The second NASA Small Astronomy Satellite (SAS-2) was dedicated to gamma-ray astronomy in the energy range above 35 MeV. SAS-2 was launched on 1972 November 15 and began operations on 1972 November 19.

To minimize the background flux from cosmic-rays, SAS-2 was placed in a low Earth equatorial orbit having a 2 degree orbital inclination. Its apogee and perigee were 610 km and 440 km respectively, with an orbital period of about 95 minutes.

During the ∼6 months of the mission, 27 pointed observations (typically a week in duration) were made, resulting in about 55 percent of the sky being observed, including most of the galactic plane. On 8 June 1973, a failure of the low-voltage power supply ended the collection of data.

Mission Characteristics

Payload

Science Highlights

• The first detailed look at the gamma-ray sky
• Established the high energy component of diffuse celestial radiation
• Correlated the gamma-ray background with galactic structural features

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