WO2007058721A1 - Premiere sous-constellation de satellites et seconde sous-constellation de satellites decalee - Google Patents

Premiere sous-constellation de satellites et seconde sous-constellation de satellites decalee Download PDF

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Publication number
WO2007058721A1
WO2007058721A1 PCT/US2006/039909 US2006039909W WO2007058721A1 WO 2007058721 A1 WO2007058721 A1 WO 2007058721A1 US 2006039909 W US2006039909 W US 2006039909W WO 2007058721 A1 WO2007058721 A1 WO 2007058721A1
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WO
WIPO (PCT)
Prior art keywords
satellite
constellation
sub
satellites
communication link
Prior art date
Application number
PCT/US2006/039909
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English (en)
Inventor
Darrell Franklin Yocam
Original Assignee
Northrop Grumman Space & Mission Systems Corp.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Northrop Grumman Space & Mission Systems Corp. filed Critical Northrop Grumman Space & Mission Systems Corp.
Publication of WO2007058721A1 publication Critical patent/WO2007058721A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/195—Non-synchronous stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
    • B64G1/00—Cosmonautic vehicles
    • B64G1/10—Artificial satellites; Systems of such satellites; Interplanetary vehicles
    • B64G1/1085—Swarms and constellations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/18521—Systems of inter linked satellites, i.e. inter satellite service
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00—Arrangements for synchronising receiver with transmitter

Definitions

  • the invention relates generally to satellites and more particularly to satellite constellations.
  • Satellite networking can be accomplished through geostationary or inclined-orbit satellites.
  • Geostationary satellites are expensive and distant, may require a heavier communication payload in the mission satellite, incur a substantial speed-of-light communication delay, and are often already heavily tasked.
  • An inclined-orbit satellite usually in a Low Earth Orbit (“LEO”) or a Medium Earth Orbit (“MEO”), may not always be positioned or equipped to contribute to the mission of the mission satellite, resulting in reduced cost efficiency.
  • Inclined-orbit satellites can store messages during times when there is no communications path toward the ground, transmitting them when such a path becomes available, but this can introduce large latencies, on the order of several minutes. To reduce these latencies, ground stations could be deployed in great numbers around the world, but they usually require manning and are vulnerable to attack, and it may not be possible politically to place them in all the optimum locations.
  • FIG. 1 is a representation of one implementation of a snake family 1 satellite constellation.
  • FIG. 2 is a representation of one implementation of a snake family 2 satellite constellation.
  • FIG. 3 is a representation of one implementation of a snake family 3 satellite constellation.
  • FIG. 4 is a representation of one implementation of an apparatus that comprises a dual snake satellite constellation.
  • FIG. 5 is a representation of one implementation of a satellite of the dual snake satellite constellation of FIG. 4.
  • Goals for satellite constellation design comprise good ground coverage that is consistent throughout the orbit, constant network connectivity to every live satellite, robust and fault-tolerant communication, fast communication to any satellite, multiple paths to any satellite, and permanent crosslinks between satellites.
  • Three approaches to constellation design comprise Walker, Polar "Star”, and Equatorial (e.g., geosynchronous) constellations.
  • Geosynchronous satellites have little movement relative to the fixed earth. However, for whole-earth coverage, equatorial constellations may be inappropriate, since they do not provide polar coverage (e.g., coverage at higher latitudes). Due to their distance from the earth, equatorial satellites have an increased speed-of-light propagation delay and may require more communication power or larger antennas to communicate with ground stations 512 (FIG. 5). In addition, there is a limited availability of equatorial slots for satellites to avoid collisions and interference between separate constellations.
  • Star constellations may provide whole-earth ground coverage, but have better coverage near the poles than at the equator, which is the opposite of what most systems require.
  • a Walker constellation may be selected with an emphasis on ground coverage rather than robust satellite networking. Double- Walker constellations offer slightly less ground coverage than the best single Walker design for the same number of satellites and thus were not previously used.
  • some solutions considered repositioning older satellites into new planes after newer ones have been launched, in order to create a new Walker constellation optimized for the larger number of satellites.
  • Other solutions considered simply adding satellites to the existing planes and rephasing within the plane.
  • the first approach burns a lot of fuel, shortening the remaining life of the satellites, and the second may result in a less-than- optimum final constellation.
  • LEO low earth orbit
  • One family of Walker constellations in particular, which John Walker called a "sigma”, others call a "wave”, and referred to herein as a “snake”, has a pattern in which the current locations of satellites projected onto the ground trace out sine waves of sub-satellite ground points, with the satellites in a continuous train that loops around the world such that each satellite can always access the satellite ahead and behind it in the train. Because of this constant access, permanent communications links are possible between consecutive satellites in the snake.
  • the satellites of a snake constellation do not cross paths. Accordingly, there is no duplication of ground coverage or risk of collision or interference.
  • the number of satellites in the constellation determines how closely the satellites are spaced along the snake.
  • a satellite's orbit is described by a set of parameters known as its orbital elements. Some embodiments apply to constellations with satellites that all operate at the same altitude, at the same inclination, and in circular orbits. Given a single "root" satellite's orbital elements, a Walker constellation can be specified by three numbers, T/P/F. T is the total number of satellites in the constellation. P is the number of orbital planes employed (spaced regularly around the earth), and F is the phasing parameter, which specifies the relative position of satellites in adjacent planes.
  • S is referred to as a Snake Family Parameter, and is an integer greater than or equal to one, which divides evenly into N, the total number of satellites.
  • the number of gaps created by such a snake is ((S+l) * 2).
  • the gaps occur regularly spaced around the world at intervals of (180/(S+l)) degrees, starting with a relative longitude of (90/(S+l)) degrees.
  • any constellation N/N/N-2 is a snake with 4 gaps (at 45, 135, 215, and 305 degrees longitude relative to the root satellite).
  • FIG. 1, FIG. 2, and FIG. 3 illustrate initial locations for satellites of snake families 1 through 3, respectively, relative to a root satellite at latitude and longitude zero.
  • a prior art satellite constellation 102 comprises twelve satellites 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, and 126.
  • the satellite constellation 102 comprises a Family 1 snake family (e.g., N / N / N-2) with the satellites configured according to a 12/12/10 pattern.
  • N / N / N-2 Family 1 snake family
  • an additional set of initial locations 128 of a 60/60/58 pattern is shown overlaid with the satellite constellation 102 to better illustrate the underlying sinusoidal pattern of initial positions that all Family 1 snakes follow.
  • a prior art satellite constellation 202 comprises twelve satellites 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, and 226.
  • the satellite constellation 202 comprises a Family 2 snake family (i.e., N / (N/2) / (N/2)-3) with the satellites configured according to a 12/6/3 pattern.
  • N / (N/2) / (N/2)-3) For clarity, an additional set of initial locations 228 of a 60/30/27 pattern is shown overlaid with the satellite constellation 202 to better illustrate the underlying sinusoidal pattern of initial positions that all Family 2 snakes follow.
  • a prior art satellite constellation 302 comprises twelve satellites 304, 306, 308, 310, 312, 314, 316, 318, 320, 322, 324, and 326.
  • the satellite constellation 302 comprises a Family 3 snake family (e.g., N / (N/3) / (N/3)-4) with the satellites configured according to a 12/4/0 pattern.
  • N / (N/3) / (N/3)-4) e.g., N / (N/3) / (N/3)-4
  • an additional set of initial locations 328 of a 60/20/16 pattern is shown overlaid with the satellite constellation 302 to better illustrate the underlying sinusoidal pattern of initial positions that all Family 3 snakes follow.
  • a hybrid constellation in one example comprises two snake sub-constellations with equal inclinations and altitudes, with a longitude offset between them, said offset being half of the gap between lobes of the sinusoidal set of initial positions of satellites of the first snake.
  • the offset amount is 1 A of a snake wave: Family 1: 45 degrees; Family 2: 30 degrees; Family 3: 22.5 degrees.
  • a satellite constellation 400 in one embodiment comprises a first sub-constellation 402 (shown as squares) and a second sub-constellation 404 (shown as circles).
  • Sub-constellation 402 comprises a first set of satellites 406, 408, 410, 412, 414, 416, 418, 420, 422, and 424.
  • Sub-constellation 404 comprises a second set of satellites 426, 428, 430, 432, 434, 436, 438, 440, 442, and 444.
  • each satellite in each constellation has a communications link, such as 450, to its buddy satellite in the other constellation.
  • Each satellite flies at approximately the same altitude and orbital inclination, and flies in a roughly circular orbit (e.g., eccentricity near zero).
  • the sub-constellations 402 and 404 in one example are in low to medium earth orbit, with altitudes ranging from several hundred kilometers to several thousand kilometers. As it orbits the earth, each satellite in sub-constellation 402 traces out an approximately sinusoidal ground trace.
  • Each satellite of sub-constellation 404 follows the same ground trace as its buddy satellite in constellation 402, at the same latitude but with a longitudinal offset, as will be appreciated by those skilled in the art.
  • the first sub-constellation is defined by a first set of orbital elements and the second sub-constellation is defined by the first set of orbital elements with a longitudinal offset.
  • the satellites of the sub-constellations 402 and 404 in one example carry three crosslink antennas (capable of communicating with the other satellites) and one groundlink antenna (capable of communicating with a ground site).
  • the antenna may be a radio frequency antenna, a laser transmitter/receiver, electromagnetic wave transmitter/receiver, or other means for line-of-sight communication with other satellites or ground stations 512 (FIG. 5).
  • the satellite 416 comprises a root satellite of the first sub-constellation 402.
  • the satellite 436 comprises a root satellite of the second sub-constellation 404.
  • the satellite 416 is offset in longitude (or equivalently, Right Ascension) from the satellite 436 by (90/(S+l)) degrees, such that the satellite 436 is placed in the middle of the first gap of the first sub- constellation 402 east of the satellite 416.
  • each satellite of the first sub- constellation 402 is communicatively coupled with one satellite of the second sub- constellation 404.
  • each satellite in the sub-constellation 402 has a "buddy" in the sub-constellation 404 that flies in formation with it.
  • the satellite 408 of the first sub-constellation 402 has the satellite 428 of the second sub-constellation 404 as a buddy.
  • Each pair of buddy satellites in one example is communicatively coupled.
  • each satellite in the first sub-constellation 402 and the second sub-constellation 404 is part of a buddy pair.
  • each satellite is communicatively coupled with its leader and follower.
  • the satellite 408 employs the three crosslink antennas for communication links to the previous satellite 406 (e.g. follower), next satellite 410 (e.g., leader), and buddy satellite 428, as will be appreciated by those skilled in the art.
  • the sub-constellations 402 and 404 must have enough satellites such that each pair of consecutive satellites (e.g., satellites 410 and 412, or satellites 416 and 418) in its snake can maintain constant communications.
  • the satellite constellation 400 may provide one or more of: 1) Fault-tolerant networking. A large number of random failures have to occur before complete connectivity to the remaining live satellites is lost. 2) All satellite-to-satellite links are permanent. This is a huge advantage over Walker constellations that must make and break transient links. 3) Additional communications paths. Because of the large number of interconnections, there are a multitude of paths for messages (or packets of data) to take. This can result in decreased communications time. 4) Constellation Buildup. As soon as the first snake sub-constellation 402 is launched, it becomes fully operational, albeit with limited communications redundancy and gaps in its earth coverage.
  • the satellite constellation 400 may comprise alternative embodiments and configurations that employ a plurality of offset (e.g., shifted) sub-constellations. Any additional sub-constellation need not be fully populated to contribute to network robustness. In fact, it need not even have the same Walker parameters as the first, as long as it is in the same Snake Family, S.
  • Satellite constellations that may benefit comprise satellites that perform earth observing (e.g., radar, IR, visual) or telephone/data-relay services, for example, Space Tracking and Surveillance System (STSS), Space-Based Radar, Space-Based Laser, Space- Based Surveillance System (SBSS).
  • STSS Space Tracking and Surveillance System
  • SBSS Space-Based Surveillance System
  • a satellite 502 in one example comprises first, second, third, and fourth antennas 504, 506, 508, and 510.
  • the satellite 502 comprises one implementation of the satellites of sub-constellations 402 and 404.
  • the antennas 504, 506, 508, and 510 comprise means for communication' with other satellites 502 and/or ground stations 512, for example, radio frequency antennas, laser transmitter/receivers, electromagnetic wave transmitter/receiver, or others, as will be appreciated by those skilled in the art.
  • the antennas 504, 506, and 508 in one example comprise crosslink antennas for communication with other satellites.
  • the antenna 510 in one example comprises a groundlink antenna for communication with one or more ground stations 512.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Remote Sensing (AREA)
  • Radio Relay Systems (AREA)

Abstract

Dans un mode de réalisation, cette invention concerne une constellation de satellites comprenant un premier ensemble de satellites configurés dans une première sous-constellation définie par un premier ensemble d’éléments orbitaux. La constellation comprend également un second ensemble de satellites configurés dans une seconde sous-constellation définie par le premier ensemble d’éléments orbitaux avec un décalage longitudinal.
PCT/US2006/039909 2005-11-16 2006-10-12 Premiere sous-constellation de satellites et seconde sous-constellation de satellites decalee WO2007058721A1 (fr)

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US60/737,307 2005-11-16

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016053389A1 (fr) * 2014-09-30 2016-04-07 Google Inc. Constellation de satellites
CN111953512A (zh) * 2020-07-02 2020-11-17 西安电子科技大学 面向Walker星座的Mobius星座拓扑构型构造方法、系统及应用
US11955719B1 (en) 2023-12-11 2024-04-09 United Arab Emirates University Antenna system comprising two oppositely directed antennas and methods for controlling transmission of radiation through a multi-layered antenna structure

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EP0814576A1 (fr) * 1996-06-18 1997-12-29 Alcatel Espace Constellation de satellites non geostationnaires à couverture permanente
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016053389A1 (fr) * 2014-09-30 2016-04-07 Google Inc. Constellation de satellites
CN106464343A (zh) * 2014-09-30 2017-02-22 谷歌公司 卫星群
US9647749B2 (en) 2014-09-30 2017-05-09 Google Inc. Satellite constellation
US9973267B2 (en) 2014-09-30 2018-05-15 Google Llc Satellite constellation
CN106464343B (zh) * 2014-09-30 2019-09-13 谷歌有限责任公司 卫星群
CN110545137A (zh) * 2014-09-30 2019-12-06 谷歌有限责任公司 卫星群
CN110545137B (zh) * 2014-09-30 2022-05-03 谷歌有限责任公司 通信系统及其方法
CN111953512A (zh) * 2020-07-02 2020-11-17 西安电子科技大学 面向Walker星座的Mobius星座拓扑构型构造方法、系统及应用
US11955719B1 (en) 2023-12-11 2024-04-09 United Arab Emirates University Antenna system comprising two oppositely directed antennas and methods for controlling transmission of radiation through a multi-layered antenna structure

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