IPB

Welcome Guest ( Log In | Register )

5 Pages V  « < 2 3 4 5 >  
Reply to this topicStart new topic
Titan Review article
rlorenz
post Dec 19 2007, 02:35 PM
Post #46


Member
***

Group: Members
Posts: 609
Joined: 23-February 07
From: Occasionally in Columbia, MD
Member No.: 1764



QUOTE (NMRguy @ Dec 19 2007, 08:14 AM) *
So perhaps I can ask a question about the currently orbiting flagship?
.....
is the "low-maintenance cycler orbit" a long term Cassini mission goal or YOUR preferred orbit evolution?


Well, you can ask, but as I have said before, I have a policy of not discussing ongoing
implementation issues, spacecraft crises etc. I can say the following, however..

First, recognize that formally speaking, even the XM is not yet approved. (Though this was the
first item on the outer solar system list of the old Decadal survey). So all this is hypothetical
until that happens.

Of all the things to do in the Saturnian system, I think it is safe to say there was some consensus
that studying the seasonally-changing system for as long as possible (i.e. longer duration, even
at the expense of lower activity) is scientifically important, more so than any specific goal.

Finally, I'd say the Cassini scientists have learned to trust the orbit wizards at JPL. Rather than
specifying lots of orbit petals in great detail and overconstraining the problem, we scientists
just say, 'Make us a pretty flower' (and after some thought) 'some big petals and a few small
ones, and a few that stick up above the plane if you can'. So the orbit designers know we
like Titan, know we like looking down on the rings, know we like enceladus etc. and will work
their magic. A Titan-Enceladus cycler may be the most efficient solution (at least for
part of XXM), or it may not be. It does have some obvious attributes, and is 'catchy' in the
sense that it sounds efficient, has a name that people 'get' instantly. A cycler by definition is in
the ring plane, so some ring/aurorae observations would suffer, so I doubt that all of XXM would
be a cycler.

While possibly good for Cassini XXM, a Titan-Enceladus cycler would be a poor substitute for
a Titan orbiter in a future mission - remember Titan and Enceladus are 3x further apart
than are the Earth and the Moon, so the cycler spends most of its time between them, rather
than at either one.
Go to the top of the page
 
+Quote Post
ngunn
post Dec 19 2007, 02:57 PM
Post #47


Senior Member
****

Group: Members
Posts: 3516
Joined: 4-November 05
From: North Wales
Member No.: 542



QUOTE (rlorenz @ Dec 19 2007, 02:35 PM) *
A cycler by definition is in
the ring plane, so some ring/aurorae observations would suffer


Wouldn't it also preclude repeated RADAR passes over Titan's polar wetlands? That must be one of the priority targets for long term observation surely.
Go to the top of the page
 
+Quote Post
NMRguy
post Dec 19 2007, 03:14 PM
Post #48


Junior Member
**

Group: Members
Posts: 98
Joined: 29-July 05
From: Amsterdam, NL
Member No.: 448



QUOTE (rlorenz @ Dec 19 2007, 03:35 PM) *
Well, you can ask, but as I have said before, I have a policy of not discussing ongoing implementation issues, spacecraft crises etc.

This is more along the lines of the reply that I was expecting, so thanks for the additional insight.

IIHO, the Saturn system really could use a longer duration observation campaign if only because the seasonal effects are so much stronger at Saturn than at Jupiter. Having a good set of eyes in the system will out-perform anything we have here on the ground.

But that being said, there’s always the trade-off between getting as much science done as possible today and saving resources in order to observe at a later date. Engineering, budgetary, and random constraints always put uncertainty on the “later date”. You guys are the experts, so keep on trucking and good luck with the real policy decisions that allow so much great work to be done in the first place.
Go to the top of the page
 
+Quote Post
JRehling
post Dec 19 2007, 10:24 PM
Post #49


Senior Member
****

Group: Members
Posts: 2530
Joined: 20-April 05
Member No.: 321



A purely equatorial orbit would preclude RADAR obervations of Titan's poles. But you could get a direct polar flyby by tipping the orbit around Saturn by only 0.14 degrees. That shouldn't take a lot of fuel. The bigger problem is that Titan's gravity will do things to the orbit after that, so you need two burns if you want just one such flyby, and then return to the equatorial orbit.

The polar regions are fairly small, and it won't take long to map them -- it's looking for change that will merit repeat coverage, and I think most of the science would come from checking them just twice -- as early as possible, and as late as possible.
Go to the top of the page
 
+Quote Post
ngunn
post Dec 19 2007, 10:38 PM
Post #50


Senior Member
****

Group: Members
Posts: 3516
Joined: 4-November 05
From: North Wales
Member No.: 542



Spot on, as usual. But why is it that I find Titan's lakes more interesting than the jets of Enceladus? It's the liquid thing. I keep harking back to that very early post by (I think) Vexgizmo - "Show me the water".
Go to the top of the page
 
+Quote Post
vjkane
post Dec 20 2007, 01:17 AM
Post #51


Member
***

Group: Members
Posts: 706
Joined: 22-April 05
Member No.: 351



QUOTE (ngunn @ Dec 19 2007, 10:38 PM) *
Spot on, as usual. But why is it that I find Titan's lakes more interesting than the jets of Enceladus? It's the liquid thing. I keep harking back to that very early post by (I think) Vexgizmo - "Show me the water".

My suspicion is that Enceladus' jets are simple geology and orbital stressing without the connection to the solid core to provide all the building blocks of life (and I'll state up front that this is strictly an armchair observation). Titan, on the other hand, is endlessly fascinating with many processes and environments.


--------------------
Go to the top of the page
 
+Quote Post
ugordan
post Dec 20 2007, 08:34 AM
Post #52


Senior Member
****

Group: Members
Posts: 3648
Joined: 1-October 05
From: Croatia
Member No.: 523



QUOTE (vjkane @ Dec 20 2007, 02:17 AM) *
My suspicion is that Enceladus' jets are simple geology and orbital stressing without the connection to the solid core to provide all the building blocks of life (and I'll state up front that this is strictly an armchair observation).

I get the same feeling myself. Cold faithful? More like Sterile faithful if you ask me.


--------------------
Go to the top of the page
 
+Quote Post
djellison
post Dec 20 2007, 08:52 AM
Post #53


Founder
****

Group: Chairman
Posts: 14431
Joined: 8-February 04
Member No.: 1



It's simple. The Enceladus plumes are indeed, a very interesting feature. Titan is an interesting world. It's not even a contest in my eyes. Sadly, my cheque book isn't big enough.

Doug
Go to the top of the page
 
+Quote Post
belleraphon1
post Dec 20 2007, 12:50 PM
Post #54


Member
***

Group: Members
Posts: 813
Joined: 29-December 05
From: NE Oh, USA
Member No.: 627



Nature is rarely simple. Too soon to declare Enceladus sterile....................

Enceladus has much to teach us about how small ice/rock worldlets (yes, I will use that word here) behave..... clues to some of the activity being glimpse on Kuiper Belt bodies perhaps....

But if a choice has to be made...... TITAN should win!!!!! No argument there.

Craig
Go to the top of the page
 
+Quote Post
Matt
post Dec 27 2007, 10:12 PM
Post #55


Junior Member
**

Group: Members
Posts: 40
Joined: 11-November 05
Member No.: 550



Worldlets.....well put, I like it; I only wish I'd thought of it before you.

But what's the critical size?

Anything below 600km is a worldlet?

Ralph I read your 'Lifting Titan's Veil' book just before Cassin/huygens reached Saturn and enjoyed it very much, it really whetted the appetite, and am looking forward to reading the new book.

I knew Titan was going to turn out to be an interesting world....but this is ridiculous.
Go to the top of the page
 
+Quote Post
nprev
post Dec 27 2007, 10:41 PM
Post #56


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



QUOTE (Matt @ Dec 27 2007, 02:12 PM) *
I knew Titan was going to turn out to be an interesting world....but this is ridiculous.


Yeah. You guys are right. We know enough about the Solar System now to say with a high degree of confidence that Titan's the only other place that has dynamic surface processes that even remotely approach (in terms of complexity) those of Earth. (Who knows what's happening on the "surfaces", if any, of the gas giants, but doesn't matter; we can't find out with current technology anyhow.)

Titan's gotta be the Cassini XM focus, and also that of all foreseeable outer-planet investigation.


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
belleraphon1
post Dec 28 2007, 02:40 PM
Post #57


Member
***

Group: Members
Posts: 813
Joined: 29-December 05
From: NE Oh, USA
Member No.: 627



QUOTE (nprev @ Dec 27 2007, 05:41 PM) *
Titan's gotta be the Cassini XM focus, and also that of all foreseeable outer-planet investigation.


Nprev....

I would not go that far. There many mysteries begging answers and further exploration.

I have to say that my choice for the next flagship mission should be the Europa Explorer. The technology is mature for a mission like that, and we need another orbiter at Jupiter to make up for the loss of downlink due to Galileo's high gain antenna problem. The Jupiter system and Europa, have much to teach us.

The tech to do a decent follow on to CASSINI at Titan (balloons, landers,etc.,) just is not here as yet. Outer planet missions take a LONG time to reach their destinations, and so, for selfish reasons, if any outer planet mission is going to happen before I hit my 70's (which is not really a bad thing, I may be retired from my day job by then and able to devote more attention), it needs to be started now.

That being said, I earnestly hope to be around for the next Titan (Enceladus) explorer, after CASSINI has done it's work!

And Matt, thanks for the compliment on the term worldlets.... actually, I think Poul Anderson might have invented that first. As for what size object deserves that word, well.... even Itokawa has it's mysterious gravel shores, and to stand on that surface, watch the stars spin, I can well imagine exclaiming "My Wor(l)d"!!!

Craig
Go to the top of the page
 
+Quote Post
nprev
post Dec 28 2007, 03:31 PM
Post #58


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Well, I was less than clear (again) in what I meant (sorry!) rolleyes.gif

Europa certainly needs & deserves attention, but frankly I'm not completely convinced that achieving major scientific objectives--confirmation of an ocean, ice thickness sounding, global high-res photographic coverage, plume search/monitoring--can't be accomplished via one or more Discovery missions in the relatively near term. We pretty much know what to look for at Europa and indeed throughout the entire Galliean satellite system. What we don't know is whether we can get to that putative ocean via any practical technology, but again that seems like something that could be determined on less than a Flagship-class level of effort. I think that the answer to that question is key for planning all future Europa exploration.

On the other hand, we've already landed on Titan; we know that we can conduct in situ exploration using reasonable evolutes of current technology, which becomes a trade-off between transit time/launch costs and science return. (Side note: this is why I still wish that there was an ongoing, organized effort by JPL or somebody to identify particularly favorable outer-planet launch opportunities). Titan is quite possibly at least as geochemically complex as Earth (with an outside chance of being more so). Therefore, to me, it seems as if there is a lot more science to be done at Titan than anywhere else in the Solar System


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
ugordan
post Dec 28 2007, 04:12 PM
Post #59


Senior Member
****

Group: Members
Posts: 3648
Joined: 1-October 05
From: Croatia
Member No.: 523



QUOTE (nprev @ Dec 28 2007, 04:31 PM) *
... I'm not completely convinced that achieving major scientific objectives ... can't be accomplished via one or more Discovery missions in the relatively near term.

We're straying to the old Jovian-Saturnian system debate once again, which seems to come down to personal preference biasing everyone's opinions so we'll never all agree on what should be explored first.

I'd be interested in hearing how you envision a Discovery mission getting to Jupiter and doing any global coverage of Europa of the type you proposed? All the more importantly since IIRC the Delta II is being retired and causing the more expensive Atlas V to be used. Forgive me, but sending Discovery missions (which were all pretty much confined to a bit outside of Mars' orbit) to Jupiter seems like a far-fetched idea. Is there any document I missed that discusses such possibilities? We've had discussions about even New Frontiers missions being inadequate for in-depth Europa investigation.


--------------------
Go to the top of the page
 
+Quote Post
nprev
post Dec 28 2007, 05:28 PM
Post #60


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



The strategy I envision is sort of a "one-note pony" theme; maybe two or three instruments per mission designed to answer a specific research question, that's it. Core assumption is that the launch vehicle is the vast majority of cost (and, yeah, the demise of the Delta II is a huge blow... sad.gif...hopefully new LVs from the independent launch enterprises like SpaceX will prove both more capable and less costly over time.)


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post

5 Pages V  « < 2 3 4 5 >
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 29th March 2024 - 01:55 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.