OREKIT: AN OPEN SOURCE LIBRARY FOR OPERATIONAL FLIGHT DYNAMICS APPLICATIONS

Abstract

The Orekit library is a space flight dynamics library developed since 2002 by CS. It was operationally used during the Jules Verne ATV mission. Since 2008, the library is freely available as an open-source product under the terms of the business-friendly Apache V2.0 license. Given the small size of the market and the still high need for advanced tailored solutions for space systems, the service based business model for added value is much more suited than the license based business model or its new version, the Software As a Service. There are several business models that can be used for economically sound open-source systems. Some are well suited for the space field and will be explained. Some are not adapted and the reasons for this will also been explained. Open-source is an approach that proved efficient in mainstream software industry. It does not always need a very large community as was once thought, but still needs some involvement. The return on investment increases for all contributors as the project expands and the risks decrease at the same time as more and more people use it. The model is attractive for both public entities, academics, industry and SMEs, bringing something to each one of them. It also increases the yield of public funding. OREKIT is an example of a successful open-source project initiated by private industry and operationally during ATV rendezvous. Since its inception, the OREKIT library was aimed both towards quick development for simple use cases and towards fine tuning for expert users. In order to fulfill the first goal, the programming interface provides high level features like attitude modes, automatic discrete events handling within propagation (ground station visibilities, eclipses, maneuver start/stop, altitude crossing, user defined event …), transparent handling of leap seconds, automatic transforms between all frames, transparent use of Earth Orientation Parameters and much more. In order to fulfill the second goal, several physical models are provided for many concepts (orbits, propagators, frames, events, attitudes, time scales, ephemerides …) and all of them can be extended naturally to add user specific models or change the behavior of the provided ones. Since many models offer similar user interfaces, it is possible to build applications that can be used both in a mission analysis configuration with fast models and in an operational configuration with accurate models with a single switch. The presentation will provide both a business view and a technical view of OREKIT. It will explain the benefits of open-source and business models. It will present an overview of the library features and available physical models. A focus on a few innovative concepts will be made, like for example discrete events, time scale handling, slave and master propagation modes, management of time-dependent frames, models switching or transparent handling of complex models that need lots of configuration data. Some examples of how the tool can be used in different operational contexts will be given. The roadmap for the future of the tool will be presented.

Full text

Orekit : an Open-source Library for Operational Flight Dynamics Applications

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1 OPEN-SOURCE FOR SPACE FLIGHT
DYNAMICS LIBRARY
1.1 Historical context
0++1##23  4  2  "   5
4#   66# %/1"    1
" 6##31 "    1
#21     3   73  1
21##6"4##6#31" 
84##"6"1 21
###3 # 6    1      1  2
#11  " 1 6#
1 464 2#"
9"#.61""#3
1  " 1   ### 6"1
6  ""    2  1  6"3  ###
66 7##1 28 "2  
"0 2#"#3  21 16" -1  #
64".64"6 

/1#.1""4#6
2"6#31  "  # 21  #
"1#""  #"3#8#31
"      "  2#"  ##2      2
7:-9;99:<   %/ 18 1 2

718"43166
11#3 6"61 #
"#16'
7## 1288 6#2 ++ "++(21
6  ""2 63    #
6 2#2  "#"
1 -13 6" 6 ++, 21 #3
16-1#36"2#2#4##
211 43"   "4#6#3
6    "  61 #  "#  "  131#  #"
#31$1 6" 2"7-=0
">43
01"  98?    ##2"    66
"#6"
1.2 Strategic choices and business model
0++)  1" 3" "8  985 
21# 1#"
23"1""""6# 
"#31646## 7-3&
  2  ##    83  #    66  "#
"  "4 63 #"
#23"2"4#6
/  1      """    ++(    13
#3  "" 98   6
6"
-1 "2 66" 861 6"#4
18        #3  @ A  "  ##2"    
66    44  #4      6
66 6"
1.2.1 License choice
#13    6  #    6  #31
"   6#    6  1    8
3#
4#  "  6  #   6  .
211 14" 21 6
"
"3#66"7211
"4#61"""7?".#"
&"#46#66#5
7
7?
&

➢0 7   6#1"  "  1       BC3
6 #CD  #5 7?7;E  &    ""
"1#0"4#
6#"
➢0  7   6#1"  "  1        BCF8
6 #CD#5# 7?"""
1 # 7 &  """
"#
➢0 7    6#1"  "  1        BC&
"# CD  #5  1  7?    &  14    
"""13##7
G.6#    3  6 #  #    H  "
0.6#286 ##H
G  "  0  .6#    "#
#&E0-"761
12"1##23# 5
➢Bad example of the JAT I4  7" 
-#8  211    6'"  ++  
"" 2  "4#6"  1# .
#98?-1#12strong
copyleft license2111#"1"
"""4"#"#"113
1  #      ++(    4  1
"28
➢Orekit context:
◦  ""    1  8 21  3  "
"#    #   1  143  3
    ###  66
64J
◦"1#8131#
#"1#"1"J
◦  "#  1    "    4
"316"
7##    1  #"      1  1  761  +
BC"# CD  # 7   1 
64#2"# 82 1## 
1 " 898""211221
.6 31124 1343
16 311"7"66#1
986#1"3 #
-1###2#"#5
➢;  663    #      1  
"
➢;
➢/###12K"5
◦/"163
◦/"" 1216328
""6
◦/""6
◦/"    64  1  63  "
#164
9811312"5BC
"61CD
/498*2#") 1
I# ++(
1.2.2 Business model
96      661  1  64"    
2" 0"#2 "
4  #3     2    131   ##
"    4#4  -1      4
##16'.6""
1 8" 1    "
66#  -1  "#4   1  6#
  "  "  "  G  33
13    1     1  0  #    1
#"6#"3
7  "    1  6    "#  
6# " 4  "  66   
#-1"##"5
➢3##663
➢#    9%GL0-      6  #31
" 
➢36# 21"6
➢6"4#6
◦2"#
◦13
2 FROM BASIC TO EXPERT USE OF OREKIT
F?##2126##"#31" 
66#98
/?66198# 
"#4#0#3."'#
"
0"3"1"8"4#6

6#  "  " 6 "
.6
2.1 High level features for easy, fast
development
9864"#2#4#'"
#310    #### ""  
6  #31  "   #8      #
6663" ##"
"#I 61"  /1
.46664""
F?##      1  ##23  131  #4#  
64""613#53 5
•""
•1"#3
•663"
•#
•G16
Attitude modes
4#  6""  "  "    4##  1
-16#11#5
1BC# CD#2#85
➢&" =##" 63
➢-3="=9/63
➢9/."6#>"
1  BC6#.CD  #2  211    6#>  
# #25 23= 26
3"63
7##1"6## 13# "
111 6#1
 21#21;4
 6# " #  #2"
#6#.21# 131
#2#>"## 131
63"
Frames
/3>"1#16
2#311#8 
17 2        #    "3  1
  1  #8        6  J  1
    1      1    "
##23#  1
-1"1."4#
  #      1      
"6"  #2    1    "    
##  6""            
#  "6"  #2    1      6""  
14"# #12
"1 7-  3 21     ,+
"
7  #    6""      #  64""  
6###1G1"#
Orbit Propagation
98    "  8"    6""  
663    1      #8  86#
6631#663
96   66"  ##  663
1# 1"#"4"1#
"3  1     1  663  -1  663
   2 " "5 BC#4CD "
BCCD"
0  1     BC#4CD  "  1  1"#3    1
#66 6"6# 10?
21 2"## "#3 25 #6
42166"#1
6
0BCCD "1 1"#3   1    #6  
"#3"    1  663  #  "  #  1
63"11#612
  13121  ##"BC61"#CD-1
# 1663##21 1"#3
1#  #6 1BC1"#  6CD1" 16
1"#2####"##  1663
16-1"6#""
1  "6#3  2  1  #6#    1"#3
" "1 6#.6 21 
6" 16"163-1
6#  31#6 21" 4
""""13##6.6#"#
-16631"#1."6"6"
6;#>"61"###23"
 ."64  4#63
1
4  4  "      ##
6"  1663 ""321 ##"
BC4  "CD  9  3    #3  6#  
6""  4  "    4##   4
3#  4  4  4  "      "
1 2 494 """"1
6632##18161
  "  4  "  33      1  666
  G4         6""    
"4"    1  #  "3  1  663  21
"""
G4"works in both slave and master mode
#4"1"31"
 21 1 433"1# 1 1 #
  1  8"  1"In master mode
intermediary state corresponding to event time is
computed at the exact time event happens, no matter
step size
F1    4    33"        "  
##3 1663 #8 .6#133

1 "#21 4  6 4
    4  6##  663  1  663
21    #"  11#"    "  "3  
 # .6# -1  # "
  6#  6#  4  #333 3 " 
4# #6
Earth orientation parameters
7##  G1    4    66"  
6  "    "#  0G%  ++*  2
4  "  0G%  MM,    4  
4##    1  .3  G1      21  
2112133
9        4    .  21
1      1  4   1  
66#16"3"##
#""2131#431
  1  6#    1"#  1  1#  "
4"38
-11"#31136#""
4      3"            "
## 9.6 ##3
18 "#2?-131
6121#31" .6"
" 82 21 6  6#1" 
98?"8161
 2135 1 '68 6G1
"
Time scale
4##66":--70H--
"##""#4# -70#7"
"" 1#4##1"
  1    #  -1  4    1"#"
## #8#
-:#6"#1"#"6# J
21"821"?"1
1
2.2 Fine tuning for expert use
& "  ##  1  3"    1  #  
# 3 98    3  "      
"3#  66#21.6  3
 6
Force models
1   "#      #  6    6  #31
" #"7#36#1# "
"#    64""    98    1    ##  
""?"6# .""
4 6 "#  " 1
 # >"6# 6#.
7    .6#  "3  "  "  6    
161#16#."" 4#
#6#"# 21#3
416"#
…........
Events
G4"#6>#6
:31""461
66#    2  4  1"#      "
"34"
41 # 4 "#.#
31      1  3  664    
.#      @.A  "  & "  .3
@##A 4 #"3 
98?  4  1"#3  1    "  
      "  6  "3  1
663 1#"  6#6#   "31
6"336
Frames
:   2 "6" 1 "
"311#8 @6A
  1 .3 -1  
 # "6"-1 .# 21 2
"7- 3  21    1  ,+  
4#4""1# 141#"#

9  3       6"        
"6##     
1-1##2 .6#36#
16134  41#83
    1  6##.    1  ##  
211"" 2#31# 
…........
Time scale
G4   31 "" 98 #"
64"2"#6#2###
 " 6# 216 "01
6# 1"21"-70
Data
0  "    6#  3    98"
66#    #3     "  #"3    
>"216#311 
.3#"
3 ACKNOWLEDGEMENTS
F  181 /"> 1
66 1 6' "##239811
6##"
F  18  ##  1      98  "4#6
++,2112"1"4#4
16' F #  18  ##  1 211#6
"3"64316"
4 REFERENCES
 -  "  /  #4    
6E #8*""++

  #4  14 Stratégies et potentiels de l'open
source dans les entreprises et les administrations
françaises  ++M+  9609    96
F#"/++M
* E  E    1  "  H"   IERS
Conventions (2003)  0#  G1  %
"% 4
K Free Software Foundation, GNU General Public
License
165==22233=#=36#*+
"#1# I++)
$ G7  ;%  0;%07  0 Free Software
License Agreement6++,
165==222##=#=
N0N1#
, The BSD License
165==22263=#="#616
) 761+I ++K
165==222613=#=0G;G+
( E4"7##"# 2" %1"O'8
"-L#73++, Revisiting Spacetrack
Report #3, 2006 AIAA/AAS Astrodynamics Specialist
Conference
M G  O     4  #  ;P    H1"
FSolving Ordinary Differential Equations I.
Nonstiff Problems      6#
1#( 63#3 M()"
4""MM*
+     /">    
Building a community, an approach for
Space Flight Dynamics6++M