A standard silicon-on-insulator (SOI) CMOS process has been used to fabricate metal-semiconductor field-effect transistors (MESFETs). MESFETs with gate lengths as small as 0.4 microns were demonstrated. The devices have been tested at room temperature in the frequency range DC to 20 GHz. Excellent DC and small-signal transfer characteristics were obtained with device breakdown voltages greatly exceeding those of the CMOS devices. The DC parameters of the device were measured over the temperature range -196°C to +150°C and used to develop a TOM3 Spice model that accurately describes MESFET operation over the entire temperature range. We have used the model to demonstrate a number of SOI MESFET based circuits including an operational amplifier and a proportional-to-absolute-temperature (PTAT) voltage source. Measurements of the device after irradiation with up to 100 krad(Si) x-rays show a 20 mV shift in the threshold voltage. The results demonstrate that SOI MESFETs may be a viable technology for analog and mixed signal circuits that are required to operate in the Moon and Mars environments.