Evolution of orbits about comets with arbitrary comae
- PDF / 1,215,262 Bytes
- 28 Pages / 439.37 x 666.142 pts Page_size
- 88 Downloads / 124 Views
(2020) 132:37
ORIGINAL ARTICLE
Evolution of orbits about comets with arbitrary comae Mark Moretto1
· Jay McMahon1
Received: 1 April 2020 / Revised: 8 June 2020 / Accepted: 15 June 2020 © The Author(s) 2020
Abstract Spacecraft and natural objects orbiting an active comet are perturbed by gas drag from the coma. These gases expand radially at about 0.5 km/s, much faster than orbital velocities that are on the order of meters per second. The coma has complex gas distributions and is difficult to model. Accelerations from gas drag can be on the same order of gravity and are currently poorly understood. Semi-analytical solutions for the evolution of the Keplerian orbital elements of a spacecraft orbiting a comet using simplified drag and coma models are derived using a Fourier series expansion in the argument of latitude. It is found that the mean element evolution is only dependent on the zeroth- and first-order terms of the Fourier series expansion. For an arbitrary, inverse-square, radial, perturbing force, there are no frozen orbits; however, the argument of pericenter has a stable equilibrium and an unstable equilibrium and the angular momentum vector of the orbit is constant. Furthermore, the radius of the orbit at two specific angles relative to the ascending node is preserved. The evolution of the orbit is governed by the argument of pericenter, resulting in orientations that raise and lower the radius of pericenter and implying safe and unsafe orbit orientations for spacecraft operations. Keywords Comets · Perturbations · Drag · Averaging
1 Introduction Comets are valuable targets for science and exploration missions. It is widely accepted that comets are among the most chemically pristine remnants of the early Solar system, thus allowing glimpses into the chemical and physical properties of the solar nebula at the time and location of their formation. Comets also contain vast amounts of easy-to-access water ice that can be leveraged in future manned and robotic mission architectures through in situ resource utilization (ISRU). In order to access the scientific and economic benefits of comets, one must be able to conduct precise operations near and on their surfaces. Several comet missions have been flown in the past, though all but one have been flyby missions where the spacecraft was only in the vicinity of the comet for several hours and was never gravitationally bound, e.g., Giotto, Deep Space 1, Deep Impact, EPOXI, Stardust,
B 1
Mark Moretto [email protected] Aerospace Engineering Sciences, University of Colorado Boulder, 3775 Discovery Drive, Boulder, CO 80303, USA 0123456789().: V,-vol
123
37
Page 2 of 28
M. Moretto, J. McMahon
and Stardust-NExT. To date the only mission to orbit a comet is the Rosetta mission that operated at comet 67P/Churyumov–Gerasimenko (CG) from August 2014 to September 2016 (Accomazzo et al. 2016, 2017). Difficulty in accurately modeling the drag forces resulting from the coma resulted in significant operational costs and effort for Rosetta, where uncertainty
Data Loading...
