Denpa (電波, denpa, literally "electromagnetic wave") was a Japanese artificial satellite launched to carry out studies of space radiation. The spacecraft is commonly described by its mission type as a radiation experiments satellite (REXS).

Mission purpose

Denpa was equipped with instruments intended to measure and characterise radiation in the near-Earth environment. Its primary objective was to gather experimental data on energetic particles and other radiation phenomena that affect spacecraft and spaceborne systems.

Development and operator

The project was developed and managed by the Institute of Space and Astronautical Science, an organization affiliated with the University of Tokyo. Development reflected early Japanese efforts to build and operate scientific satellites.

Launch

The satellite was placed into orbit on 19 February 1972. Records list this date as the time when Denpa began its on-orbit activities.

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