Astronaut's photo of amateur astronomers "flashing" space station

 Pettit Files 2012 03 Iss-Flash-Crop-470

On Sunday morning, a group of amateur astronomers in San Antonio "flashed" the International Space Station with a blue laser and spotlight (sorry to disappoint) as it passed overhead. Astronaut Don Pettit snapped the photo above from the window of the ISS. This was way, way more complicated to achieve than you might think. From Pettit's post at Air & Space:

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. 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.

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