  We present a study of the expected precision of the top quark mass
determination, measured at a linear e+ e- collider based on CLIC technology.
GEANT4-based detector simulation and full event reconstruction including
realistic physics and beam-induced background levels are used. Two different
techniques to measure the top mass are studied: The direct reconstruction of
the invariant mass of the top quark decay products and the measurement of the
mass together with the strong coupling constant in a threshold scan, in both
cases including first studies of expected systematic uncertainties. For the
direct reconstruction, experimental uncertainties around 100 MeV are achieved,
which are at present not matched by a theoretical understanding on a similar
level. With a threshold scan, total uncertainties of around 100 MeV are
achieved, including theoretical uncertainties in a well-defined top mass
scheme. For the threshold scan, the precision at ILC is also studied to provide
a comparison of the two linear collider technologies.
