The satellite, built by the Johns Hopkins University Applied Physics Laboratory (APL), was proposed and operated by MIT's Center for Space Research (CSR).

It was launched on a Scout vehicle from the Italian San Marco platform (Broglio Space Center) near Malindi, Kenya, into a low-Earth, nearly equatorial orbit.

The spacecraft typically operated in a rotating mode, spinning at one revolution per 95-minute orbit, so that the LEDs, tube and slat collimator experiments, which looked out along the Y-axis, could view and scan the sky almost continuously.

The spacecraft was launched from the San Marco platform off the coast of Kenya, Africa, into a near-circular, near-equatorial orbit.

The instrumentation consisted of one 2.5-arc-minutes and one 4.5-arc-minutes Full width at half maximum (FWHM) modulation collimator, as well as proportional counters sensitive over the energy range from 1.5 to 10-keV.

[6] The density and distribution of interstellar matter were determined by measuring the variation in the intensity of the low-energy diffuse X-ray background as a function of galactic latitude.

This collimator was inclined by 31° with respect to the equatorial plane of the satellite so that Scorpio X-1 was observed while the Z-axis was oriented to the Virgo Cluster of galaxies.

Among its most important results were: Lead investigators on SAS 3 were MIT professors George W. Clark, Hale V. Bradt, and Walter H. G. Lewin.

Other major contributors were Profs Claude R. Canizares and Saul Rappaport, and Drs Jeffrey A. Hoffman, George Ricker, Jeff McClintock, Rodger Doxsey, Garrett Jernigan, Lynn Cominsky, John Doty, and many others, including numerous graduate students.