Benchmarking the rotating jet model of cometary activity with the trajectory of comet 67P/Churyumov-Gerasimenko

An important tool to assess the composition and the spatial origin of cometary material is the analysis of its trajectory reflecting gravitational acceleration due to solar system bodies complemented by non-gravitational accelerations (NGA).

The rotating jet model (RJM) as introduced by Chesley and Yeomans [1] reveals information about the orientation of the rotation axis and thus it contains additional parameters compared to the standard model for non-gravitational forces known from Marsden et al. [2]. The RJM is partly based on a thermophysical model of cometary activity and it usually assumes two jets (one per hemisphere) to describe the resulting NGA.
We discuss the derivation of the RJM and address the jet location on the surface assuming thermophysical models. In particular we relate the total production rate of a comet to the local sublimation rate induced by known data of torques.
All models are applied to the case of comet 67P/Churyumov-Gerasimenko, for which Rosetta data provides an independent data set of NGA [3].

Earthbound astrometry provides another tool to study the orbital changes caused by NGA. We analyze quantitatively how the astrometry determines open parameters of the RJM for comet 67P/Churyumov-Gerasimenko.

[1] S. R. Chesley and D. K. Yeomans, “Nongravitational Accelerations on Comets,” Proceedings of the International Astronomical Union, vol. 2004, no. IAUC197, pp. 289–302, 2004, doi: 10.1017/S1743921304008786.

[2] B. G. Marsden, Z. Sekanina, and D. K. Yeomans, Comets and nongravitational forces. V, The Astronomical Journal, vol. 78, p. 211, 1973, doi: 10.1086/111402

[3] T. Kramer and M. Läuter, “Outgassing-induced acceleration of comet 67P/Churyumov-Gerasimenko,” Astronomy & Astrophysics, vol. 630, p. A4, 2019, doi: 10.1051/0004-6361/201935229.