Radar polarimeter measures orientation of calibration corner reflectors

We have analyzed radar polarimeter signals from a set of trihedral corner reflectors located in the Goldstone Dry Lake in Cafifornia, and observed three types of scattering behavior: i) Bragg-like slightly rough surface scattering that represents the background signal from the dry lake, ii) trihedral corner reflector scattering that returns the incident polarization, and iii) two-bounce corner reflector scattering resulting from a particular alignment of a trihedral reflector. In the latter case, we can measure within about 3° the orientation angle of the apparent dihedral trough, even though the 2-m reflector is much smaller than the 10-m resolution element of our radar. Thus a radar calibration approach using trihedral corner reflectors should be designed such that precise alignment of the reflectors is ensured, as three-bounce and two-bounce geometries lead to very different cross sections and hence very different inferred calibration factors.