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Description

The NOrthern Extended Millimeter Array (NOEMA) is located in the South of the French Alps, near St Etienne en Dévoluy in the Départment Hautes Alpes. The interferometer's altitude is 2560 m at the intersection of the Azimuth and Elevation axes of the telescopes, and its longitude and latitude are 05:54:28.5 E and 44:38:02.0 N at the array phase center. The interferometer currently comprises

The seven antennas of the interferometer can be positioned on 32 stations layed out along a ``T'' shaped track (see Figure[*]).

The north-south arm is 368 m long, and the east-west oriented arm extends 216 m west and 544 m east of the intersection. The angle between the arms is 75$^\circ$. The station names are taken from the arm orientation and a two digit code indicating the distance from the track intersection (station W00) in 8 m units.

Each antenna is a 15 m diameter Cassegrain telescope constructed largely of carbon fiber. The primary mirrors have a surface accuracy below 50 $\mu$m rms. The antenna mounts incorporate self propelled transporters for moving the antennas along the tracks between stations. The antennas are equipped with four receiver bands, observing in dual polarization in the 3 mm, 2 mm, 1.3 mm, and 0.8 mm atmospheric windows, respectively. The 3 mm SIS mixers have typical SSB receiver noise temperature between 40 K and 55 K, the 2 mm mixers have typical noise temperature between 30 K and 60 K, the 1.3 mm SIS mixers have typical receiver noise temperature between 40 K and 60 K, and the noise temperatures at 0.8 mm are typically 30-50 K. More details about the receivers are given in Sect.[*], a summary can be found in Table[*].

The two IF-channels (one per polarization), each 3.6 GHz wide, are transmitted by optical fibers to the central building. Details on the IF transport and processing are given in Sect.[*].

The wide-band correlator WideX with fixed spectral resolution, capable of processing 28 baselines (8 antennas), is available in parallel with a narrow-band correlator, the latter comprising eight correlator units. Each of the eight units is a fully independent, flexible entity, capable of processing 15 baselines (6 antennas). Full 2-bit sampling scheme is used to give 88% efficiency. For details of the unit capabilities, see Sect.[*].

A 64-bit Linux computer and several embedded processors control the interferometer and acquire the data. The user interface is a variant of PaKo, familiar to most users of the IRAM 30 m telescope.

Each interferometer ``configuration'', i.e. the placement of the 7 antennas on given stations within the array, simultaneously provides 21 baselines. The interferometer is run with several projects progressing in parallel, allowing for a flexible scheduling of the observations well adapted to the actual meteorological conditions. Depending on the weather and on the season (antenna maintenance period in the summer semester, i.e. the array is observing in its 6 antenna D configuration), configurations are changed every two to six months, so a project that requires two configurations will on average take about four months to be completed.

Figure: Example of uv-coverage (left) and interferometer station layout (right) for the 7D configuration, as produced by the ASTRO UV_TRACK command. The shaded circle at the center of the uv-plane shows the antenna shadowing region.
\includegraphics[width=\textwidth]{noema-intro-uv-cover}


next up previous contents index
Next: Capabilities Up: An Introduction to the Previous: Contents   Contents   Index
Gildas manager 2015-03-01