National Radio Astronomy Observatory

Green Bank, West Virginia

Technical Discription: 140 Foot Radio Telescope

    Paraboloid diameter: 140 feet. Surface: 1/8 inch aluminum plate. Surface 
    tolerance:  0.030 inches at zenith.  Contains:  350 tons of aluminum, 35
    tons of concrete ballast, 5 tons of balancing blocks.

    60 feet above the surface.  Carries 1/2 tons of receiving equipment. 
    Position relative to paraboloid stable to 1/4 of an inch.

Declination Axis Shaft:
    Length: 67-1/2 feet overall; 57 feet between bearings. Diameter: 2 feet.
    Material: composite aluminum and steel shaft running in two spherical 
    roller bearings. Rotates 145degrees to -53degrees north of zenith and 92 
    degrees south.

    Serves to support the declination shaft and to rotate the antenna east
    and west about the polar axis by means of the polar gear.

Polar axis Shaft:
    Length: 67 feet. Diameter: 12 feet. Weight: 555 tons of steel; 170 tons
    of high density concrete ballast. Rotates 220degrees -110degrees east
    of meridian and 110degrees west.

Gear Sectors:
    Diameter of polar sector: 84 feet. Diameter of declination sector: 71

Spherical Bearing:
    Diameter: 17-1/2 feet. Surface tolerance: 0.003 inches. Floats on oil film
    0.005 inches thick.

    Height: 60 feet; 41 feet 6 inches to observation deck. Contains: 5700 tons
    of concrete and 140 tons of steel. Wall thickness: 3 feet. Houses control
    room, hydraulic and electric equipment, transformer vault, and electronic

Total Moving Weight:
    About 2,500 tons.

    Equatorial - Two mutually perpendicular axes.

Pointing Precision:
    10 arc seconds - about the diameter of a dime at 400 yards.

Research Program:
    Studies of known element and molecular spectral lines. Continuim research
    at other than line frequencies. Generally at wavelenghts between 2 and 40
    cm. Very-long base interferometry (VLB) using the 140-foot and non-NRAO

Date of Completion:
    Spring, 1965