Noise correlation matrices and noise parameters are useful for low-noise amplifier designers seeking to achieve the best noise performance out of their circuits. In some applications, such as radio astronomy, antennas and antenna arrays are part of receivers and, thus, modeling of the antenna noise is useful. Currently, antenna noise is modeled through antenna efficiency. A more accurate information on the highest-possible antenna efficiency is obtained from its S-parameters or noise parameters. In this letter, we show how the two-port S-parameters of an antenna can be determined by measuring its reflection coefficients inside two specifically sized Wheeler caps, in addition to a free-space measurement. We use the measurement to determine the noise correlation matrices and noise parameters of an antenna. The challenges of constructing appropriately sized Wheeler caps are discussed, and a new way of constructing a Wheeler cap is shown.