Despite its size and complexity, the PMBSS is one of the most lightweight precision-alignment truss structures ever designed and built. When fully deployed, it measures approximately 24 feet tall by 19.5 feet wide by more than 11.5 feet deep, and weighs only 2,180 pounds. Once fully assembled and populated, the PMBSS will support a mission payload and instruments that weigh more than 7,300 pounds. With a full launch load, it will support the equivalent of 12 times its own weight.

 

Read: Testing Completed on NASA’s James Webb Space Telescope Backplane

 

The backplane of NASA’s James Webb Space Telescope was mounted to a structure for static load testing to verify it can withstand the rigors of launch and hold the weight needed to support the telescope in space. Image Credit: Northrop Grumman

The PMBSS is the stable platform that holds the telescope’s science instruments and the 18 beryllium mirror-segments that form the 21-foot-diameter primary mirror nearly motionless while the telescope peers into deep space. The primary mirror is the largest mirror in the telescope — the one starlight will hit first.