Near-Field Measurements of the SWAS Antenna

ERICKSON, N.; Tolls, V.

20th ESTEC Antenna Workshop on Millimetre Wave Antenna Technology and Antenna Measurements


The SWAS spacecraft contains two receiver systems operating at frequencies near 490 and 550 GHz, coupled to an off-axis Cassegrain antenna having an aperture of 53 x 68 cm. Alignment of the antenna and proper focus and co-alignment of the receivers was a significant challenge for the program. Near field scanning was chosen as the lowest risk, most feasible option. The hardware used worked with the existing receivers in their flight configuration and produced a very large signal to noise ratio in the measurements with no apparent spurious contributions. Measurements were performed on the antenna which completely verified the alignment and predicted far field patterns consistent with a beam efficiency of 90 %. The scans also verified the co-alignment of the beams of the two receivers to within <0.4 arcmin.