titolo
bandiera

RESULTS

Antenna efficiency measurements aims to verify:

  1. if enhancing the surface accuracy with new panels increases the antenna gain peak value
  2. if the antenna gain curve is flat over elevation, so confirming that the active surface is properly working.

The gain curve will be flat if the deformations are known with good accuracy at the different elevations. On order to get deformations data, measurements on the mirror were made both using the theodolite (at EL=45°, 60°, 75°, 90°) and photogrammetry (at EL=15°, 30°, 45°, 60°). 45° and 60° data allow to cross check the two techniques and to be confident that merging the two set of data is appropriate. Applying a polinomial fit to the 15°÷90° data set a complete map of deformations is available. The rms of the residuals of the best fit parabola is the primary mirror accuracy term to be composed with panels and subreflector rms. A remind of the Noto surfaces accuracy is:


Comparing measurements at 22GHz with and without enabling the active surface.

The known surface deformation was not optimized at the date of this measure because El ≥ 45° data only were available.

Comparing measurements at 32GHz with and without enabling the active surface.

Available a complete set of deformation. The receiver is a primary focus mounting.

Comparing measurements at 43GHz with and without enabling the active surface.

Available a complete set of deformation. The receiver is a secondary focus mounting.In this case the active surface is also used to recover manufacturing inaccuracy of the subreflector surface.

Measurements at 43GHz complete

In this case the active surface is also used to recover manufacturing inaccuracy of the subreflector surface.
For more information on the system contact: Alessandro Orfei Web page maintained by: Gian Paolo Vargiu
a.orfei@ira.cnr.it g.vargiu@ira.cnr.it