Cassini's last flyby of Enceladus until 2015

May 02, 2012 By Nancy Atkinson
Cassini’s last flyby of Enceladus until 2015
Below a darkened Enceladus, a plume of water ice is backlit in this view. Credit: NASA/JPL-Caltech/Space Science Institute

On May 2, the Cassini spacecraft will be swooping past the moon we all love to love — Enceladus — and coming within 74 kilometers (46 miles) of its fractured, jet-spewing surface.

The images should be spectacular, and the science should be just as enticing. With Cassini’s radio science experiment, scientists hope to learn more about how mass is distributed under Enceladus’ south polar region, the very interesting place which features jets of water ice, water vapor and organic compounds spraying out of long fractures.

This is the last close flyby of Enceladus until 2015, so we have to take advantage of the views!

Cassini scientists will be looking specifically for a concentration of mass in that region could indicate subsurface liquid water or an intrusion of warmer-than-average ice that might explain the unusual plume activity. They’ll also be observing the plumes and looking for hot spots to try and understand the global energy balance of Enceladus.

They also hope to learn more about the moon’s internal structure by measuring variations in the gravitational pull of Enceladus against the steady radio link to NASA’s Deep Space Network on Earth.

Additionally, Cassini’s composite infrared spectrometer instrument will be observing the side of that always faces away from Saturn to monitor for hot spots. The imaging camera team also plans to take images of the plume to look for variability in the jets.

Cassini will also be flying by Dione at a distance of about 8,000 kilometers (5,000 miles), enabling the imaging cameras to create several mosaic images of the icy , and the composite infrared spectrometer to monitor heat emission.

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Meyer
not rated yet May 02, 2012
2015, isn't that when New Horizons is scheduled to reach Pluto? Sorry Enceladus, but you may have to yield the spotlight.
Lurker2358
1 / 5 (4) May 02, 2012
2015, isn't that when New Horizons is scheduled to reach Pluto? Sorry Enceladus, but you may have to yield the spotlight.


Not for long. New Horizons was ill-conceived and has no form of retro rockets, which means it gets a one-shot fly-by at break-neck speed.

Better hope everything's calibrated just right, and nothing breaks, because they only get one go.

It's unlikely they'll even get a full surface map out of it.
Jonseer
1 / 5 (3) May 02, 2012
Not for long. New Horizons was ill-conceived and has no form of retro rockets, which means it gets a one-shot fly-by at break-neck speed.

Better hope everything's calibrated just right, and nothing breaks, because they only get one go.

It's unlikely they'll even get a full surface map out of it.


I have to agree.
dschlink
5 / 5 (3) May 02, 2012
New Horizons is more a mission to the Kuiper Belt, so why would it have retro rockets? To stop at Pluto and then continue would have required a much larger, much more expensive mission.
Lurker2358
1 / 5 (2) May 02, 2012
New Horizons is more a mission to the Kuiper Belt, so why would it have retro rockets? To stop at Pluto and then continue would have required a much larger, much more expensive mission.


Even if you wanted to keep going to the other objects, not that NH has the ability to navigate to anything, it's just going to drift in space; you could still have the probe be a two part system, and have one of them slow down and orbit the planet and do some real up close science.

They chose not to do that.

Unless NH happens to fly by some undiscovered object over it's life time, it's approach to Pluto will be by far it's closest encounter with anything.

Sure, there could be any number of unknown objects out there, even where it is between its present location and Pluto, so maybe it gets lucky and has a few other close flybys. Very low odds of that.

Voyager 1, 2 and Pioneers already been out there for decades now, and they never had a chance encounter with anything...
nkalanaga
4 / 5 (4) May 02, 2012
Dschlink: Agreed. The entire purpose was to get a mission to Pluto as soon as possible, preferably before its atmosphere freezes out, as it moves further from the Sun. And, there are precedents for the first mission to be a flyby. We have never sent an orbiter or lander to a planet without at least one flyby first. Planning an orbiter without knowing at least a little about the target would be difficult, as we wouldn't know what instruments should be included.
Lurker2358
1 / 5 (2) May 02, 2012
Agreed. The entire purpose was to get a mission to Pluto as soon as possible, preferably before its atmosphere freezes out, as it moves further from the Sun. And, there are precedents for the first mission to be a flyby. We have never sent an orbiter or lander to a planet without at least one flyby first.


You realize that because of Pluto's orbit's extreme eccentricity, it is currently near it's closest approach, ok, having been moving away for a few decades now, but they also had some gravity assist advantages due to planetary alignments.

It is too late to launch a lander or orbiter again for the next 200 years, because the cost of RTG fuel to keep the probe and lander alive long enough on the trajectory they'd have to use now is orders of magnitude higher.

You'd basically need a nuclear rocket engine in order to make a lander viable now for the next 200 years, because they missed that opportunity.

The last time pluto was where it is now was around 1760 to 1770...
Lurker2358
1.8 / 5 (6) May 02, 2012
Not to mention, besides all that, it remains to be seen whether any of these space probes is ever going to pay for itself through discovering fundamental scientific knowledge (or resources?) which might lead to technology capable of paying it's cost back.

Most of this stuff has unfortunately produced little more than some photos for a text book or photo album. It hasn't produced new raw materials, or a new fundamental technology or theory of matter, etc.

That's not to say space exploration is useless, but without practical applications that affect ordinary people's lives, it just hasn't paid for itself at all.

NASA should be focusing on practical space applications. We've done enough discovery for now, it's time to find real uses for Mars, the Moon, and asteroids.
nkalanaga
1 / 5 (1) May 03, 2012
Lurker: Yes, that's why the atmosphere has thawed, and is expected to freeze out again in the near future. And, as you said, the gravity assist from Jupiter was a big help. As far as I know that was the only one, as they headed straight for Jupiter from Earth. But if we'd missed that, we'd have to wait at least twelve years, and Pluto would be cooling all that time. Basically it was launch now, and on the fastest possible trajectory, or lose a lot of the science.
LordKinyambiss
not rated yet May 03, 2012
I think what is really needed to answer the big question of life in the Solar System is a mission back to Saturn and specifically Enceladus to stick out a tongue and taste those ice geysers and see what organics and possibly microbial life resides therein. Finding life out there would be a paradigm changing discovery, at par with discovering fire..
nkalanaga
1 / 5 (1) May 03, 2012
Such a mission has been proposed. As usual, the problem is funding...space microbes don't vote!
TheGhostofOtto1923
1 / 5 (2) May 03, 2012
Even if you wanted to keep going to the other objects, not that NH has the ability to navigate to anything, it's just going to drift in space; you could still have the probe be a two part system, and have one of them slow down and orbit the planet and do some real up close science.
Heck they should have included a rover to land and dig some trenches. Heck china missed the opportunity to send astronauts didnt they?

These missions are designed pragmatically to achieve as much as possible given the available funding, resources, and technology. They are not designed to give you the opportunity to second guess them in your ignorance although I could believe that you might THINK they are.
nkalanaga
1 / 5 (1) May 03, 2012
Lurker: In NASA's words, NH's "maneuvering capability is limited", but it does have some, as it won't have used all of its midcourse correction fuel by Pluto.

Quote, "The available region, being fairly close to the plane of the Milky Way and thus difficult to survey for dim objects, is one that has not been well-covered by previous KBO search efforts. The public is being encouraged to help scan telescopic images for possible mission candidates by participating in the Ice Hunters project."

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