The selection of the Gregorian antenna configuration is the result of a multidisciplinary trade-off analysis involving the main antenna fields:
• RF design,
• mechanical design,
• thermal design,
• thermo-elastic performances,
• accommodation (envelop, earth deck footprint, height).
The main and sub reflectors of the EM, having respectively a diameter of 1.2 m and 0.7 m, consist of sandwiches composed by Ultra High Module CFRP facesheets and Aramidic honeycomb core. It shall be noted that the adoption of an Aramidic core was decided in order to reduce the EM model cost and comply with the budget of the project. The flight model will be provided of a CFRP core. The main reflector is supported by a CFRP tube. The sub-reflector is supported by a dedicated tower composed by 6 CFRP struts and a triangular sandwich plate.
The two reflectors, with their respective supports, are installed on a sandwich baseplate (Al facesheets and Al honeycomb-core). The thickness of the baseplate sandwich of the EM model is much higher than the flight model. The reason is that during the RF tests the EM model is supported in a cantilever configuration, having the I/F to the Compact Range positioner coaxial with the main reflector tube. Moreover the baseplate of the flight model has CFRP facesheets.
In figure 2 is shown the EM model of the FLANT antenna during the alignment activities. The verification of the contours of the two reflectors, as well as the alignment of the main component (main reflector, sub reflector, feed and baseplate) were performed using a Laser Tracker measurement system.
Figure 2: FLANT EM model during the alignment activities performed with a laser tracker (HPS GmbH)