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 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
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).