ISO/TR 22639:2021

TECHNICAL ISO/TR
REPORT 22639
First edition
Space systems – Design guidelines for
multi-geo spacecraft collocation
PROOF/ÉPREUVE
Reference number
ISO/TR 22639:2021(E)
©
ISO 2021

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ISO/TR 22639:2021(E)

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© ISO 2021
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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 4
4 Collocation design process . 4
5 Basic contents of collocation design process . 6
5.1 Considerations . 6
5.2 Initial collocation strategy design . 6
5.2.1 Fundamental principle of separation strategy . 6
5.2.2 The available separation strategy . 6
5.2.3 Selection of collocation strategy. 7
5.2.4 Simulation Evaluation of Collocation Strategy . 7
5.3 Final collocation strategy . 7
5.4 Collocation agreement. 7
Annex A (informative) Fundamental principle of available separation strategy .10
Annex B (informative) Characteristics of separation strategy .15
Annex C (Informative) Fundamental principle of separation strategy .17
Annex D (Informative) Sample of collocation evaluation strategy .19
Annex E (Informative) Common collocation cases and strategies .20
Bibliography .21
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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 14, Space systems and operations.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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Introduction
With the wide application of geostationary orbit in spacecraft navigation, spacecraft communication
and remote sensing, there comes a dramatic increase in the number of geostationary spacecraft while
the orbit position of geostationary spacecraft is limited. In order to solve this problem, it is often
necessary for spacecraft operators to collocate their spacecraft with spacecraft operated by other
agencies in order to deliver their services.
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TECHNICAL REPORT ISO/TR 22639:2021(E)
Space systems – Design guidelines for multi-geo spacecraft
collocation
1 Scope
This document addresses the design process of a collocation and the basic contents of collocation
design process which include considerations, initial collocation strategy design, simulation evaluation
of collocation strategy, optimal collocation strategy selection and collocation agreement.
This document gives guidelines for multi-geo spacecraft collocation, and it applies in particular to
multi-geo constellation.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1.1
orbit maintenance
orbit control for maintaining the spacecraft’s orbit in certain prediction error around the nominal orbit
3.1.2
inclination vector
vector which points to the ascending node and which is measured from the vernal equinox
Note 1 to entry: The x and y components of the vector can be expressed as Formulae (1) and (2).
ii=sincos()Ω (1)
x
ii=sinsin()Ω (2)
y
where
i
is the magnitude of the inclination vector;
Ω
is the raan in J2000 geocentric equatorial coordinate system (3.1.5);
i is the x component of the inclination vector coordinate;
x
i

is the y component of the inclination vector coordinate.
y
Note 2 to entry: Figure 1 shows the definition of the inclination vector.
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Key
i inclination vector which points to the ascending node
X direction of vernal equinox
Figure 1 — Inclination vector
3.1.3
eccentricity vector
vector which points to the orbit perigee and which is measured from the vernal equinox
Note 1 to entry: The x and y components of the vector can be expressed as Formulae (3) and (4).
ee=+cos(Ωω) (3)
x
ee=+sin(Ωω) (4)
y
where
e
is the magnitude of the eccentricity vector;
e
is the x component of the eccentricity vector coordinate;
x
e
is the y component of the eccentricity vector coordinate;
y
ω
is the argument of perigee.
Note 2 to entry: Figure 2 shows the definition of the eccentricity vector.
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Key
e eccentricity vector which points to the orbit perigee
X direction of the vernal equinox
Figure 2 — Eccentricity vector
3.1.4
mean longitude
l
sum of the right ascension of the ascending node, the augment of perigee and the mean anomaly
Note 1 to entry: It can further be interpreted as the approximate right ascension of the near-circular orbits with
small inclination.
3.1.5
J2000 geocentric equatorial coordinate system
coordinate system with origin at the Earth’s centre
Note 1 to entry: The positive x-axis points in the direction of the mean vernal equinox of Earth at J2000 epoch.
The positive z-axis points in the direction of the normal direction of the mean equator at J2000 epoch. The y-axis
is orthogonal to both the x-axis and the z-axis and completes a right-handed frame.
Note 2 to entry: J2000 epoch: JD=2451545,0, which is 1 Jan 2000 12:00:00 TDB.
Note 3 to entry: Figure 3 shows this coordinate system.
Key
E earth equator plane
Figure 3 — J2000 geocentric equatorial coordinate system
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3.1.6
spacecraft coordinate system of geo spacecraft
RTN
coordinate system with origin at the centre of the geo spacecraft’s positioned point
Note 1 to entry: The R axis is outward along radial. The N axis points in the direction of the normal direction of
J2000 mean equator. The T axis is constructed as N×R.
Note 2 to entry: Figure 4 shows this coordinate system.
Figure 4 — Spacecraft coordinate system of geo spacecraft (RTN)
3.2 Abbreviated terms
E/W east/west
geo geostationary earth orbit
raan right ascension of the ascending node (the angle between the vernal equinox and the orbit
ascending node)
OD orbit determination
4 Collocation design process
Design process of a collocation includes considerations, initial collocation strategy design, simulation
evaluation of collocation strategy, initial selection of collocation strategy, optimal collocation strategy
selection and collocation agreement.
The collocation design process is basically carried out according to the following steps, which are
represented in the collocation working flow (see Figure 5).
a) Delegations of different spacecraft operators with diversity needs hold an orbit safety consultation
meeting. Commonly, the operator of spacecraft that has to collocate with other spacecraft that is
already located at the position brings forward the consultation meeting, negotiates and organizes
the meeting.
b) In the consultation meeting, each operator presents the operation status, operational issue and
then brings forward and confirms the considerations of collocation design.
c) The initial collocation strategy is designed according to the considerations. Each collocation
spacecraft operator selects and proposes the preferred collocation strategy. The collocation
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strategy includes the strategy during mission period and the initial phase strategy to move a
spacecraft into position of collocation configuration and the deorbit strategy.
d) Simulation is carried out to evaluate whether the collocation strategies meet the demanded
requirements of all parties.
e) If the selected initial collocation strategy can’t meet the specified requirements, the collocation
strategies are reviewed in order to identify what can be improved. If improvements are identified,
the collocation strategies are revised and the simulation evaluation step d) is carried out again.
Else, the initial design of collocation strategy step c) is carried out again.
f) If the chosen strategy meets all the specified requirements then the strategy can be confirmed as
the decided solution.
g) Once the optimal strategy is selected then the collocation agreement formalized and signed in
accordance with Clause 5.
Figure 5 — Collocation working flow
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5 Basic contents of collocation design process
5.1 Considerations
In the orbit safety consultation meeting, each operator presents operation status and operational issue
and then brings forward and confirms the considerations of collocation design.
The following considerations are at least involved in the process:
a) ITU regulations about frequency allocation and assigned orbital slots of the geo spacecraft;
b) number of collocated spacecraft;
c) safety separation distance between collocated spacecraft;
d) orbit maintenance requirements of collocated spacecraft;
e) precision of orbit determination of collocated spacecraft;
f) flight dynamics characteristics, e.g. Earth gravity, solar radiation pressure;
g) fuel consumption of collocated spacecraft;
h) number and ability of central management of collocated spacecraft;
i) other special restrictions of collocated spacecraft.
5.2 Initial collocation strategy design
5.2.1 Fundamental principle of separation strategy
Assuming d is the relative distance between any two collocated spacecraft, d is the required
min
minimum safe separation distance, then the collocation strategy is to make the relative distance d
qualify the demanded condition which is d ≥ d . Generally, the value of d is 10 km based on the
min min
successful experience of international collocation cases.
The common method of the relative distance between any two collocated spacecraft is shown in
Annex C.
5.2.2 The available separation strategy
The fundamental separation strategies are listed as follows and the detailed principle about each
strategy is given in Annex A. The characteristics of each separation strategy are shown in Annex B (see
Table B.1).
a) the complete longitude separation strategy;
b) coordinated station keeping strategy;
c) the absolute eccentricity separation strategy;
d) the relative eccentricity vector separation strategy;
e) the eccentricity and inclination vector separation strategy.
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5.2.3 Selection of collocation strategy
5.2.3.1 Selection principle
The separation strategy is one of the fundamental strategies of 5.2.2, some other new strategies or the
combination of them. In any case, the separation strategy to be selected meets the following design
considerations:
a) safety assured: the design ensures that the in-flight safety of the spacecraft involved in the
collocation strategy;
b) operational mission: the design takes into account all the operational specifications;
c) experience-based: the design is based on current operational best practices and return of
experience (lessons learned); for the common collocation cases and strategies, refer to Annex E;
d) easily realized: the designed separation strategy is operationally feasible.
5.2.3.2 Selection method
During the selection process, the selection principle listed in 5.2.3.1 is always applied. Annex D (see
Table D.1) provides common collocation cases as well as commonly adopted collocation design results.
5.2.4 Simulation Evaluation of Collocation Strategy
The strategy is usually evaluated through simulation considering the orbit perturbation, orbit control,
OD error and some other error sources. The detailed evaluation items are listed as follows:
a) evaluate whether the safety separation distances between collocated spacecraft are ensured;
b) evaluate whether the orbit maintenance period qualifies the perspective requirements;
c) evaluate whether the fuel consumption of collocation spacecraft is within the budget requirement.
Based on the designed collocation strategy, some factors are considered, such as orbit perturbation,
orbit maintenance error, orbit determination error, to evaluate whether the considerations including
the safety separation distance, orbit maintenance period, fuel consumption and other factors are
sufficiently taken into account.
5.3 Final collocation strategy
Once the selected strategy meets all specifications, it is confirmed as the decided optimal collo
...