News from the PdBI

Maintenances and improvements during summer

The maintenance of the antennas is on schedule and should finish (hopefully) by the end of September. The antennas 1, 2, 4 and 6 have been thoroughly revised and the third is currently in the hall. Antenna 5 will be the last to enter maintenance. A complete check-up of each antenna was carried out on the mechanical level (engines, main reflector control, etc.) and on the electrical level (wire tightening, control of the sensors, etc). Apart from traditional maintenance, certain antennas underwent particular operations, for example the change of the secondary reflectors of antennas 1 and 4 by a new mirror in aluminium and a repaired aluminium mirror, respectively. On antenna 6, the overall sealing was improved. In spite of its recent commissioning, the surface of this antenna shows some degradations on its painted panels. After analysis, it seems that the silicon joints ensuring the panel sealing modified the paint chemically. A close monitoring of the panels is thus foreseen. Lastly, some strongly degraded carbonfiber/hostaflon panels of antenna 4 were painted at the SITEL Company and re-installed (essentially contiguous panels to the quadrupods with specially cut-out sections, of which we do not have spares). In parallel to the maintenance of the antennas, a number of operations were launched which are still on-going. The main items are:

• The rehabilitation of the gallery connecting the hall to the upper cable car station. This will facilitate the transport of goods when the reconstructed cable car starts its service as a freight elevator between St. Etienne en Devoluy and the Plateau de Bure.
• The installation of a centralized fire detection for all parts of our buildings.
• The revision of our electrical system and the change of the high voltage cell towards remote control, which will improve the security during operations.
• The installation of an optical fiber network between the correlator and the antennas. This operation will allow to increase the observing bandwidth in preparation for the next receiver generation.
• A feasibility study of a possible extension of the EAST tracks. A geophysical study is under way which shall determine if obstacles (caves, unstable grounds) are present between the station E24 (192 m from the NS/EW crossing) out to a future E72 (576 m from the crossing).
• maintenance of buildings (Painting, sealing, etc).

All in all, the observatory is having a quite busy summer season.

Bertrand GAUTIER

Preparation of the PdBI as VLBI station

The transport of the elements of the VLBI station (Maser and Recorder) was carried out mid-July. Taking into account the value and sensitivity of these elements, particular precautions were taken in order to ensure their safety during the transfer operations. After the tests in the IRAM Grenoble laboratories, the recorder was put back into its original casing and then transported to the lower cable car station under control of M.Torres. The maser was conveyed to the same point by J.M.Torre from the CERGA. A professional conditioner then created a double shock-proof packing around these two devices, thus protecting them from buffeting which could occur during the transport by helicopter. The recorder, not being able to support a tilt by more than 20$^\circ$ from the vertical below the helicopter, made it necessary to wait several days for sufficiently calm weather conditions for this delicate operation. On July 23th, the transfer could be carried out under perfect conditions (Fig 1).

  

Figure 1: Transport of the VLBI Terminal by helicopter

The cases were then transported inside the hall and carefully unpacked before setting up the recorder and the maser at their designated place in the correlator room (Fig. 2). A preliminary control of the devices showed that everything was operational. J.M.Torre carried out the start-up of the maser on Monday, July 29th. The current of the ionic pump is stable, and the drift of the Maser presently under study. All seems ready for the preliminary tests, which will take place in a few weeks.

Bertrand GAUTIER

  

Figure 2: The VLBI terminal at its final destination.