Variable emittance vane type louvers are flight proven, lightweight assemblies for temperature control of spacecraft equipment and structures. Applications have included both exposed and covered configurations, depending upon spacecraft performance requirements. One of the most recent applications of a new covered configuration is the louver assembly flying on the Extreme Ultraviolet Explorer (EUVE), which was successfully launched on a Delta II expendable launch vehicle (ELV) from Cape Canaveral Air Force Station (CCAFS) on June 7, 1992 into a 528 kilometer circular orbit.
Because EUVE was designed for on-orbit exchange of payload and bus equipment, a new louver-cover design was required which provided protection of the astronauts and louvers during on-orbit servicing in the Space Transportation System (STS).
Described in this paper are features of the louver-cover design which were implemented to provide equal or better thermal control compared to that of the traditional louver-sunshield assembly. Data from thermal vacuum performance testing are included and results are compared to those for a traditional louver-sunshield assembly. The comparisons indicate better than expected performance was achieved for the new louver-cover design.
The enhanced thermal performance and increased durability of the improved louver-cover design make it an ideal application for future missions where on-orbit servicing or extreme micrometeorite environments are encountered.