Northrop Grumman Corporation accepted delivery of the aft-optical system (AOS) from teammate Ball Aerospace, marking the completion of all flight optics for NASA's James Webb Space Telescope.

Northrop Grumman is under contract to NASA's Goddard Space Flight Center in Greenbelt, Md., for the design and development of the Webb Telescope's optics, sunshield and spacecraft.

The AOS is a precision beryllium rectangular optical bench that houses the tertiary mirror and the fine steering mechanism installed at the center of the Webb Telescope's primary mirror.

The AOS is surrounded by a shroud to eliminate stray light and two large radiator panels to keep the assembly cold. This subsystem collects and focuses the light from the secondary mirror and feeds it into the science instruments.

"Our teammates at Ball Aerospace have done an excellent job on all of the optical elements, including the testing and completion of the aft-optical system," said Scott Texter, Webb Optical Telescope Element manager for Northrop Grumman Aerospace Systems.

Since May 2012, the AOS has undergone a series of thermal, vibration and cryogenic testing to demonstrate that it can withstand the rigorous vibration environment of launch and remain precisely aligned to function at extremely cold temperatures in space. The system successfully completed all performance testing earlier this month.

"This was a unique technical challenge, requiring unprecedented fabrication and testing of the mirrors to ensure operation at the cryogenic temperature of 40 Kelvin," said Texter.

The AOS will remain at Ball Aerospace to be used in integrated testing with the flight actuator drive unit. The team will finish building the cryogenic electronics that control the mirrors and the source plate assembly that is used to test the complete Optical Telescope Element for the Webb Telescope.