DSAP-4A (Defense Satellite Application Program Block 4A) was the fourth version of the military meteorological satellites of the Defense Meteorological Satellite Program.

The DSAP-4A satellites, slightly larger than their predecessors, was 30 inches in diameter, 29 inches high, and weighed 175 pounds. Still spin-stabilized, the satellite nonetheless provided improved weather coverage.

Previously, the single 1/2-inch focal length RCA vidicon television camera in Block 1 and Block 2 satellites furnished a nadir resolution of 3-to-4 nautical miles (nm) over an 800 nm swath, with significant gaps in coverage of the Earth at the equator.