Flag of the Space Shuttle Challenger.  The shuttle flags are generally flown at the Kennedy Space Center while the orbiter was on the launch pad or on a mission, though possibly the practice did not start until after the Challenger disaster.  NASA did have a Challenger flag at the shuttle program retirement ceremony in 2011.[1]
Self-made, with all dimensions guesstimated from looking at images of shuttle flags.  Space Flight Awareness logo copied from File:NASA-SpaceFlightAwareness-Logo.svg.  For example, this image of a Challenger flag for sale on EBay shows the design.
Carl Lindberg