Abstract: This disclosure relates to the field of space and can be used for radio navigation determinations using man-made satellites of the Earth, in particular, for monitoring the integrity of a system without participation of ground control segment facilities and monitoring stations allocated globally. The apparatus includes: enhancement of responsiveness of a user's notification about navigation signal uncertainty; reduction of costs for solving the problem of the system integrity monitoring due to absence of ground control and monitoring complexes allocated globally; exclusion of complementary radio links; improvement of system integrity monitoring certainty; growth of reliability.