A code to describe satellite constellations
draft-piraux-space-constellation-code-02
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Maxime Piraux , Juan A. Fraire | ||
| Last updated | 2026-07-06 | ||
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| Intended RFC status | (None) | ||
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draft-piraux-space-constellation-code-02
Systems and Protocol Aspects for Circumstellar Environments RG M. Piraux
Internet-Draft Aerospacelab
Intended status: Informational J. A. Fraire
Expires: 7 January 2027 Inria / Saarland University
6 July 2026
A code to describe satellite constellations
draft-piraux-space-constellation-code-02
Abstract
When considering a satellite constellation forming a non-terrestrial
network, the characteristics of this constellation heavily influence
the network topology it forms. To improve the analysis of such non-
terrestrial networks across various tools developed by the network
community, this document defines a constellation code to describe
common orbital shell patterns, and specification formats to describe
inter-satellite link topologies and ground stations, covering the
Core and Ground Networks of a constellation. In addition, this
document may serve as an introduction to satellite constellations for
IETF participants.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://mpiraux.github.io/draft-piraux-space-constellation-code/
draft-piraux-space-constellation-code.html. Status information for
this document may be found at https://datatracker.ietf.org/doc/draft-
piraux-space-constellation-code/.
Discussion of this document takes place on the Systems and Protocol
Aspects for Circumstellar Environments RG Research Group mailing list
(mailto:space@irtf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/space/. Subscribe at
https://www.ietf.org/mailman/listinfo/space/.
Source for this draft and an issue tracker can be found at
https://github.com/mpiraux/draft-piraux-space-constellation-code.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on 7 January 2027.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 5
3. Describing the Core Network . . . . . . . . . . . . . . . . . 5
3.1. Satellite constellations . . . . . . . . . . . . . . . . 5
3.1.1. Walker constellations . . . . . . . . . . . . . . . . 5
3.2. Constellation code . . . . . . . . . . . . . . . . . . . 8
3.3. Examples of constellation codes . . . . . . . . . . . . . 10
3.4. Link specification . . . . . . . . . . . . . . . . . . . 10
3.4.1. constellation-specs fields . . . . . . . . . . . . . 12
4. Describing the Ground Network . . . . . . . . . . . . . . . . 13
4.1. Ground station specification . . . . . . . . . . . . . . 14
4.1.1. ground-stations-specs fields . . . . . . . . . . . . 14
5. Considerations for future versions of this document . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.1. Normative References . . . . . . . . . . . . . . . . . . 16
8.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . 17
A.1. Since draft-piraux-space-constellation-code-01 . . . . . 17
A.2. Since draft-piraux-space-constellation-code-00 . . . . . 17
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
A satellite constellation spans three networks to deliver their
services as illustrated by Figure 1. First, an Access Network
enables User Equipment (UE) to connect to the constellation. This is
realised by the establishment of a Service Link to exchange UE
traffic. Then, the UE traffic is forwarded over a Core Network
consisting of the different interconnected satellites. Finally, the
UE traffic is sent back to ground via the Feeder Link, which connects
a satellite to a ground station. A ground station is usually
colocated with the infrastructure required to deliver the service.
In the case of Internet broadband access, this can be a Point-of-
Presence (PoP) connecting to the Internet.
Access Network | Core Network | Ground Network
| |
UE ------- Service ---> *---*---*---* ---- Feeder --> Ground --- PoP
Link : : : : Link Station
| *---*---*---* |
| |
Figure 1: A satellite constellation spans three networks
The network topology of the Core Network of a satellite constellation
is heavily influenced by its orbital characteristics. A network is
formed in space by establishing Inter-Satellite Links (ISL) between
neighbour satellites, notably enabled by recent technologies such as
Optical ISLs (OISL). The resulting topology can be dynamic as the
distance between neighbour satellites changes throughout their
orbital period.
A key characteristic of satellite constellations is the ephemeral
nature of the Feeder Links. They may only be established when a
satellite and a ground station are in range of each other.
Typically, ground stations can establish links within a defined cone
of coverage. This cone is often characterised by a Minimum Elevation
Angle (MEA), such that Feeder Links can only be established when
their elevation is above the MEA. Consequently, satellites are often
engineered such that Feeder Links are feasible within the entire cone
of coverage of ground stations. A ground station often includes
several antennas such that a certain number of Feeder Links can be
established from a given location. Satellites may include several
antennas as well to establish several Feeder Links or enable make-
before-break transitions.
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A common notation for the network community to describe these
constellations could improve the reproducibility of evaluations,
measurements and simulations of satellite constellation networks.
This document focuses on describing some elements of the Core and
Ground Networks.
The approach of this document is based on the mission parameters of a
satellite constellation. Based on these parameters, the expected
position of each satellite within the constellation can then be
computed. Tools using the notation described in this document are
free to choose how they propagate the positions of satellites. This
may be revised in later versions of this document. The two practical
options are:
* Keplerian-based propagation, focusing on the theoretical position
of satellites.
* Perturbation-based propagation, such as using Simplified General
Perturbations 4 (SGP4) or Simplified Deep Space Perturbations 4
(SDP4) [HoRo1980] [VaCrHuKe2006].
This version of the specification applies only to circular orbital
shells. The rationale for this restriction is that circular orbits
are the most common in current satellite constellations and simplify
the code syntax. Elliptical orbits, such as those used in Molniya or
Flower constellations, are outside the current scope but could be
supported in a future extension of this document.
The notation defined in this document can also specify patterns for
links within a shell of a constellation. Each pattern is repeated to
establish the connectivity of a satellite with its neighbours within
the shell. This is inspired by the works of network researchers on
constellation network topology design [BhSi2019].
The rest of this document is organised as follows. Section 3
describes the Core Network of a constellation. Section 3.1
introduces two variants of the Walker pattern for orbital shells,
used to define many of the existing satellite constellations.
Section 3.2 defines the constellation code syntax using an ABNF
grammar [RFC5234] and its semantics. Section 3.3 contains examples
of existing constellations defined using the constellation code.
Section 3.4 extends the code with a specification format for link
patterns within a shell. Section 4 describes the Ground Network of a
constellation. Section 4.1 defines a specification format for ground
stations. Finally, Section 5 concludes with considerations for
future versions of this document.
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2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Describing the Core Network
This section describes how the Core Network of a constellation is
specified.
3.1. Satellite constellations
A constellation greatly improves the availability of a satellite
service up to global or near-global coverage on Earth. From the user
perspective, a constellation offers more guarantees that a satellite
can be reached at all times. A constellation is composed of a set of
orbital planes. Typically, several satellites are present on an
orbital plane. They can be close together to perform formation
flying or are equally spread within the plane. Orbital planes are
distributed in a complementary manner, i.e., they share some
properties (e.g. altitude and inclination) but differ in others (e.g.
longitude of ascending node).
When all orbital planes of a constellation are circular orbits
sharing the same altitude, they are said to constitute an orbital
shell. Constellations often consist of a single orbital shell but
more complex deployments can have several shells.
The rest of this section describes two common shells based on the
Walker pattern.
3.1.1. Walker constellations
A Walker constellation consists of circular orbits sharing the same
inclination. Two variants of the Walker pattern exist:
* Walker Star, where orbits are distributed over 180 degrees around
the equator.
* Walker Delta, where orbits are distributed over 360 degrees around
the equator.
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3.1.1.1. Walker Star
Figure 2 is an illustration of a Walker Star constellation
considering the Earth equator as horizontal in the Figure. The orbit
trajectories are depicted by a dashed line, while satellites and
their travel direction are indicated by arrow heads.
The orbits of a Walker Star constellation typically have an
inclination close to 90 degrees with respect to the equator plane,
though this is not a geometric constraint and other inclinations are
possible. Given that they are distributed over 180 degrees around
the equator plane, one half-sphere has satellites ascending from the
south pole to the north pole while the other has them descending from
north pole to south pole. This is depicted on the two sides of
Figure 2. Over the south and north poles, all orbits are crossing
paths before going over the other half-sphere.
/ / \ \
, - ~ ~ ~ - ,
, '/ ^ v \' ,
, ^ / \ v ,
, / ^ v \ ,
, ^ | | v ,
, | ^ v | ,
, ^ | | v ,
, \ ^ v / ,
, ^ \ / v ,
, \ ^ v / , '
' - , _ _ _ , '
\ \ / /
Figure 2: A Walker Star constellation
In a Walker Star constellation, a seam can be observed at the start
and end of the orbit distribution around the equator plane. That is
the first orbit (resp. last orbit) is next to the last orbit (resp.
first orbit) going in the opposite direction of the sphere. It can
be observed at the center of the Figure 2. The seam effect in Walker
Star constellations may limit cross-plane ISL links at the seam
boundary, though cross-plane links are still possible elsewhere; for
instance, the Iridium constellation uses a Walker Star pattern with
cross-plane ISLs. However, the Delta variant is often preferred for
OISL-capable constellations due to the absence of the seam effect.
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Figure 3 illustrates a part of a possible network topology for Walker
Star constellations, with four orbital planes depicted vertically,
each containing three satellites. In this example, links are only
established in-plane, i.e., within the same orbit, though cross-plane
links are also possible. Each orbit forms a ring, where the last
satellite is connected to the first satellite.
: : : :
| | | |
+~~~+ +~~~+ +~~~+ +~~~+
[0/0] [1/0] [2/0] [3/0]
+~~~+ +~~~+ +~~~+ +~~~+
| | | |
| | | |
+~~~+ +~~~+ +~~~+ +~~~+
[0/1] [1/1] [2/1] [3/1]
+~~~+ +~~~+ +~~~+ +~~~+
| | | |
| | | |
+~~~+ +~~~+ +~~~+ +~~~+
[0/2] [1/2] [2/2] [3/2]
+~~~+ +~~~+ +~~~+ +~~~+
| | | |
: : : :
Figure 3: A Walker Star constellation network topology
3.1.1.2. Walker Delta
Figure 4 is an illustration of a Walker Delta constellation with only
two orbits due to graphical constraints. The orbits of a Walker
Delta constellation typically have an inclination ranging from 45 to
65 degrees with respect to the equator plane, though any inclination
is geometrically valid. Combined with the altitude, the inclination
directly limits the latitude coverage of a constellation, while
Walker Star constellations have a complete latitude coverage.
Given that the orbits are distributed around the entire equator
plane, there is no seam effect as in the Walker Star pattern.
Instead, each orbit progresses in the same direction and cross paths
twice with every other orbit. In this case, satellites can establish
links with neighbouring orbits in addition to links within the same
orbit.
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/ , - ~ ~ ~ - , \
, ' ' ,
, \ ,
, ^ / ,
, \ v ,
, ^ / ,
, \v ,
, / ^ ,
, v \ ,
, / , '
' - , _ _ _ , '
\ /
Figure 4: A Walker Delta constellation
Figure 5 illustrates a part of a possible network topology for Walker
Delta constellations, with four orbital planes depicted vertically,
each containing three satellites. Links are established in-plane and
cross-plane, i.e., from one orbit to the other.
: : : :
| | | |
+~~~+ +~~~+ +~~~+ +~~~+
..--[0/0]----[1/0]----[2/0]----[3/0]--..
+~~~+ +~~~+ +~~~+ +~~~+
| | | |
| | | |
+~~~+ +~~~+ +~~~+ +~~~+
..--[0/1]----[1/1]----[2/1]----[3/1]--..
+~~~+ +~~~+ +~~~+ +~~~+
| | | |
| | | |
+~~~+ +~~~+ +~~~+ +~~~+
..--[0/2]----[1/2]----[2/2]----[3/2]--..
+~~~+ +~~~+ +~~~+ +~~~+
| | | |
: : : :
Figure 5: A Walker Delta constellation network topology
3.2. Constellation code
Figure 6 defines the constellation code using an ABNF grammar
[RFC5234]. The code can define a constellation with multiple shells.
Each shell can follow a Walker Star or Walker Delta pattern.
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constellation = shell [ "+" constellation ]
shell = walker ":" altitude ":" inclination ":" plane-params
[ ":" mean-anomaly ]
walker = "D" / "S"
altitude = float
inclination = float
plane-params = no-sats "/" no-planes "/" phasing-factor
no-sats = int
no-planes = int
phasing-factor = int
mean-anomaly = float
int = 1*DIGIT
float = 1*DIGIT [ "." 1*DIGIT ]
Figure 6: ABNF Grammar for the constellation code
In addition to the grammar presented above defining the syntax of the
code, a number of requirements on the semantics of the code are
listed below.
* The altitude is expressed in kilometres with reference to the
Earth's surface.
* The inclination is expressed in degrees and MUST be within the
range of [0, 180] degrees. Inclinations greater than 90°
represent retrograde orbits.
* The number of satellites must be evenly divisible by the number of
planes.
* The phasing factor must be within the range [0, no-planes - 1].
It represents the relative offset between satellites in adjacent
orbital planes. It determines how satellites in one plane are
shifted in their orbital position compared to the satellites in
the neighbouring plane, enabling optimal coverage patterns.
* The mean anomaly is expressed in degrees and MUST be within the
range of [0, 360] degrees. It is optional and represents the
orbital position of the first satellite in the first plane of the
constellation. When absent it is considered equal to zero. The
reference epoch for the mean anomaly is defined by the user's
simulation environment or application context.
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3.3. Examples of constellation codes
This section provides some examples of how the constellation code can
be used to define existing satellite constellations sourced from
public information. In some cases, when the phasing factor is not
known, it is speculative.
+==========+==============================+=======================+
| Name | Description | Constellation code |
+==========+==============================+=======================+
| Iridium | Walker Star, 780 km | S:780:86.4:66/6/1 |
| | altitude, 86.4° inclination, | |
| | 66 satellites, 6 planes | |
+----------+------------------------------+-----------------------+
| OneWeb | Walker Star, 1 200 km | S:1200:87.9:672/12/11 |
| | altitude, 87.9° inclination, | |
| | 672 satellites, 12 planes | |
+----------+------------------------------+-----------------------+
| Starlink | Walker Delta, 550 km | D:550:53:1584/72/39 |
| (shell | altitude, 53° inclination, | [StFrHe2022] |
| 1) | 1584 satellites, 72 planes | |
+----------+------------------------------+-----------------------+
| GPS | Walker Delta, 20 180 km, 55° | D:20180:55:24/6/1 |
| | inclination, 24 satellites, | |
| | 6 planes | |
+----------+------------------------------+-----------------------+
Table 1: Examples of constellation codes
3.4. Link specification
In this section, we extend the code notation with the following
Concise Data Definition Language (CDDL) schema [RFC8610] to specify
the patterns of links within a shell.
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constellation-specs = {
version: tstr,
shells: [+ shell-entry],
}
shell-entry = {
code: tstr, ; Constellation code as specified in this document
link-patterns: [* link-pattern],
}
link-pattern = {
(
(rank-offset: int, ? plane-offset: int) //
(? rank-offset: int, plane-offset: int)
),
? conditions: [* condition],
}
condition = { eq: [expression, expression] }
expression = int
/ context-element
/ operation
context-element = "rank" / "plane"
operation = { mod: [expression, expression] }
Figure 7: CDDL schema for constellation links
Each data item specifies a constellation that may be composed of
several shells. An example specifying a two-shell constellation is
given below in Extended Diagnostic Notation (EDN) [RFC8949]:
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{
"version": "draft-piraux-space-constellation-code-02",
"shells": [
{
"code": "D:1200:55:400/20/19",
"link-patterns": [
{ "rank-offset": 1 }, / in-plane link to the next satellite /
{
"plane-offset": 1, / cross-plane link in a staggered pattern /
"conditions": [ / e.g., when only three links are possible /
{ "eq": [{ "mod": ["rank", 2] }, { "mod": ["plane", 2] }] }
/ rank % 2 == plane % 2 /
]
}
]
},
{
"code": "S:1210:89:52/4/1",
"link-patterns": [
{ "rank-offset": 1 }
]
}
]
}
Figure 8: Example constellation-specs data item
Figure 8 specifies a two-shell constellation. The first shell is a
Walker Delta shell in which satellites have three links towards
neighbours. The second is a Walker Star pattern with two in-plane
links per satellite.
These patterns are encoded through the link-patterns key. It
contains a list of patterns with optional conditions. Each pattern
specifies how to reach a neighbour given local plane and rank offsets
to establish a bidirectional link. For instance, the first pattern
of the first shell specifies that a link is formed with the next
satellite in the same orbit.
For each pattern, a list of conditions can be expressed with the
conditions key. These are evaluated for each satellite within the
shell to determine whether the corresponding pattern should be
applied to form a link. By applying each pattern to all satellites,
the set of links within the constellation shell is established.
3.4.1. constellation-specs fields
version Indicates the version of this I-D that the data item should
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be interpreted with.
shells A list of shell entries.
3.4.1.1. Shell entry
code The shell code following the specification in Section 3.2.
link-patterns A list of link patterns applied to every satellite in
the shell.
3.4.1.2. Link pattern
rank-offset An integer specifying the offset in rank to reach the
neighbour for this link.
plane-offset An integer specifying the offset in plane to reach the
neighbour for this link. When this offset causes the plane index
to wrap around to the first plane, the rank index of the target
satellite is adjusted according to the phasing factor of the
shell.
At least one of the two offsets MUST be present and non-zero. The
other defaults to zero when absent. They naturally wrap around at
the boundaries of a shell.
conditions A list of conditions that must all be met for the
corresponding link to be added to a given satellite.
3.4.1.3. Condition
A condition is a predicate applied to two expressions. This version
of the document only specifies the equality predicate, indicated by
the eq key.
3.4.1.4. Expression
An expression is one of: an integer literal, a context element, or an
operation on two sub-expressions. Context elements are represented
by strings and two of them are defined. rank refers to the current
rank index and plane refers to the current plane index of the
satellite being evaluated. This version of the document only
specifies the modulo operation, indicated by the mod key.
4. Describing the Ground Network
This section describes how the Ground Network of a constellation is
specified.
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4.1. Ground station specification
In this section, we describe ground stations using the following CDDL
schema [RFC8610].
ground-stations-specs = {
version: tstr,
ground-stations: [+ ground-station],
}
ground-station = {
name: tstr,
latitude: float, ; degrees
longitude: float, ; degrees
altitude: float, ; metres above Earth surface
min-elevation: float, ; degrees
antennas: uint,
}
Figure 9: CDDL schema for ground stations
An example specifying a single ground station is as follows:
{
"version": "draft-piraux-space-constellation-code-02",
"ground-stations": [
{
"name": "Charleroi",
"latitude": 50.403,
"longitude": 4.428,
"altitude": 109.0,
"min-elevation": 10.0,
"antennas": 8
}
]
}
Figure 10: Example ground-stations-specs data item
Figure 10 specifies a single ground station with an associated
location. It has a MEA of 10 degrees and 8 antennas that can be used
simultaneously.
4.1.1. ground-stations-specs fields
version Indicates the version of this I-D that the data item should
be interpreted with.
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ground-stations A list of ground stations.
4.1.1.1. Ground station
name A string to identify the ground station.
latitude The latitude of the ground station location, expressed in
degrees.
longitude The longitude of the ground station location, expressed in
degrees.
altitude The altitude of the ground station location, expressed in
metres above the Earth's surface.
min-elevation The Minimum Elevation Angle above which Feeder Links
can be established, expressed in degrees.
antennas The number of antennas available to establish Feeder Links
simultaneously.
5. Considerations for future versions of this document
The code and specification formats presented in this document do not
consider the capabilities of satellites within a constellation to
establish links. It focuses on defining the stable network topology
that is expected for a constellation. Future versions of this
document could consider means to define the capabilities of Optical
Communication Terminals (OCTs) used to establish ISLs. This is
complementary to the description of the network topology, which forms
more of an intent, while capabilities define the space of possible
links.
6. Security Considerations
As the code and specification formats specified in this document are
foreseen as user input into software that performs simulations,
evaluations and analysis of satellite constellations, implementers
SHOULD consider validation and sanitisation measures.
In particular, the expression and operation types (Section 3.4) are
recursively defined and could be nested arbitrarily deeply, and the
shells, link-patterns, conditions, and ground-stations lists are
unbounded in size. Implementers SHOULD bound recursion depth and
collection sizes to mitigate resources exhaustion when processing
untrusted input.
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7. IANA Considerations
This document has no IANA actions.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/rfc/rfc5234>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
8.2. Informative References
[BhSi2019] Bhattacherjee, D. and A. Singla, "Network topology design
at 27,000 km/hour", ACM, Proceedings of the 15th
International Conference on Emerging Networking
Experiments And Technologies pp. 341-354,
DOI 10.1145/3359989.3365407, December 2019,
<https://doi.org/10.1145/3359989.3365407>.
[HoRo1980] Hoots, F. R. and R. L. Roehrich, "Spacetrack Report No. 3:
Models for Propagation of NORAD Element Sets", December
1980.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
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[StFrHe2022]
Stock, G., Fraire, J., and H. Hermanns, "Distributed On-
Demand Routing for LEO Mega-Constellations: A Starlink
Case Study", IEEE, 2022 11th Advanced Satellite Multimedia
Systems Conference and the 17th Signal Processing for
Space Communications Workshop (ASMS/SPSC) pp. 1-8,
DOI 10.1109/asms/spsc55670.2022.9914716, September 2022,
<https://doi.org/10.1109/asms/spsc55670.2022.9914716>.
[TvdLCode] Tim van der Lee, "Constellation Code", July 2023,
<https://github.com/Tim024/ConstellationCode>.
[VaCrHuKe2006]
Vallado, D., Crawford, P., Hujsak, R., and T. Kelso,
"Revisiting Spacetrack Report #3", American Institute of
Aeronautics and Astronautics, AIAA/AAS Astrodynamics
Specialist Conference and Exhibit,
DOI 10.2514/6.2006-6753, June 2006,
<https://doi.org/10.2514/6.2006-6753>.
Appendix A. Changelog
A.1. Since draft-piraux-space-constellation-code-01
* Replaced YAML by CDDL.
* Include description of ground stations.
* Reorganised the document into Core Network and Ground Network
sections following the revised introduction.
A.2. Since draft-piraux-space-constellation-code-00
* Add YAML format to specify link patterns within shells of a
constellation.
* Improvement of the text and examples.
Acknowledgments
We thank Tim van der Lee for his work on a code [TvdLCode] that
served as the basis for this document.
Authors' Addresses
Maxime Piraux
Aerospacelab
Email: maxime.piraux@aerospacelab.com
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Juan A. Fraire
Inria / Saarland University
Email: juan.fraire@inria.fr
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