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I'm making a spacecraft maneuver from one orbit to another. Firstly, I'm going to change the inclination, therefore, moving to a coplanar orbit.

  1. Where is it better to change the inclination, in terms of less Delta-V?
  2. If I know the current keplerian elements for my spacecraft, how to calculate the time, when the spacecraft will be on the above point, to make an optimal maneuver?

Found, that the optimal points are the orbital nodes. Are the orbital nodes at 90 and 270 degrees of true anomaly?

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If we neglect various perturbations and assume just Keplerian motion then the motion is planar and it all comes from basic geometry. If you make some idealized maneveur (instanteneous change of velocity) in some point then this point should lie on the initial orbital plane and simultaneously on the final orbital plane. So the point of this idealized maneuver must be at the intersections of the initial and desired orbital planes. If the maneuver is performed anywhere else the resulting orbit will never be coplanar with the desired one.

Because there are two orbits involved of course you can't say anything general about true anomaly of these intersection points. The periapsis/apoapsis line may have any angle with the desired orbital plane.

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