|
The 2013 saw the completion of the Atacama Large Millimeter Array (ALMA). The array consists of 66 antennas and
operates in Chile at the Chajnantor plateau at 5000 m altitude.
25 of the 12 meter diameter antennas have been delivered by the AEM consortium constituted by Thales Alenia Space
France, Thales Alenia Space Italy, European Industrial Engineering (EIE GROUP), and MT Mechatronics.
The purpose of this paper is to present a summary of the results obtained by the antennas during the different test
campaign and a summary of the problems aroused during the erection and the assembly phases and the relative lesson
learned.
The results of the engineering performances and antenna systems, performed during the acceptance phases of the first
antennas, have shown the full correspondence between what was expected during the design phase and what has been
achieved in the final product, with a difference of less than 10% and the trend tends to be conservative.
As for "on sky antennas performances", all the tests done in the 25 antennas showed excellent results. The antenna All
Sky Pointing Error and Offset Pointing Error with and without metrology correction turned to be always excellent. The
Fast Motion Capability with the tracking requirements after a step motion was better than an order of magnitude
compared to the requests.
Four years of on-site activities and the various phases of construction and assembly of 25 antennas have been a major
challenge for the European Consortium. The problems encountered in this phase were many and varied: interfaces
issues, design and foundation problems, manufacturing and assembly errors, electrical installation, shipment delays,
human errors, adverse weather conditions, financial aspects, schedule, etc.
The important is being prepared with an "a priori", that is a risk assessment which helps ensuring the best solution for
the complete customer satisfaction of the scientific and technical requests. Despite the already excellent knowledge in
the field by the companies involved, this period has undoubtedly represented an opportunity for growth and learning. A
better understanding of the problems relates to such large project, will be essential for the future major projects.
|
