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John Shelton, an engineer at Green Bank, uses a transit scope to align the quadrant detector under the dish of the Green Bank Telescope. In order to measure the precise amount of movement of the feed arm due to wind, and to temperature and gravitational fluctuations, engineers installed a rangefinder and mirror system beneath the surface of the dish. The rangefinder is on the feed arm and points directly through a hole in the dish surface. There, it is reflected by a mirror into a measurement device that compares all relative movements of the feed arm that affect the distance measured by the ranger.

Telescope Technicians J. D. Nelson and Nathan Sharp examine the position of one of the Green Bank Telescope’s 2004 surface panels. Their goal is to get the entire surface shaped into a section of a perfect parabola, so that it will reflect radio waves precisely to a point 200 feet above it, called the prime focus.

Telescope Technician Nathan Sharp uses this panel adjustment tool to slightly change the position of one of the Green Bank Telescope’s 2004 surface panels. His goal is to get the entire surface shaped into a section of a perfect parabola, so that it will reflect radio waves precisely to a point 200 feet above it, called the prime focus.

It takes years to completely repaint the Green Bank Telescope, and painters arrive every summer to keep this endless task going. Here, a painter is suspended beneath the backup structure of the GBT where he and his fellow painters have 7,652 trusses to paint.

Green Bank Engineers Ike Johnson (lying down at the finder scope) and Jeff Cromer are aligning the mount for the Green Bank Telescope’s quadrant detector. Ike is viewing a beam that has come from the feed arm of the GBT over 60 feet above them. In wind and temperature extremes, and under its own weight, the long feed arm sways. A laser from the arm gets aligned down to a reflector and into a rangefinder that helps the telescope operators know how well the GBT’s receivers are aligned to the waves bouncing up from the dish.

The Green Bank Telescope’s 2.3-acre dish is supported by 7,652 pieces of steel welded and joined together in a complex framework known as a backup structure, or BUS. It weighs around 2.3 million pounds. Keeping the GBT strong and sound requires constant vigilance.