軌き道どう長ちょう半はん径けい

• 軌き道どう短たん半はん径けい

  Refers to the semi-minor axis, the shortest radius of an elliptical orbit, in contrast to 軌道長半径.

• 長ちょう半はん径けい

  A more general term for semi-major axis, not limited to orbits; 軌道長半径 explicitly specifies orbital context.

Compound of 軌道 (orbit), 長 (long), and 半径 (radius), directly translating the concept of semi-major axis.