A crowdsourced image of the sky. Multiple observers are positioned at GPS coordinates that form the points of a grid. At the moment of the satellite flyover, they take photographs looking directly up. Their images are stitched together to form a single large image, opposite to the one taken by the satellite.
A smartphone app will let the observers self-organize at the times of satellite flyovers in any geolocation, coordinate the action, take the pictures in sync, and see the resulting crowdsourced image and the satellite image.
The human array forms an optical sensor, a large eye of a new socio-technological apparatus.