12 Meter Telescope - General Description


The National Radio Astronomy Observatory Arizona Operations 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 NRAO 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 12 Meter Telescope is the only millimeter-wavelength telescope in the U.S. operated full-time as a national facility. More than 150 visitors make use of the telescope annually. It 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 300 GHz. Operational reliability throughout is emphasized. Flexible spectral line and continuum backends allow the observer to match the instrument to the scientific goals. The development of multi-beam receivers and the new on-the-fly observing technique has inaugurated a new era of high-speed source mapping on angular scales complementary to those of the millimeter-wave interferometers. The telescope control system offers great flexibility, efficiency, and convenience, and provides a proven remote observing capability.

Present Instrumentation

Telescope -- The basic specifications of the 12 Meter Telescope, its site, receivers, and spectrometers are:


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 8 SIS receivers. A complete set of dual-channel SIS receivers is operational over the entire 68 - 300 GHz range.


The Observatory maintains two spectrometer systems: filter banks and an analog/digital Hybrid Spectrometer. There are 8 filter bank spectrometers with resolutions ranging from 30 to 2000 kHz. The Hybrid Spectrometer consists of 8 independent tunable IF sections and 1536 spectral channels. The Hybrid Spectrometer can be configured to 1, 2, 4, and 8 independent sections. The frequency spacing per channel is variable in steps of two continuously between 1.56 MHz and 24 kHz for each of two IF's. The maximum instantaneous bandwidth is limited by the receiver IF bandwidth, which is currently about 600 MHz.
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Last modified 25 April 2000; Webmaster