Playing Space Invaders on a mountain
October 10, 2013 8:10 AM   Subscribe

Here's three minutes of giant telescopes shooting lasers into space. (Also on Youtube).

The lasers are laser guide stars, used to measure and compensate for optical distortions in the atmosphere caused by temperature differences. More on the process from the European Southern Observatory. Video by Sean Goebel, who does lots more timelapse videos.

Via Colossal.
posted by echo target (38 comments total) 25 users marked this as a favorite
Wow. At 1:46, you can see a faint, dispersing cloud of dust left behind by a passing meteor.
posted by teraflop at 8:17 AM on October 10, 2013 [1 favorite]

The clouds at 1:10 are incredible.
posted by permafrost at 8:28 AM on October 10, 2013

posted by MrMoonPie at 8:41 AM on October 10, 2013

Playing Missile Command on a mountain
posted by SharkParty at 8:43 AM on October 10, 2013 [5 favorites]

I saw this a few days ago, and I've watched it a bunch of times since. So endlessly cool.
posted by nevercalm at 8:45 AM on October 10, 2013

Better to Yakety Sax.
posted by Devonian at 8:48 AM on October 10, 2013 [1 favorite]

This is the first vimeo video I've seen that didn't have horrible lag and snag issues.

In the initial five seconds.
posted by clarknova at 8:53 AM on October 10, 2013 [1 favorite]

posted by islander at 8:54 AM on October 10, 2013

A friend was an astronomy/astrophysics major and spent many nights working at the university's telescope. The undergrad's jobs were to stand outside in shifts, watching for airplanes and calling inside to turn off the lasers until they had passed.

I get the feeling that he appreciated time outside under the stars, but I can't imagine it was very pleasant during the winters here in Minnesota or over 13,000 feet at Mauna Kea.
posted by Woodroar at 8:55 AM on October 10, 2013

It's all fun and games until they get a lock on your location and shoot back.
posted by elmer benson at 9:08 AM on October 10, 2013 [2 favorites]

Fortunately we have millions of years before that happens. We should have deflector shields by then, right?
posted by echo target at 9:15 AM on October 10, 2013

I'm amazed at how those stations move in unison. Knowing absolutely nothing about astrophysics, I'm guessing those highly complicated machines require absolute precision. To see several of them perform the exact same motions so closely is wildly cool. I wish I knew more about what they're actually doing.

Better to Yakety Sax.
posted by Devonian at 11:48 on October 10 [+] [!]

Isn't everything?
posted by slogger at 9:20 AM on October 10, 2013

Beautiful, but this gave me motion sickness.
posted by andromache at 9:24 AM on October 10, 2013

I thought they just stuck these out in the middle of nowhere to cut down on light pollution, but the FAQ says the observatories are 14,000 feet above sea level, which must help with the view.

The FAQ also says that at that height,
All the observatories have oxygen bottles. It's not uncommon for tourists to step out of their vehicles and immediately pass out.

Sounds like a good time.
posted by Nonsteroidal Anti-Inflammatory Drug at 9:51 AM on October 10, 2013 [1 favorite]

I grew up in the unsettling core of spook country, surrounded by mysterious facilities employed for various heavy government projects. On some nights, I'd lie in bed, restless, with my huge old shortwave burbling quietly along to the tune of the creaking of our two hundred year-old log farmhouse and the scritching of mice running in the walls, and would get out of bed, gently raise the sash to my window, and climb out and onto the porch roof, where I could lie on my back at look up at the stars.

There were rare nights, packed with flurries of meteors streaking to flaming doom, and rarer nights, when I'd catch the hair-thin traces of lights in the sky, slicing through the bare branches of oaks in autumn. I'd stand in my pyjamas, right at the corner of the roof, straining to see, and from reading stacks of yard sale Popular Science magazines, I knew they were laser lines set against the black, out somewhere not far to the south and east.

"I'm serious," I told my dad after the second occasion. "Someone's shootin' lasers out there."

"Where did you say you were seeing them?"

"Down there, that way, over where the highway is."

"Probably something at the Space Flight Center," he said. "Wake me up and show me, sometime."

The mystery would be solved a decade later, though not as soon as it ought to have been. With the advent of a driver's license and the acquisition of a serviceable beige Datsun once owned by the champion of all cigarette smokers, I started chasing the lights. I'd catch them, grab my keys, and race down the twisting back roads with the lines getting clearer until they'd just...go, always when they seemed so close I could reach up and pluck them like harp strings.

I knew they were coming from somewhere on the sprawling campus of the Goddard Space Flight Center, and it is one of the signs of my fragmented way of investigating the world that I never thought to ask any of our adult sponsors in my GSFC-based Explorer Post in the years during which I was a practicing member of the Post.

Some time later, when I'd found myself deciding between returning to the nest with my tail between my legs, as my father had predicted when I left home at seventeen, and being creatively homeless, I chose the latter and took up residence in a commodious abandoned industrial chicken house on the campus of the Beltsville Agricultural Research Center, a WPA-era campus for agricultural experimentation that wrapped around and through Goddard like the earthy Yin to the Goddard's space-age Yang. The place was clean and well-hidden behind decorative hedges that had grown up between it and the road, and there was good electricity and running water, and I was homeless with privilege there, rising in the early summer mornings to swim naked in the creek beside fields sown with radioactive corn.

On some nights, lying on my army surplus cot unable to sleep, I'd slip out, climb up a rusty metal ladder to the roof of the chicken house, and sit with my back against a big aluminum ventilator and my bare feet on the gritty asphalt shingles and watch the sky.

And then, on that one perfect night, the lights came on—

I stood and stared up at them with my mouth open and they were bright and clear and coming from almost right there. I scaled the rusty ladder as fast as I could, ran out to Springfield road, racing south to the sound of my pounding heartbeat and bare feet slapping the pavement, and I ran and ran and ran, dragged forward by the panic that I would miss my best chance yet, and passed the low outbuilding where the Explorer Post kept its tents, canoes, and camping supplies, skirted the barbed wire-topped fence until the trees opened out and there they were—metal domes peeled open and laser beams tracing a line from here to who knows where.

I clung onto the chain link fence like I was welded to it, until I could feel the Earth turning under my feet at a thousand miles an hour and the Earth rocketing around the sun at nearly sixty thousand miles an hour and I was as alone as I have ever been and in the company of everyone else in the world in a way one only gets to be a few times in this life, if we're lucky.

It was a place I had passed on a thousand rambling wandering road trips, and that I'd passed by on the way to stow supplies after our Post adventures, and I'd seen the domes up there and asked one of the advisors about the strange piece of hydraulic equipment that stood just south of the Optics Facility, and had even noted the giant laser radiation warning signs, but we just fall asleep in ourselves, sometimes, and miss the whole world that's right there.

I scrunched my toes in the cool, damp grass, felt the way the chain link felt in my hands, and stayed there until my heartbeat slowed, and my breathing calmed from a wheezy pant into a steady cycle of oxygen exchange in an organic system, until I caught up with a thousand miles an hour of spin and sixty thousand miles an hour of revolution and the laser traces flicked off for the last time like a fluorescent tube in a bathroom going out. I let the fence go, turned back, just in case, and trudged home having experienced another perfect moment in an existence marked more by failure than such things.

Curled up in my army cot, the glow lingered even as consciousness left me behind.

O light! This is the cry of all the characters of ancient drama brought face to face with their fate. This last resort was ours, too, and I knew it now.

In the middle of winter I at last discovered that there was in me an invincible summer.

— Albert Camus

posted by sonascope at 10:01 AM on October 10, 2013 [21 favorites]

My favourite atmospheric distortion reduction technique is lucky imaging, which may sound like a Chinese camera shop but is in fact taking a whole load of short exposure pictures of the target and then selecting the ones that coincide with a peaceful moment in the air. Like laser guide stars, this is only practicable now because Moore's Law has made it feasible to capture and process lots of data very quickly, and unlike laser guide stars you can do it at home without risking the wrath of bears in the air.

But my very favourite thing at the moment is using spectral analysis of pulsars to map the interstellar medium. It's laser guide star in reverse - as the pulsar radio beam moves through space towards us, its radio frequency spectrum twinkles - it scintillates according to the turbulence of the atoms in the thousands of light years of ISM along the way. Map those over time, and you get some fascinating diagrams of how that changes over days or months. There's all sorts of weird structure in there. I'm still reading up on this and I can't get at the paper I wanted to quote here (#shutdown woes) but if you Google Image interstellar medium pulsar or ISM turbulence spectral or suchlike, there's an awful lot of astroporn out there.
posted by Devonian at 10:12 AM on October 10, 2013 [2 favorites]

All the observatories have oxygen bottles. It's not uncommon for tourists to step out of their vehicles and immediately pass out.

Sounds like a good time.

True story: I'm on Mount Evans, another fourteener, and the highest peak accessible by road in the US. There's a 100 meter path to a little promontory above the parking lot. I'm wearing my heaviest winter gear, and huffing and puffing my way up to take some snapshots. At least five times I get dizzy and have to lean against some boulders to catch my breath. Despite the burning in my chest I'm freezing in the wind.

I get to the top, take some pictures, and pause to look around. Suddenly a woman ten years my senior comes bounding up from behind some rocks. She's wearing a tank top and little green jogging shorts. She's tanned and limber, stopping to do that bounce stretch thing that runners do.

"Woah. Where'd YOU come from?"
"Oh over there."

She points to a peak in the distance. To me it looks a hundred miles away with another 14k feet of elevation in between. I have no idea how she could have gotten from here to there without a helicopter. But I just saw the trail she came from, the landscape is laid out in front of us, and there's pretty much no other place she could have started, other than the spaces betwixt the air.

"Well good luck!" I replied lamley.
"Eh, I do this a couple times a week."

Derive from that whatever tourist homily you will.
posted by clarknova at 10:14 AM on October 10, 2013 [5 favorites]

I wish I knew more about what they're actually doing.

Astronomical Interferometry. It permits you to use several collection devices simultaneously, and gives you resolution (though not light-gathering sensitivity) equal to a single device with a diameter of the distance between the outermost devices.

They first started doing it with radio telescopes, which in some cases were thousands of miles apart. At radio frequencies they don't even have to collect data at the same time, so there have been cases where they've used a single radio telescope twice, six months apart, resulting in resolution equal to a scope 180 million miles across.

The VLA is the grand champion of this trick at radio frequencies. Doing it at optical frequencies is a lot more difficult.

The Keck scopes on Mauna Loa were one of the early attempts at doing this at optical wavelengths. But probably the best one existing now is the VLT.
posted by Chocolate Pickle at 10:24 AM on October 10, 2013

This is a comment I made in another conference on a post about the revelation that the Starfire project wasn't necessarily just an astronomy project:

I visited the Starfire facility in the mid-'90s. Now, it seems to me that if they'd let me, a long-haired, hippie-lookin' mofo whose only reason for being there was I was schtupping the Colonel's daughter and had mentioned in small talk with him that I was interested in lasers and built that nitrogen job out of Scientific American in high school, it can't be that classified. It's not like they said anything about keep your mouth shut or made me sign anything. We did pass through a gate guarded by some serious lookin' dudes who pointed their rifles at me, but they didn't even take my name that I recall.

After we got to the top of the mountain, we went into the main building. There were a couple of dudes in suits there. I was introduced, but I don't remember who they were. Not sure if they were Congressional types or Pentagon guys or what, but the people who worked there were nice to them so I tried to be on my best behavior. We got a short lecture about the project and some of the photos they had produced were handed around.

The purpose of Starfire is to use a projected laser dot to configure an adaptive-optics mirror to compensate for atmospheric distortion and allow for better terrestrial astronomy. It works pretty damn good too. The photos I saw were very impressive. Better than Hubble in some cases, which they were justifiably very proud of. They sure were a helluva lot cheaper to get than Hubble photos.

After the lecture we got a tour of the facility. There were several telescopes on the mountain, a couple of which were capable of projecting a laser. The main 'scope had a really neat setup where they could have several experiments going at once and rotate a mirror to pick which one went up the tube. Other than that there were the optical experiment tables, the adaptive-optics setup, the imaging system, and several different kinds of lasers of varying impressive powers.

Next we went into the main dome. We were informed that the main telescope could depress below 0 degrees and the dome could be lowered in 30 seconds, and raised in two minutes by machine, or ten minutes if the hand cranks had to be employed. At the end of the telescope I spotted a disc with "Raytheon" on it. I casually asked, "What's the radar for?"

"To make sure there are no aircraft entering the beam path," the tour guide replied. The suit dudes were very surprised by my question so I mostly shut up for the rest of the tour. We then exited the platform so they could open the dome and slew the telescope.

Next came the control room. There were a bunch of guys in there, some in uniform and some in civvies. The were all business and didn't say much. They showed us the computer that had the ephemeris of every object in orbit. All the computers were UNIX and X Windows, FYI. As a software guy, I thought the interface left something to be desired, but that's just me. Tracking an object with the 'scope was as simple as clicking on the desired target. We watched the 'scope slew through a CCTV monitor located near the target computer. Sadly, conditions were unfavorable for a test firing, so I didn't get to see the big mother fire.

Last they took us down to the "shack" where the guide-star laser was produced and sent through a smaller scope. The guys in here were friendlier, hippie/scientist types. I rapped with them a little while the brass talked amongst themselves. They were really excited about their laser because it was very powerful and very yellow, which worked out good for their astronomy.

Understand, the men who worked on this project never, ever said anything about it's use as a weapon. They always talked about it in terms of the astronomy. They had a nice telescope with a honkin' big laser under it, a radar on the front of it, and a computer that could track the 'scope on every object in orbit, up on a mountain in the middle of nowhere, but officially the fact that Starfire could be used as a weapon never occurred to them.

As we went down the mountain, and I looked back saw that the main 'scope could also cover the road up to the summit, it sure as hell occurred to me. I thought to myself, "You magnificent bastards. You've got yourselves a nice little laser artillery piece there, and it can even fire in it's own defense. Yet every dime that's paid for it comes out of astronomic research money."

All of which is to say, I'm really surprised anybody is surprised by this.
posted by ob1quixote at 10:51 AM on October 10, 2013 [3 favorites]

The laser is yellow because it's tuned to one of the sodium spectrum lines. They use it to activate sodium atoms in the air.
posted by Chocolate Pickle at 10:57 AM on October 10, 2013 [1 favorite]

Devonian: my very favourite thing at the moment is using spectral analysis of pulsars to map the interstellar medium.

You're kidding, right? I can't believe that something in my thesis work is actually someone else's "favourite thing at the moment".

Do I already know you IRL?
posted by RedOrGreen at 10:57 AM on October 10, 2013 [3 favorites]

Chocolate Pickle: Astronomical Interferometry. [...] They first started doing it with radio telescopes, which in some cases were thousands of miles apart. At radio frequencies they don't even have to collect data at the same time, so there have been cases where they've used a single radio telescope twice, six months apart, resulting in resolution equal to a scope 180 million miles across.

Mostly right, but a couple of things:

- The Keck telescopes (the twin rounded domes in the video) can in fact operate as interferometers, although they frequently don't. But the laser beams are used to create laser guide stars that sample the atmospheric distortions so that computer-driven mirrors in the instruments can compensate for the twinkling. (AKA "Adaptive optics".)

- Coherent interferometry must be done at the same time at all telescopes, otherwise the wave fronts would not interfere. So you can't use the same telescope 6 months apart for interferometry. We do use telescopes that span the globe (the Very Long Baseline Array, currently shut down thank you Congress) for observations. Confusingly, we (I, even) do use the VLBA at different times of the year (including six months apart) for parallax measurements.

We track the apparent position of a target against the position of distant reference sources. Here "distant" means hundreds of millions of light years, and as the Earth goes around the Sun, the apparent wiggle of the "nearby" target compared to the reference source gives us its distance. My personal record distance is about 33,000 light years for a pulsar; others have done better for other kinds of targets.
posted by RedOrGreen at 11:13 AM on October 10, 2013

You can take a tour to the top of Mauna Kea. My wife and I did it when we visited Hawaii about 20 years ago (the top looks a lot more crowded now). We stopped for a while at 10,000 feet for a little acclimation, then continued on in our van, up roads so steep it felt like we might flip over backwards. It was totally worth the trip for the Mars-like landscape and views on and from the mountaintop.
posted by underthehat at 11:34 AM on October 10, 2013

Ob1quixote - the only trouble with the secret laser cannon project idea is that lasers aren't very good at being death rays, and the pointing-at-things technology isn't tricksy enough to warrant a disguised-in-plain-sight project. Seeing that they got to play with a 747 with a ginormous death laser anyway...

There are various laser satellite communication things that might fit well with a telescope project, but again I'd be surprised if there was much engineering that would transfer well. Not that would probably stop some inventive funding, of course.

RedOrGreen. I have a serious radio fetish, a serious astronomy fetish, and a serious weird physics fetish. You don't get much weirder physics than pulsars - nearly all the fun of black holes, but with so much more edge of reality mucking about with energetic processes. Checking out the ISM counts as some of the most unashamed chutzpah going in astronomy - we're pulling apart huge dynamic systems composed of just about nothing, with cosmological variations over periods of days - and if you like radio and don't go weak at the knees thinking about pulling so much information out the sky from tiny, distant yet ultimately weird sources, I just don't know what to say. I'm trying to write a history of radio at the moment, and believe me when I say this is far more the sort of thing I like to have an excuse to dig into than how RCA screwed CBS over when colour telly got going. But it's strictly amateur hour here - I watch and cheer from the sidelines.

(But you may get a MefiMail from me at some point, now you've decloaked and become my lawful prey. A journo in research mode is not shy...)
posted by Devonian at 12:00 PM on October 10, 2013 [1 favorite]

You magnificent bastards. You've got yourselves a nice little laser artillery piece there, and it can even fire in it's own defense. Yet every dime that's paid for it comes out of astronomic research money.

the only trouble with the secret laser cannon project idea is that lasers aren't very good at being death rays, and the pointing-at-things technology isn't tricksy enough to warrant a disguised-in-plain-sight project.

The military application of adaptive optics technology is not laser weaponry.

If you have a technology that can eliminate atmospheric distortion in imaging, it works going through the atmosphere in both directions. You can look up from the surface of the earth, or down from low-earth orbit....
posted by mr_roboto at 12:18 PM on October 10, 2013

Mr_roboto, I don't think it would work going down. The laser fires through the atmosphere and creates something that should look to the scope like a point. The reason it can be sensed that way is because the background is dark, so it's easy to separate out the glowing sodium from the black background.

Going down, though? The background is the Earth; busy and bright. Even at night time it's busy and bright, relatively speaking.
posted by Chocolate Pickle at 12:21 PM on October 10, 2013

lasers aren't very good at being death rays

Generally true, but this is actually one situation where it might work. You've got large ground-based lasers with sophisticated tracking and presumably large and capable cooling systems, capable of running continuously. Your target is a small isolated object with little ability to either evade or cool itself. It's plausible that you could track a satellite for a few hours and heat it up enough to damage it. No doubt there's a lot of engineering problems to be solved, but I don't see any reason it couldn't possibly work.
posted by echo target at 12:57 PM on October 10, 2013

Turns out that Starfire was Air Force funded, but for basic experiments in adaptive optics, the idea being to use the guide star to pre-distort a much beefier laser going up, as atmospheric turbulence is a problem if you want to deliver enough oomph to toast space hardware.

Not much of a secret, though.
posted by Devonian at 1:29 PM on October 10, 2013 [1 favorite]

There are a lot more observatories on Mauna Kea than I had previously suspected.
posted by ckape at 1:31 PM on October 10, 2013

Devonian: “Not much of a secret, though.”
All I can say is that 10 years earlier they were still pretending they had no idea the system might could maybe roast a satellite to civilian visitors. For what it's worth, I pretended not to notice until around the time that article came out, which is when I wrote my comment posted above.
posted by ob1quixote at 2:05 PM on October 10, 2013

Hmm. I haven't had time to go digging too much this evening, but the New Scientist article suggests that it wasn't until tests in 1997 that they realised they needed to do this, following some attempts at just blasting away. Other sources say that adaptive optics were first thought of in the 1950s, but needed more computation than was required. As this is pre-laser, I would think that was astronomical in nature.

I can't find a reference to the history of sodium ion excitation laser guide stars prior to Starfire in 2005. Which makes me wonder if this is one of those military technologies that proved useless to its inventors (I can only find references to the Starfire facility stuff not being continued, Who knows) but is really handy somewhere else. The story of who did what and why would be good to find out. One of the interesting questions is whether you can maintain phase coherence in reverse - might you have to spread the laser beam out to the diameter of the adaptive mirror system before illuminating it? - and another is the small matter of making it work with weapon-grade local power levels instead of the rather more genteel sprinkling of photons from a long, long way away.

Yes, I would like to read the final report.

Meanwhile, you know who else is getting good at this stuff...
posted by Devonian at 4:53 PM on October 10, 2013

Who coordinates where the lasers are being aimed? Seems like they'd ruin a lot of astrophotography if fired in the wrong direction.
posted by jiawen at 9:25 PM on October 10, 2013

My understanding is that there's been plenty of technology transfer from the military to astronomy in the development of adaptive optics techniques, but it primarily came from the Strategic Defense Initiative (Reagan's "Star Wars" program) -- it looks like some of that is described here. A lot of the early astronomical development of AO was done at Lawrence Livermore Lab, which was heavily involved in SDI.

ckape: It's actually a problem that there are so many telescopes on Mauna Kea (not Mauna Loa as someone said earlier in the thread, we prefer to put our telescopes on extinct volcanoes rather than active ones) -- by agreement with the native Hawaiians, there's a maximum number of telescopes that can be placed on the mountain (which is sacred to them). That maximum was hit some years ago; now, to put a telescope up, you also need to find one that can be removed to make quota space.

jiawen: the impact on astrophotography can't be all that big. The laser guide star is about 100 times fainter than the faintest stars you can see with the naked eye. Even stars that faint are relatively rare compared to the separation you can have between the guide star and what you want to look at with adaptive optics, though; laser guide stars allow you to do AO over a much greater fraction of the sky than natural guide stars would allow.
posted by janewman at 10:24 PM on October 10, 2013

Huh, really? Guess I've always seen those lasers in high-exposure photographs, so I assumed they were a lot more powerful than smaller lasers. (I have a 20 mW green laser that I use for astronomy, but I'm careful not to use it around folks doing astrophotography, because the beam is very apparent, even pretty far off axis.)
posted by jiawen at 4:25 AM on October 11, 2013

jiawen: the lasers have power in the tens of watts (i.e., less than a typical incandescent light bulb). It's lighting up the sodium layer in the atmosphere 50 miles up - quite faint by that point from our perspective. Photographs may show the lasers via scattered light, but that's all being seen from close to the telescope, and there aren't amateur astronomers on Mauna Kea (or at Paranal where the VLT telescopes are).
posted by janewman at 12:59 AM on October 12, 2013

Guess I'm still confused. My 50 mW laser (thousands of times dimmer than those lasers, if they're in the ~10 watts range) shows up easily on my crappy camera when I have it set for astronomy purposes, even when the laser is far off axis. So why do the multi-10s-of-watts lasers show up in the video but not ruin astrophotography (etc.)? Is it because the scopes all have extremely narrow fields of view? Or extremely narrow spectrum sensitivity? I totally understand the use and importance of artificial guidestars, I just don't get how they don't mess up data for other nearby scopes.
posted by jiawen at 2:25 PM on October 12, 2013

Ah, I see the point of confusion. To me, astrophotography is something done by amateurs (we do 'imaging' instead, though now that most peoples' cameras are using CCDs -- the same technology used by astronomers, though we use lower-noise versions -- the differences are smaller than they used to be).

You're right on both points: the fields of view over which adaptive optics may be used are extremely narrow - generally an arcminute (=1/30 of the diameter of the full moon) or less; and adaptive optics is only useful for observations in the infrared, while the laser is shining in the optical.
posted by janewman at 11:34 PM on October 12, 2013 [1 favorite]

Where's that "best answer" button?

Anyway, thank you for confirming my suspicions! That clears up a lot.
posted by jiawen at 12:20 AM on October 13, 2013

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