Determination of an Intermediate Perturbed Orbit from Range and Range Rate Measurements at Three Time Instances . ... Very Long Baseline Interferometry (VLBI), Small Solar System Body (SSSB), an intermediate perturbed orbit, a fourth-order tangency to the trajectory of perturbed motion, range measurements, range rate measurements, range observations, range rate observations, computing the preliminary orbit of a small celestial body, the degree of approximation of the real motion, the Keplerian orbit. ...