It was folded and carried into orbit, together with ejection and inflation equipment, as part of the payload of Explorer 40.

Since that time it has been necessary to rely solely on the Smithsonian Astrophysical Observatory (SAO) Baker-Nunn camera network for tracking.

The data are derived from studies of the drag on a 3.6 m (12 ft) in diameter low-density sphere caused by short-term differences in solar activity.

Density values near perigee were deduced from sequential observations of the spacecraft position using optical (Baker-Nunn camera network) and radio and/or radar tracking techniques.

[4] This experiment was designed to determine systematic changes of air density as a function of altitude, latitude, and time of day, by measuring the drag on a 3.6 m (12 ft) in diameter low-density sphere with ground tracking.