Estimates for the Set-theoretic Distance between Orbits of Celestial Bodies . ... It is reasonable to use preliminary simple criteria for the proximity to intersection based on estimates of set-theoretic distance ( , 0 ) between orbits , 0 of celestial bodies , 0 . ... We describe here two simple criteria and one more complicated one. ... The third one requires calculation of the distance itself and it amounts to solving a trigonometric equation of the 8-th degree. ...