Optical fiber waveguides may be subjected to unique adverse environments onboard spacecraft, including wide temperature ranges and low dose rate radiation exposures. Since fiber reliability is essential, an accelerated lifetest has been designed to simulate deployment on the Space Station. The initial induced losses following exposure at -150 C are much lower in the fibers with pure than in those with doped silica cores. Good long term recovery is evident at this low temperature in fibers which do not contain P provided light is being transmitted in the waveguide since photobleaching is the dominant recovery mechanism in both types of fiber at -150 C. Except for the P-doped waveguides, the worst-case incremental losses are extrapolated to be < 10 dB/km for a 10 year, 1 rad/day exposure at -150 C with a -20 dBm signal in the fiber. Thus, optical fibers are attractive for use in spacecraft exposed to low dose rate natural space radiation environments.