From: "Dave McCarter" 
To: "ATM" 
Reply-To: "Dave McCarter" 


The Purple Crow LIDAR operates just south of here, at Deleware, Ontario,
that uses 7 nanosecond pulses, each of 75MW green light, 20 times per
second. It sends the beam straight up, and collects the echo light from
sodium atoms 80 to 100 km up with a rotating Mercury mirror. Despite
rumours to the contrary, it never gets cold enough in this part of Canada
for the mirror to solidify and so point off the zenith.

There is a Ku band radar also looking up, that shuts the beam off if an
aircraft gets too close. Not so much because it would blind the pilot, but
more to keep from punching holes in the wings, fuel tanks, etc. I have
observed from the driveway while the laser was running, and it is amazing
how the moths that are attracted to the beam go poof when they enter it.

Their URL is:http://pcl.physics.uwo.ca/pclhtml/mainpage.html Very
instructive on a number of counts.

Dave

--- BBBS/NT v4.00 MP