Just had a thought -- maybe GRBs are generated when our Universe's 'brane touches another 'brane? I mean, membrane theory proposes the possibility that the Big Bang was generated when our 'brane had a full-on collision with another. Maybe GRBs are the result of small, glancing contacts?

Just a thought...

-the other Doug

I was in high school from 1969 through 1973. Mariners 6 and 7 flew past Mars in the summer before I started high school. Mariner 9 went into Martian orbit when I was a junior.

I can remember watching the live feed of Ranger IX images broadcast on TV, and seeing for the first time *ever* the title on my screen "Live from the Moon." Heck, the *launch* of Ranger IX was covered live on television.

-the other Doug

I agree, EC, very good work. And the interesting linearities of the terrain show up quite well. I'm almost tempted to say that, at a certain scale, Rhea looks grooved.

-the other Doug

The selection makes sense to me. After all, we've had many years to wring every last little bit of interpretation we can manage from the Galileo data, and even longer to analyze the Voyager and Pioneer data from Jupiter.

Cassini is still going strong at Saturn, and may find even more new things that could, conceivably, impact the kinds of sensors we might want to load onto the next Saturn probe. But there is almost nothing new waiting in the wings that will affect what you'd want to put onto a Jupiter mission.

So, from a mission design and planning point of view, I think this was the best decision. I truly think there are wondrous things yet to behold in Jupiter space. And I'd hate to be bending tin for a Saturn/Titan probe when I found out that there's a truly interesting phenomenon to be studied that our design is ill-equipped to look at.

-the other Doug

I seem to recall asking, in the extensive and now closed discussions with Herr Doktor Professor about alternate theories on the development of the Meridiani deposits, whether what we're seeing might not be the result of Meridiani at one time being much nearer the pole, i.e., that there may have been glacial alteration in this region.

Nice to see that my vagrant thoughts occasionally pop up in other peoples' serious theories...

-the other Doug

Mike, I work for a big cable company, doing internet tech support over the phone. One time, I had a somewhat elderly woman on the phone whose internet connection seemed to be running slow. I asked her, "Have you cleaned out your cache and cookies recently?" She replied with an indignant "I beg your pardon!"



-the other Doug

I just love the technical quality of the discourse, here...

(Could be worse, though. Instead of doohickies, they might have been doomaflickies.... )

-the other Doug

Ted -- is it true that Endeavour Crater is resolved in these mosaics?

-the other Doug

Um, yeah -- I mean, it's either hot pixels or you've caught the Barsoom Airlines flight pattern out of Helium, all the commuter aircraft bound for the great thoat roundup...

-the other Doug

Let's add a little more of hard reality to your analysis, here...

"2 Sojourner-mass rovers but fitted with better instruments and cryoprotection" -- the better instruments and cryoprotection will add mass. I'd guess that these two rovers plus the descent system needed to land them will mass at least as much as Huygens, if not quite a bit more. Plus, add a power system that will keep these rovers going for more than a few hours, and you're talking considerably more mass than Huygens. (Solar cells, as used by Sojourner, aren't really an option on Titan's surface, what with the extreme distance from the Sun and the filtering of Titan's heavy atmosphere.)

"2 hydrofoils that can really be as small as allowed for not being affected too much by waves etc." -- again, each needs its own separate power supply, radio communications links, and also a landing system capable of delivering them in usable condition to a liquid environment. Off the top of my head, I'd have to think this would mass more than Huygens, perhaps even drastically.

"2 choppers which can be as small as allowed for them not to be smacked around by winds" -- these can be smaller than the rovers and the hydrofoils, but what kinds of instrumentation can you fit on a really small chopper? A camera? I doubt you could fit a multispectral camera in such a small platform, much less a useful spectrometer or magnetometer. So, yes, you could deliver a couple of little toy choppers with webcams in them for pretty cheap, but would they be worth all that much, scientifically? Anything that would let you do extensive science is going to be getting you into multiples of Huygens' mass. And as for all of these probes, you need to design a power system that will let them operate for more than an hour or two.

"2 dirigibles - same as above applies here" -- and same as above applies here, too.

"2 tiny submarines which just need to be manouverable" -- and again, how much in terms of sensor technology, power systems, cryoprotection, etc., can be built into a tiny submarine? Each one would have to be at least Huygens' mass, if not more, just to contain the systems needed to operate and do any reasonable science.

Altogether, you might be able to piggyback a couple of these things, but your communications relays would already have to be in place (requiring still more launches), and you literally could not send all of these 10 suggested probes on a single lander, since some of these things would need to head for polar lakes while others would best be targeted for the equatorial sand seas and for suspected cryovolcanic locations.

I stand by my concept that you would need a dozen launches to put all of these assets in place. If not more.

And please note the other thread in re ion engines -- to send large payloads long distances, you need to either use a lot of reaction mass to get there within a reasonable (less than a decade) timeframe, or you use low-thrust engines (which is all that ion engine technology offers at present) and take 20 to 50 years to get out to Saturn. And actually, RTGs don't put out the kind of amperage you really want to drive ion engines. If you're going to go that route, you need to use actual nuclear reactors, and I will refer you to the failure of the Prometheus project to gain funding in the early days of this decade as to why we will likely not go that way any time soon.

-the other Doug

A few general replies:

- We may not re-use a lot of hardware designs, but we re-use information, and that saves a lot more money than you might think. For example, the Viking program ran hundreds of millions of dollars' worth of tests on its entry vehicle shape and dynamics, and of its parachute system. Every successful landing on Mars since then has re-used the Viking developmental data, thus saving hundreds of millions of dollars in developmental testing.

- You can design a general spacecraft bus for destinations with similar environmental characteristics, true. But how many destinations have similar environments? The Moon is unique in terms of thermal environment, as are each of the rocky planets. Vacuum operations are the same on the Moon and on asteroids, but there are large differences in how much you can rely on gravity between the Moon and an asteroid -- gravity not only helps you move around (it keeps your wheels in contact with the ground), it also keeps your lander from flying off the surface if you use, say, a pneumatic drill or a rock chipper. Also, power systems must differ drastically depending on periodicity of insolation, degree of insolation, etc., and that's just when you're using solar power.

- Again, if you're going to find the money needed to launch a fleet of probes, then yes, it makes sense to make a bunch of the same probe and send them all over a period of a year or three. That was proven in the American lunar probes of the 60s. But a fleet of probes means a fleet of launch vehicles, and launch vehicles are the most expensive single part of the equation. You want to send five probes using Atlas V or Delta IV as launch vehicles? Then you need to add at least a half a billion dollars to your budget, just for the launch vehicles. Even if Falcon 9 works the first time and every time and you can buy one for only $50 million as opposed to the $100 million for an Atlas V, then your five probes still require a quarter of a billion dollars for launchers. And, it can be asked, why did you need to have five probes when one could have given you 90% or more of the data returned by all five?

- You seem to think that ion propulsion is the overlooked savior of sending huge probes all over the solar system cheaply. The only reason the existing ion engines have been successful in sending small probes around a variety of locations is that they are very low thrust engines, and thus require a relatively small reaction mass. (Ion engines work like any other rocket engine in that they expel mass out of a nozzle to make the spacecraft go the other way, so your total amount of delta-V is limited by the reaction mass you can carry with you.) Ion engines are low-thrust affairs, it's not just a matter of "Hey, let's scale this up and make ourselves a big, powerful ion engine that still only needs a couple of hundred kg of fuel to go from here to Mars!" That violates the physics of how ion engines work; if you want big, powerful engines, you really need to carry a lot of reaction mass, whether you use chemical, nuclear or electrical energy to force that mass out of a nozzle. There's no current way around that.

- You say we've spent all this money but not made any real progress on understanding Mars. I beg to disagree. We have a tremendously greater understanding of Mars than we did even 10 years ago. Yes, we don't understand entirely what might be happening in terms of life on Mars, but we *do* understand that life is not widespread, that if it exists it evades detection sensors that would detect even a devastated ecology, and that if it does exist, it must be hiding in places so well-protected from inimical factors that it will be difficult to well-nigh impossible for easily-affordable probes to find and study. I'd say that's an understanding several orders of magnitude more sophisticated than we had when we launched Mariner IV 35 years ago, and that understanding has been refined by only six successful landers and nine or ten orbiters (depending on how you classify some of the Soviet orbiters in terms of adding to our information). Just because they haven't found what you wanted them to find doesn't mean that these spacecraft have made no progress. They've not found what we were looking for in all cases, true -- but, far more importantly, they've found what is there.

- The MERs are fitted out with the best AI we've been able to design, in terms of what AI is useful for on a MER-like mission. The girls have even gotten smarter as the missions have progressed, thanks to upgrades to their AI-like autonavigation capabilities. That's what AI is right now, and the MERs have it. And as Dan asked, in what way does AI enhance your mission? Does it make it cheaper? If so, how? I don't care how good I think I have made an AI, I'd want to monitor it, improve it, and make sure it doesn't do something stupid pretty much constantly. There is literally no way to make AI any better than it is right now; increases in computer power and the subtlety of programming languages has not brought us nearer to, say, allowing AI routines to run our cars or our air traffic control networks. It would have to get at *least* that good in order to be useful on a space probe, right? And, trust me, the economic advantages of AI that can run air traffic control, or drive you car, are such that those types of applications are already driving AI development. This isn't a case where you can develop AI for your favorite Titan lander and then make up the trillions of dollars you need for your exploration plans by selling your AI to the car companies -- you are *much* more likely to adapt whatever AI DARPA, or the airline industry, or the car companies come out with for your space probe, and consequently will need to find the trillions of dollars you need for your exploration plan somewhere else.

-the other Doug

To get that many things out to Titan, deliver them in one piece, and be able to keep them running for more than a day or two, takes a lot of mass. We're not talking two Ariane 5 launches, here. We're talking a dozen. And there is no such thing as a "really powerful ion engine" in existence -- ion engines are low-thrust, takes-a-long-time-to-get-there propulsion solutions, and will be for decades to come.

I would absolutely love to see all of the Titan probes you suggest, Karol. But realistically, you're talking about a half-trillion-dollar project. With as much as there is to explore in the solar system right now, I can't see putting that much money into a single moon, no matter how interesting it is.

-the other Doug

This has been discussed a number of times here, and most all of your points have been addressed. And, I must say, there are several areas in which you are not correct in your assumptions.

First, you're generally incorrect about "how we did it in the 1960s." The first successful American planetary probe, Mariner 2, was a Ranger Block II spacecraft fitted with a large parabolic antenna and some alternative sensors to those generally carried by the early Rangers. It was not custom-designed for a mission to Venus, and nearly succumbed to the increasing solar constant as it approached our nearest planetary neighbor.

We planned entire series of spacecraft for given missions back in the 60s. Each of the first three American attempts to reach Mars were designed as dual-spacecraft missions. Mariners 3 and 8 never even got into Earth orbit, but there were originally to be flotillas of Mariners 3 and 4, 6 and 7, and finally 8 and 9.

Ranger, Lunar Orbiter and Surveyor lunar probes were designed as a series of missions to be flown by the same base spacecraft, with minor changes to the sensor packages between flights. And this was even rather program-specific; all five Lunar Orbiters were nearly identical, the Surveyors only differed in the various experiments attached, and Ranger went through five spacecraft iterations, only one of which (the Block V) actually succeeded.

Even into the 70s, we sent pairs of spacecraft on every mission. Vikings 1 and 2, Pioneers 10 and 11, Voyagers 1 and 2. And as for not knowing what's happening during critical events such as landings, our ability to monitor such things back in the 60s had a lot more to do with limitations of communications and data processing techniques. Once we developed ways of monitoring these mission segments, we started doing it.

It wasn't just the pairs of spacecraft on a given mission that shared design elements -- Mariners used the same octagonal spacecraft bus starting with Mariner 3 and ending with Mariner 9, and even the Voyagers house their "guts" in octagonal buses that are similar in size to the first Mariner ever designed.

By saying "never re-invent the wheel again," you put on blinders that don't let you take advantage of new developments in a variety of engineering and scientific fields. It makes absolutely no sense to be forced to carry forward antiquated power, imaging, data processing or propulsion technologies. And trust me, it's not just a matter of "Hey, just fly Cassini or MER or Galileo again and just update whatever has been improved in the meantime." Once you factor in such technology advances, you end up re-engineering a "carry-forward" design so much that you're essentially designing a new vehicle every time.

Now, I'm speaking primarily of the American program. If you want to argue any illogic to the progression of the Soviet planetary exploration program, you need to read up on how the Soviet system worked -- there was little to no actual planning in terms of progressions of missions, each building upon the last. Each Soviet probe was an engineering demonstration championed by a specific design bureau, or most often by the little kingdom-holder of a given design bureau. As with many things, the Soviet space program reflected a nearly Byzantine maze of personal relationships and antagonisms more than it did a well-thought-out plan for planetary exploration.

So, I would agree that we ought not do many of the things you say we ought not do, Karol. The problem is, we didn't do those things back in the '60s. Please read your histories a little more thoroughly...

Why don't we send things in twos any more? Without exception, it's because of cost. When your launch vehicle accounts for a good 40% to 60% of your total mission cost, you just often can't afford to use two of them. And the MER experience tells you pretty solidly that it *does* take nearly twice as much money to make two of something as it does to make just one.

As for your insistence that we only send little tiny probes, micro-robots, things with limited resources, but with robust designs, well, that really limits what you can get out of a mission. If you're going to spend $100 million for a booster, you need to get as much as you can out of the spacecraft you're delivering. And the best example of a "small" rover vs. a "big" rover would be Sojourner vs. MER. I don't care if you landed three Sojourners at each of the MER landing sites, you would *never* have gotten the amount of science out of them that you've gotten out of the MERs. (In general, "small" means more limited, less able to handle adverse or unforeseen conditions, less capable -- be wary when recommending such approaches, as far too many *failed* missions have ascribed to that philosophy.)

-the other Doug

Oh, you betcha! If I occasionally sound melancholy or morose over the fact that some planned missions will come too late for me, please forgive me -- I am far and away happier having lived through the early years of space exploration than I would be having to just read about our initial lunar and planetary explorations in books.

As for which of the upcoming outer planet flagship missions comes first, I guess I'm not all that picky. I tend a little more towards the Titan lander concepts, simply because I enjoy seeing an alien planet/moon from its surface, and the current Jupiter mission proposals don't include any landers. But a really good Jupiter orbiter, concentrating on the moons, would provide a lot of grist for my sense-of-wonder mill, too. I'll be happy to see either of them.

-the other Doug

The dynamics of the impact also affect the kinetic energy transfer. Remember, you don't just "lose" energy, it's translated into other forms of energy, other vectors, etc.

If the two bodies hit pretty much directly, then much of the "lost" orbital energy would be used up in melting, shattering and vaporizing the structures of the bodies. If the collision path would have only a half or a quarter of one of the bodies intersecting the other, less kinetic energy is used up in vaporization and the resulting debris' orbits are altered less than in a direct impact. If only a very small physical interaction occurs (i.e., if an antenna on one vehicle snags an antenna on the other vehicle), the two bodies will still break up (especially if the "just barely" contact comes at 11 km/sec!), but they'll break up due to the extreme rotational rates imparted by the "brush-by". This last scenario changes the orbits of the resulting debris the least.

I don't know if our "security assets" are able to image satellites at 800km range well enough to characterize the resulting debris from the Cosmos-Iridium collision, but the extent of debris and its orbital characteristics (as tracked by radar) ought to give us some idea as to how direct a hit they endured.

-the other Doug

I may not have my flying car, and I can't book my tourist trip to the Moon, but at least I do have my information terminal (e.g., the Internet) and I can take a look at the latest pictures straight from Mars whenever I like. That's enough, for now.

Personally, though, anything scheduled to fly after about 2025 is something that I have to realistically estimate I will never see. So I'm hopeful we'll find a way to get to as many places as possible in the next 15 years or so...

-the other Doug

p.s. -- I have to admit, I'm happy to see LRO survive its development pangs and a shifting economic landscape. Why? Because it doesn't take the better part of a decade for it to reach its target...

Statistics are what people play around with while awaiting actual empirical data.

We now have empirical data. Put enough satellites and associated pieces of crap in orbit and, eventually, things start colliding. That's not a statistical analysis -- it's the empirical description of an observed phenomenon.

Also remember that, for everything that actually occurs, the statistical likelihood of it having happened is exactly 1 in 1. And as for the "lottery-winning" odds, please keep in mind that, at least in the United States, lotteries with odds of a single given person winning that work out to something like 100 million to one are won by *someone* every few weeks. So, while the odds that one given satellite may impact another given satellite may be very, very low, the odds that *some* satellite out there will collide with some *other* satellite are obviously a lot higher.

-the other Doug

The only way in which I think you could say that the collision was Iridium's fault is in the fact that, of the two satellites, Iridium was the only one that was still "live" and had any capacity for collision avoidance.

However, just because Iridium was capable of maneuvering doesn't mean that its controllers were aware of the collision threat. I think if there is any "blame" to lay here, it's with the agencies that track the satellites, who could have sounded a warning and given Iridium's controllers the opportunity to make a collision avoidance maneuver.

-the other Doug

I don't know, it seems to me that, with the number of objects in orbit, this kind of thing was bound to happen sometime. I'm a little surprised that the event wasn't predicted, since there are several agencies across the globe that skin-track everything in orbit. (Where do you think those predictions come from that result in all those collision-avoidance maneuvers?)

-the other Doug

All I can say is that while a baker's dozen of people (or so, not counting members who have left in the meantime) joined the then mer.rlproject forum on its first day of 2/8/04, I can proudly say that I was the first person to join on the following day, 2/9/04. So today is actually my own five-year anniversary here.

I know it can be a huge pain to be in charge of such a big thing, Doug, and I know it can get stressful at times. But I'm impressed that the young, wide-eyed and joyful British hotshot who thought up this site is still wide-eyed and joyful as much as you are. Me, I'd probably be growling at the cats by now...

If we don't express our appreciation often enough, I apologize. You provide a unique and valuable portion of my intellectual life, and I dunno what I'd do without this place. Thanks for doing it for us... for the field... and mostly, for yourself!

Enjoy.

-the other Doug

It occurs to me that, with the exception of the one Soviet attempt, there have not been any serious proposed landing sites within Hellas.

The atmosphere is thicker at the floor of the basin than elsewhere on the planet, offering both more effective parachute braking (and thus a heavier lander, potentially) and the rare possibility of liquid standing water. There are more clouds and therefore a potentially more active hydrologic cycle. Rainfall on Mars post-dated the basin formation, as there are dry riverbeds observed on both the inner and outer slopes of the basin walls. And while some of Hellas' interior appears to be relatively unaltered lava fill, some good amount of it appears altered, while a small but significant portion of the basin floor appears not to have been covered by lava fill at all.

Is the only negative to a Hellas landing the fact that it's not representative of the rest of the planet? I'd think the interesting positives would outweigh that negative, especially when Mars sports such a wide variety of terrains and surface conditions...

-the other Doug

I was impressed by the very accurate 3d renderings of locations where they have been able to interpolate good terrain models. For example, I was able to see, with a very high degree of accuracy, what Victoria looks like from on top of the Soup Dragon...

-the other Doug

Not sure... let's see, Spirit arrived at the Columbia Hills on Sol 156, right? So this would be 24 sols later... right around then I think they were finishing up work on Pot'o'Gold and were planning a drive to the north face of Husband. Sounds about right, anyway.

Is there a sol-by-sol record that would give any details on Sol 180? (If I were awake enough, I'd figure 180 sols out from landing day and look at UMSF posts from the day... )

-the other Doug

Hmmm... Spirit had a problem on Sol 1800?

Maybe it's good that we will almost definitely never see Sol 18000...

-the other Doug

Actually, that deployable umbrella-dish antenna design wasn't new for Galileo, it had been used dozens of times on big communications satellites. It was considered pretty low-risk, it had worked pretty much every time it had been used.

Galileo's antenna failed, more than likely, because its deployment mechanism was lubricated, the antenna stowed, and then the whole thing was unexpectedly put in storage for something like six years. The antenna was never unstowed and "exercised" after storage prior to flight; the lubricants apparently dried out and the deployment mechanism stuck irretrievably.

There's normally nothing wrong with using backup flight hardware on later vehicles. You just have to make certain it still works...

-the other Doug