Radiation in space is a potential risk to human health and electronic systems. Spacepix-3, the successor of Spacepix-2 , is a high voltage monolithic active pixel sensor (HV-MAPS) ASIC capable of measuring flux and distinguishing between types of radiation, protons, electrons, and ions. SpacePix3, improved version of the former SpacePix2, features a 64 × 64 pixel matrix with a pixel pitch of 60 µm and a total sensitive area of 3.84 × 3.84 mm$^2$. Analog signals from pixels are digitized by 32 10-bit column ADCs with a successive approximation register (SAR). The total power consumption is 43 mA from a 1.8 V power supply. Sensor diodes are biased at -150 V. Special Spacepix-3 functions are backside channel signal processing, SPI/LVDS readout modes, hit trigger output, debugging features, thermometer, radiation-hardened, multichip operation, and analog pixel output. Chip is implemented in 180 nm SoI technology.