CONTENTS

 1 Introduction
2 RET input parameters
3 Phase function measurements
        3.1 Choosing the measurement site
        3.2 Measurement geometry
        3.3 Antenna characteristics
                  3.3.1 Transmit antenna
                  3.3.2 Receive antenna
        3.4 Receiver antenna displacement
        3.5 Link budget considerations
        3.6 Determination of parameters α and β
4 Excess attenuation curve measurements
        4.1 Determination of parameter σ_τ using initial slope
        4.2 Determination of parameter W (albedo) by curve fitting
        4.3 Determination of parameter W, α and β by curve fitting, when phase function data are not available