Complex sentence: At that point, it would begin to oscillate between approaching Earth and receding from Earth, before finally approaching close enough to fall along a path which would lead to a moderate-velocity impact (at a glancing angle) with Earth.
Split into simpler sentences: At that point, its orbital path began to oscillate between approaching Earth and receding from Earth. Its fate decided, it followed a path that would lead to a moderate-velocity impact (at a glancing angle) with Earth.