Slashdot Mirror

I went over the NASA site to see if anything was mentioned about this. Eventually, I ended up at the Ames Res. Center site and found this interesting related item. It turns out that ARC/NASA does work in robotics and sponsors a contest for middle and high school students called Botball. This from their press release.

Two robot teams will `do battle' at a time, trying to put the most Ping-Pong balls into a target within a set time limit. The small, one-foot robots compete on a smooth, 4-foot by 8-foot playing surface.

The botball program teaches students C computer programming as well as increases their skills and interest in mathematics, science, physics and design, according to organizers.

These is the contest rules.
There is going to a live webcast (real video) of the finals on July 20 and 21. So it is too late for this year.

Sorry for the off-topic post but I love it when there is something like this that gets kids interested in science/engineering/computers.

I went over the NASA site to see if anything was mentioned about this. Eventually, I ended up at the Ames Res. Center site and found this interesting related item. It turns out that ARC/NASA does work in robotics and sponsors a contest for middle and high school students called Botball. This from their press release.

Two robot teams will `do battle' at a time, trying to put the most Ping-Pong balls into a target within a set time limit. The small, one-foot robots compete on a smooth, 4-foot by 8-foot playing surface.

The botball program teaches students C computer programming as well as increases their skills and interest in mathematics, science, physics and design, according to organizers.

These is the contest rules.
There is going to a live webcast (real video) of the finals on July 20 and 21. So it is too late for this year.

Sorry for the off-topic post but I love it when there is something like this that gets kids interested in science/engineering/computers.

• The 6502 appeared in 1975.
• Apollo was designed in the 1960's and the last mission was in 1972.

The X37 gets launched into orbit by something else, it doesn't get there on its own. From the Marshall fact sheet, it's a testbed for "the orbital and reentry phases of flight". It's not nearly as cool as the article lead made it sound. OTOH, the X38 "Space Lifeboat" has a certain sort of appeal... "We're hit! Order the crew to the escape pods!"

What the original poster is talking about is a massive sky hook, I think, which isn't a loop. Check out the link.

Actually, there's more information about this at NASA, in an article entitled Integrated thin-film solar power satellite. It goes into more detail about the part we care about -- the satellite and its uses -- instead of the robot being developed at CMU to help construct the darn thing. It even has a couple of MacPaint-like pictures of what this thing might look like.

What about (as someone else mentioned) flying objects which end up in the path of the beam? Even if it would pass through us, it would get absorbed by rain clouds (making it just as effective as those solar panels we were all promised in the late '70s), or worse yet, by birds, airplanes, and other flying objects... Certainly, the danger of the solar collector crashing to the ground is less than that of an orbiting nuclear reactor or black hole...but it still seems a bit unsafe. For this thing to be useful at all, it's got to transmit multi-megawatts of energy from point A to point B, and that energy will inevitably get absorbed by SOMETHING in the area. And if the levels are low enough to be "human-safe," then they're barely going to be able to light a bulb, let alone run something useful (like a section of a power grid).

That's why NASA is looking at using these things more to transmit power to lunar bases, Mars missions, and the like. In these controlled environments, something like a giant orbiting solar panel make a heck of a lot of sense:

However, it is quite likely that some of the most important applications, and certainly some of the initial applications, will be in space. Here atmospheric attenuation does not limit the frequency choices and transmission distances may be less. Further, because of the high total mass of the power systems (including storage, PMAD, thermal control and structures) and the high transportation costs, existing power sources for use in space provide power at a considerably higher effective price ($800/kW-hr) than terrestrial power sources ($.10/kW-hr)

P.S. Anyone reading this remember when parts of your 'Net link were transmitted by microwave? Our link in college used to go down regularly, and a call to MIT confirmed that their microwave link to BU (or was it BC? I can never remember) was down due to rain. Sure adds another dimension to the concept of "Internet Weather Forecasting!" :)

Techniques for finding biosystems elsewhere in the universe, and trying to figure out how life gets started; finding other places amenable to human life; how those places formed.... it's fairly broad.

As for the 512-processor Origin, the only thing that jumps to mind is modeling a single-celled organism, down to the molecular level.

The NASA Astrobiology Institute site has more, though it's scarce on useful details.

These spacecraft are part of the Discovery class of spacecraft. This was started to achieve the "faster, better, cheaper" goal that Dan Goldin has preached about. The total cost of Discovery missions cannot be more than $299million which is a far cry from the billion plus dollar pricetags of the huge inter-planetary spacecraft missions from a few years ago (Cassini, Mar Observer, etc.).

The actual price tag of Mercury is $286million and for Deep Impact $240million. Check out the press release.

It's exciting that these scientific missions, with advanced technology, can be accomplished with money that is less than the earnings of many blockbuster movies.

~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"

These spacecraft are part of the Discovery class of spacecraft. This was started to achieve the "faster, better, cheaper" goal that Dan Goldin has preached about. The total cost of Discovery missions cannot be more than $299million which is a far cry from the billion plus dollar pricetags of the huge inter-planetary spacecraft missions from a few years ago (Cassini, Mar Observer, etc.).

The actual price tag of Mercury is $286million and for Deep Impact $240million. Check out the press release.

It's exciting that these scientific missions, with advanced technology, can be accomplished with money that is less than the earnings of many blockbuster movies.

~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"

A better article can be found at NASA. If that doesn't work check out the list of press releases.

Some cool facts. There will be no harpooning of the comet. A 1100lb (yes, 500kg) copper projectile (or impactor, as it is called here at Ball) into the comet, to measure the constituents of the debris and find out what makes up the interior of a comet. None of the copper tipped bullet, that the article aludes too. Imagine slamming a 500kg projectile into the surface of the comet!

This particular project (called Deep Impact, BTW) is about $240million. My company, Ball Aerospace, is contracted to build it. Our part I guess is $200million. This comes at just the right time when people are scrapping for work. This is the first time we will build an inter-planetary spacecraft, so it will certainly be exciting.

I don't know much about the Messenger project. Check the press release mentioned above for more.


~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"

A better article can be found at NASA. If that doesn't work check out the list of press releases.

Some cool facts. There will be no harpooning of the comet. A 1100lb (yes, 500kg) copper projectile (or impactor, as it is called here at Ball) into the comet, to measure the constituents of the debris and find out what makes up the interior of a comet. None of the copper tipped bullet, that the article aludes too. Imagine slamming a 500kg projectile into the surface of the comet!

This particular project (called Deep Impact, BTW) is about $240million. My company, Ball Aerospace, is contracted to build it. Our part I guess is $200million. This comes at just the right time when people are scrapping for work. This is the first time we will build an inter-planetary spacecraft, so it will certainly be exciting.

I don't know much about the Messenger project. Check the press release mentioned above for more.


~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"

I have a good friend/old drinking buddy from my grad school days that now works for NASA supervising the making of craters! The last time I visited his lab, he had this real nice rail gun that shot high velocity projectiles at a target. The propellant was gunpowder that was stuffed into condoms! Or as he politely puts it we load gunpowder into a shell or other receptacle He said that getting the condoms (in bulk of course), initially raised some eyebrows in the government purchasing office.

Here's the web site. that describes the lab.

Ain't science great!

BTW, the study of impact craters is important to understanding many aspect of planetary science and other topics like why the dinosaurs died. I know that Bruce Willis would agree with me on this.

Acutally, if the engines are working, but they aren't going into the right orbit, they would AOA-Abort Once Around. Go in to orbit, drop the ET and SRB, and deboost and come home.

Check out this for a comprehensive covereage of the mission profile-and the oops lists-AOA, ATO, ATL, ATLS and Contingency Aborts.

The operations recorders are powered by the shuttle's main power system, connect to, IIRC, bus MNA. You can read about the power system here.

Note that all the power comes from the fuel cells under the payload bay. Note that the cabin was seperated from the orbiter at the moment of the expolsion. Note no batteries on the shuttle. The AC inverters were located forward-but AC would have dried up the moment DC died. So...

The power was disconnect at the moment of explosion.

The operations recorders require power to operate, therefore:

There was no voice recording following the explosion. QED

The last recorded clear voice record from the Challenger was "Rodger, go at throttle up" - this is when the shuttle is through the densest part of the atmosphere, and can push the engines back to full throttle. There is another word/sound shortlu, which in buried in static, but all you can hear are the vowels. They do sound alot like "UhOh", but with the static, there's no sure way to tell.

Here's the report on the Challenger crash:
http://www.hq.nasa.gov/office /pao/History/kerwin.html, its "inconclusive".

The trouble with asteroids is that while the risk may be great (we are reasonably certain it's led to mass extinctions before), the risk in any given time period -- say, a human life of 75 years -- is rather small. This leads to an underappreciation of the overall risk.

Nobody needs to lose sleep over this; the largest impact we've seen this century is Tunguska, and the odds are still rather small that a Tunguska event will strike a populated area. On the other hand, the odds are higher that an impact tsunami will cause widespread coastal destruction and loss of life. Our only chance is to have sufficient warning time. By definition, an undiscovered object could strike with warning time == zero. It's estimated that we know of maybe 10% of the large-enough-to-hurt-sized rocks that cross the earth's orbit, so the job of finding them isn't trivial.

The good news is that there is modest funding for a hazardous objects search.

The NASA Impact Hazards site has lots more info, including the search project called "Spaceguard".

My take on this is not so much worry that something might happen, as sardonic awareness that it would be Really, Really Stupid to finally figure out this is a problem (last 20 years) and then have our civilization wiped out. Especially if we really are the only intelligent one around ...

Giotto is still up there and is due to fly-by the earth this month

Although damaged by it's close encounter with Halley's comet, the probe was reused to study Comet Grigg-Skjellerup on July 10, 1992.

NASA hopes to do something similar in 2005 -- check out the ST4/Chompollion mission site. (The ST4 project used to be called DS4, one of the New Millenium missions)

And here's a reference:

http://nssdc.gsfc.nasa.gov/planeta ry/giotto.html

ThoughtTreasure understands questions and gives answers. Uses assortment of methods to analyze text, understand problem, apply common sense, and find answer to problem.

CLIPS rule and object expert system tool.

Knowledge Server Toolkit is a Perl-based system for monitoring and acting on continuous information flows, such as alerting when telemetry indicates unusual conditions.

i'd just like to point out that the energy of an electromagnetic emmission does not vary with the type or frequency of emission. a 10 watt FM broadcast radio wave (~100 MHz) carries just as much energy as a 10 watt PCS signal (~1.8 GHz), or a 10 watt light bulb (~700 nm to ~350 nm, or ~400 GHz to ~1000 GHz). as the frequency changes, the signal's ability to interact with your body changes -- your body is resonant at about 100 MHz, and your head is resonant at about 1 GHz.

the fact that cell phones use microwaves to communicate doesn't prevent them from potentially harming you, even at 100 mW. not that they do, but they might. no one knows for sure.

your cell phone would only have to generate about 1 watt to cause gradual damage to your eyes, usually leading to glaucoma and cataracts over a span of years. this could also cause cancer, or have other unpredictable side effects, in your brain. one report even suggested that using a cell phone makes your brain work and respond faster.

gamma and X-rays don't cause mutuations, usually. they cause cancer. (although, if you wanted to argue that cancer was a mutation, i guess i couldn't present a good counter argument.) nuclear radiation only causes superpowers in comic books.

a good link to check if you're interested in the spectrum: NASA's page on the spectrum.

Oh, sure, they claim it's Japanese for "hope," but we know better...

Eric
--

Having said that, I think that it's very unlikely that NASA will send any microbes to Mars. To quote David Dubov concerning the Mars Pathfinder:

There are internationally accepted guidelines that NASA has adopted as rules that govern the number and distribution of Earth "spores" (bacteria or other biological contaminate) that we can sprinkle (intentionlly or otherwise) on the surface of another planet (or moon) believed to have had the potential of harboring life in the past or present.

The two Viking landers were sterilized in a large oven and then encapsulated just before they were rocketed to Mars. This means that there were minimal concerns about the spacecraft inadvertantly crashing onto the Martian surface and spraying Earth spores everywhere. Baking the Viking spacecraft was considered very controversial in its day however. The builders were very concerned that the high temperatures would damage or degrade the materials used in the construction. On Pathfinder we were very reluctant to bake the whole spacecraft. Instead, we opted for baking bits and pieces (low gain antenna, parachute, etc.), and cleaning the rest (wiping or immersing in cleaning solvents).

The end result is that the outside of Pathfinder is clean to within the allotment set by the international guidelines (we know this because we were continously taking bio-assays to count the bugs). But what if we inadvertantly put it onto a collision course with Mars and then somehow lost control of the spacecraft? Wouldn't the Earth-bacteria sealed on the inside escape onto the surface when it crash landed?

We don't know, but we could avoid the issue altogether by putting the spacecraft on a collision course in the first place. By keeping the trajectory near the edge (limb) of Mars we could make sure that, if the spacecraft is lost control of, either it misses Mars altogether, or crash lands with a velocity slow enough so it doesn't spew the bugs all over the surface. Of course, this won't happen!

It's already in use. It's floating around in space. We'll know what it is doing only by what it chooses to tell us...of maybe that's why we're taking pictures of the probe from Earth. :-)

• It hasn't been up long enough to get to many places to take pictures of.
• A lot of its experiments are not cameras.
• Low-resolution pictures on the Web are of limited scientific use. The pictures have certainly been given to the appropriate researchers.

Or maybe you thought it odd that there are no pictures of DS-1 itself in flight? Well, it's not as if there are other probes flitting around close enough to take pictures of each other. Oh, all, right, if you insist.. Here is a photograph of DS-1 in flight. I hope it is all that you expected.

• It hasn't been up long enough to get to many places to take pictures of.
• A lot of its experiments are not cameras.
• Low-resolution pictures on the Web are of limited scientific use. The pictures have certainly been given to the appropriate researchers.

Or maybe you thought it odd that there are no pictures of DS-1 itself in flight? Well, it's not as if there are other probes flitting around close enough to take pictures of each other. Oh, all, right, if you insist.. Here is a photograph of DS-1 in flight. I hope it is all that you expected.

Posted by kurien:

The MIR software is more a continuation of the model-based diagnosis work that came out of Xerox PARC and other places in the past decade.

Model-based diagnosis uses Bayes' rule as do Bayes' nets, but it is specialized to the problem of diagnosis, and now recovery/reconfiguration. This specialization allows very fast inference on this restricted class of problem. There are some systems that do diagnosis strictly with Bayes' nets as well, but MIR uses additional techniques such as conflict directed search from the model-based diagnosis world.

The MIR system on DS1 was provided by an inference engine called "Livingstone", after the doctor and explorer, which was written at NASA Ames. You can grab papers and other info at NASA Model-based Autonomy Home Page.

Cheers,
James Kurien
Remote Agent Team

• Since this was just an experiment, the failures we injected were carefully chosen so that the recovery RA would recommend had as little risk and impact on the spacecraft as possible.
  
  Therefore the recoveries are fairly trivial, such as switching control modes in the attitude control system. In simulation, where there is no spacecraft at risk, RA has taken on much more critical situations such as engine failure during the Cassini orbital insertion.
  
  I view personally view this experiment as the "thin end of the wedge" for AI, or automated reasoning if that's a less controversial term, in space.
  
  RA has done a simple demo in space, more complex scenarios on the ground, and now is being evaluated by a number of NASA centers for future missions. At the same time, a great many people are working on systems which improve upon RA's capabilities.
  
  
• Another post suggests that it takes an hour for Remote Agent to determine that it can switch thrusters after a failure.
  
  On an Ultrasparc or my Linux laptop this takes well under a second. On the rad-hard (read slow) spacecraft processor I believe it takes on the order of a minute do to the actual diagnosis and make the recovery recommendation.
• 
  Much more info can be found on http://rax.arc.nasa.gov in the "How it works" area.
  

  
  Cheers,
  
  James Kurien
  
  Remote Agent Team
  
  
  
  
  
  

take a look at the telemetry log - it contains lines such as:

;; [:EXEC-ACT :INTERESTING 43645139.016] ;; Simulating NEB1 status throw failure ;;

this is not only lisp/scheme syntax, but the colon-prefix notation is typical lisp. it's also one of the ways one could represent phenomena in lisp-based inference engines.

granted, the evidence is circumstantial, but fits lisp better than any other language! :)

On the whole, Deep Space 1 is just a robot with some extremely cool sensors and actuators in an adverse environment. Until now, all such robots launched by NASA have been, at best, remote control "toys" (albeit extremely cool ones). This new software makes the first jump by NASA from remote control to teleautonomous.

This new field that NASA has entered, teleautonomous robotics, allows ground controllers to spend less time actually controlling the robot saving some serious cash for the NASA budget. This will allow even cooler robots to be built in the future, such as their proposed Mission to Pluto.

Is this really an AI? Aren't there a set of laws that define what is truly an AI and what is just Agent software [...]?

oh, but it is ai. this system uses a full inference engine - formal inference being one of the 'classic areas' in ai research.

here's what happens. you give the computer information about the components of the system (in this case, all the parts of the proble that it needs to know about: probably thrusters, sensors, etc.), information about what inputs/outputs these components handle, and what are the effects of those components on other components. these details should be numerous, but fairly simple - after all, one thingy can be causally directly connected to only so many other thingies.

and then once you have this network in place, you can tell the machine to achieve some goal - for example, once it reaches one a.u. from the earth it should take photos of the earth every hour.

the computer will now perform 'inference' - grovel through its network of dependencies, find all conditions that need to be satisfied for the task to be successful (open camera lens, etc.:), will satisfy them, and perform the task. furthermore, if equipment fails (as it invariably does), the internal network will get updated with the information that the goal is not achievable because of some X, and the engine will find some other way of achieving or maintaining the goal state.

judging from the telemetry log, i'm pretty sure that's the type of engine they use. high intelligence it ain't, but hey, it's better than doing everything manually the way nasa used to do it... but the term 'agent' is really ill-fitted to this application (not the least because 'agent' is one of the most widely abused terms in computer science today) - so the whole probe may be an autonomous agent in a sense that it has a concept of 'survival goals' and takes actions to make sure they are achieved, but it would be much clearer to call it an inference engine...

Hi,

C also the NASA DS1 Mission , testing even more cool stuff like ion_engines...

Joerg

According to the article, the filtering software favored by the Ausie censors bans things with "names such as Pamela". Are they completely out of their head?!?

I guess they don't want to hear about the international space station project (one of the Astronauts is Lt. Col. Pamela Ann Melroy).

There goes Australian Women's Lib history, where Pamela Denoon was apparently a major player.

I wonder if it will also filter out info on the PAMELA Magnetic Spectrometer, scheduled for launch two years from now.

Do these censors have any idea how stupid they look when they suggest things like this.

Here is a link. And another, and another. Funky!

Shoemaker "culminated his lunar research as science-team leader on the 1994 Clementine mission.

The Clementine mission included a deliberate search for water near the poles of the moon, Carolyn Shoemaker noted, but Clementine data did not settle the question. The search for water at the lunar poles is a key goal of Lunar Prospector."

And...

"After a 105-hour cruise to the moon, the spacecraft will be placed in lunar orbit and begin a one-year mapping mission from 63 miles above the lunar surface. When its battery fails at the end of its lifetime, an estimated 18 months [the press release was dated Jan 6/98] or more from now, Lunar Prospector and its special payload will crash on the moon."

They knew it was going to crash from the beginning, so they don't need to slam it into the lunar poles to bury him. But they ARE trying to continue Shoemaker's research by hurling the probe containing his ashes at a specific place. Way, way, way cool. Gotta love those NASA guys. Let's hope the experiment is a success.

No, it's not. It's LM (Lunar Module), formerly known as LEM (Lunar Excursion Module). I don't think that LLM was ever used as a name for the LM, at least officially.

Check out Chariots for Apollo by NASA history, and S/Cat Remembered, a site by one of the guys who worked on building the thing.

That's why the mission to Saturn raised such a stink. It was the first nuclear-powered mission since 1979. Pretty much any missions that are staying inside the orbit of Jupiter will be solar powered.

See this link and look toward the bottom for "...surface mounted solar cells..."

Or this one for more info on the vehicle. Or, finally, the FAQ, which says:

What powers Prospector?

Lunar Prospector is run by rechargeable, solar-powered nickel-hydrogen batteries.

That's why the mission to Saturn raised such a stink. It was the first nuclear-powered mission since 1979. Pretty much any missions that are staying inside the orbit of Jupiter will be solar powered.

See this link and look toward the bottom for "...surface mounted solar cells..."

Or this one for more info on the vehicle. Or, finally, the FAQ, which says:

What powers Prospector?

Lunar Prospector is run by rechargeable, solar-powered nickel-hydrogen batteries.

That's why the mission to Saturn raised such a stink. It was the first nuclear-powered mission since 1979. Pretty much any missions that are staying inside the orbit of Jupiter will be solar powered.

See this link and look toward the bottom for "...surface mounted solar cells..."

Or this one for more info on the vehicle. Or, finally, the FAQ, which says:

What powers Prospector?

Lunar Prospector is run by rechargeable, solar-powered nickel-hydrogen batteries.

• Spinoffs from the space program
  
• NASA Tech Briefs
  
• Space Awareness Alliance; Space Benefits
  

Of course, real-time fly-bys and ultra-high resolution images would be much better. Anyone have any ideas?

http://pao.gsfc.nas a.gov/gsfc/spacesci/pictures/mola/mars3d.htm - pictures

and

http://ltpwww.gsfc.nasa.gov/tharsis/m ola.html - links to the EQ used.

http://pao.gsfc.nas a.gov/gsfc/spacesci/pictures/mola/mars3d.htm - pictures

and

http://ltpwww.gsfc.nasa.gov/tharsis/m ola.html - links to the EQ used.

This paper is part of the ongoing abstract research into the possibility of travelling faster than light without breaking the laws of relativity. There are two leading proposals, usually referred in laymans terms as "Warp Drives" and "Wormholes".

The Warp Drive idea was first formalized (i.e. given all the math to show it should work, given sufficient engineering prowess) by M. Alcubierre, so it is sometimes called the Alcubierre Warp Drive. It has three big drawbacks: it requires an absurd amount of exotic energy and matter (some of which we don't yet know how to make), you can't see anything while Warping, and there is no theory on how to stop. This paper addresses the first problem, with the equations given, you need far less exotic energy and matter.

For some excellent laymans info on Faster Than Light issues, check out NASA's Warp Drive, When? site.

Nick

>For someone who acts so holier-than-thou, you should at least get your facts right.

I suppose I'm arrogant when excitable, yes. Consider me desecrated.

>The year that we measure on the planet is 365.24 days (hence the leap year every 4 years). A sidreal year is actually 366.24 years . . .

It's a variable quantity, yes, unless one knows what is meant by "sidereal". (Rotation, not measured against local conditions, "tropical" or the like, but physical rotation). Whom is "we"? Civilian? US Naval Research Lab scientist? Astronomer? Julian calandar, Lunar? After reading countless differing constant lists, the consensus as I view it seems to be 365.26 days (sidereal).

JPL Solar System Dynamics lists: Sidereal year (quasar ref.frame) 365.25636 d
Nine Planets holds at 365.26 days.

I'll consider JPL the authority. They've operated our most successful probes, after all else.
So, aye, I wish to know. Perhaps you're yet following this thread. Illuminate for me, sir or madam.

The IKONOS-1 people aren't too bothered, these things happen and of course they were fully insured - IKONOS-2 is complete and will be launched by the end of the year. My theory is that the launch was disrupted by SPOT :-)

As far as the guff people are talking about spy satellites - remote sensing imagery has a THEORETICAL resolution of about 15cm. This is imposed by atmospheric disturbance. Spy satellites are designed for this resolution but the resulting imagery rarely approaches it. The main difference between spy satellites and RS satellites is that the spy satellites can execute orbit transfers a limited number of times (before they run out of propellant), resulting in an increased revist rate. They also of course do stereo (like SPOT). Unfortunately the military aren't exactly clued on how to analyse satellite data - we're talking transparencies, light tables and magic markers - don't believe the stuff you see in the movies.

Actually, the allies in the gulf war ended up buying a shitload of imagery from SPOT simply because the spy satellite stuff wasn't up to scratch (not multispectral, images too small and too high resolution to go launcher-hunting in the desert). The French government tried to lean on SPOT to give a discount but they actually upped their rates realising they had a monopoly...

Nick

The IKONOS-1 people aren't too bothered, these things happen and of course they were fully insured - IKONOS-2 is complete and will be launched by the end of the year. My theory is that the launch was disrupted by SPOT :-)

As far as the guff people are talking about spy satellites - remote sensing imagery has a THEORETICAL resolution of about 15cm. This is imposed by atmospheric disturbance. Spy satellites are designed for this resolution but the resulting imagery rarely approaches it. The main difference between spy satellites and RS satellites is that the spy satellites can execute orbit transfers a limited number of times (before they run out of propellant), resulting in an increased revist rate. They also of course do stereo (like SPOT). Unfortunately the military aren't exactly clued on how to analyse satellite data - we're talking transparencies, light tables and magic markers - don't believe the stuff you see in the movies.

Actually, the allies in the gulf war ended up buying a shitload of imagery from SPOT simply because the spy satellite stuff wasn't up to scratch (not multispectral, images too small and too high resolution to go launcher-hunting in the desert). The French government tried to lean on SPOT to give a discount but they actually upped their rates realising they had a monopoly...

Nick

Put this in your .xinitrc:

xloadimage -onroot -fullscreen -border black /tmp/astro.jpg -display localhost:0

And run this daily in a cron, and you'll get the The Astronomy Picture of the Day everyday as your background automatically.

Fun with perl!

-=Julian=-

Posted by bodhidogma:

There is actually a cool site with many photos like this:

Astronomy picture of the day