Hay, Paolo! I saw and heard you today on NASA TV! Looked like you were having tons of fun dumping DE into the pit from the wheelbarrow and then raking it down...

You're a TV star, dude!

-the other Doug

Back in the '70s, when I seriously looked into HAM radio, there was still a requirement to learn Morse code, both sending and receiving, at a minimum rate of 12 wpm in order to achieve your HAM license. Learning all that felt a lot too much like work, especially since I didn't anticipate using Morse at any point. So, I sort of lost interest.

My understanding is that the Morse code requirement was dropped several years ago.

-the other Doug

I'm impressed that the first calibration image, from the "commissioning" orbit (higher than the final science orbit, IIRC) is stated to have a resolution of 73cm per pixel.

Wow!

-the other Doug

Back in the late '70s or early '80s, Geraldo Rivera pushed this major network special, "The Secret of Al Capone's Vaults," during which these supposed hidey-holes once used by mobster Al Capone were opened up on live television. There was absolutely nothing in the "vaults," and ever since Rivera has been held up as the textbook example of all-hype, no-substance television programming.

-the other Doug

Partially closing the MI's lens cap has been discussed here to achieve this, but as far as I know hasn't been tried.

-the other Doug

Actually, PDP8E is operating under a misapprehension. I can tell his logical thought process was "If you get greater depth of field by reducing your aperture and thus cutting down on the light entering the camera, maybe you'll get greater depth of field merely by reducing the overall light level." And that's a fallacious logic chain.

You see, in the physics of photography, it's the actual size of the aperture, and not the amount of light reaching the photosensitive surface, that determines your depth of field (i.e., the range of distance from the camera in which objects are in focus). Focus has to do with the collimation (i.e., the parallel-ness) of the rays of light when they hit the film/CCDs. The smaller the aperture, the less "spread" you get from a beam of light entering, say, from the upper-right corner of the lens and then painted into the bottom-left corner of the film plane. The absolute greatest depth of field comes from a pinhole aperture, since there is almost no practical room for the light from any given area in the field of view to spread across the width of the aperture.

I have a degree in photojournalism -- some things you learn empirically, even if you're not a physicist...

-the other Doug

p.s. -- looking at PDP8E's other point, that reducing exposure time would increase depth of field, again that's not a truthful statement. The only thing that really increases depth of field is reducing aperture. If you increase the light on the subject, you can reduce aperture and thus increase depth of field, and perhaps at the same time you might need to reduce your exposure time in order to get a properly exposed image. That's the only way in which exposure time could work in with depth of field. But in general, photographers use exposure time to determine proper exposure (i.e., total amount of light) and aperture to determine proper depth of field. dvd

Actually the A14 EVA-2 track is quite well worked out, based on the pics the crew took on the surface during the EVA. What I'm more interested in seeing is if the MET tracks are visible. LRV tracks will likely be easier to spot in LRO images than the MET tracks, since the open-mesh LRV tires disturbed the soil more and spun up rooster tails. The MET had actual rubber tires, which left smooth tracks. I'll be mighty interested in seeing if MET tracks are visible (or are as visible as LRV tracks).

Then I want to see those compared to Lunakhod tracks...

-the other Doug

"Aye," says Taurus.....

-the other Doug

Zvezdichko already created one -- LROC news and images -- a couple of days ago. Seems an appropriate place for LROC images, though a separate LCROSS topic may indeed be called for.

-the other Doug

Also, please remember that cratering studies have proven that unless an impactor hits at an *extremely* shallow angle (like less than a degree or two), it still leaves a circular crater. Ejecta can be asymmetric, but the crater itself is almost always round. I know it's counter-intuitive, but it's a fact...

-the other Doug

Naw... I can remember watching Ranger IX's launch, and then watching the pictures from its video cameras come streaming in "live from the Moon" three days later. And, of course, I'm used to this kind of timing from all those Apollo flights.

I suppose that when you are limited to relatively small boosters and need to get as much mass out to the Moon as you can for the least number of ergs expended, it makes sense to run orbits out farther and farther and to arrive at the Moon months after launch. (That does have its own costs, of course, not least of which is the repeated passage of your probe through the most energetic portions of Earth's Van Allen belts.) But if you have a heavy-lift booster, it can make sense to just get out there as fast as you reasonably can.

I also imagine that LCROSS needs a fairly fast approach to create the big, looping orbits it needs to achieve its desired impact geometry. All told, I imagine this mission simply requires the faster, more direct translunar trajectory.

I'm glad she's off, though, and I'm glad we'll be seeing high-res images of old familiar places (plus new, exciting places) very soon. At least partially as an accident of my birthdate, I've become quite fascinated with lunar geology -- I'm really looking forward to some of the really kewl things we're about to see!



-the other Doug

No, Hypnotoad, please... don't make me kill myself... pleeaase... argh! umph! grrrrgggggllle.... <thump>

-the other Doug

Ooops -- the typo fairies strike again! (I meant to type MB, I really did... )

-the other Doug

The numbers you mention just describe the "resolution" between sample strips, Tom. There is also the question of resolution along the strip -- i.e., what was the interval between laser returns?

Also, "resolution" isn't exactly the right term, I think -- the *spacing* between sample strips is anywhere from 1/128 to 1/256 of a degree. The actual width of the strip of terrain from which a laser return is detected is somewhat narrower than that, I believe. So, instead of having a constant "pixel" coverage of laser returns, there is a matrix of laser-return dots which represent terrain elevation data, but for which no single dot "touches" any of its adjacent dots. In other words, there are from tens to several hundreds of meters of terrain between each sampled "pixel" and the next closest "pixel."

Think of it this way -- go to a plot of land 25 km on a side, lay out ten lines 250 meters apart and 25 km long. Walk along each of those lines and take an elevation reading every 100 meters or so. Then plot all of your elevation readings as a series of dots on a grid. That's the raw MOLA data. (Totally unsure about the spacing along the lines, but ~100 meters sounds about right, at least for illustration purposes.) Add in beam spread, and you can see how difficult it was to create elevation maps from the data.

I believe the pretty maps that the MOLA team created *all* used smoothing algorithms to present the instrument's data as general elevation maps.

-the other Doug

Thanks, Paolo -- I was thinking this looked like what you'd get if you ran the RAT into the soil. Good to know it's just the MI noseplate.

-the other Doug

Just today saw "Direct from the Moon" on the National Geographic Channel. It's a compilation, among other things, of some of the best Kaguya HD camera sequences.

And I managed to record it and watch it in HD.

Oh.

My.

God.

My swear jar just reached critical density and has developed a Schwarzchild radius...

-the other Doug

Here's another nightmare scenario -- a large comet rounds the sun, its projected path bringing it close to Earth but showing a miss prior to aphelion. Comet breaks up into several fragments as it rounds the sun in a fairly tight aphelion, some of them larger than 1km, and one of the fragments manages to alter course just enough to go into an Earth-impact trajectory.

Fortunately, we have at least some assets monitoring the Sun from other viewing angles than our own, we might be aware that the comet had broken up -- but we'd still have a relatively short period of time to react.

-the other Doug

That's exactly the point I was about to make, tty. My concern is more for getting extremely accurate predictions of the trajectories of bodies on parabolic (and heck, even hyperbolic) trajectories. The ability to predict a trajectory after perihelion is affected not only by even minute errors in our knowledge of the pre-perihelion trajectory, but also by myriad factors including gravitational perturbations from Mercury, Venus, and even Earth, as well as the current state of solar weather. An active Sun blows more mass out into near-solar space than a quiet Sun, thereby increasing (minutely) the drag such an object will encounter "coming 'round the horn".

It's also possible (if not likely) that a rather dim object, a km or more in longest dimension, could even now be wandering in on a relatively steep fall to Sol that is targeted for a pretty wide perihelion, a fairly minimal solar deflection, and a trajectory that would cross Earth's orbit (where Earth might happen to be located at the time) on its outbound leg. Such a body could be dim enough that it wouldn't be easily spotted if it sweeps in from a vector roughly opposite that of the Sun from Earth (i.e., spending a lot, though not all, of its of time hidden in the glare), and/or, even if it's spotted, not being noticed until it's too late to get a great hack on its trajectory prior to its disappearing completely behind the Sun.

Yes, Greg seems to be quite correct, that once we get some of these telescopes up and running we'll have enough observing time/power to find most outlying threats with lots of time to spare. There's a short window, though, in which an object could announce itself with only days or weeks to spare. (Of course, if something did happen in that window, it's not like we have the deployable technology at present to do anything about an object of any size, even with a few years of warning... *sigh*... )

-the other Doug

If all you're worried about are NEOs (insert Matrix joke here), then you're absolutely right. Why do I get the feeling, though, that a supremely smug human race, having cataloged every NEO which could possibly threaten, will expire with absolute shock and surprise when that 10-km comet comes around from the opposite side of the Sun and smacks us at solar near-parabolic velocity mere days or weeks after we first detect it.

In other words, it's not good enough to know about all the NEOs around, since it's an observed fact that such things only hit us every 50 to 100 million years. It's the body that sneaks in and provides us only days or weeks of warning that is more likely to kill us. (Not more likely to come in on an impact trajectory, just more likely to kill us since we will have insufficient time to respond.)

I think we need to have Solar System monitors that can scan on the far side of the Sun from us, as well as on the side we can easily scan from our own planetary neighborhood.

-the other Doug

My concern is that we may not get a chance to see Spirit come back to this place... as in you can't come back to a place you're unable to leave...

-the other Doug

I think he was going for an abyssal plain, something like that...

-the other Doug

My only problem with the concept going around that the *entire* Martian northern hemisphere was excavated down a few km below mean by an enormous impact, whose basin is the entire northern half of the planet, is that I'd have to think such an impact would disrupt the entire planet, causing it to re-accrete rather as Earth and Moon re-accreted after the impact of a Mars-sized body on the proto-Earth.

How could Mars retain its structural integrity during an impact whose crater is roughly half the size of the planet? I'm not a mathematician, but it seems to me that the energies released by such an impact would have to be enough to disrupt the entire planet... in other words, I can't imagine a solid body that wouldn't come apart under such an impact, no matter the angle of impact.

-the other Doug

However, one of the datasets that is not all that well constrained that impacts on this issue (pardon the pun) is the relative flux of impactors of all sizes at Earth's orbit and at Mars' orbit. I'm not certain it's fair to assume that the flux is constant throughout the inner solar system.

I know that on our Moon, the best way to tell a primary from a secondary is to try and quantify the amount of energy released in the impact event. Without an atmosphere, lunar primary craters retain the glassy impact melt created by high-energy impacts and display a lot of regolith breccia formation, while secondaries don't show the same level of energetic materials transformation.

This kind of thing has long since been eroded away or covered up in most Martian craters, but for the micro-craters it just seems to me there has to be some kind of threshold of size-to-crater that, if primaries, would have to have been formed by really tiny, like smaller-than-sand-grain-sized, impactors...

-the other Doug

I have a bad feeling about this -- look at how much trouble the Japanese are currently having making Asimo walk up and down stairs.

Bipedal locomotion is not intuitive or simple for machines. Add in the entirely different ways in which mass responds to force applied in a lowered G-field, and I'd really hate to see their walking robot take two steps, fall over, and not be able to stand back up... *sigh*...

-the other Doug

There goes the concept of guarding against terrestrial contamination on Mars!


-the other Doug