This would be the start of an algorithm for either transferring to a moon or to another planet and accurately targeting the periapsis radius:

https://space.stackexchange.com/questions/9304/finding-accurate-periapse-rendezvous-radius-using-interplanetary-lambert-solver?rq=1

B-plane matlab code:

https://www.mathworks.com/matlabcentral/fileexchange/39100-b-plane-coordinates?s_tid=prof_contriblnk