  Many existing optical meteor trajectory estimation methods use the
approximation that the velocity of the meteor at the beginning of its luminous
phase is equivalent to its velocity before atmospheric entry. Meteoroid kinetic
energy loss prior to the luminous phase cannot be measured, but for some masses
and entry geometries neglecting this loss may lead to non-negligible
deceleration prior to thermal ablation. Using a numerical meteoroid ablation
model, we simulate the kinematics of meteoroids beginning at 180 km with
initial velocities ranging from 11 km/s to 71 km/s, and compare model
velocities at the moment of detection to measurements. We validate the
simulations by comparing the simulated luminous beginning heights with observed
beginning heights of different populations of meteors detected with different
optical systems. We find that most low-velocity meteoroids have a significant
velocity difference of 100 m/s to 750 m/s (depending on meteoroid type, mass,
and observation system). This systematic underestimate of meteoroid speeds also
results in systematically lower semi-major axes for meteoroid orbits.
