12 Meter Description


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12 Meter Telescope - General Description


The Arizona Radio Observatory operates and maintains a 12 meter diameter telescope on Kitt Peak, 50 miles (80 km) WSW of Tucson, Arizona, for astronomical observations at millimeter wavelengths.

The ARO 12 Meter Telescope began as the 36 Foot Telescope, the telescope responsible for the birth of millimeter-wavelength molecular astronomy. During a period of explosive growth in this new area of astronomical research dozens of molecular species known to exist in the interstellar medium were first detected at the 36 Foot. In 1984, the telescope's reflecting surface and surface support structure were replaced and the 36 Foot was re-christened the 12 Meter. Subsequently, the scientific program has evolved from one dominated by observing programs in Astrochemistry to one with a broader mix of studies of molecular clouds and Galactic star formation, evolved stars, Astrochemistry, and external galaxies. The 12m offers users flexibility and the opportunity to respond quickly to new scientific developments. The Observatory maintains low-noise receiving systems covering all atmospheric windows form 68 GHz to 180 GHz. Operational reliability throughout is emphasized. Flexible spectral line and continuum backends allow the observer to match the instrument to the scientific goals. The telescope control system offers great flexibility, efficiency, and convenience, and provides a proven remote observing capability.

 

Telescope:


  
Table 1: Telescope and Site Characteristics
Site    
  East Longitude: -111 36 53.475
  North Latitude: +31 57 12.0
  Elevation: 1914 meters (6280 feet)
Telescope    
  Primary Reflector Diameter: 12.0 meters
     
  Focal Ratio  (f/D)  
  Prime Focus: 0.42
  Cassegrain Focus: 13.8
     
  Surface Accuracy : 75 m rms
  Mount: Elevation over Azimuth
  Slew Rate : 68"/minute
  Pointing Accuracy : 5" rms
  Elevation Limit : 14.7 degrees
  Enclosure: Tracking astrodome with movable door
  Aperture Efficiencies: 52% at 70 GHz
    49% at 115 GHz

 

Present Instrumentation:

 

Receivers

As many as four receivers are mounted simultaneously at offset Cassegrain foci on the telescope. Receiver selection is by means of a rotating central mirror and can be accomplished in minutes. The receivers are configured remotely from the control room with a computer-aided tuning system. The standard receiver system at the 12 Meter telescope consists of a 4 K closed-cycle cryostat containing up to 6 SIS receivers. A complete set of dual-channel SIS receivers is operational over the entire 68 - 180 GHz range.

 

 

Spectrometers

The Observatory maintains two spectrometer systems: filter banks and an a Digital Correlator.  

Filters:

There are 8 filter bank spectrometers with resolutions ranging from 30 to 2000 kHz.

Table 3: 12m Filter Spectrometer Characteristics
Filter Resolution Channels per Bank Filter Banks Available
2 MHz 256 2
1 MHz 256 2
500 kHz 256 1
250 kHz 256 1
100 kHz 256 1
30 kHz1 128 1
1 Series option only.

 

Millimeter Auto Correlator (MAC):

  
Table 4: Millimeter Autocorrelator (MAC) Configurations
Total Bandwidth Useable Bandwidth1 Channels ∆ν2 Spectral Resolution
(MHz) (MHz)   (kHz) (kHz)
2 IF Modes
800 600* 2048 390.6 781.2
800 600 4096 195.3 390.6
400 300* 4096 97.6 195.3
400 300 8192 48.8 97.6
200 150* 8192 24.4 48.8
200 150 16384 12.2 24.4
100 75* 16384 6.1 12.2
100 75 32768 3.0 6.1
4 IF Modes
800 600* 1024 781.2 1562.0
800 600 2048 390.6 781.2
400 300* 2048 195.3 390.6
400 300 4096 97.6 195.3
200 150* 4096 48.8 97.6
200 150 8192 24.4 48.8
100 75* 8192 12.2 24.4
100 75 16384 6.1 12.2
1  The useable bandwidth takes account of the 75% efficiency of the analog filters.
2  NOTE: This is the frequency sampling interval, not the FWHM channel width,
   for a given channel. The FWHM channel width is 2.0 times this value.
All values in this table refer to each IF.
Modes tagged with a * are produced by dropping the last half of the lags.

 


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For problems or questions regarding this web contact [tfolkers{at}email{dot}arizona{dot}edu].
Last updated: 11/08/11.