[2][3] SAS 2 was the second in the series of small spacecraft designed to extend the astronomical studies in the X-ray, gamma-ray, ultraviolet, visible, and infrared regions.

The instrumentation consisted principally of a guard scintillation detector, an upper and a lower spark chamber, and a charged particle telescope.

Four solar paddles were used to recharge a 6 amp-h, eight-cell, nickel–cadmium battery and provide power to the spacecraft and telescope experiment.

Thin tungsten plates, averaging 0.010 cm (0.0039 in) thick, were interleaved between the spark chamber modules, which had an active area of 640-cm2.

The single-piece plastic scintillator dome surrounded the whole assembly except at the bottom to discriminate against charged particles.

During the lifetime of the experiment from 15 November 1972 to 8 June 1973, approximately 55% of the celestial sphere, including most of the galactic plane, was surveyed.