Time lapse of James Webb Space Telescope's Pathfinder mirror backplane arriving at Goddard Space Flight Center for critical assembly testing. Webb's backplane is the large structure which holds and supports the big hexagonal mirrors of the telescope. The backplane has an important job as it must support the weight of the 21-foot (6.5 m) diameter mirror, but it also will be carrying 5300 lbs (2400 kg) of telescope optics and instruments.