The significance of low cost small satellites used for scientific research and practical applications continuously grows. Current satellite OBC (On-Board Computer) microcontrollers have integrated various digital peripherals and interfaces. However, a common Real Time Unit (RTU) requires interfacing to simple analogue sensors and actuators. Here we present a novel RTU microcontroller which includes a 13-bit Analog-to-Digital Converter (ADC) and two 12-bit Digital-to-Analog Converters (DAC). Furthermore, it includes a 32KB internal SRAM memory and a 32 KB internal flash memory. This enables an easy construction of a software-controlled embedded system which is easily interfaced to existing hardware sensors and actuators. The chip is produced in IHP 250 nm technology using radiation hardening by design. The operating frequency is 80 MHz. A 3-bit clock divider, as well as clock- and power-gating are used for reducing power consumption which is measured to be 0,8 W in operation.