The spin-axis tilt (SAT), which is also known as dynamic imbalance or coning error, is one of the dominant errors deteriorating the attitude determination accuracy of spinning spacecraft. It is experienced as the misalignment of the major principal axis of the spacecraft from the intended body spin axis. This paper evaluates a straightforward SAT estimation algorithm by means of real in-flight data. The algorithm is based on the Singular Value Decomposition (SVD) method and makes use of the attitude rates estimated by an attitude determination filter. The accuracy of the algorithm is investigated by using telemetry data gathered by the CONTOUR spacecraft in 2002. The results are compared with those obtained by an averaging method for the SAT determination. The SVD-based SAT estimation algorithm (SVD-SAT) provides robust estimation results without being significantly affected by sensor biases. This is in contrast with the averaging method, which is shown to be more sensitive to other errors.