专利汇可以提供Eccentricity control for geosynchronous satellites专利检索,专利查询,专利分析的服务。并且Eccentricity control for a geosynchronous satellite includes: setting initial conditions, duration, and schedule for the eccentricity control; defining a plurality of parameters including control loci for centroid, semi-major axis, semi-minor axis, uncontrolled eccentricity radius, right ascension of ascending node, and inclination, wherein the plurality of parameters are defined such that when the eccentricity control is applied, a mean geodetic longitude of the geosynchronous satellite is maintained within a predefined distance from a station longitude.,下面是Eccentricity control for geosynchronous satellites专利的具体信息内容。
The invention claimed is:
This application claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/825,436, filed May 20, 2013, entitled “Eccentricity Control for Geosynchronous Satellites.” The disclosure of the above-referenced application is incorporated herein by reference.
Field of the Invention
The present invention relates to geosynchronous satellites, and more specifically, to an eccentricity control of a geosynchronous satellite.
Background
Managing orbital degradation of geosynchronous satellites over time is an on-going problem. Because of various external forces, such as forces exerted by the sun and the moon, it is necessary to correct for this degradation in order to extend the lifetime of satellites to a maximum span. Because the lifetime of a satellite depends on how long its supply of fuel lasts, any saved fuel may be used to extend the life of the satellite.
The present invention provides for eccentricity control of a geosynchronous satellite.
In one implementation, a method of eccentricity control for a geosynchronous satellite is disclosed. The method includes: setting initial conditions, duration, and schedule for the eccentricity control; defining a plurality of parameters including control loci for centroid, semi-major axis, semi-minor axis, uncontrolled eccentricity radius, right ascension of ascending node, and inclination, wherein the plurality of parameters are defined such that when the eccentricity control is applied, a mean geodetic longitude of the geosynchronous satellite is maintained within a predefined distance from a station longitude.
In another implementation, an apparatus for eccentricity control of a geosynchronous satellite is disclosed. The apparatus includes: means for setting initial conditions, duration, and schedule for the eccentricity control; means for defining a plurality of parameters including control loci for centroid, semi-major axis, semi-minor axis, uncontrolled eccentricity radius, right ascension of ascending node, and inclination, wherein the plurality of parameters are defined such that when the eccentricity control is applied, a mean geodetic longitude of the geosynchronous satellite is maintained within a predefined distance from a station longitude.
In a further implementation, a non-transitory computer-readable storage medium storing a computer program for eccentricity control of a geosynchronous satellite is disclosed. The computer program includes executable instructions that cause a computer to: set initial conditions, duration, and schedule for the eccentricity control; define a plurality of parameters including control loci for centroid, semi-major axis, semi-minor axis, uncontrolled eccentricity radius, right ascension of ascending node, and inclination, wherein the plurality of parameters are defined such that when the eccentricity control is applied, a mean geodetic longitude of the geosynchronous satellite is maintained within a predefined distance from a station longitude.
Other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings.
As described above, managing orbital degradation of geosynchronous satellites over time is an on-going problem, and it is necessary to correct for this degradation in order to extend the lifetime of satellites to a maximum span. Accordingly, what is needed is a way to provide design and implementation of eccentricity control strategies.
Certain implementations as described herein provide for eccentricity-inclination-sun synchronous eccentricity (HK) control for geosynchronous satellites in both equatorial and inclined orbits. After reading this description it will become apparent how to implement the invention in various implementations and applications. Although various implementations of the present invention will be described herein, it is understood that these implementations are presented by way of example only, and not limitation. As such, this detailed description of various implementations should not be construed to limit the scope or breadth of the present invention.
As illustrated in
A beginning-of-life (BOL) inclined orbit scenario and a middle-of-life (MOL) equatorial orbit scenario are each subject to two instances of EISK eccentricity control. The first instance emulates Node-Synchronous Station Keeping (eNSSK) node-synchronous eccentricity control using the Eccentricity-Inclination-Synchronous-Station-Keeping (EISK) implementation, while the second instance offers a minimum fuel alternative to the maximum compensation strategy. Thus, the first instance provides a maximum compensation control (eNSSK), while the second instance provides a minimum fuel control (EISK). The BOL scenarios demonstrate that eNSSK node-synchronous HK control may be rendered as a special case of EISK, and that EISK configured for minimum fuel consumption offers significant fuel savings over the maximum compensation strategy. The MOL scenarios demonstrate that EISK offers a seamless and fuel-optimal continuously variable transition between BOL and end-of-life (EOL) inclined orbit operations and MOL equatorial operations.
Term Node-Synchronous Station Keeping (NSSK) refers to an open loop control algorithm for eccentricity control in geosynchronous inclined orbit, which only applies control deltas orthogonal to the inclined orbit line of nodes. In contrast, term EISK is a closed loop control which represents a major departure from NSSK.
As for each of the EISK control space, longitude and drift (LD), eccentricity (HK), and inclination (PQ), the station keeping (SK) control locus paradigm defines a desired continuously-controlled mean element locus which is then rendered in practice by episodic discrete control impulses. The LD is the in-orbit phase of satellite and its rate of change, the HK is the shape and orientation of orbit ellipse, and the PQ is the orientation of the orbit plane in inertial space. The control schedules and control loci are operator-defined. In particular, the EISK HK control locus is an ellipse in the HK vector plane and the ellipse centroid and semi-axis lengths and orientations are operator defined. One or both control locus semi-diameters may be zero.
Accordingly, the station keeping function manages six orbital elements in three pairs: longitude and drift (LD), eccentricity trajectories (HK), and inclination (PQ). The LD is the in-orbit phase of satellite and its rate of change, the HK is the shape and orientation of orbit ellipse, and the PQ is the orientation of the orbit plane in inertial space. Thus, the orbital elements are defined as follows:
A BOL inclined orbit scenario, subject to eNSSK (maximum compensation control) and EISK (minimum fuel control) eccentricity controls, is illustrated in and described with respect to
The BOL configuration settings common to the two control instances are as follows:
1) Initial Conditions
2) Duration and Schedule
3) Control Locus Definition
The two instances are distinguished only by the value of F, the semi-minor axis of the control locus. That is, when F=0, maximum compensation control (eNSSK) is selected, while when F=200, EISK minimum fuel control is selected. The sun is approximately at the vernal equinox (raSun=10 deg) at t0=2014.25 (the BOL simulation start date).
In conclusion regarding the BOL eccentricity control, the eNSSK max compensation control (as configured for this BOL inclined orbit scenario) provides a 47 mdeg MGL control margin year round, which is nearly the entire longitude slot radius. A typical MGL control margin for a 50 mdeg slot is 25 mdeg or less. The annual eccentricity control authority demand of the eNSSK control is 1400 micros. Further, the EISK minimum fuel control (as configured for this BOL inclined orbit scenario) provides at least 27 mdeg MGL control margin for the 50 mdeg radius slot. The annual eccentricity control authority demand of the control is 600 micros, 43% of the eNSSK demand. Decreasing the EISK semi-minor axis from 200 micros to 100 micros increases the year round minimum MGL control margin from 27 mdeg to 35 mdeg at the cost of increasing the eccentricity control authority demand from 600 micros to 1000 micros, 71% of the eNSSK demand.
A MOL equatorial orbit scenario subject to eNSSK (maximum compensation control) and EISK (minimum fuel control) eccentricity controls is illustrated and described with respect to
The MOL configuration settings common to the two control instances are as follows:
1) Initial Conditions
2) Duration and Schedule
3) Control Locus Definition
The MOL inclination represents a near-miss of the inclination vector origin by 100 mdeg in the direction of the vernal equinox. The two controls are distinguished only by the values of E and F, the semi-axes of the control locus. In one case for eNSSK maximum compensation control, E=350 and F=0. In one case for EISK minimum fuel sun synchronous control circular radius, E=200 and F=200. The sun is approximately in the autumnal equinox (raSun=190 deg) at t0=2021.75, the MOL simulation start date.
In conclusion regarding the MOL eccentricity control, the eNSSK max compensation control provides 10 mdeg of MGL control margin year-round. The margin is small, but could in fact be supported by the Long/Drift Station Keeping MGL control algorithm with a 7 day maneuver period at longitude stations for which tri-axiality is less than, say, 0.75 mdeg/day2 in magnitude. The EISK min fuel sun synchronous control as configured for this MOL equatorial orbit scenario provides a year-round minimum of 27 mdeg MGL control radius margin for the 50 mdeg radius slot. The annual eccentricity authority demanded by the control is 950 micros, 58% greater than the demand of its antecedent BOL EISK control. Decreasing the EISK circular sun synchronous control locus semi-axes from 200 micros to 100 micros increases the year-round minimum MGL control margin from 25 mdeg to 32.5 mdeg at the cost of increasing the eccentricity control authority demand from 950 micros to 1250 micros, a 32% increase over the control authority demand for the 200 micro sun synchronous control radius.
As stated above, NSSK eccentricity control for inclined orbit operations may be instantiated as a special limit-value case of EISK eccentricity-inclination-sun synchronous control. NSSK may be emulated as EISK configured with control locus semi-major axis aligned with the orbit line of nodes and having magnitude equal to the satellite's natural (uncontrolled) eccentricity radius, and with the control locus semi-minor axis maximally controlled to magnitude zero. Relaxing the maximum compensation control for inclined operations to admit a semi-minor axis magnitude commensurate with the sun synchronous control radius one would use for equatorial operations with the same vehicle offers significant control authority demand savings without compromising MGL control for BOL to MOL and for MOL to EOL inclined orbit operations.
MOL equatorial sun synchronous operations may be achieved seamlessly from BOL inclined operations by annual reduction of the EISK semi-major axis from its BOL uncontrolled maximum value to the MOL sun synchronous radius while holding the semi-minor axis at the MOL sun synchronous radius throughout. The MOL to EOL evolution of the semi-major axis magnitude would retrace the BOL to MOL semi-major axis values in ascending order. Optimization of the annual progression of EISK semi-major axis magnitudes may halve the eccentricity control fuel loading for a fixed vehicle lifespan, or alternatively, double the eccentricity fuel life span for a fixed fuel loading relative to the NSSK baseline.
The above description of the disclosed implementations is provided to enable any person skilled in the art to make or use the invention. Various modifications to these implementations will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other implementations without departing from the spirit or scope of the invention. Accordingly, additional implementations and variations are also within the scope of the invention. For example, although the implementations discussed above focus on canceling the interfering signal, the envelope feedback interference reduction systems and techniques described above can be used to enable cancel each signal individually so that both signals can be processed allowing for a blind dual-carrier process to maximize data throughput on an RF system, or to allow characterize and capture, but not cancel the interfering signal for real-time or post process analysis. Further, it is to be understood that the description and drawings presented herein are representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other implementations that may become obvious to those skilled in the art and that the scope of the present invention is accordingly limited by nothing other than the appended claims.
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