Making accurate orbits of all the solar system moons

[johnsonme06]

Hi everyone, just purchased Universe Sandbox 2 and was trying to accurately place all the planet's moons and their orbits. Most of the planet's moons' data i have found from various wikipedia pages and such and those have been great but I'm having trouble with Uranus' moon Sycorax and some of the other irregular moons especially since Uranus is tipped over on its side. I've also added a lot of moons in manually since they aren't in the game yet and found the mass and density values from the wikipedia page as well. According to that page though it shows the inclination to be 159 degrees to the ecliptic, does that translate to the game as the "grid" with the sun? Also found a handy pdf that shows the right ascension to be 272.154 and the declination to be 66.466 in reference to the ICRF. So does any of this information translate to the game at all for the longitude of the ascending node or the argument of the pericenter values? I know this might be over thinking things a lot but this sandbox can be very accurate and its fun to place it in the right place and see how these celestial bodies actually move. Thanks.

[Jar]

Glad you're diving into the details! Which moons are you referring to, though? It should be up to date, though you won't get all moons in each of the Solar System sims -- some sims include fewer database objects as a trade-off for better performance. If you load "Solar System All Planets & All Moons" you should see all of them (including Sycorax), or for just looking at the Uranus system, you can load "Uranus & Moons."

It can still be fun to try to add them yourself though, so to answer your questions: yes, in this case, the ecliptic is equivalent to the grid; and Right Ascension and Declination are normally used for defining positions of objects in the sky for observing, so they're not particularly useful for setting orbital elements in Universe Sandbox.

Hope this helps! Let me know if you have other questions about this.

[johnsonme06]

I have actually been adding them myself to each planet in the default solar system with just the information given from Wikipedia pages and the Space Engine app. I actually didn't know there was a full simulation with all the moons lol. I'll give that a peek but adding them myself has been a blast. I've completed all the planets' moons except Jupiter and Saturn which of course has a lot of moons so that will take time. Thanks for clearing up the grid/ecliptic question as well. This sandbox has been an amazing experience so far. Keep up the great work!

PS: If you don't mind me asking, where do you reference the argument of the pericenter degrees and the longitude of the ascending node degrees from for the moon orbits? Those have been the absolute hardest for me to find any numbers on and my orbits look slightly different, I know its a game but I love accuracy lol.

[Jar]

Don't mind at all! We love accuracy, too. For planet and moon positions we use NASA / JPL's HORIZONS system: https://ssd.jpl.nasa.gov/?horizons

There's a web interface that's very powerful, but also a bit intimidating to use at first. Essentially, for using the data in Universe Sandbox, you need to set the ephemeris type to Elements, change the Target body to whatever you're trying to simulate, then set the Center to whatever will be the orbital parent in Universe Sandbox. Then it'll spit out a bunch of numbers that you can match to the Universe Sandbox orbital elements values.

And just FYI, we actually have this listed in our Credits, along with some other resources you might be interested in: https://docs.google.com/document/d/1uCZC8kaLVQvg_jkpIncqM1uATZfeWgrJLZreFGWLIg0/edit#heading=h.wsye1y9ymaaq

[johnsonme06]

Holy cow Jar, you weren't kidding about it spitting out a bunch of numbers lol. I'm glad they give a symbol meaning at the bottom telling you what each element is!! Thanks so much for your help and input, nice to hear directly from a developer as well. This will definitely give me hours of entertainment with Universe Sandbox 2! Hope to talk to you again soon. Best of luck!