Four primary 6 antenna configurations (see Table ) are
available that can be combined to produce maps with different angular
resolution. All four configurations are usually scheduled during the
course of a year. During the summer period (May until September) each
antenna undergoes a thorough maintenance and the interferometer is
operated in the 5 antenna D configuration (equal to the 6 antenna D
configuration given in Table
but without station N02).
The combinations, named AB, BC, CD are reasonably suited for all
declinations above 0 (see Tables
to
).
For lower source declinations, the beam becomes increasingly
elliptical. Sources lower than -25
declination cannot
reasonably be observed from Plateau de Bure.
The four configurations can be used in different combinations to achieve complementary sampling of the uv-plane, and to improve on angular resolution and sensitivity. Mosaicing is usually done with D or CD, but the combination BCD can also be requested for high resolution mosaics.
The antenna half-power beam size
is 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
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 30m 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.
Tables -
give a summary of beam sizes
for natural weighting and various observing
frequencies. Observing was supposed to be limited to 6 hours before
and after transit and to elevations higher than 20 degrees. Typical
uv-coverages and resulting beam shapes for the six-element array are
shown in Fig.
(D and CD),
(BCD and
BC), and
(A and AB).
Dec. | 85 GHz | 115 GHz | 230 GHz | PA | |||
Maj. | Min. | Maj. | Min. | Maj. | Min. | ||
80 | 6.41 | 5.88 | 4.74 | 4.35 | 2.37 | 2.17 | 92 |
60 | 6.45 | 5.45 | 4.77 | 4.03 | 2.38 | 2.01 | 96 |
40 | 6.45 | 5.54 | 4.77 | 4.09 | 2.38 | 2.04 | 104 |
20 | 6.13 | 6.04 | 4.53 | 4.46 | 2.26 | 2.23 | 91 |
0 | 7.35 | 6.12 | 5.43 | 4.52 | 2.71 | 2.26 | -18 |
-20 | 11.43 | 5.68 | 8.44 | 4.20 | 4.22 | 2.10 | -6 |
Dec. | 85 GHz | 115 GHz | 230 GHz | PA | |||
Maj. | Min. | Maj. | Min. | Maj. | Min. | ||
80 | 4.48 | 4.15 | 3.31 | 3.06 | 1.65 | 1.53 | -90 |
60 | 4.35 | 3.86 | 3.21 | 2.85 | 1.60 | 1.42 | 86 |
40 | 4.44 | 4.02 | 3.28 | 2.97 | 1.64 | 1.48 | 89 |
20 | 4.42 | 4.21 | 3.26 | 3.11 | 1.63 | 1.55 | 40 |
0 | 5.41 | 4.23 | 4.00 | 3.12 | 2.00 | 1.56 | 6 |
-20 | 8.38 | 3.82 | 6.19 | 2.82 | 3.09 | 1.41 | -178 |
Dec. | 85 GHz | 115 GHz | 230 GHz | PA | |||
Maj. | Min. | Maj. | Min. | Maj. | Min. | ||
80 | 2.12 | 1.96 | 1.56 | 1.45 | 0.78 | 0.72 | 79 |
60 | 2.15 | 1.86 | 1.59 | 1.37 | 0.79 | 0.68 | 80 |
40 | 2.20 | 1.93 | 1.62 | 1.42 | 0.81 | 0.71 | 69 |
20 | 2.40 | 1.96 | 1.77 | 1.45 | 0.88 | 0.72 | 37 |
0 | 3.39 | 1.99 | 2.50 | 1.47 | 1.25 | 0.73 | -166 |
-20 | 4.60 | 1.89 | 3.40 | 1.40 | 1.70 | 0.70 | 6 |
Dec. | 85 GHz | 115 GHz | 230 GHz | PA | |||
Maj. | Min. | Maj. | Min. | Maj. | Min. | ||
80 | 1.21 | 1.12 | 0.89 | 0.83 | 0.44 | 0.41 | 84 |
60 | 1.21 | 1.05 | 0.89 | 0.77 | 0.44 | 0.38 | 74 |
40 | 1.25 | 1.06 | 0.92 | 0.78 | 0.46 | 0.39 | 59 |
20 | 1.40 | 1.06 | 1.03 | 0.78 | 0.51 | 0.39 | 37 |
0 | 1.74 | 1.02 | 1.28 | 0.75 | 0.64 | 0.37 | 22 |
-20 | 2.66 | 0.98 | 1.97 | 0.72 | 0.98 | 0.36 | 10 |
Dec. | 85 GHz | 115 GHz | 230 GHz | PA | |||
Maj. | Min. | Maj. | Min. | Maj. | Min. | ||
80 | 0.97 | 0.91 | 0.71 | 0.67 | 0.35 | 0.33 | 76 |
60 | 0.99 | 0.86 | 0.73 | 0.64 | 0.36 | 0.32 | 61 |
40 | 1.07 | 0.87 | 0.79 | 0.64 | 0.39 | 0.32 | 44 |
20 | 1.29 | 0.84 | 0.95 | 0.62 | 0.47 | 0.31 | 31 |
0 | 1.70 | 0.78 | 1.25 | 0.57 | 0.62 | 0.28 | 22 |
-20 | 2.58 | 0.74 | 1.91 | 0.54 | 0.95 | 0.27 | 12 |
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