Very little fanfare around this, but apparently FDev snuck a couple of little treats into the journals with update 7. Things we've been wanting for years.
Barycenter scan events... and the missing orbital parameters for scans: Longitude of Ascending Node, and Mean Anomaly.
All of those being available will make it possible for people to create animated orreries of star systems, since they were exactly what was missing. There are some minor caveats of course: While EDDN is carrying the new orbital parameters for scans, it doesn't currently support the barycenters, since they're a new event type. EDSM probably doesn't have any support for it either. And I think all of these journal changes are in Odyssey only.
I have my API asking for the barycenter events, for those who run EDD with EDAstro submissions turned on, or are using the IGAU plugin for EDMC. And I'm tracking the orbital parameters when available. It'll probably be a long time before there's anything substantial enough recorded to do anything interesting with it. But it's a start.
I'm not sure what I'll do with it yet, but I started putting together some of the math to calculate current positions/orbits of bodies based on these orbital parameters, and discovered that it's still incomplete. Because, why not?
With newer scans, there's enough to create the complete system hierarchy now, and describe all of the individual orbits. But a 100% accurate orrery would still have to fudge some things.
Normally when you use the typical 6 or 7 parameters to describe an orbit, they're relative to a specific reference plane, and reference direction. In ED though, for moons and barycentric orbits (binaries and the like), the reference plane is the equatorial plane of the parent, depending on axial tilt. We have axial tilt for bodies, but no indication of which direction it's tilted. Plus, the new barycenter events don't record a tilt for the barycenter, since it's a virtual object. And yet it's there, internally to ED.
So the best we could do for a 3D orrery would be to treat all barycenter orbits as though the reference plane is the main reference plane for the system, instead of using the barycenter's tilt (since we don't have it), and either do the same with moons, or pick an arbitrary direction for the parent's axial tilt and then use that. For the latter, I'd go with whichever direction makes the math the simplest for tilting the moon orbits.
These things are immediately apparent when looking at Sol. Right now I don't have a barycenter at all for the Pluto/Charon system, but their orbital inclinations in the data are quite low. In reality they're pretty inclined, so that tilt must come from the barycenter in ED. Uranus is also highly tilted, and so are its moon orbits. However again, in the data the moons have low orbital inclinations, so the tilt has to come from the planet.
So with some minor fudging, it's still possible to make a pretty complete orrery. I threw together some code to step through days and see how the planetary coordinates within the system change, but this assumes that all of the orbit inclinations are relative to the horizontal main reference plane. I don't know what, or if I'll use it for anything, but it's a start in any case. And knowing the above will be useful for anyone else looking to use the data in a similar manner.
