This paper presents the design and development of a Silicon Carbide (SiC) technology-based Non-Inverting Buck-Boost (NIBB) DC-DC power conversion unit for harsh space environment application with very high temperature (HT) (>150°C) and high radiation level. This work evaluates the capability of SiC bare dies for high temperature (>150°C) power electronics. The selection of critical passive components of the power converter is done through rigorous characterization of their performance metrics such as capacitance, inductance, leakage current, etc. under influence of increasing operating temperature. In this work, the design, prototype development, operation, and testing of a 100kHz, 100W NIBB DC-DC converter over the 25°-200° C ambient temperature range is demonstrated. The designed converter provides up to a 3.5A output load and convert the input side battery voltage levels of 28V, 120V, and 160V to a configurable output voltage from 30V to 48V, used as a standard for NASA space missions. The converter power stage, including the power semiconductor devices, inductor, and ceramic input and output filter capacitors, were placed inside a temperature controlled chamber for testing and temperature-variant characterization. The MOSFET gate drive circuit, input power source, and output load were placed external to the environmental chamber. Results at 200°C environment report a peak full load efficiency of 91.3%, which validates the developed converter architecture to be a suitable candidate for high-frequency HT power conversion.