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Forum:	Free Space
Topic:	Signaling the space station from the ground

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Your Reply: HTML is ON UBB Code is ON Smilies Legend	[QUOTE]Originally posted by MCroft04: [B]Could the Astronomical Association folks see the ISS when they flashed the light?[/B][/QUOTE]
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<table border=0 cellpadding=0 cellspacing=0 width="600"><TR><td bgcolor="#000000"><TABLE BORDER=0 cellpadding=4 border=0 cellspacing=1 WIDTH="100%"><TR bgcolor="#660000"><TD COLSPAN=2><CENTER><FONT SIZE="2" COLOR="#ffffff" FACE="arial, helvetica">T O P I C     R E V I E W</font></CENTER></TD></TR><TR bgcolor="#494949"><TD valign=top><FONT SIZE="2" FACE="arial, helvetica">Robert Pearlman</FONT></TD><TD><FONT SIZE="2" FACE="arial, helvetica">Spotting the International Space Station as it flies overhead is relatively easy: all you need is to do is be along its path, go outside at the projected time and hope for clear skies. <P>Spotting someone trying to signal you — if you are an astronaut aboard the space station — may seem equally simple, but its not. In fact, all attempts to do so have failed — until this week. Expedition 30 flight engineer Don Pettit <A HREF="http://blogs.airspacemag.com/pettit/2012/03/05/a-flashing-success/" TARGET=_blank>explains</A>: <BLOCKQUOTE><I>Early Sunday morning, at 01:27 our time, the San Antonio Astronomical Association, an amateur astronomy group, succeeded in flashing the space station with a one-watt blue laser and a white spotlight as we passed overhead. <P>This took a number of engineering calculations. Projected beam diameters (assuming the propagation of a Gaussian wave for the laser) and intensity at the target had to be calculated. <P>Tracking space station's path as it streaked across the sky was another challenge. I used email to communicate with Robert Reeves, one of the association's members. Considering that it takes a day, maybe more, for a simple exchange of messages (on space station we receive email drops two to three times a day), the whole event took weeks to plan.<P>I was ready with cameras for the early morning San Antonio pass and can report that it was a flashing success. Here's one of the pictures to prove it:</I></BLOCKQUOTE> <P><center><a href="http://blogs.airspacemag.com/pettit/files/2012/03/ISS-flash-full.jpg" TARGET="AirLock"><img src="http://www.collectspace.com/review/iss30_signalstation01.jpg" WIDTH="400" HEIGHT="255" BORDER="0"></a><P><iframe width="400" height="301" src="http://www.youtube.com/embed/2UoY15WDuHQ?rel=0" frameborder="0" allowfullscreen>

MCroft04

Could the Astronomical Association folks see the ISS when they flashed the light?

Robert Pearlman

Yes, in fact they were manually focusing the lights on the station as they visually tracked its path across the sky.

Jay Chladek

Pretty nice to see a view of my childhood city from space (I lived in SA from 1975 to 78 and then from 1979 to 1983). I can see I-35 and Loop 410. Looks like the laser location was somewhere just west of I-10 to the north of the city (probably to get away from the light pollution).

And Pettit is the perfect one to take a picture like this, given that he perfected the art of night photography when he was part of Expedition 6. I wonder if he used the same IMAX camera mount for this shot?

Pretty cool experiment actually.

ejectr

We need more guys like Don Pettit. He not only knows how to make things educational and useful. He knows how to have fun.

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