News from the Plateau de Bure Interferometer

Prototype of the Next Generation Receiver

In view of current plans to upgrade the Plateau de Bure antennas by a new receiver generation, the present winter observing period started with the arrival of a prototype Next Generation Receiver (NGR). It was installed in one of the antennas (antenna 6) at the end of November, followed by a period of initial testing in December. It turned out that the receiver efficiency at certain tuning frequencies is lower than expected from previous tests carried out in the receiver lab at Grenoble. Also, the image band rejection is only about a factor 4-5, again less than what was initially expected. These issues are presently being investigated and we hope to have them solved before the start of the summer observing period.

We will report in the next Newsletter in more detail on these issues, but also offer insights on progress being made and remaining challenges in equipping all six antennas with NGRs.

To stay compatible with the present receivers, the prototype operates for the time being in dual frequency mode at 2.6mm and 1.3mm, employing a frequency scheme different from the one used in the present receivers to match the 580MHz bandwidth of the current system.

According to the different frequency scheme of the prototype receiver, proposers should be aware of the fact that observations in the image sideband at 2.6mm and 1.3mm will yield useful data only on baselines which include antennas still equipped with the current receivers.

Due to some subtleties regarding the creation of correct continuum uv-tables from data obtained with the prototype receiver, proposers whose programs were (or will be) observed after December 2005 are advised to get in touch with the Science Operations Group (sog$@$iram.fr).

Roberto NERI, Jean-Yves CHENU, & Jan Martin WINTERS

New extended configurations scheduled

The beginning of the year 2006 was highlighted on Plateau de Bure by moving the array for the first time into the new extended A-configuration, including the new stations N46 and E68. The change of configuration was accomplished on Friday, 13th January 2006 in less than one day, thanks to excellent weather conditions and a perfect preparation of the tracks, in terms of snow clearing and de-icing. Special thanks go here to Laurent Broche, Bruno Convers and Laurent Lapeyre, all three mechanics at the Plateau de Bure.

After only a few hours, André Rambaud, operator at Plateau de Bure, obtained fringes on all baselines and later in the night Patrick Chaudet (the second operator on site during that week) obtained a baseline solution with an excellent precision. The first scientific project was successfully observed in the new A configuration the following morning, again under excellent atmospheric conditions and on January 24th already 14 tracks have been completed.

This tremendous success would not have been possible without the dedication and hard work of many people, last but not least those who did the snow cleaning! Thanks to all of those involved for their enthusiasm and for their efforts that made this success possible!

Roberto NERI, Bertrand GAUTIER, & Jan Martin WINTERS

Weather conditions and proposal status

The array was moved into the new C configuration in mid December and the most extended new A configuration was scheduled from mid January on. It is planned to move to the B configuration around mid of February and to the C configuration by mid of March. The switch back to the most compact configuration D is foreseen before mid of April. According to these plans, it will not be possible to complete projects requesting deep integrations and low-resolution mapping before end of April.

The beginning of the winter period saw good observing conditions up to Christmas and excellent atmospheric stability since mid of January. Occasional high winds have somewhat reduced the observing efficiency, but by January 24 we had observed 32 out of 43 A-rated and 56 B-rated programs, and already 7 have been classified as being successfully completed.

As far as A-rated projects are concerned, we look forward to bring many of these to completion before the end of the current winter semester. B-rated projects are likely to be observed only if they fall in a favorable LST range. We remind users of the Plateau de Bure interferometer that B-rated proposals which are not started before the end of the winter period have to be resubmitted.

Global VLBI observations, which include the array in the 3mm phased-array mode, are planned from May 4 to 10, 2006.

Investigators, who wish to check the status of their project, may consult the interferometer schedule on the Web at ../PDBI/ongoing.html. The page is updated daily.

Roberto NERI & Jan Martin WINTERS