Data from JPL vs original data

[babacry]

Hi, mercury,

I was using mercury with different step sizes and different integrators with original data from mercury and new data from mercury(JPL:16-12). For original data, the Pluto is stable, however, with JPL's data in mercury, the Pluto is not stable (the semi-major axis is not stable) in 1M years. Do you know which data is more reliable?

Best, Renyi

[idovgalyov-4xxi]

Hello, @babacry ! Sorry for delay, it have not sent me a notification by some unknown reasons =(

We derived these "new" data from JPL HORIZONS system. As far as I remember, the orbital parameters were calculated using DE431 ephemerides and could be useful within the period of several thousand years. For instance, in our work we used it for integration on 100Kyr interval (and that is why we did not meet any troubles). However, it should be noted that mercury can be very sensible to different initial conditions, step sizes (as well as output intervals), methods, even different number of bodies. Therefore, the stability over 1Myr integration period may be not guaranteed (although is desirable, yeah).

I reproduced the simulation with several different inputs based on both original and JPL data to make sure that the issue touches the whole set of initial parameters (not only referred to Pluto as I supposed before). For now, I recommend to use original data if the orbital stability over 1Myr is needed. At least until we find another solution...

BTW, did You try to use any other initial data? Maybe the situation will look better after getting up-to-date orbital parameters...

[babacry]

Thanks for your suggestions, Ilya! I will use the original data. For other initial data, I also used JPL's data with the epoch 2000-01-01, which also leads to chaotic behaviours of Pluto.