# US 11,029,412 B2 · System and method for efficient broadcast of satellite constellation ephemeris information

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- Number: US 11,029,412 B2
- Document ID: US11029412B2
- Status: Granted
- Kind: B2
- Application number: 15/700,098
- Filed: 2017-09-09
- Published: 2018-03-15
- Granted: 2021-06-08
- Earliest claimed: 2016-09-10
- Assignees: Hughes Network Systems, LLC
- Applicants: Hughes Network Systems, LLC
- Inventors: Channasandra Ravishankar; John Corrigan; Deepak Arur; Yash Vasavada
- Web page: https://patentgrep.com/patent/US11029412B2

## CPC

- G01S 19/258: {relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view}
- G01S 19/05: providing aiding data
- G01S 19/00: Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S 19/02: Details of the space or ground control segments
- G01S 19/06: employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
- H04B 7/18519: {Operations control, administration or maintenance}
- H04B 7/18591: {Arrangements for interconnecting multiple systems (data switching networks H04L12/00)}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- H04B: TRANSMISSION

## Abstract

Approaches for efficient broadcast of satellite ephemeris information or data in NGSO satellite systems, based on Keplerian parametric models of the satellite orbits, are provided. Keplerian orbit parameters are utilized (e.g., parametric orbit models) for improved efficiency in broadcast of ephemeris data over use of point-wise vectors. The linear change and harmonic variations in Keplerian orbit parameters are accounted for, for example, based on the specification of the linear and harmonic terms, increasing accuracy and extending duration of validity of the orbit parameters. Data compression is employed by (i) differential encoding of orbital parameters, and (ii) exploiting the correlation between the harmonic (Fourier) coefficients model of the orbit parameters. An efficient transport mechanism entails classification of information in Classes with different repetition/update rates based on information types, significantly reducing required broadcast/update data rates while allowing for a wide variation in the orbit orientation.

## Claims

### Claim 1

A method for broadcasting satellite ephemeris data for a constellation of a plurality of satellites comprising:
characterizing each of a set of orbital parameters for each of the plurality of satellites as a function x(t) of a plurality of terms including a constant, a linear function of time and a number of harmonics, wherein each set of orbital parameters collectively reflects a position of the respective satellite as a function of time (t),
classifying each of the plurality of terms for each orbital parameter in one of a plurality of information classes, wherein each information class is subject to a respective update frequency for the respective terms classified therein, and wherein each of the plurality of terms for each orbital parameter is classified based on a rate of change over time (t) of the term;
determining an updated value for each of the terms of each frequency class based on the respective update frequency for the frequency class; and
broadcasting, by each of the plurality of satellites of the constellation, a current value for each of the terms of each frequency class at a frequency relative to the respective update frequency for the frequency class in order for a user terminal to determine a position of the respective satellite at a time (t).

### Claim 2 (depends on 1)

The method according to claim 1, wherein, for each of the plurality of satellites, the plurality of orbital parameters comprise the Radius r(t) of the orbit of the respective satellite, the inclination i(t) of the orbit of the respective satellite, the Argument of Latitude L(t) of the respective satellite, and the Longitude of Ascending Node Ω(t) of the respective satellite.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the function x(t) for each orbital parameter is
x(t)=A0x+A1x×t+x1,orbit(t)+x2,orbit(t),
wherein
A0xis the constant which is an initial value at a reference time,
A1x×t is the linear function of time which reflects a rate of linear change,
x1,orbit(t) is a first harmonic which comprises an amplitude A1,orbitxand a phase θ1,orbitfor the first harmonic for the orbit of the respective satellite, where
x1,orbit(t) is a complex function of the amplitude A1,orbitxand phase θ1,orbitxfor the first harmonic, and
x2,orbit(t) is a second harmonic which comprises an amplitude A2,orbitxand a phase θ2, orbitxfor the second harmonic for the orbit of the respective satellite, where
x2,orbit(t) is a complex function of the amplitude A 2,orbitxand phase θ2,orbitxfor the second harmonic.

### Claim 4 (depends on 3)

The method according to claim 3, further comprising:
reducing the number of terms for each orbital parameter in each frequency class based on correlation and predictability factors of the orbital parameters comprising (i) orbital parameters that apply commonly for all of the plurality of satellites, (ii) orbital parameters that are common or highly correlated for the satellites of a common orbital plane (intra-plane satellites), (iii) orbital parameters for which time-variation follows a predictable temporal trajectory determined by Newtonian mechanics, and (iv) orbital parameters for which Fourier coefficients of the harmonic terms exhibit a high degree of correlation.

### Claim 5 (depends on 4)

The method according to claim 4, wherein the terms are classified based on their respective rates of change relative to the other terms.

### Claim 6 (depends on 4)

The method according to claim 4, wherein terms that exhibit higher rates of change relative to other terms are classified in an information class broadcast on a logical channel with a high periodicity, and terms that exhibit lower rates of change relative to other terms and near-constant terms are conveyed on transport channels of respective lower periodicities.

### Claim 7 (depends on 4)

The method according to claim 4, wherein there are three frequency classes Class A, Class B and Class C, wherein:
Class A is for terms reflecting relatively fast changing per-satellite information, which includes factor values reflecting delta changes in A0L, A0 Ω, A1r, orbit, θ1,orbitr, A2,orbitr, θ2,orbitr, for each orbital parameter, with a faster update frequency relative to Class B;
Class B is for relatively slow changing per-satellite information, which includes factor values reflecting values, relative to base values for terms that are common or highly correlated across the entire constellation, for the terms A0r, A0hu i, A0L, A0Ω, A1,orbitr, θ1,orbitr A2,orbitr, θ2,orbitr for each orbital parameter; and
Class C is for the base values for the terms that are common or highly correlated across the entire constellation.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the function x(t) for each orbital parameter is
x(t)=A 0x+A1x×t+x1,orbit(t)+x2,orbit(t),
wherein
A0 xis the constant which is an initial value at a reference time,
A1 x×t is the linear function of time which reflects a rate of linear change,
x1,orbit(t) is a first harmonic which comprises an amplitude A1,orbitxand a phase θ1,orbitxfor the first harmonic for the orbit of the respective satellite, where
x1,orbit(t) is a complex function of the amplitude A1,orbitxand phase θ1,orbitxfor the first harmonic, and
x2,orbit(t) is a second harmonic which comprises an amplitude A2,orbitxand a phase θ2,orbitxfor the second harmonic for the orbit of the respective satellite, where x2,orbit(t) is a complex function of the amplitude A2,orbitxand phase θ2,orbitxfor the second harmonic.

### Claim 9 (depends on 8)

The method according to claim 8, further comprising:
reducing the number of terms for each orbital parameter in each frequency class based on correlation and predictability factors of the orbital parameters comprising (i) orbital parameters that apply commonly for all of the plurality of satellites, (ii) orbital parameters that are common or highly correlated for the satellites of a common orbital plane (intra-plane satellites), (iii) orbital parameters for which time-variation follows a predictable temporal trajectory determined by Newtonian mechanics, and (iv) orbital parameters for which Fourier coefficients of the harmonic terms exhibit a high degree of correlation.

### Claim 10 (depends on 9)

The method according to claim 9, wherein the terms are classified based on their respective rates of change relative to the other terms.

### Claim 11 (depends on 9)

The method according to claim 9, wherein terms that exhibit higher rates of change relative to other terms are classified in an information class broadcast on a logical channel with a high periodicity, and terms that exhibit lower rates of change relative to other terms and near-constant terms are conveyed on transport channels of respective lower periodicities.

### Claim 12 (depends on 9)

The method according to claim 9, wherein there are three frequency classes Class A, Class B and Class C, wherein:
Class A is for terms reflecting relatively fast changing per-satellite information, which includes factor values reflecting delta changes in AL0, A0 Ω, A1,orbitr, A2,orbitr, θ2,orbitr for each orbital parameter, with a faster update frequency relative to Class B;
Class B is for relatively slow changing per-satellite information, which includes factor values reflecting values, relative to base values for terms that are common or highly correlated across the entire constellation, for the terms A0 r, A0 i, A0 L, A0 Ω, A1,orbitr, θ1,orbitr, Ar2,orbit, θ2,orbitr for each orbital parameter; and
Class C is for the base values for the terms that are common or highly correlated across the entire constellation.