[X] My Assistant

[imran]

Aerobot aims for Titan

An intelligent floating robot could help to explore Saturn's moon Titan, following flight tests that prove it can survey large areas of land completely autonomously. The aerobot is even smart enough to avoid dangerous turbulence.

This summer, aerobot's team got further funding to develop a full mission proposal, which may lead to a launch in 2012.

Good news and I hope this happens but a more realistic timeframe is late next decade, more likely after an Europa mission.

[Guest_Richard Trigaux_*]

The ideas for a flying probe were already discussed here.

Eventually amateur ideas could be useful for a space mission.

[Guest_BruceMoomaw_*]

The Solar System Roadmap has this one pretty firmly pegged as the next "Small Flagship" solar system mission after the Europa Orbiter (although there's a small chance that a Venus surface explorer of some sort could supplant it). But this still means a launch in 2019 at earliest, and the National Science Foundation's review board has just said that the Roadmap schedule may be too optimistic.

[imran]

Some related news today:

A recent study performed by Langley Research Center for NASA's science mission directorate recommends an airship as the best vehicle for the future exploration of Saturn's moon Titan.

The highly autonomous, helium-filled airship would be 18 meters (59 feet) long and 3.5 meters (11.5 feet) in diameter, carrying a science payload of 26 kilograms (57 pounds). Its normal operating altitude would be one to five kilometers (.62 to 3.1 miles), although it would also have the capability to land periodically and take direct measurements of Titan's surface, Wright said. The study team picked a baseline mission duration of 90 days, the same as the original baseline for the Mars Exploration Rovers.

One potential obstacle to the mounting of such a mission is its estimated price tag of $2 billion to $2.5 billion. However, "there's a big mission pull," Wright said. "There are a lot of people who are very interested in an aerial exploration of Titan, so there are a lot of these outer planets road maps that show an aerial-type vehicle exploring Titan."

http://aviationnow.ecnext.com/free-scripts...ticle=TITA10035

With the price tag between $2-2.5 billion, they may need international support to get the funding that they need.

[Guest_BruceMoomaw_*]

That price tag is ominous -- the Solar System Strategic Roadmap Committee had counted on being able to do this within the "Small Flagship" cost cap of $1.4 billion. Indeed, the most serious objection the NRC review panel had to the Roadmap was its confidence that both this mission and the following Venus Surface Explorer could be done within the Small Flagship cost cap. Instead it looks like the upper half of the "Large Flagship" cost band -- and we can afford only one of those per decade (if we skip all Small Flagships during that decade).

[Guest_Richard Trigaux_*]

mmmmh ... alway the problem of cost.

Let us say:

-it is better an expensive mission which fulfills its goal, rather than a cheap one which is just present on the place.

-if there are money limitation, it is better to limit the number of mission rather than reducing the quality of each mission.

-The childish game of "competition" should left place to international cooperation. Many countries could provide subsystems, or even simply money or ground support. When we deal with billions, even only some millions can make a difference.

[JRehling]

-if there are money limitation, it is better to limit the number of mission rather than reducing the quality of each mission.

I think you mean rather than many reduced missions to different worlds. However, if there were an option for many (or two) aerobots to Titan within the same cap as one larger one, the option of many would be appealing. With Titan's winds being what they are, it may be impossible for an aerobot to travel very far north-south during its lifetime. Imagine Mars after only Viking 1 and Viking 2 -- even now we've seen five locations (with a few km roving in two of those). Huygens has shown us one location (and its surroundings) -- a single big aerobot would probably be sent either to the equatorial area, to overfly a variety of dark/light terrain (as Huygens did), or to the deep south, to investigate, eg, Mezzoramia. Two Titan aerobots would make even more sense than two MERs for Mars -- if only a 90-day mission can be guaranteed. Now, if a longer life were likely, a single craft might eventually travel long distances in latitude and perform a more complete overview of Titan. Unfortunately, a helium balloon is likely to have problems with longevity that a wheeled vehicle does not -- you can sit on wheels forever and not sustain much disrepair, while the helium supply can only decrease over time unless a zero-leak system can be guaranteed.

The Pioneer Venus solution was to send one probe that contained the superset of atmospheric instruments along with smaller ones that probed basic quantities in a variety of places. That could perhaps be an option at Titan, to have one aerobot along with several very minimal (no need to probe isotope ratios in multiple locations) sounding probes that drop in at a carefully-selected variety of locations. Of course, all of this talk pushes the cost higher and higher.

[Bob Shaw]

Unfortunately, a helium balloon is likely to have problems with longevity that a wheeled vehicle does not -- you can sit on wheels forever and not sustain much disrepair, while the helium supply can only decrease over time unless a zero-leak system can be guaranteed.

Which is why an RTG-heated hot-air balloon is so attractive!

[Guest_Richard Trigaux_*]

Which is why an RTG-heated hot-air balloon is so attractive!

This was already discussed. As for me I came with a part hot air baloon, par gaz baloon, shaped like a wing, and inflated with hydrogen (which can be produced on the spot). The wing/gaz baloon can fly faster than only a gaz baloon, while the hot air/gaz baloon can manoeuver near the groung far better than a wing. And there is no problem of helium leak. I am not sure at all that we cn garanty a zero leak for helium, at it can leak even through plastics, rubber, etc.

[Guest_Richard Trigaux_*]

I think you mean rather than many reduced missions to different worlds. However, if there were an option for many (or two) aerobots to Titan within the same cap as one larger one, the option of many would be appealing.

One expensive mission can of course include this option, as development costs are not reccurent, and the ground support too. The MER mission showed that it is a good choice, and it would be an even better choice if one of the craft fails.

[imran]

One expensive mission can of course include this option, as development costs are not reccurent, and the ground support too. The MER mission showed that it is a good choice, and it would be an even better choice if one of the craft fails.

I would be in favor of this mission as it would increase the chance of success with double the science. Without a significant international investment, however, I just don't see this happening. The price tag would be unbearably high.

[Guest_BruceMoomaw_*]

A thought: if -- as the new Langley study suggests -- a flat-out
Titan aerobot mission that would cruise along and periodically scoop up
surface samples for organic analysis is indeed prohibitively expensive at $2
to $2.5 billion, would a lower-cost mission be worthwhile consisting of a
stationary lander that touches down on one such dome -- where we're most
likely to find complex water-created organics -- combined with a small
passive balloon that drifts along providing aerial images of Titan's
surface? We clearly need much better images of its surface formations than
we're going to get from either Cassini or Huygens in order to properly
understand this place. (Relaying back images from the latter without a Titan orbiter, however, might be unworkable.)

[imran]

Here are the two Titan Mission Concepts presented at the OPAG meeting thanks to the link posted by Bruce:

Titan Vision Study 1
Titan Vision Study 2

Lunine is suggesting a self-propelled airship that would fit within the New Frontier Mission cost cap of ~$750M. This price tag I believe would leave out an orbiter. Langley is proposing a similar airship that includes an orbiter. This of course would fall under the Flagship Mission cost cap, although Langley doesn't provide an estimate on the cost except that it exceeds the $700M limit. The general consensus is to go with some sort of aerial platform, most likely an airship or blimp. The question is whether there will be a complementary orbiter, which I think is necessary because we need high resolution global coverage of Titan. They need to find a way to somehow bring the total cost down to $1.5B or less from the original $2-2.5B estimate.

[Guest_BruceMoomaw_*]

I intend to do a little more grilling of the OPAG people (especially Lorenz) about these Titan studies -- the debate over what to do about Titan was clearly the dominant theme of this OPAG meeting. (There was barely any discussion of Europa; the decision seems to have been firmly reahced by NASA to go on with Europa orbiter as the next big non-Mars planetary mission, and the only remaining questions are whether they can cram a small lander onto it and whether they should collaborate with the ESA.)

The Titan Working Group also featured a brief summary ( http://www.lpi.usra.edu/opag/oct_05_meetin...an_work_grp.pdf ) of the examination of the two Titan mission concepts presented at the last OPAG meeting: a surface rover, and an orbiter with some small lander or flyer of unspecified type. They take a very dim view of a Titan surface rover -- it can't cover enough ground, especially on that rugged terrain. But they think an orbiter with some small in-situ package of unspecified sort -- stationary lander, or maybe drifting and non-landing balloon? -- might be a good and affordable first step toward later exploration

However, the other affordable concept for a first mission seems to be the fallback version of the "Titan Organics Explorer" described in the first of the two newest OPAG mission studies: instead of a powered hydrogen-filled blimp, a drifting, wind-driven Montgolfiere balloon inflated by heat from the same RTG that powers it, which might be doable "within a New Frontiers budget". The big question is how such a balloon could identify and touch down at good sites for surface organics analysis -- it might have to include an awful lot of onboard autonomous scientific judgement, since it couldn't actively inspect a possible site and then hover there waiting for orders from Earth. As I say, I intend to look into all this further.

But note Slide #13 of that presentation -- they are explicitly mentioning a search for honest-to-God Titanian life, not just for interesting prebiotic chemicals.

[JRehling]

The question is whether there will be a complementary orbiter, which I think is necessary because we need high resolution global coverage of Titan.  They need to find a way to somehow bring the total cost down to $1.5B or less from the original $2-2.5B estimate.

Can an orbiter do high resolution global coverage of Titan? Above and beyond what Cassini will perform?

In IR, I think the answer will be: marginally better. And that would make it hard to validate a high price tag.

Note that the limit on the resolution that ISS is returning has nothing to do with the power of the camera -- the blurring effects of the atmosphere are the bottleneck. Also, it is not possible to dip much lower than Cassini does, because the atmosphere would quickly degrade a lower orbit. The only way to beat Cassini coverage is to find a better spectral hole than ISS exploits. In fact, VIMS does this, although it presents other constraints.

You may be stating that ISS's resolution is high, but not broad enough spatially. And at present, that is true, but as the extended mission goes on, the coverage by ISS should end up really very extensive -- we are only a fraction of the way into the primary mission. Unless seasonal/orbital resonances that I'm not aware of prohibit coverage of large areas, we should, before 2020, have Titan mapped nearly as well as is possible with the 938 nm filter.

Now a superior radar mapping, at higher cost, is always possible. But nothing going to Titan would ever touch the Shuttle-based radar mapping of Earth, which provided better than 30 m/pix resolution... but was orbiting 2.5x closer to Earth than any orbiter can get to Titan. So even an awesome (-ly expensive) radar mapper would only double or treble Cassini's resolution. That's a lot of buck for the bang.

I think the best bang for the buck will be to get excellent detail mapping from an aerobot that wraps around the globe a couple of times at different latitude, giving us some outstanding noodles that no orbiter could touch (unless it's a massive radar orbiter).