On May/29/2016 at 6:18 PM, Joe Pfeiffer wrote:
(Steve Willner) writes:

In article ,
Alain Fournier writes:
But as you have already pointed out, you really would want to do
computations using more than one body for this.

In principle, you need to take all bodies in the system into
account. Depending on the accuracy desired and on the masses and
distances, you may be able to ignore some of the least massive.

If you want to know which single body is the most influential, look
at references for "Hill Sphere."

Thank you! I hadn't encountered that term (no, I'm not even an amateur
astronomer), and what I found made for some interesting reading.

Yes it is interesting. But I'm not sure if it is the best answer for the
question this thread is concerned with. The Hill Sphere indicates the
region where a satellite will orbit the planet. But for computing a
spacecraft trajectory, you might prefer to use for a while a planet
centric system rather than a Sun centric system even if you are outside
the Hill Sphere. The spacecraft will move further away from the planet
so that won't last long and you will go back to the Sun centric system.
But the planet centric system might be a better approximation of the
trajectory for a while.

But that is being somewhat pedantic. If you are not to far from the
limit of the Hill Sphere, either inside or outside, I simply wouldn't
use a single body system as an approximation and go to a multi-body system.


Alain Fournier