Calibration of a Large Array of Reflectors Using Lunar InSAR Imagery

Feinian Wang, and K. Sarabandi

Ground array of reflector antennas is being considered for deep-space communications by NASA. An external phase calibration is necessary to ensure constructive interference of all array elements in a desired direction. Moon is selected as the calibration target since it falls within the array far-field. With the help of SAR (Synthetic Aperture Radar) imaging technique, each array element can form a SAR image of a same lunar surface pixel, and the phase differences (interferograms) among these images can be used to perform phase calibration. Orthogonal PN (pseudo-noise) codes are employed to modulate the transmit signals of different array elements, in order to distinguish their backscatter at a common receiver.

Figure 1: Concept of ground array calibration using Moon as calibration target.

Figure 2: Lunar SAR imagery obtained by two ground array elements.