When the 200-foot tall telescope in Green Bank, West Virginia needs feed maintenance, operators drive its 140-foot (43-meter) dish to within four feet of the ground and set its parking brakes. An engineering tower is winched on railway wheels until the apex of the telescope is nestled inside. Then, in a protected space, the sensitive equipment can be removed, replaced, and finely adjusted. These days, the 140-foot has not been using a receiver at its apex. Instead, a sophisticated second reflector sits here to bounce waves to receivers nestled in the hole in the center of the dish.
Telescope Converter Parts
Dish-shaped radio telescopes can focus their radio waves directly up to the focus and into a receiver there or use a second reflector at the focus to shoot the waves to a suite of receivers in the middle of the dish. The 140-foot telescope in Green Bank, West Virginia was originally a prime focus type, but in 1974 was adapted into the other type, known as a Cassegrain. In the ever-busy machine shop on site, Basil Gum, Tony Haerl, and Herb Hanes construct casings that will nestle in the throat of the 43-meter dish and safely protect its new receiver family.
Rare Look at 140-foot Maintenance
When the 200-foot tall 140-foot dish telescope in Green Bank, West Virginia needs feed maintenance, operators drive its dish to within four feet of the ground. An engineering tower is winched up until the apex of the telescope is nestled inside. Then, in a protected space, the sensitive equipment can be removed, replaced, and finely adjusted. These days, the 140-foot (43-meter) has not been using a receiver at its apex. Instead, a sophisticated second reflector sits here to bounce waves to receivers nestled in the hole in the center of the dish.
The Teeth of a Beast
To tilt up and down, the 140-foot (43-meter) telescope in Green Bank, West Virginia rides on an enormous toothy gear. The 42-foot diameter gear is bolted to the back of the dish’s superstructure. Two brass pinions engage this bull gear. The brake, which you can see to far right, is one of several designed and built by Goodyear Tire and Rubber Company.
Fitting the Yoke
Assembled yoke of the 140-foot (43-meter) telescope on the ground in Green Bank, West Virginia during its construction in the 1960s. The yoke supports the telescope’s tilt axis and keeps the giant telescope balanced as it arcs across the sky. Pacific Crane and Rigging Company completing the final assembly of the yoke components (made by Sun Shipbuilding) to the hub section (built and machined by Westinghouse). The hub section consists of a 3.5% nickel steel casting welded to 6 inch, A 201 plate for a finished machined weight of 190 tons. When completed the entire yoke is a single weldment. Its completed weight is 1,125,000 pounds of steel to which are added 1,300,000 pounds of counterweight concrete and portable ballast rocks in the tubular, bottom sections.
140-foot Control Room Upgrade
In 1972, the control room of the 140-foot telescope in Green Bank, West Virginia got an upgrade. Analog systems were replaced by computer systems, and by the time of this photo in 1985, operation of the telescope required only one staff member instead of four.