The MAGSAT satellite was launched on October 30, 1979 into a sun-synchronous dawn-dusk orbit, of 97° inclination, 350 km perigee, and 550 km apogee. It contains a precision vector magnetometer and a cesium-vapor scalar magnetometer at the end of a 6m long graphite epoxy scissors boom. The magnetometers are accurate to 2γ. A pair of star cameras are used to define the body orientation to 10 arc sec rms. An "attitude transfer system" measures the orientation of the magnetometer sensors relative to the star cameras to ∼ 5 arc sec rms. The satellite position is determined to 70 meters rms by Doppler tracking. The overall objective is to determine each component of the earth's vector magnetic field to an accuracy of 6γ rms. The MAGSAT satellite gathers a complete picture of the earth's magnetic field every 12 hours. The vector components are sampled 16 times per second with a resolution of 0.5γ. The data will be used by the US Geological Survey to prepare 1980 world magnetic field charts and to detect large-scale magnetic anomalies in the earth's crust for use in planning resource exploration strategy in the years to come.