Changes In Orbital Elements Research Articles

The Effect of Atmospheric Drag Force on the Elements of Low Earth Orbital Satellites at Minimum Solar Activity

Researching and modeling perturbations is essential in astrodynamics because it gives information on the deviations from the satellite's normal, idealized, or unperturbed motion. Examined the impact of non-conservative atmospheric drag and orbital elements of low-earth-orbit satellites under low solar activity. The study is consisting of parts, the first looks at the effects of atmospheric drag on LEO satellites different area to mass ratios, and the second looks at different inclination values. Modeling the impacts of perturbation is included in each section, and the final portion determines the effects of atmospheric drag at various node values. The simulation was run using the Celestial Mechanics software system's SATORB module (Beutler, 2005), which solves the perturbation equations via numerical integration. The findings were examined using Matlab 2012. Conclusion that the impacts are stronger for retrograde orbits, which is due to the fact that the satellite moves in the opposite direction. The atmospheric drag effects for all orbital elements were increased by increasing the area to mass ratio. When the node value rises, the size parameter changes slightly, but the other orbital elements change. At varying inclinations, it is found that the changes in orbital elements due to atmospheric drug.

Low-thrust planar transfer for co-planar low Earth orbit satellites considering self-induced collision avoidance

This paper deals with the planar transfer problems (orbit raising and de-orbiting) for co-planar satellites with low-thrust propulsion, taking the self-induced collision avoidance into consideration at the mission design stage. A Blended Error-Correction steering law, with which the thrust direction changes in a self-adaptive way, is developed by blending two types of efficient steering laws and offsetting the errors of the instantaneous orbit with respect to the target orbit. The semi-analytical solutions for orbital elements, which reduce the computational load of propagating long-duration trajectories, are derived by computing the analytical incremental changes in orbital elements after every revolution with an orbital averaging technique. Based on the analytical Blended Error-Correction steering law and semi-analytical solutions, transfers can be computed quickly for any starting times. Finally, the self-induced collision, which is modeled by miss distance, is avoided by scheduling properly the timing to start transfer for every satellite.

Analysis of the change of orbital elements in the process of gravity assist

Gravity assist is widely applied in the deep space exploration because of its reliability and practicability. There are lots of research in the literature about the nearly coplanar situations. In this work, a three-dimensional model of gravity assist model is developed in a semi-analytical manner on the basis of the geometry relationship between the parameters of spacecraft before gravity assist and the orbital elements after gravity assist. The parameters include V∞in (the hyperbolic excess velocity vector of the spacecraft before fly-by), H (the height of fly-by) and θ (the dihedral angle between approach plane and fly-by plane). These equations can be used for analyzing the change of orbital elements in the process of gravity assist, discussing the influence of different parameters on them and deriving the condition that remains the semi-major axis unchanged. Curve fitting of the feasible region boundary of Δi and contour plot of Δi are utilized to analyze the pattern of Δi changing with different parameters. This method is a valuable reference for designing gravity assist trajectories to high inclination targets in the Solar system.

Atmospheric drag force on LAPAN-TUBSAT during geomagnetic storm 2015

The purposes of this research are (1) determine the relationship between LAPAN-TUBSAT orbital elements and geomagnetic activity; (2) estimate daily drag acceleration; (3) determine the relationship between drag acceleration and geomagnetic activity. We used STK (System Tool Kit), python, and CCMC (Community Coordinated Modeling Center) interactive model to process the data. To calculate the drag acceleration, it takes data of satellite’s velocity that obtained from STK and atmospheric density. To generate atmospheric density, we used CCMC with MSISE-90 (Mass Spectrometer – Incoherent Scatter Extended 1990) and IRI (International Reference Ionosphere) atmospheric model. In addition, it takes the satellite’s position (latitude, longitude, and height – taken from STK) as input. On March 2015, geomagnetic storm index (daily Dst) had a minimum value of -105 nT on March 18, 2015. According to hourly Dst data, the minimum value of Dst reached -223 nT at 23:00 UT on March 17, 2015. Changes of orbital elements were influenced by geomagnetic storms through the Dst index. Maximum changes of semi-major axis, inclination, argument of perigee, and longitude of ascending node occurred on March 17-21, 2015 (geomagnetic storm period). Minimum change of eccentricity occurred on March 15-16, 2015 when Dst reached a maximum value. Atmospheric model is influenced most by solar conditions both during periods of calm or storm. Atmospheric density generated by MSISE-90 and IRI, both of them has 10−6 order difference. MSISE-90 is 10−16 while IRI 10−22. For MSISE-90, maximum drag acceleration reached 451,4416 m/hari2 occurred on March 17, 2015, along with a strong geomagnetic storm phenomenon. For IRI, the value of drag acceleration during peak geomagnetic storm (March 18, 2015) reached 0,000373 m/hari2 (close to the minimum value in March 2015). Drag acceleration of LAPAN-TUBSAT is linear to the Dst index with a correlation coefficient of -0,51.

Atmospheric drag effect on LAPAN A1 orbit during geomagnetic storm 2017

Satellites moving through the atmosphere and experience a drag force in the opposite direction of their orbital motion. Atmospheric drag is the largest perturbations for low earth orbit satellites beside earth gravitation. We calculate the atmospheric drag on LAPAN A1 in a sun-synchronous circular orbit with an inclination of 97.60°, eccentricity of 0.0014, period of 99.039 minutes and an altitude of 630 km, during September in 2017. Data of orbital elements (Two Line Elements) taken from www.celestrak.com. Geomagnetic activity data (Dst index) taken from https://omniweb.gsfc.nasa.gov. The purpose of this study is to determine the relationship between atmospheric drag, orbital elements, and a geomagnetic storm. In 2017, hourly Dst index had a minimum value of -124 nT at 18:00 UTC, on September 8. But the geomagnetic storm in 2017 didn’t influence significantly to drag acceleration of LAPAN A1. During geomagnetic storm period in 2017, the changes of orbital elements were really small and the data is too scattered to be concluded as the effect of the geomagnetic storm.

Long-term evaluation of orbital dynamics in the Sun-planet system considering axial-tilt

In this paper, the axial-tilt (obliquity) effect of planets on the motion of planets’ orbiter in prolonged space missions has been investigated in the presence of the Sun gravity. The proposed model is based on non-simplified perturbed dynamic equations of planetary orbiter motion. From a new point of view, in this work, the dynamic equations regarding a disturbing body in elliptic inclined three-dimensional orbit are derived. The accuracy of this non-simplified method is validated with dual-averaged method employed on a generalized Earth–Moon system. It is shown that the neglected short-time oscillations in dual-averaged technique can accumulate and propel to remarkable errors in the prolonged evolution. After validation, the effects of the planet’s axial-tilt on eccentricity, inclination and right ascension of the ascending node of the orbiter are investigated. Moreover, a generalized model is provided to study the effects of third-body inclination and eccentricity on orbit characteristics. It is shown that the planet’s axial-tilt is the key to facilitating some significant changes in orbital elements in long-term mission and short-time oscillations must be considered in accurate prolonged evaluation.

Investigating the Relativistic Motion of the Stars Near the Supermassive Black Hole in the Galactic Center

Abstract The S-star cluster in the Galactic center allows us to study the physics close to a supermassive black hole, including distinctive dynamical tests of general relativity. Our best estimates for the mass of and the distance to Sgr A* using the three stars with the shortest period (S2, S38, and S55/S0-102) and Newtonian models are M BH = (4.15 ± 0.13 ± 0.57) × 106 M ⊙ and R 0 = 8.19 ± 0.11 ± 0.34 kpc. Additionally, we aim at a new and practical method to investigate the relativistic orbits of stars in the gravitational field near Sgr A*. We use a first-order post-Newtonian approximation to calculate the stellar orbits with a broad range of periapse distance r p . We present a method that employs the changes in orbital elements derived from elliptical fits to different sections of the orbit. These changes are correlated with the relativistic parameter defined as ϒ ≡ r s /r p (with r s being the Schwarzschild radius) and can be used to derive ϒ from observational data. For S2 we find a value of ϒ = 0.00088 ± 0.00080, which is consistent, within the uncertainty, with the expected value of ϒ = 0.00065 derived from M BH and the orbit of S2. We argue that the derived quantity is unlikely to be dominated by perturbing influences such as noise on the derived stellar positions, field rotation, and drifts in black hole mass.

Dynamical lifetimes of asteroids in retrograde orbits

The population of known minor bodies in retrograde orbits ($i > 90 ^{\circ}$) that are classified as asteroids is still growing. The aim of our study was to estimate the dynamical lifetimes of these bodies by use of the latest observational data, including astrometry and physical properties. We selected 25 asteroids with the best determined orbital elements. We studied their dynamical evolution in the past and future for $\pm$ 100 My ($\pm$ 1 Gy for three particular cases). We first used orbit determination and cloning to produce swarms of test particles. These swarms were then input into long-term numerical integrations and orbital elements were averaged. Next, we collected the available thermal properties of our objects and used them in an enhanced dynamical model with Yarkovsky forces. We also used a gravitational model for comparison. Finally, we estimated the median lifetimes of 25 asteroids. We found three objects whose retrograde orbits were stable with a dynamical lifetime $\tau \sim 10 \div 100$ My. A large portion of the objects studied displayed smaller values of $\tau$ ($\tau \sim 1$ My). In addition, we studied the possible influence of the Yarkovsky effect on our results. We found that the Yarkovsky effect can have a significant influence on the lifetimes of asteroids in retrograde orbits. Due to the presence of this effect, it is possible that the median lifetimes of these objects are extended. Additionally, the changes in orbital elements, caused by Yarkovsky forces, appear to depend on the integration direction. To explain this more precisely, the same model based on new physical parameters, determined from future observations, will be required.

Impact of interactive chemistry of stratospheric ozone on Southern Hemisphere paleoclimate simulation

AbstractA series of numerical simulations of the mid‐Holocene (6 kyr B.P.) climate are performed by using an Earth System Model of the Meteorological Research Institute of the Japan Meteorological Agency to investigate the impact of stratospheric ozone distribution, which is modulated by the change in orbital elements of the Earth, on the surface climate. The results of interactive ozone chemistry calculations for the mid‐Holocene and preindustrial periods are compared with those of the corresponding experiments in the fifth Coupled Model Intercomparison Project (CMIP5), in which the ozone distribution was prescribed to the 1850 Common Era level. The contribution of the interactive ozone chemistry in a quasi‐equilibrium state reveals a significant anomaly of up to +1.7 K in the Antarctic region for the annual mean zonal mean surface air temperature. This impact on the surface climate is explained by a similar mechanism to the cooling influence of the Antarctic ozone hole but opposite in sign: Weakening of the westerly jet associated with the Southern Annular Mode provides weakening of equatorward ocean surface current, sea ice retreat, and then warm sea surface temperature and surface air temperature. All the mid‐Holocene runs by CMIP5 models with the prescribed ozone had cold bias in sea surface temperature when compared with geological proxy data, whereas the bias is reduced in our simulations by using interactive ozone chemistry. We recommend that climate models include interactive sea ice and ozone distribution that are consistent with paleosolar insolation.

Satellite orbit under influence of a drag - analytical approach

The report studies some changes in orbital elements of the artificial satellites of Earth under influence of atmospheric drag. In order to develop possibilities of applying the results in many future cases, an analytical interpretation of the orbital element perturbations is given via useful, but very long expressions. The development is based on the TD88 air density model, recently upgraded with some additional terms. Some expressions and formulae were developed by the computer algebra system Mathematica and tested in some hypothetical cases. The results have good agreement with iterative (numerical) approach.

Spacecraft Propulsion Using Angular Momentum Transfer Based on Gravity Gradient Effects

Typical spacecraft propulsion systems depend upon the transfer of linear momentum through the expulsion of propellant using rocket motors or ion thrusters. This paper presents a method of spacecraft propulsion in which rotational angular momentum is transferred to orbital angular momentum due to the influence of gravity gradient effects. By applying torque to maintain a specific orientation with respect to the gravity gradient, the spacecraft orbital angular momentum is increased or decreased. If momentum wheels or control moment gyroscopes are used, no propellant is required and orbital maneuvers may be performed using solely electrical power. The equations of motion are presented along with analysis of the resulting change in orbital elements, demonstrating the relationship between spacecraft orientation and effective propulsive thrust. Simulation of the equations of motion is used to demonstrate the performance of the proposed technique and is verified by comparing results using both Lagrange dynamics and Newton–Euler dynamics. Although the resulting effects of this approach are small in comparison with conventional propulsion methods, it may be useful in applications such as exploration of asteroids and small moons, deorbiting of decommissioned satellites, or simply to reduce the requirements of a primary propulsion system.

Averaged changes in the orbital elements of meteoroids due to Yarkovsky-Radzievskij force

AbstractYarkovsky-Radzievskij effect exceeds the Poynting-Robertson effect in the perturbing action on particles larger than 100 μm. We obtained formulae for averaged changes in a meteoroid's Keplerian orbital elements and used them to estimate dispersion in the Geminid meteoroid stream. It was found that dispersion in semi-major axis of the model shower increased nearly three times on condition that meteoroids rotation is fast, and the rotation axis is stable.

Electrochromic Orbit Control for Smart-Dust Devices

Recent advances in MEMS (micro electromechanical systems) technology are leading to spacecraft which are the shape and size of computer chips, so-called SpaceChips, or ‘smart dust devices’. These devices can offer highly distributed sensing when used in future swarm applications. However, they currently lack a feasible strategy for active orbit control. This paper proposes an orbit control methodology for future SpaceChip devices which is based on exploiting the effects of solar radiation pressure using electrochromic coatings. The concept presented makes use of the high area-to-mass ratio of these devices, and consequently the large force exerted upon them by solar radiation pressure, to control their orbit evolution by altering their surface optical properties. The orbital evolution of Space Chips due to solar radiation pressure can be represented by a Hamiltonian system, allowing an analytic development of the control methodology. The motion in the orbital element phase space resembles that of a linear oscillator, which is used to formulate a switching control law. Additional perturbations and the effect of eclipses are accounted for by modifying the linearized equations of the secular change in orbital elements around an equilibrium point in the phase space of the problem. Finally, the effectiveness of the method is demonstrated in a test case scenario.

TELAH ORBIT SATELIT LAPAN-TUBSAT

The study of orbit characteristics of LAPAN-TUBSAT can be done by using some microsatellites which identical in the case of mission and its orbit. This knowledge is usefull to reduce the failure of mission. This characteristics can be seen from the change of orbital elements caused by perturbation forces. LAPAN-TUBSAT is placed in Low Earth Orbit (LEO) at altitude about 630 km which has orbit near polar (i≈98˚). At this altitude, the perturbations come from non-gravitation force such as atmospheric drag and gravitation force from earth oblatness. From the simulation can be predicted that in the early years of its operation, the variation in altitude and semi major axis is relatively small. The means that this satellite could have the life time more than 50 years. The effect of earth oblatness will cause the regression of the nodes of about 1˚/day and the rotation of the line of apsides of about -3˚/day. These changes are not too critical for near polar orbit which means that satellite keeps conducted the mission goal such as satellite imaging.

A SYMPLECTIC INTEGRATOR FOR HILL'S EQUATIONS

Hill's equations are an approximation that is useful in a number of areas of astrophysics including planetary rings and planetesimal disks. We derive a symplectic method for integrating Hill's equations based on a generalized leapfrog. This method is implemented in the parallel N-body code, PKDGRAV and tested on some simple orbits. The method demonstrates a lack of secular changes in orbital elements, making it a very useful technique for integrating Hill's equations over many dynamical times. Furthermore, the method allows for efficient collision searching using linear extrapolation of particle positions.

Dynamics of dust grains with a vaporable icy mantle

We show the effects of solar gravity, electromagnetic radiation and solar wind on the motion of micrometre-sized interplanetary dust grains for initially small eccentric orbits and for heliocentric distances less than 10 au. The traditional approach is that the solar wind effect and the Poynting-Robertson (P-R) effect are simultaneously taken into account through the numerical factor 1 + ηA/C pr , which is multiplied by the P-R effect. In reality, solar wind corpusculae erode the surface of the interplanetary grain. As a consequence, the value of the solar electromagnetic radiation pressure term increases, as it is inversely proportional to the size of the grain. In addition, the radiation pressure efficiency also varies because of the changes to the optical properties of the grain. Both these physical processes are taken into account, and the secular evolution of orbital elements for a Gaussian sphere with a volatile icy coating exhibits a secular increase of the semimajor axis and eccentricity as well as the longitude of perihelion. These secular changes of orbital elements do not exist in the conventional approach for the P-R and solar wind effects. The conventional approach yields 10 4 yr for the lifetime of inspiralling toward the Sun, if the evolution starts from the initial values of the semimajor axis a in = 4 au and eccentricity e in = 0.2. The Gaussian sphere with a volatile icy coating exhibits a semimajor axis greater than 10 au for t > 3 x 10 2 yr for the same initial orbital elements.

New Synchronous Orbits Using the Geomagnetic Lorentz Force

The Lorentz-augmented orbits concept provides propellantless electromagnetic propulsion without a tether, using the interaction between an electrostatically charged satellite and the Earth's magnetic field to provide a useful thrust. New types of Earth-synchronous orbits are found from equations governing the motion of satellites experiencing the Lorentz force in orbit. The equations of motion for such a spacecraft are derived based on a simplified magnetic field model, in which the dipole is aligned with true north. For a polar-orbiting satellite, a constant electrical charge can create arbitrary changes in the right-ascension angle. This method allows for single-orbit repeat-groundtrack low-Earth-orbit satellites. Analytical expressions for changes in orbital elements due to Lorentz forces are verified by numerical simulation for the polar and equatorial cases. In the equatorial case, manipulation of the longitude of perigee by constant electrostatic charge is possible. Perigee movement also allows for the creation of an Earth-synchronous type of orbit. The case of a dipole field, for which the north pole is not aligned with true north, is also examined. Feedback control using only the Lorentz force for actuation is shown to stabilize this general case.

New Class of Optimal Plane Change Maneuvers

For planetary satellite orbiters (such as the Europa Orbiter Mission) and planet orbiters (such as the Mercury Messenger Mission), third-body forces can induce large changes in orbital elements over one orbit. As a result, transfers involving an ellipse cannot be considered without taking these forces into account, and two- and three-impulse transfers must model these effects at larger distances from the central body. A new use of third-body perturbations is presented to effect plane changes. It is shown, in particular, that large plane changes can be obtained by using only two impulsive maneuvers and a proper timing of the first burn. The resulting plane change maneuvers are shown to be optimal over classical one-impulse maneuvers for large enough inclination change values, replacing the classical optimality of bielliptic transfers (as compared to one-impulse plane changes) in the case of environments perturbed by a large, third body. The investigation is performed by solving an optimization problem with constraints and using the Hill three-body problem to describe the underlying dynamics. Savings on the order of 25% are obtained when compared to the one-impulse transfers for plane changes of ∼60 deg, and plane changes of ′180 deg are shown to be possible without escaping.

Orbital Maneuvering with Electrodynamic Tethers

expendables. 1;2 The nearly propellantless nature of maneuvering with electrodynamics tethers could potentially enable new ways of operating in space. Some of these possibilities could be achieved in the near term. For example, techniques for boost and reentry of spacecraft has been developed by several researchers 2i8 and will be demonstrated in the NASA ProSEDS mission. Other applications are also beingconsidered and couldreap tremendous benee t. For example,a satellite servicing vehicle could rendezvous with multiple satellites in different orbits to transfer fuel or replace components to extend the lifetime of expensive space assets. An orbital tug could change the orbits of low-Earth-orbit (LEO) satellites. 9 A space surveillance satellite could obtain intelligence on foreign space assets and even perform counterspace missions if necessary. There are two practical disadvantages to electrodynamic tethers. The e rst is that the ionosphere density is not sufe cient for maneuvering out beyond LEO.Second,for practicalcurrents, forexample, a few amperes, the achievable thrust is low, and maneuvers can take many weeks to realize. Therefore, it is necessary to make an electrodynamic tether as autonomous as possible. When human support is limited for these long-duration operations, the electrodynamic tether concept can be made more cost effective. This paper provides the guidance equations for the tether current to effect a desired change in orbital elements. The guidance is capable of simultaneously changing the orbit size, shape, and plane,thatis,semimajoraxis,eccentricity,inclination,lineofnodes, and argument of perigee. These guidance laws could be used in a mission planner to perform trade studies and to evaluate the performance of a given electrodynamic tether design. The guidance laws may be suitable for onboard implementation as well,

A new formulation of the viscosity in planetary rings

We present a new formulation of the viscosity in planetary rings, where particles interact through their gravitational forces and direct collisions. In the previous studies on the viscosity in self-gravitating rings, the viscosity consists of three components, which are defined separately in different ways. The complex definitions make it difficult to evaluate the viscosity in N-body simulation of rings. In our new formulation, the viscosity is expressed in terms of changes in orbital elements of particles due to particle interactions. This makes the expression of the viscosity simple. The new formulation gives a simple way to evaluate the viscosity in N-body simulation. We find that for practical evaluation of the viscosity of planetary rings, only energy dissipation at direct inelastic collisions is needed. For tenuous particle disks (i.e., optically thin disks), we further derive a formula of the viscosity. The formula requires only a numerical coefficient that can be obtained from three-body calculation. Since planetesimal disks are also tenuous, the viscosity in planetesimal disks can be also obtained from this formula. In a subsequent paper, we will evaluate this coefficient through three-body calculation and obtain the viscosity for a wide range of parameters such as the restitution coefficient and the radial location in rings.