The main objective of the HINOTORI mission was the detailed study of solar flares during solar maximum. Principal investigations were (1) imaging of solar flare X rays in the range 10 to 40 keV by means of rotating modulation collimators and (2) spectroscopy of X-ray emission lines from highly ionized iron in solar flares in the range 1.7 to 2.0 A by means of a Bragg spectrometer. Wavelength scanning was achieved by the spacecraft revolution, with an offset pointing of the spin axis with respect to the sun. Investigations (1) and (2) each had a time resolution of 6 s. In addition, the following investigations were included: three solar flare X-ray monitors that recorded the time profile and spectrum of the X-ray flares in the range 2 to 20 keV, a solar flare gamma-ray detector for the range 0.2 to 9.0 MeV, a particle detector that monitored electron flux above 100 keV, and plasma probes for the measurement of electron density and temperature.