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Unmanned Spaceflight.com _ Exploration Strategy _ AVIATR - Titan Airplane Mission Concept

Posted by: Juramike Apr 16 2010, 12:20 AM

The AVIATR mission concept is an unmanned aerial vehicle that would fly over Titan’s surface. It’s nominal one year mission would enable detailed high-resolution images of Titan’s diverse landscapes for better comparison to Earth’s geological processes. Selected regions could be imaged at resolutions near 30 cm/pixel, equivalent to current HiRise imaging of Mars. In addition, atmospheric sampling would allow a profile of Titan’s thick lower atmosphere and how it relates to Earth’s atmospheric processes and weather systems.

Further details of the AVIATR mission concept were presented at the Lunar and Planetary Sciences Conference 2010 and at Titan Through Time 2010.
See: Barnes et al. LPSC 41 (2010) Abstract 2551. “AVIATR: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance.”
Freely available here: http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2551.pdf

And also: http://www.info.uidaho.edu/documents/2010%2001%2025%20Barnes.pdf?pid=118467&doc=1

Posted by: Juramike Apr 16 2010, 12:23 AM

This is an artist's impression of the AVIATR airplane flying over a northern Titan lake:



This image was the background for the LPSC and Titan Through Time AVIATR mission poster.

-Mike

Link to a full size graphic here: http://www.flickr.com/photos/31678681@N07/4524067323/

Posted by: nprev Apr 16 2010, 12:33 AM

ohmy.gif ...niiiiiiiice!!!! Sweet image, Mike, and that's an exciting concept!

Posted by: vjkane Apr 16 2010, 06:08 AM

Also check out http://futureplanets.blogspot.com/2010/02/aviatr-titan-plane-proposal.html

Fantastic graphic!

Posted by: Juramike Apr 20 2010, 03:14 AM

Image showing the proposed AVIATR Titan airplane flying over mountainous bright terrain:



Higher resolution here: http://www.flickr.com/photos/31678681@N07/4536966474/
Full resolution detail of the AVIATR aircraft here: http://www.flickr.com/photos/31678681@N07/4536967404/in/photostream/

(I've no clue why the thumbnail looks fuzzy.)

Posted by: Juramike Apr 30 2010, 01:12 PM

Recent video showing NASA's Global Hawk UAV research platform:
http://www.youtube.com/watch?v=p2qyiwt1_68


Also a TED talk by Joel Levine describing the Mars ARES UAV proposed mission:
http://www.ted.com/talks/lang/eng/joel_levine.html


Posted by: Juramike May 20 2010, 05:35 PM

Smithsonian Air and Space article on Titan AVIATR mission:
http://www.airspacemag.com/space-exploration/Titan-Air-.html#

Posted by: Juramike Jun 13 2010, 03:32 AM

Video of Jason Barnes presenting the AVIATR mission concept during the Huygens legacy conference Jan 15, 2010:

http://vimeo.com/11432536



Posted by: Juramike Jun 17 2010, 01:44 PM

Future Planetary Exploration blog entry on AVIATR mission details: hthttp://futureplanets.blogspot.com/2010/06/aviatr-titan-plane-details.html

Posted by: algorimancer Jun 23 2010, 01:30 PM

I'm really bothered by the very low (2 Gb) projected data return. This just doesn't sound like a lot of return for a billion dollar investment. Even with compression, 2 Gb doesn't add up to a lot of images (try going on vacation with only a 2 Gb flash card for your digicam), and this mission has the potential to explore much of Titan. Also, the 30 cm/pixel maximum resolution of the surface is on par with what I would expect from an orbiter, not an aircraft. I'd be reasonably happy with 3 mm per pixel (presumably associated with occasional low passes over targets of interest), and I'd like to see data return increased by at least a factor of 10, preferably 100. Possibly the greater data return might be achieved by storing much of the data until near end of mission, then achieving an intact landing and then leisurely transmitting the remainder over a period of months or years; I could even envision adding a very lightweight parabolic antenna to be deployed post-landing to accelerate data return.

Posted by: djellison Jun 23 2010, 04:16 PM

You're not going to get 30cm resolution from orbit around Titan. Furthermore, you're not going to get 3mm resolution from an aircraft. Infact, I've never ever heard of an aircraft getting 3mm/pixel on EARTH, let alone on Titan. Google Earth imagery is mainly aerial photography, and is typically at about 25cm/pixel - maybe 12.5cm in some places. That's still a factor of 40 (1600x fewer pixels) lower than the 3mm you're suggesting. If you COULD - you wouldn't need a 10 or 100 fold increase in data return - you would need 10,000 fold increase.

Covering just 0.1% of Titan's surface at 3mm/pixel, at 8 bits per pixel, with 10:1 compression?

83,000 sqkm. At 72 Gigabits per sqkm. 5,976 TERRABITS of data.

At 30cm/pixel 0.0072 Gigabits per sqKm. 598 Gigabits.

MRO with it's huge high gain antenna, in our back-garden at Mars (compared to a flight to Titan) has sent back just 42 Gigabits of data to date.

I'm afraid your expectations are unrealistic, and your engineering suggestions are just in the wrong place in terms of complexity, feasibility etc given the budget, mass, volume etc.

If we're going to go back to Titan, I don't think AVIATR is the way to do it. The way to do it is with TSSM, so you can have the montgolfière + an orbiter for relay. You're still not going to get anywhere near your requirements. But you've going to get a lot more data, that's for sure.

Posted by: stevesliva Jun 23 2010, 04:52 PM

Note that the figure is two gigabytes, and calling it 2 Gb rather than the correct 2 GB reduces the figure by a factor of eight to some eyes.

And 2 GB can be thousands of compressed photos. And they will be choosing the best from thumbnails, they say, which does sort of admit the data return would ideally be higher.

Posted by: Drkskywxlt Jun 23 2010, 05:08 PM

QUOTE (djellison @ Jun 23 2010, 11:16 AM) *
MRO with it's huge high gain antenna, in our back-garden at Mars (compared to a flight to Titan) has sent back just 42 Gigabits of data to date.

Doug...You're way low with the MRO data return. I'm analyzing MCS data, and there's about 20GB of MCS data publically available alone.

This article says that by March, 100 TERABITS of data had been returned by MRO.
http://www.space.com/missionlaunches/mro-data-milestone-100315.html

Posted by: djellison Jun 23 2010, 06:00 PM

I was going from http://mars.jpl.nasa.gov/mro/ (bottom left corner ) - but you're right, that widget's clearly WAY out of date. Perhaps they mean 142Tb

Still - the point I was making (even the very highest downlink in planetary exploration is a LOT less than the requirements algorimancer was trying to place on a Titan aircraft.) holds true.


Posted by: Drkskywxlt Jun 23 2010, 06:25 PM

QUOTE (djellison @ Jun 23 2010, 01:00 PM) *
I was going from http://mars.jpl.nasa.gov/mro/ (bottom left corner ) - but you're right, that widget's clearly WAY out of date. Perhaps they mean 142Tb

Still - the point I was making (even the very highest downlink in planetary exploration is a LOT less than the requirements algorimancer was trying to place on a Titan aircraft.) holds true.


Perhaps you need to hit refresh wink.gif. When I load that page, it says 115.7 TB.

Your point was correct, I agree.

Posted by: djellison Jun 23 2010, 06:27 PM

The internet hates me.

smile.gif

 

Posted by: algorimancer Jun 23 2010, 08:18 PM

Doug, my intent wasn't to suggest 30mm/pixel routinely -- as I parenthesized, I suggested this might be associated with diving to lower altitude over targets of interest. I'm very aware that it is ludicrous to attempt this (or even 30 cm/pixel) for the entire surface of Titan. Essentially what I'm getting at is that I would like to see lander-like resolution for select spots of interest.

Posted by: Jason W Barnes Jun 28 2010, 03:51 AM

QUOTE (algorimancer @ Jun 23 2010, 06:30 AM) *
the 30 cm/pixel maximum resolution of the surface is on par with what I would expect from an orbiter, not an aircraft. I'd be reasonably happy with 3 mm per pixel (presumably associated with occasional low passes over targets of interest),


Hi -- this is Jason Barnes. I'm proposing AVIATR as Principal Investigator. I appreciate the attention to AVIATR around here -- keep up the comments!

While 30cm/pixel is what HiRISE is getting at Mars, you're not ever going to get that from an orbiter at Titan. Here's why. Because Mars' atmosphere is so thin, and because its gravity is relatively high, you can orbit Mars at just 150 km altitude safely to take pictures. In contrast, Titan's atmosphere is super-thick and its gravity only 1/7 that of the Earth -- this means that if you're orbiting Titan, you need to be orbiting at 1500 km instead of 150 km. That's a degradation of a factor of 10 in spatial resolution. In addition, you're at 10AU from the Sun so you'd need to have a primary mirror 6 times the diameter of the equivalent for Mars, even with the lower resolution. Now take into account that HiRISE at Titan would see nothing but haze. You'll need to go out to 5 microns, where the atmosphere is nearly transparent, to do as well at Titan. But the Sun is much dimmer at 5-microns than it is in the visible. And this would mean super-cooled optics, and an infrared detection system.

The bottom line is that to do the equivalent of HiRISE at Titan would require something like a 10-meter JWST sent out to Saturn and burned into orbit around Titan. Not going to happen. Even TSSM was baselining 50-meters-per-pixel global imaging for the orbiter.

Taking high-resolution imagery for Titan's surface makes sense from an aerial platform. You can use all of that pesky air to your advantage, instead of fighting it with a giant orbiter. AVIATR would have 100 times better resolution than the TSSM orbiter. Resolution isn't everything, though, and we're going to great lengths in order to gather context imaging in order to be able to interpret our high-resolution postage stamps, too.

- Jason W. Barnes

Posted by: Jason W Barnes Jun 28 2010, 04:07 AM

QUOTE (algorimancer @ Jun 23 2010, 06:30 AM) *
I'm really bothered by the very low (2 Gb) projected data return. This just doesn't sound like a lot of return for a billion dollar investment.


That should be 2 gigabytes (GB) and not 2 gigabits as written.

While AVIATR certainly is not going to be like MRO blasting back terabytes and terabytes of data, let me take this opportunity to suggest that data is not knowledge. Put another way, more bits does not always mean more science.

At Mars there's been 40 years of exploration. In order to make new scientific discoveries from a orbiter taking pictures, you need to do more and better than the missions that have gone before you. Because HiRISE is following on a very capable, very successful imager on MGS, it needed to do better in order be able to do things that MOC was unable to do. In the planetary exploration business, the general rule of thumb is that you need to do about 10 times better than the previous mission in order to be compelling enough to fly. HiRISE's pixel scale is 3 times better than MOC, its swath width at least 5 times wider, and it can send back more images due to the greater bandwidth available on MRO. Hence it was deemed a compelling investigation.

Cassini's RADAR has a best pixel scale of about 300 meters per pixel. Since pixel scale is not resolution, the actual resolution of the RADAR images is more like 750 - 1000 meters due to inherent speckle noise in the RADAR data. The best VIMS data are 250 meters per pixel, but those noodles are only 13 pixels across. AVIATR would do 1000 times better than these in terms of spatial resolution.

A better comparison for AVIATR would be Huygens. Huygens returned mosaics from around its landing site of varying resolution. Obviously the picture from the surface had spatial resolution that we can't match from an airplane! But our image mosaics from sites of interest will resemble Huygens', but with better control, higher spatial resolution where desired, and better signal-to-noise since we're imaging in the infrared.

If you think that 2GB is too little for a mission, then would you fly a mission that would return a total of just 60 MB of data? That's all that we got from Huygens. AVIATR would return 30 times the total data that we got from from Huygens. The reason that 2GB is enough isn't because of the quantity of data -- its that we'll be returning images that can't be obtained any other way. AVIATR will have a huge science and exploration impact because we're looking where nobody's looked before.

It's not the number of bits that you have. Its how you use them wink.gif

- Jason W. Barnes

Posted by: Jason W Barnes Jun 28 2010, 04:23 AM

QUOTE (djellison @ Jun 23 2010, 09:16 AM) *
If we're going to go back to Titan, I don't think AVIATR is the way to do it. The way to do it is with TSSM, so you can have the montgolfière + an orbiter for relay. You're still not going to get anywhere near your requirements. But you've going to get a lot more data, that's for sure.


I'd love to have a $4 Billion dollar Titan mission! But unfortunately, TSSM is dead. We're going to Europa instead.

The question now becomes: do we wait and hold our breath demanding a new $4 Billion Titan mission, or do we explore piecemeal instead of all at once? Even if Europa flies on time, and that's a big if, a future Titan flagship wouldn't get a new start until after EJSM launches. That's in 2020. So say we get a new start in 2020. And we take 10 years building before we launch, too. Then we launch in 2030. We have a 7-year, Cassini-like cruise, say. Now it's 2037, and we're finally back at Titan with a flagship, if everything goes perfectly. The flagship has a 4-year nominal mission, say. Without any extended mission, it would end in 2041.

Who among us will still be alive then, and not in a nursing home? I'm pretty young as far as these things go, and I'd be 64 then if everything went like that.

Instead I suggest that we take another approach. The Mars Exploration Program was implemented after Mars Observer blew up in 1993, and they realized that they could put together a more compelling scientific program by flying a small mission every 26 months rather than a giant mission every 20 years. This approach has been so successful that today more planetary dollars are spent at Mars than for any other target, by far. When you stop to think about it, this is pretty amazing. As recently as the mid-'90s it was not clear that Mars would become the focus of the American planetary program. The smaller, more frequent Mars missions keep the scientific community interested, have less programmatic risk, and allow follow-ups on previous discoveries in a human lifetime. They built an amazing program. Then they pissed it all away with MSL. But I digress.

We should be exploring Titan the same way as we used to explore Mars. One reason to do this is that we can. Numerous mission concept studies have shown that you can't get anything even into orbit around Europa for less than $1B. By the time that you get into orbit around Europa, the radiation will fry you in 6 months. This is why EJSM is going to cost $3B and only live for 6 months -- it's inherent in the physics of getting to Europa and doing science there.

In contrast Titan is easy to get to and explore. AVIATR is going to just fly straight into Titan's atmosphere without any engine burns at all. Just like Mars Pathfinder, or Mars Phoenix, or the MER rovers. Moreover Titan's atmosphere is so light and fluffy that we'll have very low heat loads and accelerations on entry -- 5 times easier than the easiest Mars entry. This is why it's possible to get to Titan on a Discovery budget.

If we launch a Discovery or New Frontiers class Titan mission every 5 years or so, we'll be in a great position to do amazing and sustainable science, on a budget that might actually get approved, and on a timescale over which we'll still be alive to care!

- Jason W. Barnes

Posted by: jekbradbury Jun 28 2010, 02:59 PM

It's certainly a shame the mass spectrometer can't be included (Mike's got me hooked on Titan chemistry) but this mission, if it can stand up to its objective of "flagship-class science with a Discovery-class cost", will revolutionize our understanding of one of the most interesting destinations in the solar system. I can't wait.

Posted by: algorimancer Jun 28 2010, 05:45 PM

QUOTE (Jason W Barnes @ Jun 27 2010, 10:51 PM) *
While 30cm/pixel is what HiRISE is getting at Mars, you're not ever going to get that from an orbiter at Titan.
...
Taking high-resolution imagery for Titan's surface makes sense from an aerial platform.

My original post seems to have stirred a lot of discussion, and apparently it could have been more clearly written, as it seems to have spurred some misconceptions and overreactions. For the record, I am overall very impressed and even excited about the AVIATR proposal, but my perspective on its capabilities are shaded by experience with MER and MRO. I do realize that this is a small mission to a place orders of magnitude more remote than Mars. My fantasy mission would be something like AVIATR that lands periodically to provide both broad overview and local focus.

My critique of "30cm/pixel" was in the context of seeking a bit of that local focus which a landed vehicle would provide. Essentially I'm advocating that, for particularly interesting targets, that the aircraft fly closer to the ground such that millimeter-scale imagery can be acquired. This might be just a few times over the course of the mission, once the topography is better understood so as to avoid accidents, and would be the equivalent of sending multiple landed vehicles -- very cost-effective. Worst case, if engineering and environment provide a fundamental limit on how low the vehicle can fly and continue flying, this might be a single descent near the end of the mission. Beyond this, I'm really quite happy with 30cm/pixel -- this has worked beautifully with MRO -- but the benefit of an aircraft versus an orbiter is that an aircraft has the option to maneuver in altitude without much difficulty. Oh, I definitely agree that an aircraft is optimal for Titan, while an orbiter would border on a waste of time (possibly excepting an imaging radar mission).

The 2 GB limitation is less of an issue to me, but I feel that with a bit of creativity it is not out of the question that this might be expanded by a factor of 10. Potentially, if Cassini is still functioning, it might act as a local relay. Does AVIATR use a directional antenna? If not, might the dorsal surface be contoured to function as one, even perhaps only intermittently when the flight orientation is congruent with transmission to Earth, thus allowing higher rater transmission on those occasions? I realize that there would be a compromise between optimizing a surface for aerodynamics and as a directional antenna, but the low gravity and high density of Titan's atmosphere would seem to permit a fair amount of flexibility in this regard.

Overall, I would be ecstatic to see AVIATR fly as currently designed -- to me, Titan is in the top 3 of interesting places to visit in the solar system, and I've been itching to see another dedicated mission ever since those tantalizing images from Huygens.

Finally, I very much appreciate your taking the time and interest to discuss the mission here. I work in orthopedic research, and involvement with the public -- even educated semi-pro amateurs -- just doesn't happen in that world, so I don't have to deal with backseat drivers second guessing my research designs.

Posted by: Jason W Barnes Jun 29 2010, 10:15 PM

QUOTE (jekbradbury @ Jun 28 2010, 07:59 AM) *
It's certainly a shame the mass spectrometer can't be included (Mike's got me hooked on Titan chemistry)


I guess that I don't consider it a shame not to have a mass spec! While the science from a mass spectrometer would be awesome, there's no need to have one on an airplane. In order to do better than Huygens you would need a high-quality, ultra-high-mass-resolution spectrometer. This would be heavy. Remember that we can only fly 10-14kg of instruments. Because the trace gas abundances should be the same all over Titan, there would seem to be no need for the mobility of an airplane. If trace gas measurements are your mission, then you should send an atmospheric probe or a lander, not an airplane (or a balloon for that matter).

- Jason

Posted by: Juramike Jun 30 2010, 04:54 PM

AVIATR image posted in Planetaria blog:

http://web.me.com/planetaria/planetaria/blog/Entries/2010/6/23_AVIATR_airplane_mission_proposal_for_Titan.html

Posted by: Drkskywxlt Jun 30 2010, 05:35 PM

Jason (or anybody in the know) --

What is the expected mission duration? Are you able to target any location on Titan? If so, do you have a particular target in mind? Is a soft landing (with a short surface operation) a possibility as the mission ends?

Posted by: Jason W Barnes Jul 1 2010, 08:27 PM

QUOTE (Drkskywxlt @ Jun 30 2010, 10:35 AM) *
Jason (or anybody in the know) --

What is the expected mission duration? Are you able to target any location on Titan? If so, do you have a particular target in mind? Is a soft landing (with a short surface operation) a possibility as the mission ends?


Our nominal mission (right now anyway) is 1-year. Since we're flying the whole year, and we can't stop, we can and will go anywhere and everywhere on Titan: dunes, mountains, channels, Xanadu, lakes, you name it.

The problem with a surface mission is thermal. We rely on the cold air that we're flying through to keep the ASRGs cooled. Once we land we lose that cooling. We do have an end-of-mission plan whereby we land, but we're not designing to be able to survive and/or do science from the surface. Note that Huygens wasn't designed to survive landing, either, though, and it did fine! Titan's atmosphere is thick enough that the speed that we're flying at is very similar to the speed of Huygens when it landed.

- Jason

Posted by: Jason W Barnes Jul 9 2010, 08:30 AM

Another point of comparison for missions' data return: Mars Pathfinder returned 2.6 gigabits, or 325 megabytes of data total, near as I can tell. It was also communicating direct-to-Earth.

- Jason

Posted by: rlorenz Jul 11 2010, 02:45 PM

QUOTE (Jason W Barnes @ Jun 27 2010, 11:07 PM) *
Cassini's RADAR has a best pixel scale of about 300 meters per pixel. Since pixel scale is not resolution, the actual resolution of the RADAR images is more like 750 - 1000 meters due to inherent speckle noise in the RADAR data. The best VIMS data are 250 meters per pixel, but those noodles are only 13 pixels across. AVIATR would do 1000 times better than these in terms of spatial resolution.


Hoi! mad.gif Misrepresentations like that will get you kicked from the team, pal.

The archive pixel scale (oversampled) is 175m/pixel. The formal range and azimuth resolutions vary throughout
a flyby, but are typically 300m (sometimes less) at closest approach - these resolution histories per flyby, and all
the other radar-voodoo parameters such as prf, bandwidth etc. are documented in the
sequence design memos (in the 'extras' directory on the PDS archive). Resolution (and thermal noise) are
separate consideration from speckle noise, which is a function of the number of looks.

Whether you consider the 'useful' resolution to be the same as the real resolution depends
on the application; some tasks require higher signal-to-noise than others. This is also true for VIMS data, which
does not always have the signal-to-noise to do what you'd like to do (and will be for AVIATR).

Posted by: Jason W Barnes Jul 12 2010, 01:29 AM

QUOTE (rlorenz @ Jul 11 2010, 07:45 AM) *
Hoi! mad.gif Misrepresentations like that will get you kicked from the team, pal.

The archive pixel scale (oversampled) is 175m/pixel.


I'm not impressed. That's like me saying that the VIMS data are 0.5 km/pixel because I've interpolated them that way. What's the actual Nyquist-sampled pixel scale? I don't think that I'm the one misrepresenting wink.gif

- Jason

Posted by: rlorenz Jul 12 2010, 12:20 PM

QUOTE (Jason W Barnes @ Jul 11 2010, 09:29 PM) *
I'm not impressed. That's like me saying that the VIMS data are 0.5 km/pixel because I've interpolated them that way. What's the actual Nyquist-sampled pixel scale? I don't think that I'm the one misrepresenting wink.gif

- Jason


No, that's why I said oversampled. (Since the resolution elements, defined by doppler bandwidth etc.
are not square, the archive product is oversampled so as not to lose information when the data are
projected onto a square grid.)
Like the post said, the real resolution can be 300-350m (and there are many good SAR tutorials on-line
to explain how we get that.)

Posted by: Greg Hullender Jul 12 2010, 08:58 PM

Forgive my ignorance, but shouldn't the resolution just be a simple calculation from the field of view, the distance to Titan, and the dimension of the camera in pixels? I realize SAR isn't quite the same as a simple picture, but can it be THAT different?

The discussion of how accurate things need to be reminds me of something a senior astronomy major told me when I was a freshman at Caltech back in the 1970s:

Mathematicians insist on exact answers. Pi is NOT 3.1416
Chemists and Engineers generally settle for a few parts per thousand error.
Physicists are happy to get the order of magnitude right.
Except Astro-Physicists, who just want to get the order of magnitude of the order of magnitude right.
And Computer Scientists only need to know if it's zero or not.

--Greg :-)

Posted by: Jason W Barnes Jul 12 2010, 11:21 PM

QUOTE (Greg Hullender @ Jul 12 2010, 01:58 PM) *
Forgive my ignorance, but shouldn't the resolution just be a simple calculation from the field of view, the distance to Titan, and the dimension of the camera in pixels? I realize SAR isn't quite the same as a simple picture, but can it be THAT different?


Short answer: yes.

The real problem, though, and one that is quite common, is that what you're describing is the pixel scale. It is not the resolution. Resolution is the smallest thing that you can resolve, which is always larger than a pixel. In fact the theoretical minimum is 2 pixels. Experience with HiRISE is that about 3 pixels is what it really takes to resolve an object.

Take Cassini ISS looking at Titan, for instance. You can do the calculation that you describe, and calculate the pixel scale. But no matter how small the pixels are, you can't achieve a true resolution better than 1 km. The atmospheric haze scatters too much to do any better.

Which is why, even with Ralph's discussion, I am still convinced that with 300m properly-sampled RADAR "pixels", the RESOLUTION is ~750m.

- Jason

Posted by: rlorenz Jul 13 2010, 12:46 AM





QUOTE (Jason W Barnes @ Jul 12 2010, 06:21 PM) *
Which is why, even with Ralph's discussion, I am still convinced that with 300m properly-sampled RADAR "pixels", the RESOLUTION is ~750m.


The definition of the SAR resolution from Doppler bandwidth etc (giving 300m) is physically equivalent to
that which defines the resolution of an optical telescope as ~1.3lambda/D. I stand by my original number. The
pixels are 175m, which as you say is irrelevant.

QUOTE (Jason W Barnes @ Jul 12 2010, 06:21 PM) *
The real problem, though, and one that is quite common, is that what you're describing is the pixel scale. It is not the resolution. Resolution is the smallest thing that you can resolve, which is always larger than a pixel. In fact the theoretical minimum is 2 pixels. Experience with HiRISE is that about 3 pixels is what it really takes to resolve an object.


On this Jason and I might agree. The original definition of resolution is all about the diffraction patterns of
point objects overlapping - so to separate 2 objects X apart, you need a resolution of 'better than X' and really
a pixel scale of better than X/3 (so you see some dark space between your two bright points). But you can
still do science at much less than the pixel scale (e.g. fitting a point spread function, so you can determine
the position of an object to not only much less than the resolution, but also much lower than the pixel scale -
1/10 of a pixel is not uncommon). But this sort of thing (and 'super-resolution' techniques) rely on well-characterized
point spread functions, and high signal to noise data. Which brings me back to my original point that 'useful'
resolution depends what you are trying to do and on the signal/noise.


Posted by: nprev Jul 13 2010, 01:00 AM

Speaking as a layperson, very interesting discussion, you guys. I had no idea that 'resolution' as a figure of merit had so many contingencies other than atmospherics; never thought about it.

Posted by: Greg Hullender Jul 13 2010, 02:33 PM

I think I see. Part of my confusion is that, in the computer biz, when we talk about the resolution of a screen, we always just mean the pixels. So, if I understand correctly, when you guys talk about resolution, you include all the factors that could degrade the image: the pixel scale, of course, but also atmospheric noise, diffraction, probably even noise in the electronics themselves. Beyond a certain point (all other things being equal) increasing the pixel scale will not improve resolution at all. And so the dispute you two are having is not over the actual hardware being used but over the effect of these other factors?

Ralph: When you talk about doing science below the pixel scale, are you talking about making repeated observations of the same thing and computing a higher-resolution model from that? That is, you have to depend on having a static target. Or do you mean something more complex? (I may be guilty of seeing Bayesian and Markov Networks everywhere these days.) ;-)

--Greg

Posted by: vjkane Jul 13 2010, 09:08 PM

Properly speaking, resolution should be interpreted in terms of what you want to detect. Haze, low contrast, size of structure (frequently referred to as 'scale'), etc. all can effect how finely you can discriminate what you want to detect. To give an example. I may want to image trees that are 10 m across in an image in which each pixel covers an area of 1x1 m. So, the pixel resolution is 1 m, but my object resolution is 10 m. If tree sizes varied, the smallest tree I could reliably detect would probably have a crown 2 m across. It's actually more complicated than this since the tree probably wouldn't be exactly centered right, and I'd end up with some pixels that are all tree and some that are a mixture of tree and background, making the tree id harder. So my best reliable resolution (i.e., smallest tree) is probably 3x3 m.

However, people who build optical and camera systems want to have a way to compare the theoretical capabilities of the hardware. Sometimes, lines per inch are quoted (I've seen this in camera lens reviews, which then ignores the grain of the film, which would be equivalent to the size and density of pixels in an electronic system). In planetary missions, the instantaneous field of view is often given, which describes the angle seen by an individual pixel. To get theoretical resolution, you need this information and the distance to the object being imaged.

Computer monitor resolution is usually quoted as an area of pixels (e.g., 1600x1200 pixels), but the pitch between pixels is somewhat equivalent to the IFV in camera systems, but not exactly. Every camera forms images in an array of pixels x by y in size (with push broom cameras have a single line of pixels and spacecraft motion creates the y dimension). Image size can be quoted in x by y dimensions, but that says nothing about the resolution. You can put the same 1000x1000 CCD chip behind both a telescopic and a wide angle lens and get very different resolutions that cover very different areas on the surface

The above is not my area of specialty, so others may add or correct.

What is my area of specialty is sub-pixel interpretation for Landsat scenes. Each pixel of a Landsat scene has several 'colors' that represent key spectral ranges. (More technically, each landsat image is really several images, each of which was imaged with one filter.) If you know the dominant materials within a scene, you can use that knowledge to determine the approximate area that each material represents within the area imaged by an individual pixel. To continue with my tree analogy, if you know that everything in the picture is tree canopy or a soil background, you can model how much of the area covered by each pixel. The technique is called spectral unmixing.

It sounds like similar approaches can be used with radar data. They key, though, is that you need to know a lot about the surface you are imaging.

Posted by: rlorenz Jul 14 2010, 04:54 PM

QUOTE (Greg Hullender @ Jul 13 2010, 10:33 AM) *
And so the dispute you two are having is not over the actual hardware being used but over the effect of these other factors?


I dont know what the dispute was about. As far as I am concerned there is no dispute, the resolution as normally
defined is 350m and that's that.


QUOTE (Greg Hullender @ Jul 13 2010, 10:33 AM) *
Ralph: When you talk about doing science below the pixel scale, are you talking about making repeated observations of the same thing and computing a higher-resolution model from that? That is, you have to depend on having a static target. Or do you mean something more complex? (I may be guilty of seeing Bayesian and Markov Networks everywhere these days.) ;-)


What you describe sounds a bit like how i understand 'super resolution' works. (I think with the procedure
can also be referred to as 'dithering' : it was used on Pathfinder, also on HST). Radio astronomers (with typically
low angular resolutions defined by the real aperture) use similar methods by e.g. allowing objects to pass
through the beam as the Earth or spacecraft rotate. The key is having a well-defined psf, and having a
precise enough pointing history to know where in the psf of the scene the pixels of the detector actually are.

But it can be as simple as taking an image (many pixels) of an object which is geometrically smaller than a
pixel (e.g. a star) but whose image, as defined by the telescope optical system, is much larger. The information
obtained by sampling many pixels allows you to estimate where the star was to much less than one pixel, if
the point-spread function is known. That's a nicely-posed problem for a point source like a star, the cleverness
(Maximum Entropy, Bayesian, whatever) comes in how you deconvolve that psf from the image to make a
best estimate of a more complex scene (non-point objects like planets, many stars, plus some noise).

Posted by: Juramike Sep 7 2010, 03:58 AM

Artists impression of AVIATR aeroshell and parachute on way to lower atmosphere of Titan:



A MUCH higher-resolution image is here: http://www.flickr.com/photos/31678681@N07/4966028229/

Posted by: Juramike Sep 28 2010, 03:28 AM

Artistic impression of AVIATR Titan Airplane over Equatorial Bright Terrain. This has the latest aircraft design configuration (Configuration 3.0).



A higher resolution version is here: http://www.flickr.com/photos/31678681@N07/5032173290/

Posted by: Juramike Jun 10 2011, 01:11 AM

Reworked some of the AVIATR images with the latest configuration (AVIATR CF 3.0):

Here is an animated GIF of a camera tracking the AVIATR craft over a north polar Titan lake:


[*animated GIF: click to animate]

Full-res still image of AVIATR flying over north polar Titan lake: http://www.flickr.com/photos/31678681@N07/5814001064/in/set-72157623741262207/

Full-res reworked image of AVIATR over Bright Terrain: http://www.flickr.com/photos/31678681@N07/5614747283/in/set-72157623741262207/

Posted by: Juramike Nov 19 2011, 06:16 PM

Link to OPAG AVIATR mission presentation slides by Jason Barnes: http://www.lpi.usra.edu/opag/Oct2011/presentations/1_AVIATR_Barnes.pdf

Posted by: ngunn Nov 19 2011, 10:58 PM

Some of your images there Mike? Don't be shy!

Good proposal and illustrations. smile.gif

Posted by: nprev Nov 20 2011, 12:23 AM

Nice. I'd like to see this one fly (literally).

Only thing that concerns me is the UAV mechanical deployment sequence (which seems complex, to say nothing of time-critical), and I suspect that this will be a major point of evaluation.

Posted by: stevesliva Nov 20 2011, 03:53 AM

Uses an ASRG now. First nuclear plane. That's pretty sexy.

Actually wonder if DARPA would fund it. Nuclear UAVs wouldn't fly now, but nuclear UAV research? Why not.

Posted by: Jason W Barnes Nov 24 2011, 01:39 AM

QUOTE (nprev @ Nov 19 2011, 06:23 PM) *
Only thing that concerns me is the UAV mechanical deployment sequence (which seems complex, to say nothing of time-critical)


The deployment isn't too bad -- one joint on each wing unfolds, and that's it. And there's plenty of time to do it -- this isn't Mars, you know! 1/7th gravity, and 4 times the air density as Earth means we've got about 12 hours between entry and when we'd hit the ground. So not nearly as hair-raising as on Mars.

- Jason

Posted by: nprev Nov 24 2011, 01:59 AM

Ah! Thanks, Jason; feelin' warmer & fuzzier! smile.gif

Posted by: Mongo Nov 26 2011, 02:35 AM

I wonder if, instead of a virtually financially impossible Titan Flagship Mission, it would be possible to have a series of lower-cost Discovery-class missions to Titan, spread over a span of years? I assume that this would be possible only if launch costs drop by an order of magnitude or more, which could happen if Elon Musk is correct about having his Falcon 9 and Falcon Heavy launch vehicles be totally or mostly reusable.

If we have launch costs be a fairly small fraction of the total program costs, then would it be feasible to have a payload launched to Titan every launch opportunity, with the first being for example an orbiter / relay station with Radar and IR imagers / spectrometers, the second being a TiME lake floater (transmitting via the orbiter for much higher data rates), the third being an AVIATR aircraft (again, transmitting to Earth via the orbiter), etc.? Similar, in other words, to the recent Mars exploration program.

How would the costs compare to a Titan Flagship mission, and how would the science results compare? Is this a foolish notion, or does it have real possibilities?

Posted by: vjkane Nov 26 2011, 05:00 PM

Your idea of a number of lower cost missions has been proposed. Titan as a target for repeated missions has pluses (pretty benign environment) and minuses (long cruise times at ~$10M/year). My blog entry next week (futureplanets.blogspot.com) will look at the options for this approach (this week will be on the Mars 2016 and 2018 missions).

Posted by: Paolo Nov 26 2011, 05:07 PM

QUOTE (Mongo @ Nov 26 2011, 03:35 AM) *
I assume that this would be possible only if launch costs drop by an order of magnitude or more


I believe launch costs amount to about 1/10 of the total for a Discovery-class mission (or rather "amounted" before the Delta 2 was retired)

Posted by: nprev Nov 26 2011, 05:09 PM

Guys, in the name of keeping this thread on topic, suggest placing any posts about other possible future missions & architectures http://www.unmannedspaceflight.com/index.php?showtopic=5565.

Posted by: Jason W Barnes Dec 23 2011, 11:25 PM

The AVIATR team has published a paper about the mission concept in Experimental Astronomy that's just come out online. You can download it http://www.springerlink.com/content/76117941970t5291/ if you're interested.

- Jason

Posted by: stevesliva Dec 24 2011, 02:43 AM

Interesting that the Mongolfiere requires an MMRTG while the plane requires an ASRG. And they both need Pu-238.

How do you predict goop accumulation on the optical windows? And ice/goop accumulation on the lifting surfaces?

Posted by: vjkane Dec 24 2011, 06:02 AM

Jason - Has your team every looked into including a small relay orbiter with the mission? At an estimated cost of ~$700M, you would seem to have ~$300M for a satellite for a New Frontiers mission. Given that the JET orbiter was a Discovery proposal ($425M) and assuming some common costs, $300M doesn't seem too far off. I presume a relay orbiter would increase data return by a couple of orders of magnitude.

Of course, we need to get Titan added to the list of New Frontiers targets...

Posted by: vjkane Dec 24 2011, 09:46 PM

QUOTE (Mongo @ Nov 25 2011, 06:35 PM) *
I wonder if, instead of a virtually financially impossible Titan Flagship Mission, it would be possible to have a series of lower-cost Discovery-class missions to Titan, spread over a span of years?

I provided my thoughts on this question http://futureplanets.blogspot.com/2011/12/titan-on-installment-plan.html

Posted by: Greg Hullender Dec 25 2011, 07:13 PM

We're looking far enough in the future that laser communications may be viable: http://www.nasa.gov/home/hqnews/2011/aug/HQ_11-272_TDM_Selections.html

If that really can deliver a 100x increase in bandwidth, I'd think that would be the way to go. Obviously a laser might have some problems getting through Titan's clouds, but a relay satellite seems like a much better deal if it can deliver such a huge improvement in the quantity of data transmitted.

Put differently, are we doing these things in the wrong order? Shouldn't we shoot for a long-lived Titan orbiter first and then plan for all the following missions to use it as a relay?

--Greg

Posted by: nprev Dec 25 2011, 10:26 PM

(sigh)...Guys, once again, please keep this thread focused on AVIATR itself. Post http://www.unmannedspaceflight.com/index.php?showtopic=5565 for other future mission concepts, proposals, and relevant, realistic enabling technologies.

Posted by: Juramike Jan 3 2012, 02:06 AM

AVIATR mission concept written up in Universe Today: http://www.universetoday.com/92286/aviatr-an-airplane-mission-for-titan/

Posted by: Juramike Jan 11 2012, 04:48 PM

space.com article: http://www.space.com/14191-titan-drone-aircraft-explore-moon.html

Posted by: nprev Jan 11 2012, 06:22 PM

Great write-up & illustrations. Congrats, Jason & Mike! smile.gif

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