Solar radiation pressure used for formation flying control around the Sun-Earth libration point

Solar radiation pressure is used to control the formation flying around the L2 libration point in the Sun-Earth system. Formation flying control around a halo orbit requires a very small thrust that cannot be satisfied by the latest thrusters. The key contribution of this paper is that the continuous low thrust is produced by solar radiation pressure to achieve the tight formation flying around the libration point. However, only certain families of formation types can be controlled by solar radiation pressure since the direction of solar radiation pressure is restricted to a certain range. Two types of feasible formations using solar radiation pressure control are designed. The conditions of feasible formations are given analytically. Simulations are presented for each case, and the results show that the formations are well controlled by solar radiation pressure.

Solar Radiation Pressure Modeling and Application of BDS Satellites

Solar radiation pressure(SRP)model is the basis of high precise orbit determination and positioning of navigation satellites.At present,it is common to see the study of SRP model of BDS satellites.However,the establishment and application of a comprehensive analytical SRP model based on satellite physical parameters are rare.Different from other conservative forces and non-conservative forces,SRP is closely related to the satellite’s physical parameters and in-orbit state.On the basis of the physical mechanism of solar radiation,BDS satellite physical parameters,in-orbit attitude control mode,and so on,a comprehensive analytical model has been studied in this paper.Based on precise ephemeris and satellite laser ranging(SLR)data,the precision of a comprehensive analytical model has been verified.And the precision of orbit determination is at the decimeter level using this comprehensive analytical SRP model.According to the satellite conservation theorem of angular momentum and change of in-orbit telemetry parameters,the difference between a comprehensive analytical model and the actual in-orbit interference force has been analyzed and calculated.The addition of empirical items on the comprehensive analytical model has been proposed.SLR validations demonstrated that the orbit precision of BDS C08 and C10 can be achieved at 0.078 m and 0.084 m respectively.Compared with using the improved CODE empirical model,precision orbit accuracy of them has increased by 0.021 m and 0.045 m respectively.

Effects of solar radiation pressure on asteroid surface hopping transfers for high area/mass ratio rovers

The high area/mass ratio hopping rovers have potential applications in future asteroid surface exploration.This paper systematically investigates the effects of solar radiation pressure(SRP)on ballistic surface hopping transfers for the asteroid 101955 Bennu.Effects of SRP on the traveled distance and the trajectory design of hopping transfers are analyzed and summarized.The simulation results indicate that it is necessary to take SRP into account to ensure the success of hopping transfers and the proper use of SRP can help design the trajectories of hopping transfers with low initial impulses and short transfer times.It also reveals the potential possibility in using SRP to control the post-hopping transfers with specific control policies in the future surface exploration of asteroids.

Analysis of Effect of Solar Radiation Pressure of Bigger Primary on the Evolution of Periodic Orbits

Evolution of periodic orbits in Sun-Mars and Sun-Earth systems are analyzed using Poincare surface of section technique and the effects of solar radiation pressure of bigger primary and actual oblateness of smaller primary on these orbits areconsidered. It is observed that solar radiation pressure of bigger primary has substantial effect on period, orbit’s shape, size and their position in the phase space. Since these orbits can be used for the design of low energy transfer trajectories, so perturbations due to solar radiation pressure has to be understood and should be taken care of during trajectory design. It is also verified that stability of such orbits are negligible so they can be used as transfer orbit. For each pair of solar radiation pressure q and Jacobi constant C we get two separatrices where stability of island becomes zero. In this paper, detailed stability analysis of periodic orbit having two loops is given when q = 0.9845.

Structural dynamic responses of a stripped solar sail subjected to solar radiation pressure

The stripped solar sail whose membrane is divided into separate narrow membrane strips is believed to have the best structural efficiency.In this paper,the stripped solar sail structure is regarded as an assembly made by connecting a number of boom-strip components in sequence.Considering the coupling effects between booms and membrane strips,an exact and semianalytical method to calculate structural dynamic responses of the stripped solar sail subjected to solar radiation pressure is established.The case study of a 100 m stripped solar sail shows that the stripped architecture helps to reduce the static deflections and amplitudes of the steady-state dynamic response.Larger prestress of the membrane strips will decrease stiffness of the sail and increase amplitudes of the steady-state dynamic response.Increasing thickness of the boom will benefit to stability of the sail and reduce the resonant amplitudes.This proposed semi-analytical method provides an efficient analysis tool for structure design and attitude control of the stripped solar sail.

Convex optimization of asteroid landing trajectories driven by solar radiation pressure

High-area/mass ratio landers driven by Solar Radiation Pressure(SRP)have potential applications for future asteroid landing missions.This paper develops a new convex optimization-based method for planning trajectories driven by SRP.A Minimum Landing Error(MLE)control problem is formulated to enable planning SRP-controlled trajectories with different flight times.It is transformed into Second Order Cone Programming(SOCP)successfully by a series of different convexification technologies.A trust region constraint and a modified MLE objective function are used to guarantee the convergence performance of the optimization algorithm.Thereafter,the SRP-driven trajectory optimal control problem is converted equivalently into a sequence of convex optimal control problems that can be solved effectively.A set of numerical simulation results has verified the effectiveness and feasibility of the proposed optimization method.

Self-excited oscillation of spinning solar sails utilizing solar radiation pressure

The present paper proposes a control method to excite spinning solar sail membranes for three-dimensional use.Using optical property switching,the input is given as the change in magnitude of the solar radiation pressure.The resonance point of this system varies with the vibration state due to its nonlinearity and the change in equilibrium state.To deal with this,a state feedback control law that automatically tracks the resonance point is developed in the present study.The proposed method enables decentralized control of the actuators on the sail,each of which determines the control input independently using only the information of vibration state.The proposed method is validated using numerical simulations.The results show that the nonlinear system behaves differently from the linear system,and the vibration grows using the decentralized control regardless of resonance point variation.

Forced motions around triangular libration points by solar radiation pressure in a binary asteroid system

By using two tri-axial ellipsoids to approximate the two asteroids,forced orbits around triangular libration points of the binary asteroid system(BAS)induced by solar radiation pressure are studied.The work is firstly carried out in the doubly synchronous binary asteroid system(DSBAS).The results show that the amplitude of the forced periodic orbit can be large,even for small to moderate surface area-to-mass ratios of the spacecraft.The position,amplitude,and stability of these forced periodic orbits are influenced by the asteroids'non-spherical terms.Also,the stability of them may be different,depending on the Sun's motion direction w.r.t.to the BAS's orbit motion direction.This study is then generalized to the asynchronous and synchronous BAS(ABAS and SBAS,respectively).The forced orbits in the complete system are quasi-periodic orbits around the forced periodic orbit of the averaged system.

Mechanism-free control method of solar/thermal radiation pressure for application to attitude control

Solar radiation pressure(SRP)impinging on spacecraft is usually regarded as a disturbance for attitude motion,but it can be harnessed to solve the very problem it creates.Active SRP control is possible with solar radiation powered thin-film devices such as reflectivity control devices or liquid crystal devices with reflective microstructure.Thermal radiation pressure(TRP)can likewise be used to solve flight attitude problems caused by SRP,TRP,or other factors.TRP on solar cells can be controlled by switching regulators under the control of them,resulting in temperature change.These SRP/TRP controls are free from mechanisms,such as reaction wheels,and thus they do not produce internal disturbances.In addition,the magnitude of SRP/TRP torques is generally much smaller than internal disturbance torques produced by reaction wheels,which creates a potential for precision far beyond that achieved with mechanical controls.This paper summarizes how SRP/TRP can be used by means of numerical simulations of typical control methods.The usefulness of this mechanism-free attitude control is verified for future use on both Earth orbiting satellites and interplanetary spacecraft including solar sails.

Design and application of solar sailing: A review on key technologies

Solar sail technology has been proposed and developed for space explorations with advantages of low launch cost,no-propellant consumption,and continuous thrust,which has great potentials in earth polar detection,interstellar explorations and etc.The development of solar sail has made significant progress in structural design,manufacturing,materials,orbit transfer,and stability control in the past few decades,which makes meaningful contributions to astronomy,physics,and aerospace science.Technological breakthroughs of Solar Radiation Pressure(SRP)propulsion and interstellar transfer have been achieved in current solar sail missions.However,there are still many challenges and problems need to be solved.This paper attempts to summarize the research schemes and potential applications of solar sailing in space missions from the viewpoint of key technologies,so as to provide an overall perspective for researchers in this field.Analyses of the key technologies of solar sailing system design are provided.Finally,challenges and prospective development of solar sailing are discussed.

Novel orbit-attitude combination mode for solar power satellites to reduce mass and fuel

Solar power satellite receives great attention because it can release the energy crisis and environmental problems in the future.However,the launch and maintenance costs are tremendous due to the large system mass and large fuel consumption to counteract space perturbations.To reduce mass and fuel,a novel quasi-Sun-pointing attitude in Sun-frozen orbit is proposed.The Sun-frozen orbit has a nonzero eccentricity vector that always points towards the Sun.The quasi-Sun-pointing attitude is a periodic solution of the Sun-pointing attitude angle.Although about 3%electricity must be given up because of the variation of Sun-pointing attitude angle,little control action is required to deal with the solar radiation pressure and gravity-gradient torque.The algorithm to obtain initial conditions is proposed.The influences of system parameters and structural flexibilities are studied.Simulation results reveal that the quasi-Sun-pointing attitude in Sunfrozen orbit dramatically reduce fuel consumption,the dry mass,and complexity of the control system.In addition,structural vibration is hardly induced by the gravity-gradient torque.Thus,the bending stiffness as well as the mass of the supporting structure can be reduced.

Solar sail attitude control using shape variation of booms

Active attitude control of solar sails is required to control the direction of the force generated by Solar Radiation Pressure(SRP). It is desirable to control the attitude through propellantfree means. This paper proposes a new method for attitude control of solar sails: A boom consisting of "smart" structural material can be deformed by the piezoelectric actuator, and Solar Radiation Pressure torque will be generated due to shape variation of sail membrane caused by boom deformation. The method has the advantages of simple structure, small disturbance and small additional load, and is not limited by the size of the solar sail. The case of rendezvous with the Asteroid 2000SG344 is used to verify the attitude control around the pitch and yaw axes.

Geophysical and orbital environments of asteroid 4692192016 HO3

Asteroid 469219 Kamo'oalewa,also named 2016 HO3,is a small-size fast-rotating near-Earth asteroid,which is a potential target for future explorations.Owing to its weak gravity and fast spin rate,the dynamics on the surface or in the vicinity of 2016 HO3 are significantly different from those of planets or other small bodies explored in previous missions.In this study,the geophysical and orbital environments of 2016 HO3 were investigated to facilitate a potential mission design.First,the geormnetric and geopotential topographies of 2016 HO3 were examined using difterent shape models.The liftoff and escape conditions on its fast-rotating surface were investigated.Then,the periodic orbits around 2016 HO3 were studied in the asteroid-fixed frame and the Sun-asteroid frame considering the solar radiation pressure.The stable regions of the terminator orbits were discussed using different parameters.Finally,the influence of the nonspherical shape on the terminator orbits was examined.The precise terminator orbits around a real shape model of 2016 HO3 were obtained and verified in the high-fidelity model.This study shows that the polar region of 2016 HO3 is the primary region for landing or sampling,and the terminator orbits are well suited for global mapping and measurements of 2016 HO3.The analysis and methods can also serve as references for the exploration of other small fast-rotating bodies.

Precise orbit determination for BDS satellites

Since the frst pair of BeiDou satellites was deployed in 2000,China has made continuous eforts to establish its own independent BeiDou Navigation Satellite System(BDS)to provide the regional radio determination satellite service as well as regional and global radio navigation satellite services,which rely on the high quality of orbit and clock products.This article summarizes the achievements in the precise orbit determination(POD)of BDS satellites in the past decade with the focus on observation and orbit dynamic models.First,the disclosed metadata of BDS satellites is presented and the contribution to BDS POD is addressed.The complete optical properties of the satellite bus as well as solar panels are derived based on the absorbed parameters as well the material properties.Secondly,the status and tracking capabilities of the L-band data from accessible ground networks are presented,while some low earth orbiter satellites with onboard BDS tracking capability are listed.The topological structure and measurement scheme of BDS Inter-Satellite-Link(ISL)data are described.After highlighting the progress on observation models as well as orbit perturbations for BDS,e.g.,phase center corrections,satellite attitude,and solar radiation pressure,diferent POD strategies used for BDS are summarized.In addition,the urgent requirement for error modeling of the ISL data is emphasized based on the analysis of the observation noises,and the incompatible characteristics of orbit and clock derived with L-band and ISL data are illuminated and discussed.The further researches on the improvement of phase center calibration and orbit dynamic models,the refnement of ISL observation models,and the potential contribution of BDS to the estimation of geodetic parameters based on L-band or ISL data are identifed.With this,it is promising that BDS can achieve better performance and provides vital contributions to the geodesy and navigation.

Artificial equilibrium points and bi-impulsive maneuvers to observe 243 Ida

In the restricted three-body problem,the traditional Lagrange points L1 and L2 are the only equilibrium points near the asteroid 243 Ida.The thrust generated by a solar sail over a spacecraft enables the existence of new artificial equilibrium points,which depend on the position of the spacecraft with respect to the asteroid and the attitude of the solar sail.Such equilibrium points generate new spots to observe the body from above or below the plane of motion.Such points are very good observational locations due to their stationary condition.This work provides a preliminary analysis to observe Ida through the use of artificial equilibrium points as spots combined with transfer maneuvers between them.Such combination can be used to observe the asteroid from more different points of view in comparison to fixed ones.The analyses are made for a spacecraft equipped with a solar sail and capable of performing bi-impulsive maneuvers.The solar radiation pressure is used both to maintain the equilibrium condition and to reduce the costs of the transfers and/or to create transfers with longer duration.This is a new aspect of the present research,because it combines the continuous thrust with initial and final small impulses,which are feasible for most of the spacecraft,because the magnitudes of the impulses are very low.These combined maneuvers may reduce the transfer times of the maneuvers in most of the cases,compared with the maneuvers based only on continuous thrust.Several options involved in these transfers are shown,like to minimize the fuel spent(Dv)as a function of the transfer time or to extend the duration of the travel between the points.Extended transfer times can be useful when observations are required during the transfers.

Orbit insertion strategy of Hayabusa2’s rover with large release uncertainty around the asteroid Ryugu

This paper describes the orbit design of the deployable payload Rover 2 of MINERVA-II,installed on the Hayabusa2 spacecraft.Because Rover 2 did not have surface exploration capabilities,the operation team decided to experiment with a new strategy for its deployment to the surface.The rover was ejected at a high altitude and made a semi-hard landing on the surface of the asteroid Ryugu after several orbits.Based on the orbital analysis around Ryugu,the expected collision speed was tolerable for the rover to function post-impact.Because the rover could not control its position,its motion was entirely governed by the initial conditions.Thus,the largest challenge was to insert the rover into a stable orbit(despite its large release uncertainty),and avoid its escape from Ryugu due to an environment strongly perturbed by solar radiation pressure and gravitational irregularities.This study investigates the solution space of the orbit around Ryugu and evaluates the orbit’s robustness by utilizing Monte Carlo simulations to determine the orbit insertion policy.Upon analyzing the flight data of the rover operation,we verified that the rover orbited Ryugu for more than one period and established the possibility of a novel method for estimating the gravity of an asteroid.

Impacts of inter-satellite links on the ECOM model performance for BDS-3 MEO satellites

Inter-satellite link(ISL)plays an essential role in current and future Global Navigation Satellite System(GNSS).In this study,we investigate the impact of ISL observations on precise orbit determination for BeiDou-3 Navigation Satellite System(BDS-3)Medium Earth Orbit(MEO)satellites based on different Extended CODE Orbit Models(ECOM).Thanks to the better observation geometry of the Ka-band ISL data compared to the L-band data for BDS-3 MEO satellites,the ISL solution substantially reduces Orbit Boundary Discontinuity(OBD)errors,except for C30,which suffers from unstable Ka-band hardware delay.From the external quality analysis,ISL significantly enhances the reliability of the orbit of MEO satellites manufactured by the China Academy of Space Technology(CAST).The standard deviation(STD)of the satellite laser ranging(SLR)residuals is approximately 2.5 cm,and the root mean square(RMS)is reduced by 10–23%compared to L-band solutions.Besides,the Sun-elongation angle dependent systematic error in SLR residuals nearly vanishes based on the reduced 5-parameter ECOM(ECOM1)or extended 7-parameter ECOM(ECOM2)with ISL data.This is because the ISL reduces the correlation between state parameters and solar radiation pressure(SRP)parameters as well as those among SRP parameters,leading to a more accurate estimation of both orbit and SRP perturbations,particularly those along B direction.This confirms that the deficiency of the SRP models for BDS-3 CAST satellites can be compensated by using better observation geometry from ISL data.On the other hand,for the satellite manufactured by Shanghai Engineering Center for Microsatellites(SECM),the ISL allows for a more accurate estimation of the Bc_(1)parameter in the ECOM1 model.This only reduces linear systematic error,possibly because the impact generated by the satellite bus cannot be entirely absorbed by the B-direction parameters.