Far-UVC light as a new tool to reduce microbial burden during spacecraft assembly

Aims: This work aims to investigate far-UVC light at 222 nm as a new microbial reduction tool for planetary protection purposes which could potentially be integrated into the spacecraft assembly process. The major advantage of far-UVC (222 nm) compared to traditional germicidal UVC (254 nm) is the potential for application throughout the spacecraft assembly process in the presence of humans. Testing the efficacy of 222-nm light at inactivating hardy bacterial cells and spores isolated from spacecraft and associated surfaces is a necessary step to evaluate this technology. Methods and Results: We assessed survival of Bacillus pumilus SAFR-032 and Acinetobacter radioresistens 50v1 exposed to 222-nm light on proxy spacecraft surfaces simulated by drying the bacteria on aluminum coupons. The survival fraction of both bacteria followed a single stage decay function up to 60 mJ/cm2, revealing similar susceptibility of both species to 222-nm light, which was independent of the fluence rate. Conclusions: Irradiation with far-UVC light at 222 nm is an effective method to decontaminate the proxy spacecraft materials tested in this study. Significance and Impact of Study: Microbial burden of spacecraft hardware is closely monitored for planetary protection purposes. Current methods of reducing surface microbial contamination such as wiping with a solvent or exposure to vapor hydrogen peroxide are time consuming, disruptive to the assembly process, and susceptible to recontamination. Exposing spacecraft surfaces to far-UVC light is a promising technique for microbial reduction during the assembly process with minimal increase in engineering scope of work.