at JPL. "Certainly there are some unknowns, but that's one of the reasons we're doing this kind of daring exploration at the end of the mission."

In mid-September, following a distant encounter with Titan, the spacecraft's path will be bent so that it dives into the planet. When Cassini makes its final plunge into Saturn's atmosphere on Sept. 15, it will send data from several instruments - most notably, data on the atmosphere's composition—until its signal is lost.

"Cassini's grand finale is so much more than a final plunge," said Spilker. "It's a thrilling final chapter for our intrepid spacecraft, and so scientifically rich that it was the clear and obvious choice for how to end the ."

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21 comments

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ricegf2015
Apr 04, 2017
This comment has been removed by a moderator.
Bart_A
5 / 5 (7) Apr 04, 2017
I have followed this mission since Cassini arrived at Saturn. My first experience with Saturn was when I was 10. I peered through a small telescope my dad had bought and saw the stunning rings for the first time. I have been fascinated ever since.
Mark Thomas
5 / 5 (5) Apr 04, 2017
Imagine how much we could learn with updated, Cassini-like orbiters around Uranus and Neptune.
Whydening Gyre
1 / 5 (2) Apr 05, 2017
Godspeed, Cassini.

Well...
Not sure 'bout the God part of that, but -
thanks for all the info..:-)
ricegf2015
3 / 5 (4) Apr 05, 2017
Godspeed, Cassini.

Well...
Not sure 'bout the God part of that, but -
thanks for all the info..:-)


Never heard of John Glenn, then. OK, kinda sad, but welcome to the world of space travel anyway!
ricegf2015
4.6 / 5 (9) Apr 05, 2017
I see that the moderator is also apparently unaware of the phrase "Godspeed, John Glenn", spoken by backup astronaut Scott Carpenter at the launch of Friendship 7, the first American orbital space flight. As such, it has become the traditional send off for those involved in space.

Mirriam-Webster defines the word "godspeed" as a wish for a "prosperous and successful journey". It is NOT listed as a religious phrase in any dictionary I can find, despite having the letters g, o, and d adjacent within it. It is much like including the phrase "acts of God" in an insurance contract, or Atheist Albert Einstein's famous statement "God doesn't play dice" (or Atheist Stephen Hawking's famous later riff, "God may play dice after all").

I would respectfully suggest that being offended by offering good wishes for Cassini's final mission using the traditional famous phrase because a word includes the letters g, o, and d is perhaps overly sensitive.
EyeNStein
3 / 5 (2) Apr 05, 2017
Godspeed ricegf2015
The moderator must have had a glitch in its AI assistant.
barakn
3.4 / 5 (5) Apr 05, 2017
The 'god' in 'godspeed' is a reference to God, if one looks up the etymology of the word. Considering the era of flag waving and mom's apple pie, it's not at all surprising that a word with religious connotations was chosen instead of a large number of other similar phrases: "good luck," "break a leg," etc.. Even if we ignore the god part, there's still the fact that the word is being used as if it was some sort magical incantation that by its mere utterance will somehow affect the prospects of a craft one and a half billion kilometers away. The very notion is unscientific.
Levantine
3 / 5 (4) Apr 05, 2017
"NASA decided to end the mission with a purposeful plunge into Saturn this year in order to protect and preserve the planet's moons"

To *protect* the moons! An interesting, and somewhat extravagant, part of the explanation.

Imagine a moon damaged by a spacecraft with dimensions of 7x5 meters. Imagine a moon infected by microbes from Cassini. ... I would like to know more about the reasoning on this matter in NASA.
ricegf2015
5 / 5 (5) Apr 05, 2017
The 'god' in 'godspeed' is a reference to God, if one looks up the etymology of the word.


You must talk very little if you constrain yourself only to words and historical references that can't be linked in any way at all to any form of religious observance, no matter how oblique - and offense at this one is *really* a stretch!

Out go the Declaration of Independence, Rev. King's Dream speech, Abraham Lincoln's Gettysburg Address and 2nd Inaugural, Winston Churchill's "We Shall Fight on the Beaches" and "Blood, Toil, Tears, and Sweat" speeches, President Reagan's Challenger address, William Wilberforce's Abolition Speech, Socrates Apology, George Washington's and Gen. Douglas MacArthur's Farewell Addresses, Patrick Henry's Give Me Liberty speech, and so many more.

Trying to cleanse all of history of any reference to religion, no matter how slight, is quite the task, isn't it? PC run amok. *sigh*
bschott
5 / 5 (1) Apr 05, 2017
Trying to cleanse all of history of any reference to religion, no matter how slight, is quite the task, isn't it? PC run amok. *sigh*

Lets not forget about the complete abolishment of all US currency...
The law was signed by President Eisenhower on July 30, 1956. The United States Code at 36 U.S.C. § 302, now states: "'In God we trust' is the national motto." The same day, the President signed into law a requirement that "In God We Trust" be printed on all U.S. currency and coins.

And apparently the US national motto, all because of peoples delicate sensibilities regarding belief systems other than their own....awwww
Bart_A
2.3 / 5 (3) Apr 06, 2017
The word godspeed, or originally "God speed", comes from the King James version of the Bible in the book of 2nd John. It is centuries old. The phrase comes from the single greek word Chario, which means to be Cheerful.

I wish all of the negative posters on this forum, godspeed. Cheer up!

antialias_physorg
5 / 5 (2) Apr 06, 2017
Imagine a moon damaged by a spacecraft with dimensions of 7x5 meters. Imagine a moon infected by microbes from Cassini.

The microbes aren't the problem. It's the 32kg of plutonium on board Cassini that would contaminate a wide area (which might be an issue if we ever start sending manned missions out for research or even colonization)
Mark Thomas
5 / 5 (1) Apr 06, 2017
"'In God we trust' is the national motto."

The whole thing reads, "In God we trust, but all others have to pay with dollars." :-)
nrauhauser
5 / 5 (4) Apr 06, 2017
"'In God we trust' is the national motto."

That has been the U.S. motto for sixty years, it's a Cold War thing, not a founding fathers thing. I think religious nuts make way too much of it.
Lex Talonis
5 / 5 (1) Apr 07, 2017
What if there are hordes of really angry brain eating space demons using Nazi technology on Saturn to get back at us, for dropping a tactical nuke on their heads.....

Imagine a moon damaged by a spacecraft with dimensions of 7x5 meters. Imagine a moon infected by microbes from Cassini.

The microbes aren't the problem. It's the 32kg of plutonium on board Cassini that would contaminate a wide area (which might be an issue if we ever start sending manned missions out for research or even colonization)


Maybe glow in the dark testicles will never catch on and they well be very upset.
barakn
4 / 5 (4) Apr 07, 2017
The word godspeed, or originally "God speed", comes from the King James version of the Bible in the book of 2nd John. It is centuries old. The phrase comes from the single greek word Chario, which means to be Cheerful. -Bart_A
Liar. "The noun "speed" (spelled spoed in Old English) originally meant "success, prosperity, good fortune; profit, advancement, furtherance," according to the Oxford English Dictionary. ...
The OED's earliest citation is from Sir Tristrem, a Middle English romance dating from around 1330: "He may bidde god me spede." And here's an example from around 1385 in the "The Knight's Tale," the first story in Chaucer's The Canterbury Tales: "God spede yow go forth and ley on faste."
source: http://www.gramma...eed.html
The King James version was completed in 1611.
Whydening Gyre
5 / 5 (4) Apr 07, 2017
Apologies for causing the re-direction of almost an entire thread. Thanks AAP. For trying (at least to bring it back to reality....
All I was trying to do was poking a little fun at a (more or less) religious term used to bid adieu to a device designed to collect information (a function we should ALL be thankful for...), as if it were a religiously aware entity.
Some of you need to grow a little sense of humor, as well as provide your religious sensibilities a thicker skin. Sheesh...

BubbaNicholson
1 / 5 (1) Apr 10, 2017
Cassini's old carcass might be useful in another purpose. We might yet send it to other star systems if we could re-course it to obtain multiple gravity accelerations through the planets and asteroids. Letting our great, great, grandchildren have a shot at getting an in close look at colony candidate worlds, now that's refreshing. Of course, smashing it into bits on Saturn has its thrills, too, the main one being the close down the cost of monitoring by shortsighted bean counters.
antialias_physorg
5 / 5 (4) Apr 10, 2017
Cassini's old carcass might be useful in another purpose. We might yet send it to other star systems if we could re-course it to obtain multiple gravity accelerations through the planets and asteroids.

I think gravity assist doesn't work the way you think it works.
Captain Stumpy
3 / 5 (2) Apr 10, 2017
Cassini's old carcass might be useful in another purpose. We might yet send it to other star systems if
@bubba
you do realise that the cost of getting someone (or something) to Cassini to replace equipment and or power (batteries etc) to retool for this would be astronomically expensive? [intended]

considering the expenses and it's finite life, they're "smashing it into bits on Saturn" to gather as much useful data as possible while still having the ability to do so

i can think of quite a few other options for Cassini as well... but regardless of the options chosen, it will be expensive

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