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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$^\circ$ declination) are:

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$^\circ$. For lower source declinations, the beam becomes increasingly elliptical. Sources lower than -25$^\circ$ 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 $^{\prime\prime}$ 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 $^{\prime\prime}$ 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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Gildas manager 2020-09-28