This experiment was designed to measure the amount of solar energy absorbed, reflected, and emitted by the Earth and its atmosphere. The experiment consisted primarily of two sets of bolometers in the form of hollow aluminum hemispheres, mounted on opposite sides of the spacecraft, whose optical axes were parallel to the spin axis. The bolometers were mounted on mirror surfaces so that the hemispheres behaved very much like isolated spheres in space. One bolometer in each set was painted black, and one was painted white. The black bolometer absorbed most of the incident radiation while the while bolometer was sensitive mainly to radiation with wavelengths longer than approximately 4 micrometers. The experiment was a success, and usable data were received from July 12, 1961, to October 20, 1961. Identical experiments were flown on TIROS 4 and 7, and a similar one was carried on Explorer 7.

From: Compendium of meteorological space programs, satellites, and experiments. NSSDC Publication no.88-03. NASA, 1988.