  Ionospheric effects degrade the quality of radar data, which are critical for
the precision of the satellite ephemeris produced by space surveillance
systems; this degradation is especially noticeable for radars such as GRAVES
that operate in the very high frequency range. This article presents a simple
and effective method to correct for ionospheric effects, with an evaluation on
data obtained with GRAVES, the French space surveillance radar. This method
relies on GPS data, and our evaluation relies on GRAVES and DORIS data. We
found that the gain in terms of evaluated radial velocity can be as high as
1.76$\kappa$, where $\kappa$ is the typical root mean square of the noise on
radial velocity measurements for GRAVES (excluding ionospheric effects): the
error decreases from 2.60$\kappa$ to 0.83$\kappa$ for daytime satellite
overhead passes. Our conclusion is that, while this method is very simple to
implement, it has proven to be a good correction for ionospheric effects in
practice.
