And what does AH stand for? Altitude Horizon sensor?



-the other Doug

Can anyone quote or point to legal documentation that states that the ESA PIs have the power to *deliberately* withhold results from the taxpayers of the European Union who paid for their results? If not, then the PIs are guilty of deliberate sabotage of data released to those who pay their salaries.

Revolution in the air? I think maybe that's the direction this needs to go... After all, the French can tell you about what happens to effete Imperialists who demand that anything new belongs to THEM -- I think they fought a revolution to kill off that kind of mind-set a few hundred years ago.

So did the Americans, actually.

Too bad the Americans seem to be the only ones who get the idea...

-the other Doug

Obviously, remnants of surficial cracking from either gravitic stresses on Enceladus or from internal stresses which caused upwelling from the cracks.

Europa, anyone? This looks like extensive cracking atop a liquid ocean...

-the other Doug

Yeah -- and NASA controls the DSN. So, if you have a good idea to use left-over planetary probes, all well and good -- but if you need to use the DSN to communicate with them, you're SOL if NASA doesn't want to give you DSN privileges.

I think we need to figure out alternatives to the DSN before we can talk about private extensions of planetary probe missions. And since there *are* no alternatives to the DSN for communicating with planetary probes, that doesn't leave much in the way of alternatives...

-the other Doug

Yes, Bob, that's exactly how the Soviets did it. They set up landing sites where their probes had to only lift straight up, angle slightly to the right declination, and cut off the motor at a precisely pre-planned time, and if the lift-off time was calculated *precisely*, the sample return capsule would land on Soviet soil. There are only a few places on the Moon that are located in the right spot to do that, and Mare Fecundatitis and the surrounding highland plateau are a couple of the places where that is possible.

The Luna sample returns happened at landings on Mare Fecunditatis and the surrounding highland plateau.

Coincidence? I think not.

-the other Doug

Is that Enceladus or a block of London flats after The Blitz?

Fascinating right angles, there...

-the other Doug

If 13 had landed at Fra Mauro and 14 at Littrow, I don't think that would have affected the selection of either Hadley or Descartes. Assuming the same eventual cancelation of the Apollo 15 H-mission and of Apollo 19, you would be looking at selecting sites for the J missions using the same requirements as were actually used -- multiple sampling opportunities, Imbrium and pre-Imbrium impact materials, lava features -- all of which drove the selection of Hadley-Appenine. And Descartes was going to get a J mission somewhere.

I will point out that Descartes was originally a prime site consideration for the *first* J mission, but was bumped to the second because of lack of good photography. When 13 aborted and was unable to get good Descartes pictures, it was left for Apollo 14 to get good coverage of Descartes so that it could be validated as a safe landing site. But since the good site photography wasn't available until after Apollo 14 (and after the site for 15 had to be selected), Descartes fell out of the running for 15. If 13 had gotten that good Descartes coverage, I think Apollo 15 *would* have flown to Descartes.

*Then* you can ask whether Hadley would have been the 16 or the 17 site. Without something like Taurus-Littrow beckoning (and I agree, if 14 had landed at the original Littrow site, Taurus-Littrow would never have been selected for a J mission), then I think it likely that 16 would have landed at Marius Hills and that 17 would have landed at Hadley.

-the other Doug

I just want to make sure that the re-statement of the driving requirements for MSL didn't result in a re-design of its motors or transmission systems, to *limit* its maximum speeds and ranges to those stated in the final spec.

Of course, if the spec was reduced not by operational considerations but by wieght factors (i.e., if a faster, longer-ranged MSL would weigh so much that you couldn't land the whole thing on Mars), then I can understand it. But if it's a matter of just changing the gearing, for instance, which doesn't cost you a lot in terms of weight, then surely there is enough time between now and MSL fabrication to add some higher-speed options...

-the other Doug

That is actually *less* mobility than has already been demonstrated by the MERs! That doesn't seem right, somehow.

-the other Doug

Actually, the camera didn't over heat -- the Lunar Communications Relay Unit (LCRU), which handled the camera's signals and generated the broadcast signal, overheated. It was cooled with radiators and beeswax, incidentally.

-the other Doug

All of the good points made about the stability of the descending MSL "stack" point out why I said that the MSL itself can't be lowered down its rope until after backshell/parachute jettison, and preferably not until the Skycrane is descending vertically or hovering, with no significant lateral velocity.

The problem is, you want to use passive deceleration (i.e., the parachute) as long as possible. The Pathfinder/MER backshell retro-rockets only had to fire a short burst to cancel the vehicle's remaining descent velocity, so they didn't have to carry much fuel and could be pretty lightweight. Skycrane will require something like 30 seconds of sustained rocket firings, at variable thrust, to achieve its 5-meter "hover" and still have enough gas left to fly away, out of range of the MSL so that it doesn't crash back down on top of the rover.

So, it's a balancing act between hanging on to the parachute until the last possible moment, thus saving fuel (and allowing Skycrane to carry enough fuel to achieve its mission), and giving Skycrane enough time and altitude to achieve its 5-meter hover.

And for those who think that the Skycrane approach enhances the chance of mission success by reducing the number of little pyro actuators that all need to work correctly (as the MERs had to do, in the deployment sequence), that *is* true -- but on MSL, you have to rely on the pyros that separate MSL from its bridle, or else Skycrane will wreck the rover as it tries to fly away. So, while you can minimize the number of critical pyro firings, you still have some *very* critical pyros that, if they misfire, will still result in a Bad Day for MSL.

-the other Doug

I think it's a cultural thing. The ESA managers and administrators seem to have this idea that the general public not only has zero interest in the results of planetary probes, we also are far too stupid to understand any of the data they develop.

We need to figure out how to knock those condescending idiots off of their high horses...



-the other Doug

Fantastic! And maybe -- just maybe -- Jack Schmitt has more than just Tsiolkovsky materials. Maybe he also has the details on the Littrow traverse plans, and the Davy traverse plans, as well. I'm as sure as I can be (without ever actually having seen them) that these must have been worked up by someone, and I'm hoping against hope that they still exist somewhere...

Do you have decent copies of the Apollo 13 traverse plans, by the way? I've seen very poor PDF scans of them -- the target point for 13 was about 300 to 500 meters further west than the point designed for Apollo 14, and Lovell was supposed to make a call during final approach as to whether it was better to land short (to the eventual Apollo 14 landing point, between Triplet and Doublet) and attempt a traverse east to Cone Crater, or land west (beyond Doublet) and attempt a traverse to the smaller, slightly less "fresh" Star Crater. Traverse plans were developed for both contingencies, plus another plan designed for landing west of Star Crater (which would have been about 1.5 to 2 km downrange of the Apollo 14 point). And after the abort, as they rounded the Moon, Lovell radioed back to the ground that he was "still looking for Star Crater," which makes you wonder whether Apollo 13 would have ever even *tried* to visit Cone.

As for myself, I never could figure out why they didn't target for a landing point in the valley between Cone Ridge and the Triplet craters -- it was relatively flat and smooth, and would have obviated the need for a 1.5 km trek to get to the most important sampling site there. It's not like Cone Ridge was so high as to pose an impact threat to the LM as it descended, and beginning with the very next flight, the descent profile was adjusted to allow for passing over *much* taller mountains on the way to the landing point. It would have been easy to do.

-the other Doug

Does anyone have addresses or contact information for members of the Apollo Site Selection Board (ASSB) or the Geology Lunar Exploration Panel (GLEP), which did most of the planning for the selected *and* unselected Apollo landing sites?

I know that Don Wilhelms refers, in his book "To a Rocky Moon," to a J-mission planned for the Davy crater chain. He speaks of it as if someone had done a first-take surface plan, including traverse plans and sampling objectives.

He also discusses sampling objectives identified for other proposed landing sites, such as Alphonsus, Copernicus, Censorinus, Marius Hills, Littrow (the H-mission site originally planned for Apollo 14, not the Apollo 17 Taurus-Littrow site), and even Tsiolkovsky. He even goes so far as to state that, as of February, 1970, the Apollo 14 crew was training for a landing at the Littrow landing site.

All of this implies that somewhere, there ought to be documentation of the sampling objectives and traverse plans worked up for the proposed Apollo landing sites that were not selected. And I would think that the members of the ASSB and/or the GLEP would be the best people to ask about it.

As for me, I would just like to see artist's representations of surface operations at these sites -- we know what the lunar surface looks like in general, and we have a fair idea of the topography of the unselected sites (since stereo imaging of the landing sites was a requirement for the later missions). In this age of CGI wizardry, it ought to be pretty easy to paint realistic pictures of what, for example, a LM landing about five kilometers away from the central peaks of Copernicus would have looked like...

-the other Doug

Amen.

-the other Doug

Now, this is frustrating.

Remember how I told y'all that Cornell's Athena website won't load at all for me if it has the numeral 1 inserted after the word "athena"? And yet, it loads for a vast majority of y'all with no prolem?

Well, this Cornell site you are all talking abouit consistently acts like it doesn't exist for me. I've tried it, and various permutations of its URL, about a hundred times, now.

Nada. Zip. Zilch. Nothing.

Sometimes I think some of you are pulling a little joke on the rest of us, privately agreeing to gush over websites that don't exist and posting faked links to them...

-the other Doug

I think that was the "cute" bear the Soviets used as their symbol for the 1980 Moscow Olympics.

For myself, I always thought "Mission to Mars" was a very good film, intelligent science fiction, and "Red Mars" (was that really it's name? -- the one with Val Kilmer, anyway) was a pretty dismal film.

Val Kilmer playing Colonel "King" Kong on a Soviet sample return booster that was *never* intended to carry more than a few ounces of rock just can't compare to Jerry McConnell telling the crew fleeing back to their ship that he had "left for Earth... FIVE... MINUTES... AGO... Please leave a message!"

-the other Doug

The MERs were literally bolted down into their folded positions when the landers bounced in. And much of the shock was attenuated by the pyramidal shell itself.

If you subjected the MERs to a 40G jolt now, in their deployed configurations, you'd wreck 'em, for sure. Depending on the vector of such a jolt, the rocker-bogie suspension system would break, solar panel connections would break, the camera mast would break -- you'd lose the vehicles, most likely.

And remember, MSL is to be dropped onto the surface, wheels-down, in its fully deployed configuration. Carrying a heavy radioisotopic thermal generator on its back. Touchdown will have to occur at something like .1 to .3 meters per second, with *no* significant lateral velocity, for this to work.

-the other Doug

I think perhaps the operation of the backshell retros on the MERs and on Pathfinder gave the JPL guys the idea of the Skycrane, in that in each case, the descent rate of the vehicle was virtually arrested and the lander package simply dropped from a safe height in each case. If we can achieve a zero descent rate at a given point above the surface, why not try to achieve it *at* the surface with a similar system?

The problem, of course, is that in each of the three airbag landings, the lateral velocity was significant -- enough to tear up MSL with no airbags. I think, though, that the dynamics of the MERs' descents show that, after the deployment of the lanyard holding the lander, the backshell is what oscillated, the parachute and the lander stayed relatively well in place. Since the backshell was oscillating in a small circle around the line between the lander and the parachute, retro fire occurred at a random angle to the descent vector. I think that's what tended to impart the lateral velocity.

If the Skycrane separates from the parachute and begins to descend on rocket power *before* MSL is belayed down its lanyard, the natural dynamics of the descending sytem will keep the random oscillation of the rocket platform from occurring, as it has on the airbag landings. Which means the main cause of lateral velocity could be removed from the system, making Skycrane viable. The problem, of course, is that additional lateral maneuvering by the Skycrane after lanyard deployment can cause MSL to swing laterally, thereby spelling disaster.

I think the best chance Skycrane has of working is if it finds its intended landing point, maneuvers to a point directly above it, starts a completely vertical descent (with no lateral velocity *at all*) to that point, and *then* belays the MSL down its lanyard. As long as you drop the lanyard while you're in a completely vertical descent, and as long as the weight on the lanyard is balanced properly, then wind is the only factor that can possibly induce lateral motion, and hopefully, unless the wind is *really* blowing hard, odds are good the final descent can proceed with little to no lateral motions developing.

But if we use the Pathfinder/MER deployment sequence, which would put the Skycrane module in the middle of the system and thereby ensure that will oscillate around the line between the parachute and the MSL, at parachute separation and rocket ignition you will almost definitely have a swinging motion going between Skycrane and MSL which will be very hard to damp down to acceptable levels before you reach the surface. So it seems to me that Skycrane can work, if it uses the proper deployment sequence.

-the other Doug

Very true -- I was expecting to see more obvious interaction between the ejecta plume(s) and the coma, some type of concentric shock pattern that would occur when the ejected particles and gasses plowed through the relatively motionless haze of gas and dust that surrounds the nucleus. But what we seem to be seeing is pure ballistic motion with radial structuring (probably controlled by topography at the impact point).

You know, Bruce asked the question earlier in this thread (or a related one) as to why this mission got approved in the first place, since its scientific harvest would be rather thin. I think one of the more interesting benefits, maybe one of the more important ones, is the observation of impact dynamics. Impact has apparently shaped every rocky/icy body in the Universe -- it's nice to finally get a first-hand look at an impact of *any* size and observe the real-world dynamics. As I've stated before, models are only good for certain things, and unless a model is as complex as the phenomenon it attempts to predict, it will never be completely accurate. Seeing and measuring an actual impact, on *any* body and of *any* size, helps us refine our models and understand the actual processes in far greater detail. I just wish we could now land at the crater we made and examine *it* in detail...

-the other Doug

That's a point I've made since even before 9/11/01. The price of liberty is vigilance, someone once said -- you have to be vigilant. As an individual. But any effective way of keeping such attacks from happening, *ever*, inevitably ends up destroying so many freedoms that, frankly, I'd rather risk such attacks to retain the freedoms I've enjoyed all my life.

For all you Christians out there, remember that Jesus told us to turn the other cheek when slapped. Absorb the pain, and go on. Not to hide in fear, and not to blindly attack anything that even remotely looks like it might slap us again...

Even though I'm not a Christian, those are really good words to live by. Especially in these troubled times.

Anyway, I'm glad to see that all of our UK friends here seem to be OK. A good friend of mine just passed away this morning after a long struggle with ALS -- I'm glad I only have one friend to mourn today.

-the other Doug

I wouldn't count the Star Trek franchise as dead yet. Just because Enterprise ran for a shorter run than was originally planned doesn't mean that Paramount isn't looking into developing more Star Trek series and films.

The franchise is worth millions of dollars even when there are no productions in process... and there are any number of directions they could take with new Star Trek projects. I'd be very surprised if we never see another Star Trek film or series again.

-the other Doug

Thank you, President Muffley.



-the other Doug

Remember the time scales. The old glacial lakes in your area probably existed during the last ice age, about 20,000 or so years ago, right?

Gusev Lake probably dried up at *least* several million years ago, and with the prominence of the basalts and pyroclastic materials overlying the ancient lakebed, it could have dried up more than two *billion* years ago.

Little wonder that shorelines are more obvious around lakes that only existed a tiny fraction of the time ago than lakes likely existed on Mars...

-the other Doug

I just wanted to check in with all of our valued members in the U.K. -- to make sure none of you were riding the Tube in London this morning. Or perhaps were on one particular double-decker bus.

I'd hate to lose anyone in this forum to such senseless acts.

-the other Doug