Evolution of Space Debris for Spacecraft in the Sun-Synchronous Orbit
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6 Orbit Relative to the Sun. Crossing Times
6 Orbit Relative to the Sun. Crossing Times We begin by studying the position of the orbit and ground track of an arbi- trary satellite relative to the direction of the Sun. We then turn more specif- ically to Sun-synchronous satellites for which this relative position provides the very definition of their orbit. 6.1 Cycle with Respect to the Sun 6.1.1 Crossing Time At a given time, it is useful to know the local time on the ground track, i.e., the LMT, deduced in a straightforward manner from the UT once the longitude of the place is given, using (4.49). The local mean time (LMT) on the ground track at this given time is called the crossing time or local crossing time. To obtain the local apparent time (LAT), one must know the day of the year to specify the equation of time ET. In all matters involving the position of the Sun (elevation and azimuth) relative to a local frame, this is the time that should be used. The ground track of the satellite can be represented by giving the crossing time. We have chosen to represent the LMT using colour on Colour Plates IIb, IIIb and VII to XI. For Sun-synchronous satellites such as MetOp-1, it is clear that the cross- ing time (in the ascending or descending direction) depends only on the latitude. At a given place (except near the poles), one crossing occurs during the day, the other at night. For the HEO of the Ellipso Borealis satellite, the stability of the crossing time also shows up clearly. -
Astrodynamics
Politecnico di Torino SEEDS SpacE Exploration and Development Systems Astrodynamics II Edition 2006 - 07 - Ver. 2.0.1 Author: Guido Colasurdo Dipartimento di Energetica Teacher: Giulio Avanzini Dipartimento di Ingegneria Aeronautica e Spaziale e-mail: [email protected] Contents 1 Two–Body Orbital Mechanics 1 1.1 BirthofAstrodynamics: Kepler’sLaws. ......... 1 1.2 Newton’sLawsofMotion ............................ ... 2 1.3 Newton’s Law of Universal Gravitation . ......... 3 1.4 The n–BodyProblem ................................. 4 1.5 Equation of Motion in the Two-Body Problem . ....... 5 1.6 PotentialEnergy ................................. ... 6 1.7 ConstantsoftheMotion . .. .. .. .. .. .. .. .. .... 7 1.8 TrajectoryEquation .............................. .... 8 1.9 ConicSections ................................... 8 1.10 Relating Energy and Semi-major Axis . ........ 9 2 Two-Dimensional Analysis of Motion 11 2.1 ReferenceFrames................................. 11 2.2 Velocity and acceleration components . ......... 12 2.3 First-Order Scalar Equations of Motion . ......... 12 2.4 PerifocalReferenceFrame . ...... 13 2.5 FlightPathAngle ................................. 14 2.6 EllipticalOrbits................................ ..... 15 2.6.1 Geometry of an Elliptical Orbit . ..... 15 2.6.2 Period of an Elliptical Orbit . ..... 16 2.7 Time–of–Flight on the Elliptical Orbit . .......... 16 2.8 Extensiontohyperbolaandparabola. ........ 18 2.9 Circular and Escape Velocity, Hyperbolic Excess Speed . .............. 18 2.10 CosmicVelocities -
Some Special Types of Orbits Around Jupiter
aerospace Article Some Special Types of Orbits around Jupiter Yongjie Liu 1, Yu Jiang 1,*, Hengnian Li 1,2,* and Hui Zhang 1 1 State Key Laboratory of Astronautic Dynamics, Xi’an Satellite Control Center, Xi’an 710043, China; [email protected] (Y.L.); [email protected] (H.Z.) 2 School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China * Correspondence: [email protected] (Y.J.); [email protected] (H.L.) Abstract: This paper intends to show some special types of orbits around Jupiter based on the mean element theory, including stationary orbits, sun-synchronous orbits, orbits at the critical inclination, and repeating ground track orbits. A gravity model concerning only the perturbations of J2 and J4 terms is used here. Compared with special orbits around the Earth, the orbit dynamics differ greatly: (1) There do not exist longitude drifts on stationary orbits due to non-spherical gravity since only J2 and J4 terms are taken into account in the gravity model. All points on stationary orbits are degenerate equilibrium points. Moreover, the satellite will oscillate in the radial and North-South directions after a sufficiently small perturbation of stationary orbits. (2) The inclinations of sun-synchronous orbits are always bigger than 90 degrees, but smaller than those for satellites around the Earth. (3) The critical inclinations are no-longer independent of the semi-major axis and eccentricity of the orbits. The results show that if the eccentricity is small, the critical inclinations will decrease as the altitudes of orbits increase; if the eccentricity is larger, the critical inclinations will increase as the altitudes of orbits increase. -
Positioning: Drift Orbit and Station Acquisition
Orbits Supplement GEOSTATIONARY ORBIT PERTURBATIONS INFLUENCE OF ASPHERICITY OF THE EARTH: The gravitational potential of the Earth is no longer µ/r, but varies with longitude. A tangential acceleration is created, depending on the longitudinal location of the satellite, with four points of stable equilibrium: two stable equilibrium points (L 75° E, 105° W) two unstable equilibrium points ( 15° W, 162° E) This tangential acceleration causes a drift of the satellite longitude. Longitudinal drift d'/dt in terms of the longitude about a point of stable equilibrium expresses as: (d/dt)2 - k cos 2 = constant Orbits Supplement GEO PERTURBATIONS (CONT'D) INFLUENCE OF EARTH ASPHERICITY VARIATION IN THE LONGITUDINAL ACCELERATION OF A GEOSTATIONARY SATELLITE: Orbits Supplement GEO PERTURBATIONS (CONT'D) INFLUENCE OF SUN & MOON ATTRACTION Gravitational attraction by the sun and moon causes the satellite orbital inclination to change with time. The evolution of the inclination vector is mainly a combination of variations: period 13.66 days with 0.0035° amplitude period 182.65 days with 0.023° amplitude long term drift The long term drift is given by: -4 dix/dt = H = (-3.6 sin M) 10 ° /day -4 diy/dt = K = (23.4 +.2.7 cos M) 10 °/day where M is the moon ascending node longitude: M = 12.111 -0.052954 T (T: days from 1/1/1950) 2 2 2 2 cos d = H / (H + K ); i/t = (H + K ) Depending on time within the 18 year period of M d varies from 81.1° to 98.9° i/t varies from 0.75°/year to 0.95°/year Orbits Supplement GEO PERTURBATIONS (CONT'D) INFLUENCE OF SUN RADIATION PRESSURE Due to sun radiation pressure, eccentricity arises: EFFECT OF NON-ZERO ECCENTRICITY L = difference between longitude of geostationary satellite and geosynchronous satellite (24 hour period orbit with e0) With non-zero eccentricity the satellite track undergoes a periodic motion about the subsatellite point at perigee. -
Tilting Saturn II. Numerical Model
Tilting Saturn II. Numerical Model Douglas P. Hamilton Astronomy Department, University of Maryland College Park, MD 20742 [email protected] and William R. Ward Southwest Research Institute Boulder, CO 80303 [email protected] Received ; accepted Submitted to the Astronomical Journal, December 2003 Resubmitted to the Astronomical Journal, June 2004 – 2 – ABSTRACT We argue that the gas giants Jupiter and Saturn were both formed with their rotation axes nearly perpendicular to their orbital planes, and that the large cur- rent tilt of the ringed planet was acquired in a post formation event. We identify the responsible mechanism as trapping into a secular spin-orbit resonance which couples the angular momentum of Saturn’s rotation to that of Neptune’s orbit. Strong support for this model comes from i) a near match between the precession frequencies of Saturn’s pole and the orbital pole of Neptune and ii) the current directions that these poles point in space. We show, with direct numerical inte- grations, that trapping into the spin-orbit resonance and the associated growth in Saturn’s obliquity is not disrupted by other planetary perturbations. Subject headings: planets and satellites: individual (Saturn, Neptune) — Solar System: formation — Solar System: general 1. INTRODUCTION The formation of the Solar System is thought to have begun with a cold interstellar gas cloud that collapsed under its own self-gravity. Angular momentum was preserved during the process so that the young Sun was initially surrounded by the Solar Nebula, a spinning disk of gas and dust. From this disk, planets formed in a sequence of stages whose details are still not fully understood. -
Orbital Dynamics and Numerical N-Body Simulations of Extrasolar Moons and Giant Planets
ORBITAL DYNAMICS AND NUMERICAL N-BODY SIMULATIONS OF EXTRASOLAR MOONS AND GIANT PLANETS. A Dissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Yu-Cian Hong August 2019 c 2019 Yu-Cian Hong ALL RIGHTS RESERVED ORBITAL DYNAMICS AND NUMERICAL N-BODY SIMULATIONS OF EXTRASOLAR MOONS AND GIANT PLANETS. Yu-Cian Hong, Ph.D. Cornell University 2019 This thesis work focuses on computational orbital dynamics of exomoons and exoplanets. Exomoons are highly sought-after astrobiological targets. Two can- didates have been discovered to-date (Bennett et al., 2014, Teachey & Kipping, 2018). We developed the first N-body integrator that can handle exomoon orbits in close planet-planet interactions, for the following three projects. (1) Instability of moons around non-oblate planets associated with slowed nodal precession and resonances with stars.This work reversed the commonsensical notion that spinning giant planets should be oblate. Moons around spherical planets were destabilized by 3:2 and 1:1 resonance overlap or the chaotic zone around 1:1 resonance between the orbital precession of the moons and the star. Normally, the torque from planet oblateness keeps the orbit of close-in moons precess fast ( period ∼ 7 yr for Io). Without planet oblateness, Io?s precession period is much longer (∼ 104 yr), which allowed resonance with the star, thus the in- stability. Therefore, realistic treatment of planet oblateness is critical in moon dynamics. (2) Orbital stability of moons in planet-planet scattering. Planet- planet scattering is the best model to date for explaining the eccentricity distri- bution of exoplanets. -
Satellite Orbits
Course Notes for Ocean Colour Remote Sensing Course Erdemli, Turkey September 11 - 22, 2000 Module 1: Satellite Orbits prepared by Assoc Professor Mervyn J Lynch Remote Sensing and Satellite Research Group School of Applied Science Curtin University of Technology PO Box U1987 Perth Western Australia 6845 AUSTRALIA tel +618-9266-7540 fax +618-9266-2377 email <[email protected]> Module 1: Satellite Orbits 1.0 Artificial Earth Orbiting Satellites The early research on orbital mechanics arose through the efforts of people such as Tyco Brahe, Copernicus, Kepler and Galileo who were clearly concerned with some of the fundamental questions about the motions of celestial objects. Their efforts led to the establishment by Keppler of the three laws of planetary motion and these, in turn, prepared the foundation for the work of Isaac Newton who formulated the Universal Law of Gravitation in 1666: namely, that F = GmM/r2 , (1) Where F = attractive force (N), r = distance separating the two masses (m), M = a mass (kg), m = a second mass (kg), G = gravitational constant. It was in the very next year, namely 1667, that Newton raised the possibility of artificial Earth orbiting satellites. A further 300 years lapsed until 1957 when the USSR achieved the first launch into earth orbit of an artificial satellite - Sputnik - occurred. Returning to Newton's equation (1), it would predict correctly (relativity aside) the motion of an artificial Earth satellite if the Earth was a perfect sphere of uniform density, there was no atmosphere or ocean or other external perturbing forces. However, in practice the situation is more complicated and prediction is a less precise science because not all the effects of relevance are accurately known or predictable. -
Sun-Synchronous Satellites
Topic: Sun-synchronous Satellites Course: Remote Sensing and GIS (CC-11) M.A. Geography (Sem.-3) By Dr. Md. Nazim Professor, Department of Geography Patna College, Patna University Lecture-3 Concept: Orbits and their Types: Any object that moves around the Earth has an orbit. An orbit is the path that a satellite follows as it revolves round the Earth. The plane in which a satellite always moves is called the orbital plane and the time taken for completing one orbit is called orbital period. Orbit is defined by the following three factors: 1. Shape of the orbit, which can be either circular or elliptical depending upon the eccentricity that gives the shape of the orbit, 2. Altitude of the orbit which remains constant for a circular orbit but changes continuously for an elliptical orbit, and 3. Angle that an orbital plane makes with the equator. Depending upon the angle between the orbital plane and equator, orbits can be categorised into three types - equatorial, inclined and polar orbits. Different orbits serve different purposes. Each has its own advantages and disadvantages. There are several types of orbits: 1. Polar 2. Sunsynchronous and 3. Geosynchronous Field of View (FOV) is the total view angle of the camera, which defines the swath. When a satellite revolves around the Earth, the sensor observes a certain portion of the Earth’s surface. Swath or swath width is the area (strip of land of Earth surface) which a sensor observes during its orbital motion. Swaths vary from one sensor to another but are generally higher for space borne sensors (ranging between tens and hundreds of kilometers wide) in comparison to airborne sensors. -
SATELLITES ORBIT ELEMENTS : EPHEMERIS, Keplerian ELEMENTS, STATE VECTORS
www.myreaders.info www.myreaders.info Return to Website SATELLITES ORBIT ELEMENTS : EPHEMERIS, Keplerian ELEMENTS, STATE VECTORS RC Chakraborty (Retd), Former Director, DRDO, Delhi & Visiting Professor, JUET, Guna, www.myreaders.info, [email protected], www.myreaders.info/html/orbital_mechanics.html, Revised Dec. 16, 2015 (This is Sec. 5, pp 164 - 192, of Orbital Mechanics - Model & Simulation Software (OM-MSS), Sec 1 to 10, pp 1 - 402.) OM-MSS Page 164 OM-MSS Section - 5 -------------------------------------------------------------------------------------------------------43 www.myreaders.info SATELLITES ORBIT ELEMENTS : EPHEMERIS, Keplerian ELEMENTS, STATE VECTORS Satellite Ephemeris is Expressed either by 'Keplerian elements' or by 'State Vectors', that uniquely identify a specific orbit. A satellite is an object that moves around a larger object. Thousands of Satellites launched into orbit around Earth. First, look into the Preliminaries about 'Satellite Orbit', before moving to Satellite Ephemeris data and conversion utilities of the OM-MSS software. (a) Satellite : An artificial object, intentionally placed into orbit. Thousands of Satellites have been launched into orbit around Earth. A few Satellites called Space Probes have been placed into orbit around Moon, Mercury, Venus, Mars, Jupiter, Saturn, etc. The Motion of a Satellite is a direct consequence of the Gravity of a body (earth), around which the satellite travels without any propulsion. The Moon is the Earth's only natural Satellite, moves around Earth in the same kind of orbit. (b) Earth Gravity and Satellite Motion : As satellite move around Earth, it is pulled in by the gravitational force (centripetal) of the Earth. Contrary to this pull, the rotating motion of satellite around Earth has an associated force (centrifugal) which pushes it away from the Earth. -
Astro 250: Solutions to Problem Set 5 by Eugene Chiang
Astro 250: Solutions to Problem Set 5 by Eugene Chiang Problem 1. Precessing Planes and the Invariable Plane Consider a star of mass mc orbited by two planets on nearly circular orbits. The mass and semi-major axis of the inner planet are m1 and a1, respectively, and those of the outer planet, m2 = (1/2) × m1 and a2 = 4 × a1. The mutual inclination between the two orbits is i 1. This problem explores the inclination and nodal behavior of the two planets. a) What is the inclination of each planet with respect to the invariable plane of the system? The invariable plane is perpendicular to the total (vector) angular momentum of all planetary orbits. Neglect the contribution of orbital eccentricity to the angular momentum. Call these inclinations i1 and i2. The masses and semi-major axes of the two planets are so chosen as to make the arithmetic easy;√ the norm of each planet’s angular momentum is the same as the other, |~l1| = |~l2| = m1 Gmca1. Orient the x-y axes in the invariable plane so that the y-axis lies along the line of intersection between the two orbit planes (the nodal line). Then in the x-z plane, the total angular momentum vector lies along the z-axis, while ~l1 lies (say) in quadrant II and makes an angle with respect to the z-axis of i1 > 0, while l~2 lies in quadrant I and makes an angle with respect to the z-axis of i2 > 0. Remember that the mutual inclination i = i1 + i2. -
The UCS Satellite Database
UCS Satellite Database User’s Manual 1-1-17 The UCS Satellite Database The UCS Satellite Database is a listing of active satellites currently in orbit around the Earth. It is available as both a downloadable Excel file and in a tab-delimited text format, and in a version (tab-delimited text) in which the "Name" column contains only the official name of the satellite in the case of government and military satellites, and the most commonly used name in the case of commercial and civil satellites. The database is updated roughly quarterly. Our intent in producing the Database is to create a research tool by collecting open-source information on active satellites and presenting it in a format that can be easily manipulated for research and analysis. The Database includes basic information about the satellites and their orbits, but does not contain the detailed information necessary to locate individual satellites. The UCS Satellite Database can be accessed at www.ucsusa.org/satellite_database. Using the Database The Database is free and its use is unrestricted. We request that its use be acknowledged and referenced in written materials. References should include the version of the Database that was used, which is indicated by the name of the Excel file, and a link to or URL for the webpage www.ucsusa.org/satellite_database. We welcome corrections, additions, and suggestions. These can be emailed to the Database manager at [email protected] If you would like to be notified when updated versions of the Database are completed, please send an email request to this address. -
Evolution of a Terrestrial Multiple Moon System
THE ASTRONOMICAL JOURNAL, 117:603È620, 1999 January ( 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. EVOLUTION OF A TERRESTRIAL MULTIPLE-MOON SYSTEM ROBIN M. CANUP AND HAROLD F. LEVISON Southwest Research Institute, 1050 Walnut Street, Suite 426, Boulder, CO 80302 AND GLEN R. STEWART Laboratory for Atmospheric and Space Physics, University of Colorado, Campus Box 392, Boulder, CO 80309-0392 Received 1998 March 30; accepted 1998 September 29 ABSTRACT The currently favored theory of lunar origin is the giant-impact hypothesis. Recent work that has modeled accretional growth in impact-generated disks has found that systems with one or two large moons and external debris are common outcomes. In this paper we investigate the evolution of terres- trial multiple-moon systems as they evolve due to mutual interactions (including mean motion resonances) and tidal interaction with Earth, using both analytical techniques and numerical integra- tions. We Ðnd that multiple-moon conÐgurations that form from impact-generated disks are typically unstable: these systems will likely evolve into a single-moon state as the moons mutually collide or as the inner moonlet crashes into Earth. Key words: Moon È planets and satellites: general È solar system: formation INTRODUCTION 1. 1000 orbits). This result was relatively independent of initial The ““ giant-impact ÏÏ scenario proposes that the impact of disk conditions and collisional parameterizations. Pertur- a Mars-sized body with early Earth ejects enough material bations by the largest moonlet(s) were very e†ective at clear- into EarthÏs orbit to form the Moon (Hartmann & Davis ing out inner disk materialÈin all of the ICS97 simulations, 1975; Cameron & Ward 1976).