ESRO-1A / Aurorae (European Space Research Organisation) was a 80 kg, cylindrically shaped, solar-cell-powered spacecraft instrumented with seven scientific experiments chosen to measure a comprehensive range of auroral effects. The measurements include auroral luminosity, ionospheric composition and temperature, and the flux, type and energy spectra of trapped and precipitated energetic particles (electrons of energies 1 to 30,000 keV. The spacecraft was placed in a low polar orbit with its axis of symmetry magnetically aligned along the earth's field. It had operated satisfactorily for 18 months, except for the tape recorder which failed after 7 months.

ESRO 1B / Boreas conducted correlative studies with the identical satellite ESRO 1A / Aurorae.