Will Cassini ever do a radar survey of Saturn proper?

Due to declining fuel and RTG power, the ability to do so decreases with time.

It is my understanding that in the Equinox orbits that there is a possibility for up to 3 close approaches of the dark side with RADAR in its lower resolution modes.

It is also my understanding that not that much reprogramming would be needed -- as the radar system has been fully mastered.

The risks of doing a radar swath would not increase substantially, versus any other close moon approach.


ADMIN - Thread title changed for clarity.

What mode of Radar, and for what purpose. What question are you trying to answer with such an observation?

Via Radiometer mode, I'm sure it already has been point at Saturn itself a great deal.

There is not a single press release or scientific research paper to provide proof that this has been done.

A SAR RADAR survey of Saturn has not been done.

Only about 3 low rez SAR surveys would be needed, as its inner core can't be that interesting.

The RADAR system is mutli-modal, so a single swath could see a lot.

I know the numbers don't reflect current membership, but those posts must count as a forum milestone of sorts (for sad numerical 'trainspotters' with nothing better to do on a cold Saturday morning). 5000 members have passed through these doors between questioner and responder.

http://www.cosis.net/abstracts/EGU06/05222...a619eee9e66d294



Someone who knows more about the different modes with Cassini's radar may be able to give you more information, but by gut feeling is that SAR mode radar at Saturn itself wouldn't return anything as the range to and density of material on the way to a Saturnian core are both too high. The short answer - the reason they've not mapped Saturns core with the RADAR is because I don't think they can. If they could - I'm sure they would have tried.

What you quote above is a passive radar study, not a core targeted SAR survey.

The highest rez SAR mode is out of the question, but all the other lower rez SAR modes will provide something -- if only the slushy reflections back due to the soppy He-H layer interactions (convection if you will) thought to be taking place.

Bouncing SAR radar at somewhat close range at the soppy inner parts of the gas planets has not been done or even tried.

The worst that could happen is total absorption of all the radar energy...

That sounds plausible, but even confirmation of a theoretically-predicted null result would be useful. However, those best placed to work out whether the usefulness of that observation justifies the cost have declined to do it. Presumably therefore the cost doesn't justify the usefulness.

Evidence for this please? What are these lower 'rez' SAR modes?

This might be more interesting during those final orbits when Cassini is passing under the rings.

Assuming they ever do get around to approving the Solstice Mission, that is.

--Greg

Yeah...I was thinking that a SAR pass of the rings might be pretty illuminating, but I can't visualize a non-fatal trajectory that would allow Cassini to pass under or over them at close enough range to return useful (hi-res) data, to say nothing of the high relative velocities involved.

Even if such a maneuver was conducted as the coup d' grace prior to EOM, the spacecraft would still have to survive long enough for data playback.

OT: just noticed the forum passed a milestone, Maxpower is member number 5001.

Then behold:




According to the Planetary Society, this really IS the plan.

http://www.planetary.org/blog/article/00001856


--Greg

Thanks for the reminder, Greg. I've no doubt that the rings will receive an excellent broadband optical exam then, but will Cassini get close enough to make SAR observations worthwhile? The outer edge of the F-ring & the inner edge of the D-ring might be close enough, but the average range to the rest of the system (esp. for perpendicular 'stare-down' observations) during these orbits will be several thousand km at least.

FWIW - current actual members = 2142. So 2850+ registrations have been spam, culled, trolled etc.

We only do SAR within about 4000km of an object - we don't get that close to Saturn except
right at the end of the mission, and in any case Saturn is a gas giant -no surface to observe!
Ammonia opacity is significant at our wavelength, so radiometry (as other posters have noted)
is somewhat useful, but must compete both with other Cassini observations at Saturn, and for
our own manpower (which is concentrated towards Titan) to plan and execute the observations,
calibrate and archive the data.

We few, we happy few....

Ah, I missed that you were talking about the rings themselves. I think everyone else is talking about the planet.

--Greg

I think, that there is possibility of some radar reflections from Saturn. This was successfully accomplished from Arecibo and Goldstone, i think.

Certainly, but how much useful information can be gained by pinging the planet itself with Cassini? My guess is not nearly enough to justify such a campaign given other types of observations that would provide a much better return-on-investment of time & spacecraft resources. That's why I was wondering about radar observations of the rings.

Since there are newbies participating in this thread, I thought it'd be beneficial to point out that this answer is from the horse's mouth, as it were; Ralph Lorenz is on the Cassini RADAR team.

...and while I'd like to take credit for that, the blog was actually written by John Spencer, who's on the Cassini CIRS team.

--Emily

I think that was the whole point of the discussion. Is there anything to be gained by using SAR on the planet itself? Even if it isn't usually used that way (or even if it isn't SAR that's used), could we get a better understanding of what's under those clouds, given Cassini will be making quite a number of cloud-skimming passes over Saturn? As far as I know, we don't currently have ANY direct measurements on Saturn below the optical limit.

If the answer is, "no one thinks there's anything for radar to bounce off of, so there's no information to be learned this way," then that'd be a fine answer. An answer of "radar might bounce off the liquid hydrogen sea, if it exists, but we think it's too deep to find with what power Cassini has" would also be a fine answer. I haven't yet heard a fine answer, though.

--Greg

I believe that a key goal of the termination orbits that pass just above Saturn is gravity measurements a la Juno. For that, the antenna needs to point at Earth.

Okay, "the spacecraft will be busy doing something else" is also a fine answer. :-)

--Greg

Yeah, what VJ said!!!

Perhaps we play too rough here. I note he's already quit. :-(

--Greg

Ralph, I apologize for not seeing your excellent response until just now. It landed at the very bottom of the last page, and I just didn't notice it. Now I feel bad about saying I hadn't "seen a fine answer" so far. Thanks for taking the time!

--Greg

There may be a chance of serendipitous discovery of something.
I'm not saying you'll spot flying mountains , but maybe
anomalous radio reflectance of the Saturn atmosphere?

If you never try, you won't know.

A saturn rainstorm, perhaps, might have detectable backscatter. But not
detectable except during the rare and oversubscribed close flybys as
discussed before, and ammonia absorption I think prevents Ku-band
radiation from getting down more than a bar or two.

There are flying mountains, but most people call them 'ring particles'.

You can do interesting science with the rings (there was an Arecibo
observation some years back, published by Nicholson et al. in Icarus in 2005)
because the frequency-domain doppler information resolves structures.
But even for the rings, Cassini has to be close to get a useful echo, and
when we are close, the geometry changes rapidly so it is hard to 'stare
and integrate' (remember the rings are spread out in space and velocity
- not like an icy satellite).

Trying a ring observation is on our wish list, but Titan observations come first.
The question isnt whether something is interesting or not, but how to manage
oversubscribed geometrical opportunities with limited planning manpower.