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. Block 4 vehicles carried two one-inch focal length vidicons canted at 26 degrees from the vertical that provided global coverage of the Earth (contiguous coverage at the equator), along a 1,500 nm swath. The resolution varied from 0.8 nm at the nadir to 3 nm at the picture's edge. Besides a multi-sensor infrared subsystem, Block 4 also incorporated a high resolution radiometer that furnished cloud-height profiles. A tape recorder of increased capacity stored pictures of the entire northern hemisphere each day, while the satellite furnished real-time, direct local tactical weather coverage to small mobile ground or shipboard terminals.
The designation DMSP-4A (Defense Meteorological Satellite Program Block 4A) was retroactively assigned to these satellites.
|Type / Application:||Meteorology|
|Operator:||US Air Force (USAF), NRO|
|Power:||Solar cells, batteries|
|DSAP-4A F1 (OPS 6026)||1966-082A||16.09.1966||Va 4300-B6||Thor-DSV2U Burner-2|
|DSAP-4A F2 (OPS 6073)||1967-010A||08.02.1967||Va 4300-B6||Thor-DSV2U Burner-2|
|DSAP-4A F3 (OPS 7202)||1967-080A||23.08.1967||Va LE-6||Thor-DSV2U Burner-2|
|DSAP-4A F4 (OPS 1264)||1967-096A||11.10.1967||Va LE-6||Thor-DSV2U Burner-2|