Keywords: noema-intro

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## Spatial Resolution

Three primary 10 antenna configurations (see Table ) are available that can be combined to produce maps with different angular resolution. All three configurations are usually scheduled during the course of a year (see Table ). During the summer period (May until September) each antenna undergoes a thorough maintenance and the interferometer is operated in a 9 antenna D configuration.

Table: Configurations of the ten-antenna array
Name | Stations
10A | W27 | W23 | W08 | E68 | E24 | E16 | E03 | N46 | N29 | N20
10C | W23 | W20 | W09 | E23 | E18 | E10 | E03 | N20 | N17 | N11
10D | W12 | W08 | W05 | E10 | E04 | N17 | N13 | N09 | N05 | N02
9D | W12 | W09 | W05 | E10 | E04 | - | N13 | N09 | N05 | N02

The general properties of these configurations (numbers refer to a source at 20 declination) are:

- D - the compact configuration with just the D array for maximum sensitivity. This configuration is best suited for detection experiments and coarse mapping (resolution at 100GHz and at 230GHz). This configuration provides the lowest phase noise and highest sensitivity.
- C - the intermediate configuration provides a fairly complete coverage of the uv-plane (low sidelobe level) and is well adapted to combine with D for low angular resolution studies (2.6 at 100GHz, 1.1 at 230GHz) and with A for higher resolution (1.4 at 100GHz, 0.6 at 230GHz). C alone (2 at 100GHz, 0.9 at 230GHz) is also well suited for snapshot and size measurements, and for detection experiments at low source declination.
- A - the most extended configuration alone is well suited for mapping or size measurements of compact, strong sources. It provides a resolution of at 100GHz, 0.4 at 230GHz.

The three configurations can be used in different combinations to achieve complementary sampling of the uv-plane, and to improve on angular resolution and sensitivity. The combinations AC, ACD, and CD are well suited for all declinations above 0. For lower source declinations, the beam becomes increasingly elliptical. Sources lower than -25 declination cannot reasonably be observed from Plateau de Bure. Mosaicing is usually done with D or CD, but the combination ACD can also be requested for high resolution mosaics.

The antenna half-power beam size is 50 at 100GHz and the shortest possible antenna spacing is 24m to avoid collisions between two antennas. Even taking into account projection effects that shorten the effective baseline, sources larger than about 15 are already heavily resolved at 100GHz. In these cases, additional short-spacing observations should be acquired by observing a raster- or OTF- (On-The-Fly) map using the IRAM 30 m telescope1. The short-spacing information can then easily be added to the uv-tables obtained from the interferometer by means of the GILDAS MAPPING software. (see also Section).

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