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First VLT Mirror Cell and 8.2-m Dummy Mirror Arrive at Paranal
17 listopada 1997
After a long journey from Europe, the first Very Large Telescope mirror cell (VLT M1 cell) and a concrete 8.2-m dummy mirror were unloaded in the Port of Antofagasta on October 31, 1997. From here, they were transported by special trucks to the Paranal Observatory.
The M1 cell - on which the first 8.2 m mirror will later be placed - measures 9 x 10 metres and stands 3.5 m tall; it weighs about 20 tonnes. Thus the special, oversize transport from Antofagasta to Paranal had to move slowly and carefully. The concrete dummy mirror with a diameter of 8.2 metres weighs the same as the real Zerodur mirrors (23 tonnes) and was stored in a special box. It took 3 days for the convoy to cover the 130 kilometres along the desert road.
Both the mirror and the cell arrived well at Paranal and a thorough check showed that they had suffered no damage during the transport from Europe. Accordingly, green light was given right away to send the first, polished 8.2-metre VLT mirror of Zerodur from the REOSC factory in St. Pierre du Perray, south of Paris, to Paranal. The mirror, securely fastened in a box of the same design as the one in which the dummy mirror was moved, departed by river barge on the Seine a few days later. It was loaded upon an ocean-going vessel in the Port of Le Havre on November 12. The expected arrival time in the Port of Antofagasta is mid-December.
After unloading of the M1 cell and the concrete dummy mirror in front of the Mirror Maintenance Building (MMB) at the base camp of the Paranal Observatory, a series of comprehensive operational tests was initiated. They will fine-tune the delicate procedures and provide the necessary experience to the involved staff so that they can later handle the large and fragile Zerodur mirrors safely. The dummy mirror allows very realistic tests of these operations, but without the risk.
The concrete mirror was first moved into the MMB and placed under the socalled "Mirror-Handling Tool" which has been specially designed to lift and handle the very thin (17 cm) mirror without any risk of breakage. The mirror was then lifted from its transport box. Thereafter, the M1 cell will be moved into position below the mirror and the mirror will be lowered down on the computer controlled (active) supports which are incorporated in the M1 cell.
At a later stage, the M1 cell and the concrete mirror will be brought up the mountain road to the first of the four 8.2-m telescopes (Unit Telescope no. 1, or UT1) and attached at the bottom of the `telescope tube'. Again, this will serve to adjust the mechanical parts and to balance the telescope without risk to the real mirror. Before First Light will be achieved next year, the cell will be taken down to the MMB for exchange of the dummy mirror with the real one and then brought back up again to the telescope.
The mechanical integration has now reached the point where the entire structure of the UT1 can be moved around its vertical axis and, since some days, also about the horizontal axis.
In the neighbouring enclosure, the erection of the mechanical structure of UT2 continues. At this moment, preparations are being made to attach the heavy centerpiece.
The following series of press photos was taken during the past 2 weeks and document the above story in some detail.
More information is available at the ESO website about the VLT project.
Please note that since these images were electronically recorded and were primarily obtained to document the VLT construction activities, they may not be of sufficient quality for all reproduction purposes.