One of the dominant features of the Webb telescope is its tennis-court-sized sunshield. The sunshield protects the observatory from unwanted light, keeping it cool and allowing it to detect heat from faraway objects in the universe.
Getting such a huge sunshield into orbit, however, is a technical feat. Webb's sunshield will be folded up during launch, and then unraveled in a seven-hour deployment process as the Webb telescope reaches its destination a million miles from Earth. Two deployable towers, or Mid Boom Assemblies (MBA), serve to stretch the sunshield open. The completion of this hour-long process triggers another mechanism that separates the sunshield's five layers, readying the sunshield for work.
NASA and Mary Estacion (STScI)
Publication: November 17, 2010