An understanding of the orbital dynamics would give a sound footing to address issues like types of orbit and their suitability for a given application, orbit stabilization, orbit correction and. It is observed that, to stabilize the system, tools from stability analysis of critical nonlinear systems must be. Smallgeo is a generalpurpose small geostationary satellite platform that is giving european industry the opportunity to play a significant role in the commercial telecom market. In 2004, ssl started flying russian hall effect thrusters manufactured by fakel known as stationary plasma thrusters or spt100s. At the cross, her station keeping, stabat mater free. The authors develop their control for a satellite equipped with three reaction wheels and six dualaxis thrusters mounted on each face of the. Global 3 station keeping supplement by blacksky global. This means that, as the deadband limits for the station ation pressure and the gravitational attraction of the sun and keeping became narrower, the reduction of the margins for the moon. Geostationary satellites are in orbit above the equator and go around the earth in the same direction as the earth rotates and at the same angular speed. Mpc for coupled station keeping, attitude control, and. A comparison of geo satellites using chemical and electric. The northsouth station keeping tolerances are the same as those for eastwest station keeping. Weekly eastwest station keeping ewsk and northsouth station keeping nssk maneuver operations are planned for the coms satellite in order to maintain the satellite in 0.
Howelleastwest stationkeeping of satellite orbits with resonant. The actual satellite orbit will be compared with model predictions assuming low, median, and high orbit perturbances to verify that the thrusters are maintaining the orbit. Study of the fuel consumption for stationkeeping maneuvers. Opaskep, being a multi satellite tool, supports the analysis of collocation problems. In order to simulate a station keeping procedure in a dynamic model as realistic as possible, lpos generated in the circular restricted threebody problem crtbp are discretized and reconverged in a geocentric inertial system for later simulations.
In section iii, focusing on prior orbit maintenance which is ground track correction and describe the manoeuvre scenario. It requires a series of orbital maneuvers made with thruster burns to keep the active craft in the same orbit as its target. The spacex nongeostationary orbit ngso satellite system the spacex system consists of a constellation of 4,425 satellites plus inorbit spares1 operating in 83 orbital planes at altitudes ranging from 1,110 km to 1,325 km, as well as associated ground control facilities, gateway earth stations and end user earth stations. Regarding station keeping maneuvers, in some situations, if the mission requirements allow,itispossibletoletthespacecra deviatesfromitsorbit. Use the map data to determine the date and time when the sun will be aligned directly behind with the earth station satellite path. This paper deals with a novel approach to geostationary satellite station keeping based on the use of a closed loop control law. Attitude control changing the attitude, that is changing the orientation of a spacecraft to the desired direction. Electric station keeping of geostationary satellites. Discussions focus on fixed, broadcast, and mobile services, complete satellite, transponders, and antennas. It does not mean that the satellite has to be constrained to a keplerian orbit all the time. The first successful use of ion thrusters in commercial station keeping applications was the hughes cm xenon ion propulsion system xips 3,4, which was launched into orbit in 1997 on the hughes pas5 satellite.
Communication satellite systems technology sciencedirect. Economiccasefortheretirementofgeosynchronouscommunication. Abstract the satellite tool kit stk astrogator software module is the third and most recent version of a program originally developed by nasa goddard space flight center gsfc. After deriving a set of dynamic equations governing the dynamics of a tethered satellite system tss, stabilizing tensioncontrol laws are derived in feedback form. A direct method based on the socalled differential inclusion approach is then proposed. Pdf linearized model for satellite stationkeeping and. Stationkeeping manoeuvres for geostationary satellites using feedback. For example, if a satellite attempts to download 10 mb of data but the ground station only receives 8 mb, that satellite keeps the 2 mb of data that werent successfully transmitted and attempts. Apollo 11 launch on the saturn v in 1969, illustrating the reliability of chemical rocketry the stationkeeping subsystem is necessary to maintain the desired orbit. The first ground track maintenance manoeuvre for theos. In section ii the nonlinear model for the orbit dynamics of a geostationary satellite is described and a timevarying. Pdf geostationary satellites autonomous closed loop. Dec 15, 2005 in particular, a linear timevarying model for the dynamics of a geostationary satellite affected by perturbations is derived and the longitude and latitude station keeping problem is then formulated as a constrained linear quadratic optimal control problem.
The operator is freed from the manual, time intensive support functions of the station to concentrate on the primary purpose of the station, satellite command and control. The method provides for station keeping of a three axis stabilized satellite 10 using only two thrusters 20 and 22. It permits, for example, the ation of the station keeping optimis manoeuvres of a cluster of satellites taking into account minimum inter satellite distance andor radio frequency interference constraints. A geo satellite is assigned a station keeping window, a rectangular region above the earth, whose sides are lines of longitude and latitude 3, ch.
Research article station keeping of constellations using. Perform station keeping maneuvers for extended periods of time to delay the orbital decay. Station keeping and momentum management of lowthrust. Due to the need for infrequent but relatively powerful thrusting maneuvers exerted at a single point on the satellite the center of mass, a. Software architecture and use of satellite tool kits. Pdf stabilization of tethered satellites during station. Up to date reports on the date and time when your satellites will be close to the centre of their station keeping box. Once the satellite runs out of propellant, it can no longer perform maneuvers, and the satellite drifts from its orbit.
This means that the orbital lifetime can be increased up to 5 months for a 15 years lifetime mission. Rockets and launch requirements 89 section 9 spacebasing 109 section 10 elements of a satellite system 117 section 11. Keeping a spacecraft in the desired mission orbit, i. A data link is configured to allow the aircraft to communicate data with at least one other aircraft in the formation flight of the plurality of aircraft. This paper introduces a novel affine formulation of the equations of motion of a satellite in a geostationary orbit and, based on this formulation, presents a method for determining station keeping maneuvers using convex optimization. Collocation of geostationary satellites using convex. Synchronous satellite station keeping, in communications satellite system technology, r.
Linearized model for satellite station keeping and tandem formations under the effects of atmospheric drag. Introduction a satellite in geostationary orbit is subjected to various corresponding author. Scheduling downloads for multisatellite, multiground. Stationkeeping, therefore, has to be instituted, and the spacecraft is manoeuvred in order to keep it within strict latitude and longitude limits defining a deadzone. Satellite antenna depointing originating from attitude. Optimization of ns, ew stationkeeping maneuvers for geo satellites. Research article searching for orbits with minimum fuel. Feb 29, 2020 this work introduces a linearized analytical model for the study of the dynamic of satellites in near circular orbits under the effects of the atmospheric drag. Pdf stationkeeping manoeuvres for geostationary satellites. Necessary keep the satellite stationary with respect to all the earth station antennas that are pointed at it. Optimal control in the eastwest stationkeeping manoeuvres for. For example, if a satellite attempts to download 10 mb of data but the ground station only receives 8 mb, that satellite keeps the 2 mb of.
Pine gap is the commonly used name for a us satellite surveillance base and australian earth station approximately 18 kilometres 11 mi southwest of the town of alice springs, northern territory in the centre of australia which is jointly operated by australia and the united states. Longterm electricpropulsion geostationary stationkeeping. This includes the evaluation of the station keeping required for each satellite subjected to a control box strategy, and also the. The longterm horizon of station keeping is divided in shorter control cycles synchronized with the cycles of orbit determination, and the longterm station keeping problem amounts to solve a sequence of similar mixed linear integer programming problems with different initial conditions. For many low earth orbit satellites, the effects of nonkeplerian forces, i. Linearized model for satellite stationkeeping and tandem. Attitude control must not be confused with station keeping, which is the term used for maintaining a satellite in its correct orbital position, although the two are closely related. Each satellite carries a thrust subsystem to give it an occasional nudge to keep it on station. Stationkeeping manoeuvres for geostationary satellites using. Download fulltext pdf download fulltext pdf read fulltext. Stationkeeping strategies for satellite constellation. Autonomous low earth orbit stationkeeping with electric. Introduction the objective of this contribution is to analyse speci. Review of station keeping strategies for elliptically.
Orbits, geosynchronous, perturbations, station keeping, communications. Our results offer interesting guidelines for the design and operation of satellite constellations using these orbits. The stationkeeping subsystem is necessary to maintain the desired orbit. Station keeping propellant use can be quite low, facilitating missions that can potentially last decades should other spacecraft systems remain operational. Pdf electric station keeping of geostationary satellites. It permits, for example, the optimisation of the station keeping manoeuvres of a cluster of satellites taking into account minimum inter satellite distance andor radio. Tugging is assumed to be of value to the satellite operator if it produces any amount. Software architecture and use of satellite tool kits astrogator module for libration point orbit missions john carrico, emmet fletcher analytical graphics, inc. The station keeping strategy is performed using pure passive. For this reason, geo satellites periodically need to perform station keeping maneuvers, namely, eastwest and northsouth maneuvers to.
The present paper is concerned with an estimation of the fuel consumption for station keeping maneuver needs to keep the satellite on its correct orbit. Method and apparatus for a satellite station keeping. Jan 04, 2011 thruster firings during the wol operations cause the satellite orbit to change two times a day. They appear stationary in the sky, so you satellite dish can see the satellite all of the time. Gws first satellite with propulsive 3axisstabilization. Method and apparatus for a satellite station keeping hughes. In the literature there is an extensive study about optimal maneuvers, some of them can be found in 1 to 21.
Advanced propulsion for geostationary orbit insertion and. Conventionally, satellites in geo use chemical propulsion for sk within this window. Pdf stationkeeping strategies for satellite constellation. Eastwest geo satellite stationkeeping with degraded. The problem of maintaining a lowthrust satellite in geo is treated in 6, where the authors propose a model predictive control mpc policy for simultaneous station keeping and momentum management. Eastwest stationkeeping maneuver strategy for coms. The basics of satellite orbits 29 section 5 types of orbits, or why satellites are where they are 49 section 6 maneuvering in space 69 section 7 implications of maneuvering for satellite mass 77 section 8 getting things into space. Us7024309b2 autonomous station keeping system for formation. Station keeping of geostationary satellites made simple, proceedings of the first western space conference, santa monica, 1970, pp. The study of orbits and trajectories of satellites and satellite launch vehicles is the most fundamental topic of the subject of satellite technology. Geostationary satellite station keeping robustness to loss of ground control hyung je woo, bjorn buckwalter journal of astronomy and space sciences vol. Operative life strictly depends on for station keeping sk recent interest in lowthrust electric propulsion impulsive maneuvers continuous thrust. Because of the low altitude of the iridium satellites, each satellite can only see a small portion of the. To exercise attitude control, there must be available some measure of a satellite s.
The goal is to determine the set of manoeuvres objectives of the station keeping strategy that have to be executed in order to keep the satellite in a latitude and longitude box centered at the station longitude l s 10 deg with half deadbands equal to. The thrusters 20 and 22 can be ion or liquid propulsion thrusters and are mounted on the antinadir face 18 of the satellite 10. Introduction to aerospace engineering iae pdf notes 2020. Keywords drift rate pole motion pole position solar radiation pressure orbit pole. In this paper, a modified targeting strategy is developed for missions on libration point orbits lpos in the real earthmoon system. Highorder optimal station keeping of geostationary satellites. The three spacecraft advanced composition explorer ace, solar heliospheric observatory soho, and the global geoscience wind satellite each have annual station keeping propellant. Large range of public domain old traditional hymns and modern songs.
At the cross, her station keeping, stabat mater quality music for congregational singing, prepared by church musicians. Satellite stationkeeping geostationary satellites are in orbit above the equator and go around the earth in the same direction as the earth rotates and at the same angular speed. Routine station keeping such as clock synchronization and keplerian element update. The publication then ponders on onboard communications equipment, logarithms and decibels, and radio frequencies and wavelengths and their allocations. This includes the evaluation of the station keeping required for each satellite subjected to a control box strategy, and also the study of the dynamic of tandem formations between two or more satellites that are located on the same. Classical methods are based on linear techniques pros. Geostationary satellite stationkeeping using convex. Nonlinear dynamics and stationkeeping control of a rotating. Topics include thermal and electrical power, station keeping, and pointing. Global 14 station keeping supplement by blacksky global. In astrodynamics, orbital stationkeeping is keeping a spacecraft at a fixed distance from another spacecraft. Simple approach to eastwest station keeping of geosynchronous longitudes about a given longitude. Three techniques for station keeping an orbiting constellation of satellites in an elliptical orbit are developed.
Orbitandattitude the reference mission orbit is a specialized sunsynchronous, repeat groundtrack and frozen. A modified targeting strategy for stationkeeping of. An improved method for satellite station keeping is disclosed. For geo orbits, a rectangle box limits of 147 km is produced. Space dynamics for geostationary satellites, cepadues editions, toulouse.
Satellite mission,scientific,military and national security,commercial,an operational satellite system,ground station,command and control center,data storage system,data analysis and distribution center,elements of a satellite,payload,bus,launch vehicle adapter assembly, satellite bus. Various forces primarily due the moon, sun, the earths oblateness, aerodynamic, gravitational, and magnetic forces would alter the orbit over time, degrading the mission effectiveness. Figures 3 and 4 show the longer term variations in the received uncorrected time codes over a period of nearly four years. Since 1988, it has been officially called the joint defence facility pine gap jdfpg. The present paper is concerned with an estimation of the fuel consumption for station keeping maneuver needs to keep the satellite.
Pdf the aim of this paper is to consider the modelling and control issues arising in the design of a station keeping system for geostationary. The orbital information for iridium is listed in table 1. A system for autonomously keeping an aircrafts station in a formation flight of a plurality of aircraft includes a navigation system configured to determine a position of an aircraft. A station keeping system for a threeaxis stabilized satellite, comprising. Pdf this paper firstly introduces the concepts on control box and control reference for absolute and relative station keeping, how to determine. The state equations are written as a linear, timevarying system and include all dominant perturbing accelerations. In the following, details of the mission, navigation requirements, and spacecraftcon. However, research on the tss station keeping nonlinear control problem along periodic orbits around libration points is limited compared with the free formation.
Constructing the lpos of variable amplitude and di. Satellite endoflife eol decision tree and outcomes. The tether is assumed to be rigid and massless, and the equations of motion are derived using the system lagrangian. Satellite orbits and trajectories satellite technology. A method of station keeping for a threeaxis stabilized satellite having four thrusters mounted in a generally rectangular configuration on an antinadir face of the satellite, each of the four thrusters having a line of thrust which passes through the center of mass of the satellite, the four thrusters including a northwest thruster, a northeast thruster, a southwest. Station keeping in longitude of geostationary satellites in the fixed satellite service 1974197819821992 the itu radiocommunication assembly, considering a that the geostationary satellite orbit gso is of unique usefulness to telecommunication services. A systematic approach to stationkeeping of constellations.
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