### Recent Posts

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##### In-Sky Safety / Re: FLARM
« Last post by Matt Wilkinson on January 11, 2018, 11:43:50 AM »
Thanks Franz.  That seems nice and easy if it is integrated in to your ADS-B receiver.

We're covered for ADS-B aircraft but not the gliders and small aircraft that FLARM is intended for. We rely on the observer.

I found a community page here with a lot of guidance for setting something up: http://wiki.glidernet.org/

And there is a live map here, but i guess it depends on the available network of receivers for its coverage: http://glidertracker.org/#lat=1105585&lon=6428048&z=5
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##### In-Sky Safety / Re: FLARM
« Last post by franzkoidl on January 10, 2018, 10:29:20 AM »
Hi

At the Graz station we are using a TRX-1500 ADS-B Receiver which includes a FLARM System.

https://www.air-avionics.com/?page_id=253
https://www.air-avionics.com/wp-content/themes/yootheme/cache/traffic_1-70910620.jpg

The data stream gives us the position of ADS-B equipped aircrafts as well as those with FLARM.

Cheers
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##### Welcome to the ILRS NESC Forum / Posting a mathematical formula
« Last post by Matt Wilkinson on January 04, 2018, 04:21:59 PM »

To help contributors who want to include formulae in their posts I've installed a program called 'mimetex' which takes LaTeX formatted text and produces a gif image.  It works like this:

[ img]/cgi-bin/mimetex.cgi?f(x)=\int_{-\infty}^xe^{-t^2}dt [/ img]

which without the tag spaces gives:

$f(x)=\int_{-\infty}^xe^{-t^2}dt$

Please test it out using the post preview.  See here http://www.forkosh.com/mimetex.html

Matt

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##### Open a Discussion / MOVED: Satellite BLITS-M
« Last post by Matt Wilkinson on January 04, 2018, 04:11:02 PM »
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##### In-Sky Safety / FLARM
« Last post by Matt Wilkinson on January 03, 2018, 09:37:05 AM »
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.

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##### Open a Discussion / Re: MPE
« Last post by Matt Wilkinson on December 21, 2017, 09:55:57 AM »
It looks like we need some kind of math support for formulas :-)

Matt?

Jens, since it is Xmas...

I've installed a mod called mimetex which takes LaTeX and produces a gif image.  It works like this:

[ img]/cgi-bin/mimetex.cgi?f(x)=\int_{-\infty}^xe^{-t^2}dt [/ img]

which without the tag spaces gives:

$f(x)=\int_{-\infty}^xe^{-t^2}dt$

Please test it out using the post preview.  See here http://www.forkosh.com/mimetex.html

Matt

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##### Mission Tracking Feedback / Re: Satellite BLITS-M
« Last post by DanielK on December 15, 2017, 12:25:57 AM »
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?
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##### Mission Tracking Feedback / Satellite BLITS-M
« Last post by Sokolov on December 05, 2017, 09:01:56 AM »
BLITS-M is the glass spherical satellite. Diameter of the satellite is 220 mm. The one half of sphere is coated by interference dielectric layers for reflecting the laser beam with wavelength 532 nm. Orbital altitude is 1500 km. The planned time of the launching is May 2018.

The satellite will rotate with speed of 10 turn per minute around the axis perpendicular to the orbital plane.

Is it possible to identify the satellite by a telescope?

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##### Open a Discussion / Re: MPE
« Last post by danielhampf on November 28, 2017, 11:02:06 AM »
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
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##### Timing / Pulse collision avoidance
« Last post by danielhampf on November 27, 2017, 08:34:48 AM »
Hello everybody,
I am currently re-working our trigger hard- and software and I was wondering about pulse collision avoidance schemes at high rep rates. Currently, we use either:
1) Standard continuous triggering, ignoring pulse collisions. Works okay up to ~5 kHz in our configuration.
2) Burst mode: One ToF fire, one ToF quiet/receive. Works well at all rep rates, but you always loose half of the time.
I suppose for the really high rep rates, burst mode is about the best we can do. But what about 1 to 10 kHz? Do you have any recommendations of pulse collision avoidance schemes? I suppose we could trigger at, say, 5 kHz and reduce to 4.5 kHz every time the ToF come close to N x LI (laser interval). But is that the best we can do? What do you use? What would be an ideal scheme?
Thanks,
Daniel
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