NRAO 12m Telescope Information

Last Update: JeffMangum - 07 Feb 2008

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The links on this page describe the 12 Meter Telescope system when it was operated by NRAO. The 12 Meter Telescope is currently being operated by the Steward Observatory as the Kitt Peak 12m Telescope.

Telescope Description

The National Radio Astronomy Observatory Arizona Operations operated and maintained a 12 meter diameter telescope on Kitt Peak, 50 miles (80 km) WSW of Tucson, Arizona, for astronomical observations at millimeter wavelengths until July 1, 2000.

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.

Telescope

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

• 12m diameter paraboloid enclosed within an astrodome
• Longitude: -111° 36´ 53.475"
• Latitude: +31° 57´ 11.99"
• Elevation: 1914 meters (6280 feet)
• Pointing Accuracy: 5 arcseconds

Receivers

As many as four receivers could be mounted simultaneously at offset Cassegrain foci on the telescope. Receiver selection was done by means of a rotating central mirror that could be accomplished in minutes. The receivers were configured remotely from the control room with a computer-aided tuning system. The standard receiver system at the 12 Meter telescope consisted of a 4 K closed-cycle cryostat containing up to 8 SIS receivers. A complete set of dual-channel SIS receivers was operational over the entire 68 - 300 GHz range.

Spectrometers

The Observatory maintained two spectrometer systems: filter banks and an analog/digital Hybrid Spectrometer. There were 8 filter bank spectrometers with resolutions ranging from 30 to 2000 kHz. The Hybrid Spectrometer consisted of 8 independent tunable IF sections and 1536 spectral channels. The Hybrid Spectrometer could be configured to 1, 2, 4, and 8 independent sections. The frequency spacing per channel was variable in steps of two continuously between 1.56 MHz and 24 kHz for each of two IF's. The maximum instantaneous bandwidth was limited by the receiver IF bandwidth, which was usually about 600 MHz.

Information for Observers

Receivers

The following table contains information about the frequency coverage, average receiver temperatures, and availability for the 12 Meter Telescope receivers. Note that the near the band edges mixer performance may be degraded.

12 Meter Telescope Receiver Information
Receiver	Frequency Range (GHz)	Trx (K)	Availability
3mmlo	68 - 90	100 (SSB)	all year
3mmhi	90 - 116	80 (SSB)	all year
2mm	133 - 180	125 (SSB)	all year
1mmlo	200 - 265	200 (SSB)	late fall through spring
1mmhi	265 - 300	300 (SSB)	late fall through spring
1mm Array	220 - 245	130 (DSB)	early winter through spring

Users Manual

Reports and Test Measurements

-- JeffMangum - 07 Feb 2008