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What is this image?

graphic of twin OWL spacecraft over the Earth

Floyd's image is a graphic of the Orbiting Wide-angle Light collectors (OWL), a proposed experiment with twin spacecraft that will help us answer some of the questions about ultra-high energy cosmic rays (UHECRs). It is some of the most exciting science now in the cosmic ray field, and something Floyd has been involved in from the start.

The two orbiting OWL 'eyes', at a constant distance of separation, simultaneously view an air shower caused by a UHECR entering Earth's atmosphere. Each spacecraft is slightly tilted so that they both view the same area. The cones in the image display the volumes of atmosphere in which the instruments can measure the ultraviolet glow caused by an air shower. Observing the air shower from space allows us to monitor a huge volume of atmosphere to increase the chances of seeing these scarce events. Two spacecraft allow for much more accurate location of the air shower than one could, and so provide a more accurate measurement of the direction the UHECR is coming from.

The white line represents the path of an air shower heading down through the atmosphere toward Earth (at a fairly steep angle in this image). The glow from the air shower interactions increases along the path, and OWL sees the brightest portion of the path, that near the Earth.

Edward Fong, who was a midshipman from the US Naval Academy at the time, created this graphics program working with the output of a Monte Carlo simulation developed by one of Floyd's colleagues - another astroparticle physics theorist, John Krizmanic.