Orbit design for future SpaceChip swarm missions in a planetary atmosphere

The effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag

Attitude and orbit coupling of planar helio-stable solar sails

The coupled attitude and orbit dynamics of solar sails is studied. The shape of the sail is a simplified quasi-rhombic-pyramid that provides the structure helio-stablility properties. After adimensionalisation, the system is put in the form of a fast-slow dynamical system where the different time scales are explicitely related to the physical parameters of the system. The orientation of the body frame with respect to the inertial orbit frame is a fast phase that can be averaged out. This gives rise to a simplified formulation that only consists of the orbit dynamics perturbed by a flat sail with fixed attitude perpendicular to the direction of the sunlight. The results are exemplified using numerical simulations.Comment: 36 pages, 31 figure

Towards a sustainable exploitation of the geosynchronous orbital region

In this work the orbital dynamics of Earth satellites about the geosynchronous altitude are explored, with primary goal to assess current mitigation guidelines as well as to discuss the future exploitation of the region. A thorough dynamical mapping was conducted in a high-definition grid of orbital elements, enabled by a fast and accurate semi-analytical propagator, which considers all the relevant perturbations. The results are presented in appropriately selected stability maps to highlight the underlying mechanisms and their interplay, that can lead to stable graveyard orbits or fast re-entry pathways. The natural separation of the long-term evolution between equatorial and inclined satellites is discussed in terms of post-mission disposal strategies. Moreover, we confirm the existence of an effective cleansing mechanism for inclined geosynchronous satellites and discuss its implications in terms of current guidelines as well as alternative mission designs that could lead to a sustainable use of the geosynchronous orbital region.Comment: Accepted for publication in Celestial Mechanics and Dynamical Astronom

Autonomous control of a reconfigurable constellation of satellites on geostationary orbit with artificial potential fields

This paper presents a method of controlling a constellation of small satellites in Geostationary Earth Orbit (GEO) such that the constellation is able to reconfigure - changing the angular position of its members relative to the Earth’s surface in order to cluster them above particular target longitudes. This is enabled through the use of an artificial potential function whose minimum value corresponds to a state where the phase angle between each satellite and its intended target is minimised. By linking the tangential low-thrust acceleration of each satellite to this artificial potential function, the altitude of each satellite relative to the nominal GEO altitude is manipulated in order to achieve the required drift rate. A demonstration of the efficacy of the method is given through a simple test case in which a constellation of 90 satellites converge upon 3 equatorial targets, with each target requiring the attention of a varying number of spacecraft from the constellation. The constellation performance is analysed in terms of the time taken for the satellites to converge over their targeted longitudes and the Dv required to actuate the phasing maneuvers. This analysis is performed across a parameter space by varying the number of satellites in the constellation, the number of targeted longitudes, and a parameter representing the maximum acceleration of the thruster

Interception and deviation of near Earth objects via solar collector strategy

A solution to the asteroid deviation problem via a low-thrust strategy is proposed. This formulation makes use of the proximal motion equations and a semi-analytical solution of the Gauss planetary equations. The average of the variation of the orbital elements is computed, together with an approximate expression of their periodic evolution. The interception and the deflection phase are optimised together through a global search. The low-thrust transfer is preliminary designed with a shape based method; subsequently the solutions are locally refined through the Differential Dynamic Programming approach. A set of optimal solutions are presented for a deflection mission to Apophis, together with a representative trajectory to Apophis including the Earth escape

Low-thrust trajectories design for the European Student Moon Orbiter mission

The following paper presents the mission analysis studies performed for the phase A of the solar electric propulsion option of the European Student Moon Orbiter (ESMO) mission. ESMO is scheduled to be launched in 2011, as an auxiliary payload on board of Ariane 5. Hence the launch date will be imposed by the primary payload. A method to efficiently assess wide launch windows for the Earth-Moon transfer is presented here. Sets of spirals starting from the GTO were propagated forward with a continuous tangential thrust until reaching an apogee of 280,000 km. Concurrently, sets of potential Moon spirals were propagated backwards from the lunar orbit injection. The method consists of ranking all the admissible lunar spiral-down orbits that arrive to the target orbit with a simple tangential thrust profile after a capture through the L1 Lagrange point. The 'best' lunar spiral is selected for each Earth spiral. Finally,comparing the value of the ranking function for each launch date, the favourable and unfavourable launch windows are identified

A passive de-orbiting strategy for high altitude CubeSat missions using a deployable reflective balloon

A de-orbiting strategy for small satellites, in particular CubeSats, is proposed which exploits the effect of solar radiation pressure to increase the spacecraft orbit eccentricity so that the perigee falls below an altitude where atmospheric drag will cause the spacecraft orbit to naturally decay. This is achieved by fitting the spacecraft with an inflatable reflective balloon. Once this is fully deployed, the overall area-to-mass ratio of the spacecraft is increased; hence solar radiation pressure and aerodynamic drag have a greatly increased effect on the spacecraft orbit. An analytical model of the orbit evolution due to solar radiation pressure and the J2 effect as a Hamiltonian system shows the evolution of an initially circular orbit. The maximum reachable orbit eccentricity as a function of semi-major axis and area-to-mass ratio can be found and used to determine the size of balloon required for de-orbiting from circular orbits of different altitudes. A system design of the device is performed and the feasibility of the proposed de-orbiting strategy is assessed and compared to the use of conventional thrusters. The use of solar radiation pressure to increase the orbit eccentricity enables passive de-orbiting from significantly higher altitudes than conventional drag augmentation devices

Stabilisation of the hyperbolic equilibrium of high area-to-mass spacecraft

In this paper we propose the exploitation of anti-heliotropic orbits, corresponding to the hyperbolic solution of the J2 and solar radiation pressure dynamical system, as gateway orbits between the low-eccentricity orbits where atmospheric drag does not affect the motion and the high eccentricity orbits which enter in drag regime. The eccentricity can be maintained in the neighborhood of the unstable point by means of a controller preserving the Hamiltonian structure of the system. In this way, any initial eccentricity close to the equilibrium conditions will lead to a bound trajectory around the controlled elliptic equilibrium. By selecting the time the controller is turned off, one of the two unstable manifolds leaving the equilibrium point can be followed, leading the orbit to become circular of to increase its eccentricity until natural decay occurs

Orbital dynamics of high area-to-mass ratio spacecraft under the influence of J2 and solar radiation pressure

This paper investigates the effect of planetary oblateness and solar radiation pressure on the orbit of high area-to-mass spacecraft. A planar Hamiltonian model shows the existence of equilibrium orbits with the orbit apogee pointing towards or away from the Sun. These solutions are numerically continued to non-zero inclinations and considering the obliquity of the ecliptic plane relative to the equator. Quasi-frozen orbits are identified in eccentricity, inclination and angle between the Sun-line and the orbit perigee. The long-term evolution of these orbits is then verified through numerical integration. A set of ‘heliotropic’ orbits with apogee pointing in direction of the Sun is proposed for enhancing imaging and telecommunication on the day side of the Earth. The effects of J2 and solar radiation pressure are exploited to obtain a passive rotation of the apsides line following the Sun; moreover the effect of solar radiation pressure enables such orbits at higher eccentricities with respect to the J2 only case

A passive high altitude deorbiting strategy

A deorbiting strategy for small satellites, in particular CubeSats, is proposed which exploits the effect of solar radiation pressure to increase the spacecraft orbit eccentricity so that the perigee falls below an altitude where atmospheric drag will cause the spacecraft orbit to naturally decay. This is achieved by fitting the spacecraft with an inflatable reflective balloon. Once this is fully deployed, the overall area-to-mass ratio of the spacecraft is increased; hence solar radiation pressure and aerodynamic drag have a greatly increased effect on the spacecraft orbit. An analytical model of the orbit evolution due to solar radiation pressure and the J2 effect as a Hamiltonian system shows the evolution of an initially circular orbit. The maximum reachable orbit eccentricity as a function of semi-major axis and area-to-mass ratio can be found and used to determine the size of balloon required for deorbiting from circular orbits of different altitudes. A system design of the device is performed and the feasibility of the proposed deorbiting strategy is assessed and compared to the use of conventional thrusters. The use of solar radiation pressure to increase the orbit eccentricity enables passive deorbiting from significantly higher altitudes than conventional drag augmentation devices