On a clear day in the spring of 1862, two orbs rose quietly into the skies above southeastern Virginia. For the soldiers in the Confederate encampment below, it must have been a wondrous, if demoralizing, sight. These strange forms were Union hot-air balloons, each with two observers in the basket, spies in the firmament. If the observers had cameras—and word was that they did—they would be able to produce perfect records of what they saw, instant maps of the Confederate positions that would soon, no doubt, be conveyed to the upper reaches of the Union Army’s chain of command. “We watched with anxious eyes their beautiful observations as they floated high up in the air,” Confederate general James Longstreet later wrote of the encounter. To Longstreet and his troops, it was clear they were witnessing a turning point in the history of war. It was also clear that there was nothing they could do about it. The balloons, Longstreet lamented, were “well out of range of our guns.” One hundred and fifty-five years later, on a searingly hot afternoon in June 2017, Steve Suddarth, a former US Air Force colonel, is radioing air traffic control for clearance to take off from Albuquerque International Sunport, the city’s main airport. The flight, he tells the tower, is a “photo mission.” Riding shotgun in Suddarth’s white single-prop Cessna, I am not sure I would have used such a mild term to describe our plan. The plane is equipped with a military-grade surveillance camera, and we intend to watch wide tracts of the city in a way many of its residents probably never imagined was even possible.