Hi Mario,
This should be easy enough to do. Take a look for these lines in 'runge.cpp' :
/* If we're closer than .1 AU, include Galileans separately: */
#define GALILEAN_LIMIT .03
#define TITAN_LIMIT .03
This is a situation where the code outpaced the comment. I originally included
the four Galilean moons as separate objects if one was closer than 0.1 AU to
Jupiter. Outside that distance, I just bumped up Jupiter's mass to include
the Galileans. (At that point, I hadn't added any of Saturn's moons as separate
perturbers.)
The inner batch of prograde irregular Jovians are within 0.1 AU. The outer
group are not.
Later on, I added Tethys, Dione, Rhea, Titan, and Iapetus as perturbers
if you were close enough to Saturn (again, just "throwing the mass into the
planet" if you were farther than TITAN_LIMIT from Saturn... the term TITAN_LIMIT
is confusing; it really should be SATURN_SATELLITE_PERTURBERS_LIMIT.)
Anyway. At about this time, I did a few tests to see how much difference
including the separate satellites made at various distances (i.e., check out
objects at various distances and see if satellite perturbers affected the
integrated motion noticeably). That led me to realize that 0.03 AU was
about right. It didn't lead me to notice that the comment still gave a
limit of 0.1 AU.
The perturbers matter a _lot_ for the inner satellites of both planets.
For example, in computing orbits for Io, Europa, Ganymede, and Callisto :
http://www.projectpluto.com/natsats/summary.htm
I obviously needed, for each object, to include the perturbations from
the other three. But even for Themisto, which orbits within 0.05 AU of
Jupiter :
http://www.projectpluto.com/natsats/J018S.htm
perturbations don't matter (which you can verify by changing GALILEAN_LIMIT
from 0.03 AU -- small enough so Themisto never "sees" the Galileans as
separate objects -- to, say, 0.07, large enough so that it always does.
The resulting orbit will be the same.)
-- Bill
On 2016-10-21 03:24, gecak3rbhlbpa5uihvgragqfq7575jiu7tbqsqkm@... [find_orb] wrote:
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> Hi, I am interested in determining the orbits of Saturn's irregular satellites. Other satellites will probably be important perturbers. Is there any way to add them to the calculations? I am looking for any pointers to go about doing this myself using the source code.
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> Cheers,
>
> Mario
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