Auto simultaneous referencing air-to-air background oriented schlieren

A system for imaging density changes in air caused by a moving target, comprising:

• a target airborne vehicle flying at a predetermined airspeed and altitude over a background;
• a sensor airborne vehicle comprising a target sensor and flying in formation with said target airborne vehicle at an airspeed and altitude such that said target airborne vehicle remains fixed in a field-of-view of said target sensor and such that refractive wake features of said target airborne vehicle are included within said field of view of said target sensor;
• and
• a computer system,
• wherein said target sensor is configured to capture a series of image airs from said sensor airborne vehicle, each image pair including a reference image of said background taken in advance of said target airborne vehicle such that said reference image is undisturbed by said target airborne vehicle, and a target image taken with said target airborne vehicle over said background, and
• wherein said computer system is configured to:
• for each image pair, time shift said reference image to adjust for a time delay relative to said target image;
• and
• process the series of image pairs by analyzing comparative displacement of features in said background between said time-shifted reference images and said target images as a result of said target airborne vehicle's refractive wake features.