HIMNL9
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Really ? ..... ok, let me try ..... damn, where the hell i placed the 100W green unit, now that i need it ? :eg:
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FrozenGate by Avery
Amateur Astronomers Flash the Space Station with 1W Blue Laser
- Thread starter madmacmo
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Really ? ..... ok, let me try ..... damn, where the hell i placed the 100W green unit, now that i need it ? :eg:
Benm
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Well, it has been discussed on LPF wether it would be possible to see a 1 watt 445 laser from the ISS, and the math showed it would be as long as its on the dark side of the earth in a area that isnt lit overly bright (such as a city center).
It's nice to see that this has now been confirmed, and kudos for the aiming ability of the people that did this experiment - it looks like they aimed by hand, not even some automated tracking system!
yobresal
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By hand?!?! That seems extremely difficult. Less so when you image the size of the laser spot at that distance. Gives you some room for error. Kind of like shining a flashlight on a field goal from the other field goal. Man I would have loved to have been there lighting up that station with my 800mW green laser or my 2.4W blue.
DrSid
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Well shining at ISS is no problem .. to make someone look back might be ..
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Nice thread (and forum)!!
I was the number cruncher, whether they wanted one or not. It isn't that hard to calculate how bright an object will appear from space, once you see how to compare one standard (e.g. Sun) to whatever light we chose to use. [inverse square law and lumens per watt]
Unfortunately, to make our spot of light at least as bright as the star Vega (0 magnitude), as I recall, we would need about 50,000 watts of light power. This assumed typical high dispersion beams (~ 65 deg.) Most lights aren't designed to illuminate orbiting spacecraft. *wink*
We got lucky and found a local hi-tech search light company, Sky View. They donated two very low dispersion lights.
The Saturday before the event, which would be 7 days later, I was shown the blog from Don Pettit stating that since they are still in sunlight during fly-overs -- when they are visible to us down below -- then a great deal of glare from the Sun is upon their windows preventing anyone from being successful at sending them a light signal or flash.
I suspected, however, that a colorful spot from a laser might make a difference by cutting through some of the glare. When I discovered that 1000 mW lasers were commercially available, I crunched more numbers and found that such a laser would only be about one or so magnitudes dimmer than the 850 watt search light, due to the very low laser dispersion angle.
It took a little doing, but Wicked Lasers hunted one down for me from their California store, whereas everyone else I tried had to order from China. I needed something fast.
It arrived on the day of the event, but I was obligated to look at granite with my wife, so I didn't get to mount it on the "gun" that I and two fellow employees designed and built during the weekdays. It finally was completed a few hours before the event, but when it arrived to the observatory site, it had gotten horribly misaligned. It got realigned with the gun scope only about 10 or 15 minutes before the event.
I am curious if anyone knows if the Arctic 1 watt laser really is 1 watt. One laser safety site mentioned 800 mW.
The other thing that I'd like to learn is more on the unusual dispersion beam. After the event, I shined the laser on a fence about 100 ft. away and the bulk of the beam was in a narrow rectangle. I could see what looked like diffraction bands around this slotted beam. Is this typical of laser beams?
George
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Sigurthr
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Welcome to the forum!
WickedLasers' products can vary a tremendous amount when it comes to actual output power. We've seen Arctics that actually do no more than 400mW before, and it is very, very rare to get one that does more than 800mW.
You should know that if your group ever wants to do a second attempt, we have members here who regularly build confirmed 1.7W output blue handheld lasers, and they are available for sale here for usually less than $400.
About the beam pattern being rectangular - yes that is completely normal. These blue lasers use what is known as a "multimode diode" which does not operate with a normal gaussian profile. The spot/beam only look round up close because of the focusing lens. The beam is actually a bar, with one axis much faster than the other. Most diode lasers above 300mW are multimode output, the "12x" 405nm diode is an exception. That one is single mode (round beam/spot) and >500mW.
WickedLasers' products can vary a tremendous amount when it comes to actual output power. We've seen Arctics that actually do no more than 400mW before, and it is very, very rare to get one that does more than 800mW.
You should know that if your group ever wants to do a second attempt, we have members here who regularly build confirmed 1.7W output blue handheld lasers, and they are available for sale here for usually less than $400.
About the beam pattern being rectangular - yes that is completely normal. These blue lasers use what is known as a "multimode diode" which does not operate with a normal gaussian profile. The spot/beam only look round up close because of the focusing lens. The beam is actually a bar, with one axis much faster than the other. Most diode lasers above 300mW are multimode output, the "12x" 405nm diode is an exception. That one is single mode (round beam/spot) and >500mW.
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That would help explain why my mag. values were a little higher than what Don Pettit reported. He said our light, including the brighter search lights, were seen as bright as a "mid Mars", which is probably between -1 and -2 mag., which is about 2 mag. dimmer than my calculations.
That is very good to know. Is a blue laser the best bang for the buck, which is why I chose blue over green? I didn't have time to shop, but if we do another flash, I might want to go shopping again.
Back in the 70's, I watched a friend of mine, W5QZ, who was with S.W. Bell at the time, demonstrate communication using amplitude modulation of a laser beam as it passed through a electrically sensitive lens. I suspect it would not be hard today to make something relatively inexpensive to transmit a great deal of information, though I wouldn't mind brushing-up on good ole CW and attempting a communication now. I've suggested the later but it is up to Don, and Robert, to initiate it.
What are the legal power levels? [I'm new to lasers.]
Yes, that makes sense. The lens may also be misleading me on the measured dispersion angle. I'll need to take more measurements to get the true angle, no doubt.
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Thanks. It was a lot of fun, but after calculating that our lights should have been seen by Don as quite bright -- and I hoped that the ISS westward position would minimize glare -- that I was surprised that the arranged phone call did not take place. As it turned out, no phone call came because Don was busy taking pictures instead. He attempted a call, but it was too late to make the connection. [I originally suggested they use their Ham station, but soon learned they have a cell phone,
, and the station is too far from the Cupola, which was where Don and Dan were when they saw us.] Both Nagel's and Mexican restaurants are doing well.
Another question I have is whether a green laser of equal wattage to a blue or red laser is distinctly brighter to the eye. I have studied a little on eye sensitivity and it seems that the very few "blue" color cones (~2% of all cones) have their signal greatly amplified within the cortex, or before, so that blue light net reception is only about 25% to 30% less than green. I was told that green is 20x better, but the source was dubious.
The reason I gave to Don and others for not using a green laser was that I did not want to be responsible for making him look sick. *wink*
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George,
My dad is retired from a rather distinguished career with NASA at KSC (Kennedy Space Center) and my brother is still working there now.
I sent them the article on your accomplishments and they were very interested in it, you guys really did a great job - especially after reading your account of how many things were put together or fixed at the last possible moment!
One thing that I am still unable to clearly understand, were they seeing the laser, the spot lights or a combination of both in the ISS?
And how did you manage to move the spot lights so quickly?
As other members have mentioned, if you try this again, you can easily get lasers of much higher tested power from forum members. Survival Lasers sells a 1.25 watt laser for under $150 here on the forum. You can find home built 1.5-2.0 watt lasers for under $200 easily.
Also, a relatively inexpensive option might be a high wattage green. An Optotronics 450mW green would be MANY orders brighter (to the human eye) than ANY blue laser available right now in pointer format. Optotronics isn't cheap, but Jack might be able to work a deal with a high visibility PR situation like yours, or o-like sells a much lower cost (but with accompanying lower quality) 500mW green (532nm) for around $300 shipped. Of course they are in China so shipping is slow.
In the future, I am sure some of our members could be of immense help with ANY laser related events or projects you might have. Some of us also are interested in astronomy as well.
I have an old (aka less than 10 years old) Celestron 8 inch mirror telescope sitting in its box in my garage waiting for my kids to get a little older and be interested in astronomy to dig it back out!
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about sensitivity as far as I know, our blue would almost be as bright as green, but it needs to be close to 419nm as our peak blue sensitivity is a very narrow band and green has a broader band but peaks at 531nm, red is brightest to us at 558nm
but the main reasons is common green dpss is very close to 531nn and 445nm blue is not that close to 419, this is based purely on cones, our rods sensitivity peeks around 500nm
funny about red is 558 is a yellow also dark adapted we don't see color well so our cones are night sensitive to 550nm favoring greens and reds to blue
oops forgot something, blue also gets absorbed more by our atmosphere, so its power loss at a distance is worse
but the main reasons is common green dpss is very close to 531nn and 445nm blue is not that close to 419, this is based purely on cones, our rods sensitivity peeks around 500nm
funny about red is 558 is a yellow also dark adapted we don't see color well so our cones are night sensitive to 550nm favoring greens and reds to blue
oops forgot something, blue also gets absorbed more by our atmosphere, so its power loss at a distance is worse
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yobresal
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Please do not think that 2.7W 445s are easy to attain and are built "regularly" I build many many 2W plus 445 lasers every week and have only seen maybe 1 hit that mark. It is frustrating for me as a builder when information like this is posted because then everyone decides they want one of these 2.7W lasers that they now believe are commonplace. Getting 2.7W out of one is rare. Very rare. The most I hope for is 2.4W and most fall between 2-2.4. Please don't confuse people with exaggerated power claims. No offense to you I just want to make it clear to everyone who is reading this that 2.7W 445s are NOT built regularly. It's the opposite. They are a rarity.
DTR
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I agree completely. As far as I know I think on one unit hit 2.7W maybe two and he probably tested a several arrays worth of diodes for just one that would hit this mark. It is just to a point with the new diodes that we can say 2W is common and easy to obtain. I have already had many people ask me for a 2.7W diode and it does get a little old trying to explain how that is not something I can do or guarantee.
Anyway George great experiment. Very interesting.:beer:
If you ever want to build your own lasers I have quite a few tutorials that can give you some direction.
If you have a lot of cash to spare, then you might want to consider a Laserglow Hercules. They are among the most powerful handheld green lasers, and also have a very low divergence. I don't have one myself, but Laserglow generally has a very good reputation around here.
Sigurthr
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Dollar per mW it is, but green is far brighter than blue, mW to mW.
That's the old way of doing it, with an AOM (AcoustoOptic Modulator). I've built a voice-over-laser transceiver that uses direct amplitude modulation of the current going to the laser diode. It's only 12mW but could easily be scaled up to a full 2W quiescent output level with funds thrown at it. You could easy send AFSK (audio freq. shift keying) data through it. I've also built from scratch a CW (morse) over laser transceiver as well. It's only at 2.5mW output but the transmitter side could control any diode based laser of any power.GeorgeHelio said:
For a "pointer" without safety features, 5mW is the limit. If you add FDA required safety features there is no power limit. If you build it yourself, there is also no power limit, instead the legality falls on application and intent.GeorgeHelio said:
and...
I agree completely. As far as I know I think on one unit hit 2.7W maybe two and he probably tested a several arrays worth of diodes for just one that would hit this mark. It is just to a point with the new diodes that we can say 2W is common and easy to obtain. I have already had many people ask me for a 2.7W diode and it does get a little old trying to explain how that is not something I can do or guarantee.
D'oh, my apologies fellas! I meant 1.7W. I'll fix it in my post. You guys are absolutely right though, and I can see how new people thinking 2.7W monsters floating around ready to grab would be a problem. I would have thought my price quote would have cast some doubt on the 2.7, but I guess it just made me look even more incorrect haha. I based my intended 1.7W on the average 1mA:1mW If
o curves on the H1600 and M140.
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At the risk of being too wordy, I would like to share things that may never get told. The story did go a bit viral, but I suspect by now it could be considered essentially dead, though Sky & Telescope may do something more elaborate. I will know more this weekend on this possibility.
So, yes, many things fell (and upward) into place. It was a little like watching dominoes stand up. For instance, Keith Little, the true coordinator for this project, on his way to the event, lost his power belt on his Suburban, but got Pep Boys to replace it in just 20 minutes. Try that sometime when they are busy on a Saturday!
Another example of fortuity, is that I was responsible for providing blocking boards used on the search lights, but I assumed I would have time to do them on Saturday. I didn't. I had just enough time to look around in the garage for some thin plyboard, but found something even better: lightweight 3/16" paneling board that just happened to be the perfect size for the lights, requiring that it be cut only in half. Also, they had to be painted black and I hadn't bought any paint in probably more than a year. The full can of spray paint failed to spray, no surprise, but the almost empty one worked, and had just happened to have just enough left so that it ran out of paint just after the last stroke to cover both boards effectively.
The most important "good luck" portion of the story is the finding of the search lights. There is no way you will get enough flash lights to do the job, as many members here likely understand. These were more important to us than the laser (hind-sight suggests this may not be the case after all). I set-up a meeting with the owner of the search light company, Sky View, who brought Ron Peters, Head of Technology & Development, with him to join Robert Reeves, Keith Little, and myself to discuss the idea of using his lights. The owner gently raised the issue that amateur astronomers, such as ourselves, are not that friendly toward his company's operations, namely flooding the sky with light, as you can imagine. Nevertheless, Keith eloquently presented our (SAAA) track record with helping thousands of kids and adults, usually at school sponsored events, learn about the universe. The meeting went well. The owner wanted to know more about us personally, and the fact that we aren't well to do, so to speak, including the fact that Robert, though a respected astrophotography author, is a diesel mechanic may have improved our position to obtain a light. [I don't know if the owner has been burned by would be competitors, or what that prompted his question, but it came across as a strategic one, and not just a casual one.] The owner elected to be very gracious and offered a light at no charge, saving us perhaps $400 or more had we rented it. [Since there was a genuine change that our flash event would be a failure -- all others had failed, apparently -- then spending much of the club's treasury would be an uncomfortable move, even if allowed.]
The extremely low dispersion angle of a laser is excellent except for one thing -- using a very narrow beam, how do you hit an astronaut's head 220 miles (or > 1000 miles if at a lower altitude angle) away and traveling at 17,500 mph.? This is analgous to hitting a small bumble bee at a distance of 13 miles that is traveling at Mach 1!! [Fortunately, we now have a blue bumble bee out there.
]Of course, when the ISS is, say, 300 miles away, the Arctic beam is about 1/2 mile wide. But any jiggle by the laser holder would easily cause only extremely brief flashes of laser light upon the astronaut. This is why I, and two fellow workers, developed a "gun" (with stand) to greatly increase targeting, which seems to have been helpful, no doubt.
The laser was just a secondary plan, and one not seriously considered until the glare issue arose, causing some investigation by me as to the use of a powerful laser. The 5 mW laser, that we were all accustomed, had little hope of working.
But the laser was still a secondary effort because, according to the calculations, the search light was more than adequate for the job, ignoring glare. [Ron Peters, with Sky View, got more and more interested in this cool event, so he decided to bring a second light as back-up, which of course, we weren't going to let it sit in his van unused. Ron is now a member of our club, and at no charge.
]Once we were offered a search light, I wanted to know just how we could use it effectively. Yvonne, receptionist at Sky-View, was a treat to talk to and she, when asked, told me where I could go and watch their light operate. Copelands, a nice local seafood restaurant, was using one a couple weeks before the big event. The manager allowed me to go out and look at it, which they had simply put on an outside table and plugged it in with a standard gauge wiring extension cord (orange).
This gave me a chance to fully test all that I needed: It is mounted on an alt-az mount, which, as you likely know, means the base turns like an old phonographic turntable, and two plates extend vertically upward from the rotating base so that the light is supported by two horizontal pins (one per side). These pins allow the light to rotate the light upward and downward. The light, unlike the WWII behemoths -- though just as powerful, was small enough and cool enough to easily maneuver by bare hand to track whatever object you might choose. Also, the low dispersion angle greatly minimized the glare that would ordinarily diminish our ability to see and track the ISS. The light had only one quirk, as you rotated the light upward, it would become jammed due to a wedging effect from the thick, hard rubber washer at the two pins, which required a hard jerk on the hand-type securing bolt to free-up the altitude rotation. [I didn't learn this till we wear actually tracking the ISS, which is why the video clip mentions that I "was too high", but only briefly.]
Yep, this is the place I'll come if we get another crack at the ISS. [It is all up to the astronauts and NASA, of course, to allow such an event. Obviously, we are greatful to both.]
I suspect this is misnomer. The output signal from the retina's color cones are not at all the final input levels used by the brain in determining color. There are some color cone reception plots that show this surprising effect. Yet, I am not well versed in visual physiology, so I could be wrong, and I am very open to correct. Though I would be a sundae I'm right. It seems to me that blue reception, after blue signal amplification, is only about 25% or 30% that of green. [It might be more than this in an overall comparison since the red cones also are stimulated by green light. I vaguely recall another plot on this and probably should use this one instead. Nevertheless, blue is still a wavelength of light we can see surprisingly well. I wonder if the high energy found in "blue" photons improves reception effectiveness of those few number (~ 2%) of "blue" cones.]
Nice, sounds like a deal. I'll help with astronomy, if y'all help me with lasers.
I too have a Celestron 8 inch, but I changed the alt-az mount to an equtorial mount so I could start doing more astrophotography.
One big rule in amateur astronomy is to own a telescope you will use. Your scope, like many, require some effort to set-up. A Dobsonian telescope is usually recommended since it is so simple, yet quite powerful for their low cost. I own a 16" Dob, and I love it. I haven't used my 8" in quite a while, though I will use it this week at "Amazing Skies" since the hundreds of youngsters will enjoy it and I don't have to risk my 16 incher.
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This is my understanding, too.
The cones are suprisingly broad in thei spectral receptivity. Peaks aren't the main thing to consider. I have been surprised by how often the peak points are used to argue issues about color. My specialty is heliochromology -- a term used to promote the odd story as to the Sun's true and natural color. More often than not, scientists, including astronomers, guess wrong regarding the Sun's true color (defined as seeing the Sun from space, and at a comfortable intensity level). [Solar phsyicists, however, seem to have a better handle on its color than the rest, no surprise.] The textbooks often describe our star as a yellow dwarf, class G2V, but is yellow its color? It is a quirky color conundrum and I have written about a time or two over the years.
"Scattering" is the better word, but the effect is very noticeable when comparing a sea level spectral irradiance of the Sun (AM1) to a data set seen from space (AM0). Yet, this extra scattering I felt would be more benefit than hinderance since the shooter would be able to see the beam a little better due to scattering. [This is Rayleigh Scattering, which demonstrates that most of the light is either scattered forward or rearward, not that much is scattered perpendicular to the beam.]
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