  Far-side images of solar active regions have become one of the routine
products of helioseismic observations, and are of importance for space weather
forecasting by allowing the detection of sunspot regions before they become
visible on the Earth side of the Sun. An accurate assessment of the quality of
the far-side maps is difficult, because there are no direct observations of the
solar far side to verify the detections. In this paper we assess far-side
imaging based on the time-distance helioseismology method, by using numerical
simulations of solar oscillations in a spherical solar model. Localized
variations in the speed of sound in the surface and subsurface layers are used
to model the perturbations associated with sunspots and active regions. We
examine how the accuracy of the resulting far-side maps of acoustic travel
times depends on the size and location of active regions. We investigate
potential artifacts in the far-side imaging procedure, such as those caused by
the presence of active regions on the solar near side, and suggest how these
artifacts can be identified in the real Sun far-side images obtained from
SOHO/MDI and GONG data.
