RM 1, 2 (Discoverer 19, 21)

RM 1 (Discoverer 19)

Although flown within the Corona program, RM 1 and 2 (Radiometer 1 and 2) were not used for reconnaissance, but technical tests of instruments for the MIDAS early warning satellite program.

The satellites consisted of an instrument package integrated with the Agena-B upper stage, which provided attitude control and power during the mission. They carried no return capsule like the contemporary Corona spy satellites, but downlinked to ground stations by radio telemetry.

The satellites carried radiometers, which characterized the planet's background infrared radiation for use calibrating the MIDAS infra-red detection system. RM 2 also tested the reignition of the Agena engine.

Both satellites successfully reached orbit. RM 1 operated for 4.25 days or 26 orbits, while RM 2 operated for only 6 orbits.