Heads up - we are now having green lasers directed at us from orbit!

[Leo S]

We are living in strange times. As astronomers we are effectively in the front line in the current conflict.

On January 28 this year astronomers at the Mount Kea observatory in Hawaii observed this:

 

It's thought that a Chinese spy satellite is to blame.

I suspect we may see similar over here, so I think it's not a bad idea that we should be aware of the possibility - so far I've not seen any mention of this anywhere, apart from the Cloudy Nights forum.

Edited February 12, 2023 by Leo S
added link

[Moonshed]

This is the first I have heard of this strange event. Pardon my ignorance but what exactly is a green laser scan?

[EarthLife]

Laser measurements/scans from orbit to the surface (done 24/7) are normally done using none-visible wavelengths I think. Using different wavelengths returns differing information on specific features of the atmosphere/ground, but not sure what green returns.

A satellite would have to be quite high up to create almost parallel beams like that.

Edited February 12, 2023 by EarthLife

[Leo S]

13 minutes ago, Moonshed said:

what exactly is a green laser scan?

If a laser beam is directed towards objects, those objects reflect light back which can be picked up by sensors and analyzed to provide information on size/shape/distance. It's a good (if rather obvious) way of spying on your adversaries, but can also have legitimate applications such as accurately mapping terrain.  As far as I'm aware, in most cases this would be done using invisible wavelengths (as EarthLive suggested above). I'm not sure why they'd use green wavelengths, but perhaps because it recently (in the last decade or two) became easy/cheap to produce frequency doubled, diode pumped lasers that emit green wavelengths.

Edited February 12, 2023 by Leo S

[AstroKeith]

Green is quite a good wavelength for getting through the atmosphere. Infrared would be more discrete, but gets absorbed quicker.

[Moonshed]

4 minutes ago, AstroKeith said:

Green is quite a good wavelength for getting through the atmosphere. Infrared would be more discrete, but gets absorbed quicker.

Thanks, that makes sense now.

[Nakedgun]

~

I wonder could some astronomer been blinded while observing in the precise direction of that satellite?

Another technological hazard to avoid.

 

.

[Craney]

14 minutes ago, Nakedgun said:

~

I wonder could some astronomer been blinded while observing in the precise direction of that satellite?

 

I would suggest that 'Heads Up'  is probably not the best advice.

 

[900SL]

I had an odd experience the other night, I noticed a flashing light on the snowy ground around my set up. Looked everywhere for where it was coming from, then heard that drone noise to find a drone sitting 100m above me with a flashing aviation light. 

Absolute pain in the butt, it was stationary for several minutes and in line with my target which was almost overhead. I got out my high powered led lenser led torch in the end and gave it some photons, they got the message

[Mr Spock]

It's ok, my tin foil hat will protect me...