Speaker
Dr
Camilla Colombo
(Astronautics Research Group, University of Southampton)
Description
Trajectory design and orbit maintenance are a challenging task when multi-body dynamics is involved or in the vicinity of a planet, where the effect of orbit perturbations is relevant. This is the case of many applications in Space Situation Awareness (SSA), for example in the design of disposal trajectories from Medium Earth Orbits, or Highly Elliptical Orbits or Libration Point Orbits, or in the prediction of spacecraft re-entry, or in the modelling of the evolution of high area-to-mass ratio objects. On the other hand, the natural dynamics can be leveraged to reduce the propellant requirements, thus creating new opportunities. Orbit perturbations due to solar radiation pressure, atmospheric drag, third body effects, non-spherical gravity field, etc., play an important role in SSA.
The semi-analytical technique based on averaging is an elegant approach to analyse the effect of orbit perturbations. It separates the constant, short periodic and long-periodic terms of the disturbing function. The short-term effect of perturbations is eliminated by averaging the variational equations, or the corresponding potential, over one orbit revolution of the small body. Indeed, averaging corresponds to filtering the higher frequencies of the motion (periodic over one orbit revolution), which typically have small amplitudes. The resulting system allows a deeper understanding of the dynamics. Moreover, using the average dynamics reduces the computational time for numerical integration as the stiffness of the problem is reduced, while maintaining sufficient accuracy compatible with problem requirements also for long-term integrations.
This paper presents the Planetary Orbital Dynamics suite for long term propagation in perturbed environment. PlanODyn implements the orbital dynamics written in orbital elements by using semi- analytical averaging techniques. The perturbed dynamics is propagated in the Earth-centred dynamics by means of the single and double averaged variation of the disturbing potential. The single averaged disturbing potential due to luni-solar perturbations is developed in series of Taylor of the ratio between the orbit semi-major axis and the distance to the third body, following the approach by Kaufmann and Dasenbrock. The effect of other orbit perturbations such as the zonal harmonics up to order 10, the effect of solar radiation pressure and aerodynamics drag are also modelled. The double averaged potential is also implemented by averaging on the variable describing the orbital motion of the perturbing body (i.e. Sun or Moon) around the Earth, but the different inclination of the perturbing bodies is retained.
Different application scenarios of PlanODyn will be shown: the behaviour of quasi-frozen solutions appearing for high inclination and high eccentricity orbits (HEO) can be reproduced and the re-entry of geostationary transfer orbits can be studied. In addition, to allow meeting specific mission constraints, stable conditions for quasi-frozen orbits can be selected as graveyard orbits for the end- of-life of HEO missions, such as XMM-Newton. On the opposite side, unstable conditions can be exploited to target an Earth re-entry; this is the case of the end-of-life of INTEGRAL mission, requiring a small delta-v manoeuvre for achieving a natural re-entry assisted by perturbations. Maps of stable and unstable HEOs are built, to be used as preliminary design tool for graveyard or frozen orbit design or natural re-entry trajectories at the end-of-life. Moreover, the application of PlanODyn to design end-of-life disposal from medium Earth orbits through passive solar sailing will be demonstrated.
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Primary author
Dr
Camilla Colombo
(Astronautics Research Group, University of Southampton)
