Total dose and single-event radiation hardness, and operation over extreme temperatures make silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) processes leading contenders for space applications. This paper reports noise degradation of 0.35-/spl mu/m partially-depleted SOI CMOS devices and a micropower, low-noise preamplifier following 63-MeV proton irradiation to 1Mrad (Si). Proton irradiation, relevant for space mission environments, was considered since it induces both ionizing and displacement damage. Preamplifier input-referred white-noise voltage was minimized at low power consumption by operating input devices in moderate inversion for high transconductance efficiency. Flicker-noise, important for gyros and other mission sensors having low-frequency outputs, was minimized by large-area pMOS input devices and careful management of noninput devices. Measured 1-Hz gate-referred, flicker-noise voltage density increased 24 and 32% for pMOS and nMOS test devices respectively following 1 Mrad (Si) irradiation. Measured 1-Hz input-referred noise voltage density increased 22% between a nonirradiated and radiated preamplifier sample, which agrees closely with the 24% increase expected since noise is dominated by pMOS input devices. Device small-signal transconductance and white-noise were largely unchanged while output conductance appeared to increase over a factor-of-three. This suggests a modest design margin is required to maintain flicker noise performance, while substantial design margin may be required to maintain open-loop voltage gain.