Scintillation

The index of refraction of air depends on many factors, including temperature, humidity, and density. If coherent (in phase) laser light travels through an inhomogeneous medium such as air, some of the light will traverse a longer optical path and destructively interfere at the receiver. If the effect varies quickly in time, this can present signal processing difficulties. A video [1] taken from the receiving station at W6YX, Stanford's Amateur Radio Station, shows the effects of suspected scintillation on a steady laser signal across a 10km path from Skyline Boulevard. Non-coherent light sources like LED’s are less prone to this phenomenon. SSI's OpComms group has not explored the math and physics behind scintillation, but is aware that it may have serious implications for eventual satellite development.