Best Laser for sending signal to space?

[MicroGuy]

Hi,

I have spent the last two days reading this wonderful forum. I am hoping that the knowledgeable experts here will have time to answer my question.

Here goes.... Imagine that I need to signal a craft orbiting the Earth as I stand near a major city at night.

See photo:

Can someone give me some insight on best wavelength (blue, green, etc.) and how much power I will need. It would be best if the laser was a hand-held style so I can be mobile and move to different areas.

Thank you very much!

 

[spyrorocks]

This should be easily doable with a high quality dealextreme newwish model 30mw 532nm laser.

 

[Gryphon]

Hmm, kinda makes me wonder if those guys floating the in ISS can see our lasers shining up into the night sky. Granted at that distance it would look more like a single color flashlight than a laser if it could be seen.

 

[MicroGuy]

Thanks for the replies guys. I tried to find the laser at dealextreme but they are blocking me from seeing anything over 5mw. So I decided to buy from Laserer.com.

For this application, would the Grenede (link below) work.

LZGN - 532nm 100mW Focusable Green Laser Pointer

I find it awkward to operate a light with the switch on the bottom and would rather have it on the side. This one looks like the switch is on the side unlike the stick. It seems like this would be easier for one-handed operation. But I also like the classic and stick hosts. Any recommendations would help. Thanks again!

 

[DrSid]

Anyway .. why would you want to do that ? Shining lasers to the sky is asking for trouble, as it is full of aircraft. Also I doubt the beam itself would be visible over large distance. Only if you point the beam exactly at the satellite it would be able to see your laser, simply as bright dot, at the place you shine from. 1W 445nm laser was used with ISS during one student experiment, and it was barely visible from ISS (as a dot). On the other hand 300mW green has even better subjective brightness and it has much better beam divergence.

 

[Lethere Belight]

The last sentence of the post sounds like it is something he actually wants to do.
Maybe he's an alien and lost his communication device and needs to signal the ship to get picked up.
Or if he's going to different areas near major cities he could be a target spotter for the alien ship.
Homeland security better look into this.

 

[Kartracer00]

That....sir.......is ridiculous. Just don't do it.

OH and radio waves work best. That's what your looking for.

But kudos to the interesting question.

 

[MicroGuy]

Only if you point the beam exactly at the satellite it would be able to see your laser, simply as bright dot, at the place you shine from. 1W 445nm laser was used with ISS during one student experiment, and it was barely visible from ISS (as a dot). On the other hand 300mW green has even better subjective brightness and it has much better beam divergence.

Thanks for this information. I will not be interfering with aircraft. I am a former pilot. This will be used only in "emergency" type situations. My plan is to use this in conjunction with a radio transmitter. The laser is for providing a more pinpoint location for the "receiver" who will be descending to my terrestrial location from an extremely high altitude.

 

[thatguynate]

I doubt you would be able to see much of a beam, although I don't have much first hand experience with high powered greens. If you are already getting a general location with a radio transmitter, is a laser going to be much better than a strong signal light? Without a prominent visible beam I would think you would need very good aim to get a laser signal to be a beacon instead of irritating, confusing blinking dot. Just my 2 cents.

 

[jcranmer]

Hmm, kinda makes me wonder if those guys floating the in ISS can see our lasers shining up into the night sky. Granted at that distance it would look more like a single color flashlight than a laser if it could be seen.

http://laserpointerforums.com/f44/amateur-astronomers-flash-space-station-1w-blue-laser-72271.html

I'm pretty certain they can.

If you still need help, you can always try what these guys did. :eg:
http://laserpointerforums.com/f65/running-whole-block-445s-77021.html

 

[MicroGuy]

http://laserpointerforums.com/f44/amateur-astronomers-flash-space-station-1w-blue-laser-72271.html

I'm pretty certain they can.

If you still need help, you can always try what these guys did. :eg:
http://laserpointerforums.com/f65/running-whole-block-445s-77021.html

I wonder if green would be even better? Any guesses?

 

[thatguynate]

Human eyes are definitely much, much more sensitive to green than ~445. I'll see if i can find where I saw the graphs, but one of the safety threads has comparisons and at the same output green was something like 4-5x as visible I believe.

 

[madmacmo]

Note the link to the digital image taken from the ISS clearly showing the < 1 watt 445nm as a bright blue dot near center frame, as the ISS orbit is nearing closest approach of 500 km (310.7 miles) over the amateur astronomer on the ground positioning the laser pointer.
http://www.universetoday.com/wp-content/uploads/2012/03/Picture-0861.jpg

Re: Amateur Astronomers Flash the Space Station with 1W Blue Laser Post #34

 

[MicroGuy]

Note the link to the digital image taken from the ISS clearly showing the < 1 watt 445nm as a bright blue dot near center frame, as the ISS orbit is nearing closest approach of 500 km (310.7 miles) over the amateur astronomer on the ground positioning the laser pointer.
http://www.universetoday.com/wp-content/uploads/2012/03/Picture-0861.jpg

Re: Amateur Astronomers Flash the Space Station with 1W Blue Laser Post #34

That is Awesome! Thanks man!! That's what I had in mind. Then as the craft comes closer, the beam will eventually become visible (if the craft has that capability. hehe).

Now the blue or green question. Hmm?

Does anyone have any ideas on how a build like this would work (link below). If so, I will see if he will make me a blue or green one.

>>>> http://laserpointerforums.com/f39/sold-2-3w-445nm-lighthound-minisabre-77083.html

 

[ZRaffleticket]

I still don't quite understand why you'd want to do this

Blue would have more photons going through the atmosphere having a higher chance of reaching the target, green would be more visible to the eye however with less photons reaching the target.

 

[DrSid]

Again, green for sure. Blue is less visible (but same dangerous), and currently available 1W 445nm diodes are multimode, ie. their beam has bad divergence. For the same money you get much more visibility from green laser. Several times more at a distance.