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Ships targeted by lasers traveling the Chesapeake bay

I've had an interest in flashing the ISS too, don't think I'd actually try due to the uber huge amount of difficulty trying to put a spot on something so far away while it is moving so fast, but theoretically. I've crunched some numbers to come up with the amount of power density delivered at extreme distances like that and found a fairly low power single mode laser diode with a beam expander on it will beat the pants off of a high power multimode diode, delivering a far brighter spot to the eye at distance due to the far lower divergence.

Edit: A 100 mw single mode diode can put a brighter spot on something at distance than a 2 watt multimode diode just due to their inherent lower divergence, but put a beam expander on that MM diode and things can equal up or exceed to where a high power multimode diode can outperform a single mode diode without one, but at added expense and complexity. However, put a beam expander with the same size of output lens on a single mode diode and the MM with a BE is left in the dust again!

God, I hope someone who wants to be malicious doesn't put a beam expander on a single mode laser pointer.
 
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Only because I like the stability of laser diodes in a pointer, that coupled with the low divergence of a single mode diode and it's a sweet deal. I do agree though, DPSS is a far nicer beam and lower divergence than a multimode diode by far. Put a BE on a DPSS laser and you can compete with a single mode laser diode, but for most DPSS pointers, the lens will need to be larger on the output to do so, or higher power DPSS output to overcome the single mode.

Edit: Back to put this photo in:

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Comparing a DPSS to a single mode and you are right, they aren't so far apart. For the above calculations I used a fairly common divergence for most 532 nm DPSS laser pointers as well as a common divergence for a 520 nm single mode laser pointer, both using 6 mm diameter collimation lenses. The single mode still out performs a DPSS (by a slight margin) side by side with the DPSS at more than twice the power though, at 1000 meters distance. Although I doubt anyone would be able to see the difference in brilliance, they would see the DPSS beam is much wider.

A wider beam is easier to hit a target with, from that, compared to SM, the annoyance factor goes up making cheap DPSS laser pointers have the advantage and why they can be such a pain to the people being flashed by them.
 
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I'd just like to say, that whomever is doing this might wanna rethink it:D You'd be surprised at what these boats have on them especially if they were anything navy related;)
 
Wtf does 'painfully bright to look at' even mean? I have a flashlight that's painfully bright, but that doesn't mean it's an eye hazard. I swear, people just get worked up any time lasers are involved even if there's no actual danger whatsoever.
 
Using either a single mode diode or dpss would be a 'must' to get a well visible signal to the ISS even with a big beam expander.

As mentioned though: actually hitting it would be pretty difficult to do.

Telescopes that track stars, or even the moon, in the sky are available to amateur astronomists, but i doubt those would be fast enough to track something like the ISS. I've seen it's reflection pass over and it takes a few minutes at best for it to appear on one horizon and disappear on another. I would see no reason that a telescope should be capable of tracking -that fast- unless specifically built for this purpose.

Also it would have to be very accurate, with such expanders you are in the (tens of) mircoradian regions, not milliradians we are used to. You are aiming for something about 20 meters in size (for the occupied area of the station, so someone could see you, not the solar panels and all that) at a distance of 500 km. That is as diffcult as hitting a 2 cm target 500 meters away from you, using a beam expander you could probably hardly lift by hand.
 
Yep, have seen that before. Wow, I've got this thread off-topic badly. :whistle:
 
Thanks, Chris. I haven't seen this before. I was a bit unhappy to see the plug for WL in the article, though. I wonder if they even used a BE, as I couldn't find mention of one. If not, that would mean a 445nm 1 watt laser is all it takes to be seen from the space station.
 
Given you are in a remote area and pointing at the station it could very well be visible to someone on the space station without a beam expander. If they are looking for you you'll stand out.

This will probably not work if you live in a big city though as the light pollution will swamp out your laser beam quite easily.

It's a similar question as to at what distance you could see something like a 100 watt incandescent lightbulb, providing you have a direct line of sight (i.e. it is not beyond the horizon or something like that). In a city this can be under a hundred meters, in the open ocean you could see the thing atop the mast of a ship miles away with the horizon being the limiting factor.
 
Paul, I saw a video of the event some time back, must have been one or the laser DPSS to have low enough divergence?

That was my earlier thought too Ben, not likely to see the beam unless in the remote outback, or bush, as we call it in Alaska.

I'm using my cell phone, can't view this ATM:



My thought is they should not have flashed the laser at the exact same rate unless you wanted to claim it could be viewed from the ISIS when confused with the other lights, or buried under them. WL may have used this as a promotional event for their laser when it was never seen at all, or the spot lights weren't seen. I just don't know.
 
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From what I saw and read, it was in the "brush" at a large telescope used for tracking the stars. It was set up way in advance and the people on the space station were aware of it before hand. It showed the WL 1 watt pointer and was done in 2012, so it must have been a 445nm. It even looked like it was that wavelength.
 
And it's also a WL PR thing.

Surely advertising your product is so bright it can be seen from space sounds cool, but the realisic question here would be if that is someting special.

Without beam expanders or anything like that, could something like a 200 mW dvd-writer based laser be seen from the ISS? I reckon it probably could if set up in a dark area and poiting in the right direction.
 
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