Hi

I'd like to know more about FLARM and what it can offer SLR stations. https://flarm.com/products/powerflarm/

I see the Graz station is using it. Is anyone else?

Despite having a cautionary/avoidance zone for aircraft around the Herstmonceux SLR station, we do get some light aircraft, gliders etc flying over, especially on nice sunny days. This means the observer has to keep a look out.

If this system can raise a proximity alarm then i guess the observer would find it very useful.

Please post your experience. Cheers

This satellite is a beautiful design.
I do not know how bright was the original BLITS, but this document:
https://cddis.nasa.gov/lw13/docs/papers/target_vasiliev_1m.pdf
indicates that BLITS-like satellite of 214 mm in diameter would have a maximum star magnitude of 11 at a distance of 2000 km (probably in zenith).

Does BLITS-M have any metallic/aluminum layers on the surface, or is it entirely dielectric body?

Hello everyone,
since our system is mentioned here I thought I should comment. I have just spoken with the laser safety expert in our institute about this. Since I personally know very little about this topic, I will only summarise his comments.
He has checked the above posts and finds many statements which he thinks might be wrong or at least misleading, and therefore dangerous. His main point was: Calculating MPE is a quite difficult business, and almost impossible to do for a general case. Pulse duration, pulse repetition rate, wavelength, beam diameter and divergence are only some of the factors to take into consideration.
We have a detailed analysis of our current system, that defines what precautions are necessary at what point. Indeed, we are currently eye-safe at a distance of a few hundred meters from the transmitter. If we decrease our divergence in the future, this might change. Our procedures will always reflect the specific analysis.
Toshi, since you helped us so much with the data analysis, I suppose we could try to help you with a safety analysis of a proposed system. However, our laser safety officer is reluctant to do public statements in this forum which people might misunderstand, but rely on and possibly do dangerous things with. But if you could send me your specs via PM, I will try to get an analysis from him.
Best regards,
Daniel

It looks like we need some kind of math support for formulas :-)

Matt?

Toshi

here are the numbers for the MPE (or class 1M) that i found for 1064 nm:

ANSI Z136.1-2007:
27*t^0.75 J/cm2 ~ 1.5e-7 J/cm2
and N^-0.25

ANSI Z136.1-2014:
2e-6 J/cm2
no reduction from repetition rate

IEC 60825-1:2014:
2e-2 J/m2
N^-0.25 for N>600 Hz

for WLRS this leads to:

2007:
~0,6 mJ

2014 (ANSI & 60825):
~8 mJ !!!

it seems that the situation for 1064 nm has relaxed in the latest documents. For all of this numbers the WLRS should be "eyesafe" in the mentioned configuration.

In Wikipedia i found from figure 1: 2e-7 J/cm2
and in figure 3: ~9e-8 J/cm2


However, there is another statement that i found in IEC 60825-1:2014, concerning a Protective Housing:
"Each laser product shall have a protective housing which, when in place, prevents human
access to laser radiation (including errant laser radiation) in excess of the AEL for Class 1,
except when human access is necessary for the performance of the function(s) of the product."

So in principle MPE (class 1M) is not eyesafe. The AEL for class 1 from IEC 60825-1:2014 is:

7.7e-7 J in a 50 mm aperture => ~ 1.2e-7 J/cm2
or ~0.17 mJ for WLRS

There is no clear definition of what needs to be done, when going with lasers through the atmosphere. So it is depending on the corresponding authority, if class 1M is sufficient...

Best regards,
Johann