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 the first prototype Next Generation Receiver. 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 solved them 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 (sogiram.fr).

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