Explorer 24 & 25

Explorer 24 was placed in orbit together with Explorer 25 from a single launch vehicle. Explorer 24 was identical in configuration to the previously launched balloon satellites Explorer 9 and 19. The spacecraft was 3.6 m in diameter, was built of alternating layers of aluminum foil and plastic film, and was covered uniformly with 5.1-cm white dots for thermal control. It was designed to yield atmospheric density near perigee as a function of space and time from sequential observations of the sphere's position in orbit.