Signal delay in the RadioAstron ground-space interferometer

The commissioning of the RadioAstron space radio telescope observing in a radio-interferometer mode with baselines exceeding the baselines of ground-based VLBI systems by more than an order of magnitude requires revision of the formula used to calculate the delay of the arrival of the signal from a distant source to the telescopes in ground-based observations. This formula is derived taking into account all corrections necessary to achieve the required accuracy; numerical estimates of the contributions of all terms are presented.