These, the newest of the DSSs to be designed and implemented, can be recognized by the hole in the middle of their main reflectors where on other DSSs you'd find a feed cone full of microwave equipment. The BWG design does not require sensitive equipment to be mounted in a cramped, moveable feedhorn or room mounted beneath the main reflector, where it is difficult to access for maintenance, repair, and upgrade. Instead, the BWG DSS directs the microwave beam through waveguides via five precision RF mirrors down into a basement room where equipment can be stably mounted on the floor and on balconies, with plenty of room for access. The image shows two of the beam waveguide reflectors inside the antenna mounting. These two reflectors maintain the microwave beam as the antenna moves around in azimuth.
Similar reflectors permit freedom of movement in elevation.
The 34-m BWG subnet supports mostly deep space missions, but may occasionally support a mission in high Earth orbit. They were originally built to support the Apollo lunar missions between 1967 and 1972. The 26-m DSSs were originally part of the Spaceflight Tracking and Data Network, STDN, operated by NASA's Goddard Space Flight Center in Greenbelt, Maryland. They were integrated into the DSN in 1985 when it needed them to track spacecraft in highly elliptical Earth orbits. Arraying A powerful technique for obtaining higher sensitivity in support of distant spacecraft is arraying .