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Description

The Plateau de Bure interferometer is located in the South of the French Alps, near St Etienne en Dévoluy in the Départment of 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 comprises

The interferometer consists of six antennas that can be positioned on 30 stations arrayed along a ``T'' shaped track as seen from this aerial view (see also Figure 1). The north-south arm is 232 m long, and the almost east-west oriented arm extends 216 m west and 192 m east of the intersection. The angle between the arms is $75\deg$. 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 of 60 $\mu$m rms. The antenna mounts incorporate self propelled transporters for moving the antennas along the tracks between stations. The antennas are equipped with dual-frequency receivers at 1.3 and 3 mm. The 3 mm SIS mixers cover the frequency range 81-115 GHz and have typical receiver noise temperature between 30 K and 50 K. The 1.3 mm SIS mixers cover the frequency range 205-250 GHz and have typical receiver noise temperature between 40 K and 60 K.

The receivers IF frequency is about 1.550 GHz, slightly variable by up to 50 MHz because one synthesizer is used to generate both the first and second local oscillator frequencies. For transmission through cables from the antennas to the correlator room, the signal is down converted to a 100-680 MHz baseband with the second local oscillator in each antenna. Additional oscillators (third LOs) select what section of the baseband is analyzed by the spectral correlator.

Eight correlator units are available. Each unit is a totally independant, 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 Section 5.2.

The receivers upper and lower sidebands are separated by the correlators using a phase switching technique. Rejections of better than 25 dB are obtained. The sideband gain ratio depends on receiver tuning, the ratio USB/LSB changing typically between <0.01 and 5.0.

An HP J200 computer and several embedded processors control the interferometer and acquire the data. The user interface is a variant of OBS, familiar to most users of the IRAM 30-m telescope. A Linux workstation is available for offline data reduction with the CLIC calibration program, and data archive before transfer to Grenoble.

Each interferometer ``configuration'', the 6 antennas on given stations, simultaneously provides 15 baselines (or uv-tracks). Since most projects will require more uv-coverage than this, the interferometer is run with several (about ten) projects progressing in parallel. All active projects that require a given configuration will be observed before the antennas are moved. Depending on the weather, configurations are changed every two months, so a project that requires two configurations will take about four months to complete.


\begin{figure}\psfig{figure=bure1.ps,width=15.0cm,angle=270.0} Figure 1: Example...
...e hatched circle
at the center shows the antenna shadowing region.
\end{figure}


next up previous contents
Next: Capabilities Up: An Introduction to the Previous: Contents
Gildas manager
2002-07-09