We are pleased to announce the IRAM highlight of 2005! First interferometric fringes have been detected on the new baseline which connects the two new stations, N46 and E68 (Fig. 1). The fringes were detected both at 3mm and 1mm, on the 730m long baseline, between the stations at the end of the northern and eastern track extensions. The new stations will be implemented into the observing schedule of the upcoming winter 2005/2006 session. We now look forward, with great expectations, to a new era of high-resolution imaging of the Plateau de Bure interferometer.
In the evening of October 24 and after a final verification of the electrical and optical fiber connections to N46, antenna 4 was moved to the end of the newly completed northern track extension and clamped on the new station. Only a few hours later, the antenna and the interferometer were ready for the crucial attempt to obtain fringes, and at 09:59 UT of October 25, Patrick Chaudet, operator at the Plateau de Bure observatory, measured fringes on all the baselines connected to N46. The following night, under excellent weather conditions and after a short baseline session to measure the position of the antenna within a few hundred microns, he was able to observe stable fringes on B0218+357, a gravitationally lensed system with strong radio emission.
Encouraged by the success in bringing station N46 on-line quickly, we rapidly proceeded to complete the eastern track extension and station E68 before the season's first snowfall. After some initial verifications, the track and the station were made available for first light on November 7h, and first fringes were obtained at 3mm on all baselines in the early morning of the following day. The most exciting result, however, was achieved in the night to November 9 when an antenna was positioned on station N46. After a few hours of debugging and trouble-shooting the operators Michel Dan and Emmanuel Salgado reported first fringes at 1mm on the 730m baseline to station N46. Subsequent baseline measurements refined the positional accuracy of the antenna on E68 and improved the fringe stability on the baseline to N46 (Fig. 2).
The successful commissioning of the new stations is the result of several years of work to achieve new horizons for high angular resolution imaging with the six-element interferometer. While the new stations are already planned for the upcoming winter period, efforts are now directed towards planning and implementing an efficient strategy for moving antennas out to (and back from) E68 and N46 under snowy winter conditions at the Plateau de Bure.