The DSAP-1 (Defense Satellite Application Program Block 1) satellites series, also known as P-35, was the first series of military meteorologal satellites of the USA. The project designation P-698BH was used concurrently with P-35 from June 1962 and P-35 became P-417 in October 1962.

Smaller and lighter than the original TIROS, the 100-pound TIROS-derived RCA satellite was shaped like a 10-sided polyhedron, 23-inches across and 21-inches high. A spinning motion, introduced on injection into orbit, was maintained on the early NRO weather satellites at about 12 rpm by small spin rockets. The spin axis was maintained perpendicular to the orbit plane by torquing the satellite against the Earth's magnetic field, the forces supplied through a direct-current loop around the satellite's perimeter. A ground command would cause the electric current to flow in the desired direction to generate the torque.