>energy levels were 100mJ/100ps pulse width or 300mJ/250ps pulse width. Just to clarify, a Joule is a watt second. AKA one watt for one second. To get 0.1 Joules packed into 100picoseconds you would need: 0.1Watt-secs/100E-12 secs = 1 billion watts But only for 100pico seconds at a time. If you pulse this five times per second as they did in the paper, it is the same amount of power as your 500mW continuous laser. But there's a huge difference between 500mW coninuous, and a billion watts on very short pulses. The beam may look the same to your eye but it's easier to detect the stronger (yet brief) pulses. A note about how it would look - they used 532 nm which I believe is right in the middle of the green color which would look exactly like your laser although at 5 flashes per second it would have a strong flicker to it. They also used 1064nm which would be invisible. - George Roberts http://gr5.org -------------------------------------------------- From: "David Tiller" <dtiller@captechventures.com> Sent: Friday, August 27, 2010 1:32 PM To: "Dale Ireland" <direland@drdale.com>; "Allen Thomson" <thomsona@flash.net>; "SeeSat" <SeeSat-L@satobs.org> Subject: RE: Laser retroreflectors on recent NOSS? > Dale, > > The paper states the the lasers used were at 532nm (and 1064nm via a > doubler), and that the average pulse energy levels were 100mJ/100ps pulse > width or 300mJ/250ps pulse width. > > Also note that the paper was from 1997, and that the one satellite > mentioned by name was TOPEX/Poseidon. They do make reference to satellites > in a particular orbit, but not by name. > > It makes a fascinating read, and if you've got a wicked-accurate clock, a > photomultiplier tube, a 10-12" telescope, and a very low pulse width > laser, you could do ~ 1cm accuracy SLR (satellite laser ranging). > > -- > David Tiller > Lead Consultant/Architect | CapTech Ventures > > > > -----Original Message----- > From: seesat-l-bounces+dtiller=captechventures.com@satobs.org on behalf of > Dale Ireland > Sent: Fri 8/27/2010 1:24 PM > To: 'Allen Thomson'; 'SeeSat' > Subject: RE: Laser retroreflectors on recent NOSS? > > I wonder how powerful of a green laser would be needed to see a > reflection? > I have a 500mw green laser. > Do you know the power and wavelength of the Navy ranging lasers? > Dale > >> -----Original Message----- >> From: seesat-l-bounces+direland=drdale.com@satobs.org >> [mailto:seesat-l-bounces+direland=drdale.com@satobs.org] On >> Behalf Of Allen Thomson >> Sent: Friday, August 27, 2010 9:31 AM >> To: SeeSat >> Subject: Laser retroreflectors on recent NOSS? >> >> >> >> I just came across a paper(*) that, viewed at the right >> angle, suggests that at least some of the more recent NOSS >> satellites carry laser retroreflectors (corner cubes). These >> may be used for precision orbit determination, with one laser >> being on the grounds of the Naval Research Laboratory's >> Midway Research Center at 38.49921 N, 77.37109 W. >> >> I'm not sure if the retroreflectors, even if present, would >> produce any visible effect under ordinary conditions, but it >> might be something to look for. >> >> >> (*) http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA334920&Locat >> >> _______________________________________________ >> Seesat-l mailing list >> http://mailman.satobs.org/mailman/listinfo/seesat-l >> > > > _______________________________________________ > Seesat-l mailing list > http://mailman.satobs.org/mailman/listinfo/seesat-l > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > http://mailman.satobs.org/mailman/private/seesat-l/attachments/20100827/9b94bdeb/attachment.html > _______________________________________________ > Seesat-l mailing list > http://mailman.satobs.org/mailman/listinfo/seesat-l > _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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