The NRL built Solrad 9 or Explorer 37 satellite was one of the Solrad series that began in 1960 to provide continuous coverage of solar radiation with a set of standard photometers.

Solrad 9 was a spin-stabilized satellite oriented with its spin axis perpendicular to the sun-satellite line so that the 14 solar X-ray and UV photometers pointing radially outward from its equatorial belt viewed the sun with each revolution. Data were simultaneously transmitted via FM/AM telemetry and recorded in a core memory that read out its contents on command. Individual scientists and institutions were invited to receive and use the data transmitted on the 136 MHz telemetry band on the standard IRIG channels 3 through 8.

For the period July 1971 to June 1973, the core memory data of Solrad 10 were used rather than those from Solrad 9. The Solrad 10 core memory failed 11 June 1973, and Solrad 9 was heavily used until 25 February 1974, when the gas supply of the attitude control system was exhausted. Lacking attitude control, Solrad 9 was operationally useless and was turned off.