ADE (Air Density Explorer) was a series of balloons, made from alternating layers of aluminum foil and Mylar polyester film, placed in orbit to study the density of the upper atmosphere and the relationship between solar radiation and air density. The Air Density Explorers were developed at NASA Langley and had a diameter of 3.7 meter (12 feet) and a mass of 7–9 kilograms. All were launched from Vandenberg Air Force Base.

 

Although Explorer 9 was the first such balloon launched (as well as being the first satellite placed in orbit by an all-solid-propellant rocket and the first to be successfully launched from Wallops Island), only its three identical successors were officially designated "Air Density Explorers."

 

ADE was a subprogram of NASA's Explorer series.

 

spacecraft	launch date	launcher	orbit
Explorer 19	Dec 19, 1963	Scout X-3	597 × 2,391 km × 78.6°
Explorer 24	Nov 21, 1964	Scout X-3	530 × 2,498 km × 81.4°
Explorer 39	Aug 8, 1968	Scout B	570 × 2,538 km × 80.7°