Geerling, Franck Germes, Gottlob Gienger, Bénédicte Girouart, Bernard Goudard, Nick Godfrey, Roy Kouga, Cosimo Greco, Robert Guilanya, Kester Habermann, Manfred Hadwiger, Ian Harrison, Angela Head, Martin Hechler, Kjeld Hjortnaes, Jacolien Hoek, Frank Hoffmann, Justin Howard, Arjan Hulsbosch, José Jiménez, Simon Kellett, Andrea Kerruish, Kevin Kewin, Oliver Kidde, Sabine Kielbassa, Volker Kirschner, Holger Krag, Benoît Lainé, Markus Landgraf, Mathias Lauer, Robert Launer, Santiago Llorente, Guillermo Lorenzo, James Madison, Filip Marinic, Arturo Martín Polegre, Ander Martínez, Marco Massaro, Luca Michizenzi, Ali Mohammadzadeh, Richard Morgan-Owen, Prisca Mühlmann, Michael Müller, Pablo Munoz, Petteri Nieminen, Alfred Nillies, Wilfried Nzoubou, Alistair O'Connell, Oscar Pace, Mohini Parameswaran, Rimon Pardo, Taniya Parikh, Panos Partheniou, Dario Pellegrinetti, José-Louis Pellon-Bailon, Michael Perryman, Christian Philippe, Alex Popescu, Alfonso Rivero, Andrew Robson, Gerd Rössling, Martina Rossmann, Markus Rückert, Jamie Salt, Giovanni Santin, Rui Santos, Stefano Scaglioni, Melanie Schabe, Dominic Schäfer, Micha Schmidt, Rudolf Schmidt, Jean Schütz, Klaus-Jürgen Schulz, Julia Schwartz, Andreas Scior, Jörg Seifert, Gunther Sessler, Felicity Sheasby, Heike Sillack, Swamy Siram, Claudio Sollazzo, Steven Straw, Mark Thompson, Raffaele Tosellini, Irren Tsu-Silva, Livio Tucci, Aileen Urwin, Jean-Baptiste Valet, Helma van de Kamp-Glasbergen, Martin Vannier, Kees van 't Klooster, Enrico Vassallo, David Verrier, Sam Verstaen, Rüdiger Vetter, José Villalvilla, Raffaele Vitulli, Mildred Vögele, Sergio Volonté, Catherine Watson, Karsten Weber, Gavin Williams, Alistair Winton, Michael Witting, Peter Wright, Karlie Yeung, Igor Zayer, and from CERN: Vincenzo Innocente. We thank the referee, Joss Bland-Hawthorn, for constructive feedback that helped to clarify several items in the text.

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6 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12–14, 69120 Heidelberg, Germany

7 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

8 Department of Astronomy, University of Geneva, Chemin des Maillettes 51, 1290 Versoix, Switzerland

9 Mission Operations Division, Operations Department, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ, Noordwijk, The Netherlands

10 Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí Franquès 1, 08028 Barcelona, Spain

11 Lohrmann Observatory, Technische Universität Dresden, Mommsenstraße 13, 01062 Dresden, Germany

12 European Space Astronomy Centre (ESA/ESAC), Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

13 Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden

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15 European Space Operations Centre (ESA/ESOC), Robert Bosch Straße 5, 64293 Darmstadt, Germany

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18 Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles CP 226, Boulevard du Triomphe, 1050 Brussels, Belgium

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20 INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy

21 Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201AZ Noordwijk, The Netherlands

22 Telespazio Vega UK Ltd for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

23 Laboratoire d'astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France

24 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium

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29 Centre for Electronic Imaging, Department of Physical Sciences, The Open University, Walton Hall MK7 6AA Milton Keynes, UK

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32 Serco Gestión de Negocios for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

33 Department of Astronomy, University of Geneva, Chemin d'Ecogia 16, 1290 Versoix, Switzerland

34 STFC, Rutherford Appleton Laboratory, Harwell, Didcot, OX11 0QX, UK

35 Gaia DPAC Project Office, ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

<footnote n="1">1 Scientific Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201AZ, Noordwijk, The Netherlands</footnote>

<footnote n="2">2 Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands</footnote>

<footnote n="3">3 INAF-Osservatorio astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy</footnote>

<footnote n="4">4 GEPI, Observatoire de Paris, PSL Research University, CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92190 Meudon, France</footnote>

<footnote n="5">5 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany</footnote>
36 SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, LNE, 61 avenue de l'Observatoire, 75014 Paris, France

37 National Observatory of Athens, I. Metaxa and Vas. Pavlou, Palaia Penteli, 15236 Athens, Greece

38 IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Lille, 77 av. Denfert-Rochereau, 75014 Paris, France

39 Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium

40 Institut d'Astrophysique Spatiale, Université Paris XI, UMR 8617, CNRS, Bâtiment 121, 91405 Orsay Cedex, France

41 Institute for Astronomy, Royal Observatory, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK

42 HE Space Operations BV for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

43 Institut d'Astrophysique et de Géophysique, Université de Liège, 19c, Allée du 6 Août, 4000 Liège, Belgium

44 Área de Lenguajes y Sistemas Informáticos, Universidad Pablo de Olavide, Ctra. de Utrera, km 1. 41013 Sevilla, Spain

45 Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l'Université, 67000 Strasbourg, France

46 Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

47 Aurora Technology for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

48 Laboratoire Univers et Particules de Montpellier, Université Montpellier, Place Eugène Bataillon, CC72, 34095 Montpellier Cedex 05, France

49 Department of Astrophysics, Astronomy and Mechanics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, 15783 Athens, Greece

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51 Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, via S. Sofia 78, 95123 Catania, Italy

52 INAF-Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy

53 Universidade da Coruña, Facultade de Informática, Campus de Elviña S/N, 15071 A Coruña, Spain

54 CENTRA, Universidade de Lisboa, FCUL, Campo Grande, Edif. C8, 1749-016 Lisboa, Portugal

55 University of Helsinki, Department of Physics, PO Box 64, 00014 Helsinki, Finland

56 Finnish Geospatial Research Institute FGI, Geodeetinrinne 2, 02430 Masala, Finland

57 Isdefe for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

58 ASI Science Data Center, via del Politecnico SNC, 00133 Roma, Italy

59 Institut UTINAM UMR6213, CNRS, OSU THETA Franche-Comté Bourgogne, Université Bourgogne Franche-Comté, 25000 Besançon, France

60 Dpto. de Inteligencia Artificial, UNED, c/ Juan del Rosal 16, 28040 Madrid, Spain

61 Elecnor Deimos Space for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

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65 Department of Physics and Astronomy, The Johns Hopkins University, 3400 N Charles St, Baltimore, MD 21218, USA

66 ON/MCTI-BR, Rua Gal. José Cristino 77, Rio de Janeiro, CEP 20921-400 RJ, Brazil

67 OV/UFRJ-BR, Ladeira Pedro Antônio 43, Rio de Janeiro, CEP 20080-090 RJ, Brazil

68 Faculdade Ciencias, Universidade do Porto, Departamento Matemática Aplicada, Rua do Campo Alegre, 687 4169-007 Porto, Portugal

69 Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal

70 Vitrociset Belgium for ESA/ESTEC, Keplerlaan 1, 2201AZ, Norderwijk, The Netherlands

71 Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), ESA-ESAC, Camino Bajo del Castillo s/n. 28692 Villanueva de la Cañada, Madrid, Spain

72 Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK

73 Deimos Space S.L.U. for ESA/ESOC, Robert-Bosch-Straße 5, 64293 Darmstadt, Germany

74 University of Oviedo, Campus Universitario, 33203 Gijón, Spain

75 University of Cádiz, Avd. De la universidad, Jerez de la Frontera, 11002 Cádiz, Spain

76 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands

77 Consorci de Serveis Universitaris de Catalunya, C/ Gran Capità, 2-4 3rd floor, 08034 Barcelona, Spain

78 University of Turin, Department of Computer Sciences, Corso Svizzera 185, 10149 Torino, Italy

79 INAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00078 Monte Porzio Catone (Roma), Italy

80 CRAAG-Centre de Recherche en Astronomie, Astrophysique et Géophysique, Route de l'Observatoire BP 63, Bouzareah 16340 Alger, Algeria

81 Universiteit Antwerpen, Onderzoeksgroep Toegepaste Wiskunde, Middelheimlaan 1, 2020 Antwerpen, Belgium

82 Department of Physics and Astronomy, University of Padova, via Marzolo 8, 35131 Padova, Italy

83 INAF-Osservatorio Astronomico di Teramo, via Mentore Magini, 64100 Teramo, Italy

84 INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy

85 Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, Cidade Universitária, 05508-900 São Paulo, SP, Brazil

86 Telespazio Vega Deutschland GmbH for ESA/ESOC, Robert-Bosch-Straße 5, 64293 Darmstadt, Germany

87 Department of Geosciences, Tel Aviv University, 6997801 Tel Aviv, Israel

88 Astronomical Institute Anton Pannekoek, University of Amsterdam, PO Box 94249, 1090 GE, Amsterdam, The Netherlands

89 Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

90 ATOS for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France

91 School of Physics and Astronomy, Tel Aviv University, 6997801 Tel Aviv, Israel

92 UNINOVA – CTS, Campus FCT-UNL, Monte da Caparica, 2829-516 Caparica, Portugal

93 Laboratoire Géoazur, Université Nice Sophia-Antipolis, UMR 7329, CNRS, Observatoire de la Côte d'Azur, 250 rue A. Einstein, 06560 Valbonne, France

94 RHEA for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

95 Astronomical Institute, Academy of Sciences of the Czech Republic, Fričova 298, 25165 Ondřejov, Czech Republic
96 Barcelona Supercomputing Center – Centro Nacional de Supercomputación, c/ Jordi Girona 29, Ed. Nexus II, 08034 Barcelona, Spain

97 Department of Mechanical Engineering, University of La Rioja, c/ San José de Calasanz, 31, 26004 Logroño, La Rioja, Spain

98 ETSE Telecomunicación, Universidade de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Galicia, Spain

99 SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584CA, Utrecht, The Netherlands

100 Faculty of Mathematics and Physics, University of Ljubljana, Jadranjska ulica 19, 1000 Ljubljana, Slovenia

101 Physics Department, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium

102 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA

103 Institut de Physique de Rennes, Université de Rennes 1, 35042 Rennes, France

104 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Rd, 200030 Shanghai, PR China

105 CSC Danmark A/S, Retortvej 8, 2500 Valby, Denmark

106 Las Cumbres Observatory Global Telescope Network, Inc., 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USA

107 CGI for ESA/ESOC, Robert-Bosch-Straße 5, 64293 Darmstadt, Germany

108 Astrophysics Research Institute, Liverpool John Moores University, L3 5RF, UK

109 LSE Space GmbH for ESA/ESOC, Robert-Bosch-Straße 5, 64293 Darmstadt, Germany

110 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklós út 15–17, 1121 Budapest, Hungary

111 Baja Observatory of University of Szeged, Szegedi út III/70, 6500 Baja, Hungary

112 Laboratoire AIM, IRFU/Service d'Astrophysique – CEA/DSM – CNRS – Université Paris Diderot, Bât 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France

113 GMV for ESA/ESOC, Robert-Bosch-Straße 5, 64293 Darmstadt, Germany

114 INAF–Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34143 Trieste, Italy

115 Laboratoire de l'Accélérateur Linéaire, Université Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91898 Orsay Cedex, France

116 École polytechnique fédérale de Lausanne, SB MATHAA STAP, MA B1 473 (Bâtiment MA), Station 8, 1015 Lausanne, Switzerland

117 INAF/IASF-Bologna, via P. Gobetti 101, 40129 Bologna, Italy

118 Technical University of Madrid, José Gutiérrez Abascal 2, 28006 Madrid, Spain

119 EQUERT International for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France

120 AKKA for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France

121 Villanova University, Dept. of Astrophysics and Planetary Science, 800 E Lancaster Ave, Villanova PA 19085, USA

122 Vitrociset Belgium for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

123 Fork Research, Rua do Cruzado Osberno, Lt. 1, 9 esq., Lisboa, Portugal

124 APAVE SUDEUROPE SAS for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France

125 Serco Services GmbH for ESA/ESOC, Robert-Bosch-Straße 5, 64293 Darmstadt, Germany

126 Spanish Virtual Observatory, Spain

127 Fundación Galileo Galilei – INAF, Rambla José Ana Fernández Pérez 7, 38712 Breña Baja, Santa Cruz de Tenerife, Spain

128 INSA for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

129 Dpto. Arquitectura de Computadores y Automática, Facultad de Informática, Universidad Complutense de Madrid, C/ Prof. José García Santesmases s/n, 28040 Madrid, Spain

130 H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK

131 Stellar Astrophysics Centre, Aarhus University, Department of Physics and Astronomy, 120 Ny Munkegade, Building 1520, 8000 Aarhus C, Denmark

132 Applied Physics Department, University of Vigo, 36310 Vigo, Spain

133 HE Space Operations BV for ESA/ESTEC, Keplerlaan 1, 2201AZ, Noordwijk, The Netherlands

134 Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland

135 Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain

136 Universidad de La Laguna, Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain

137 RHEA for ESA/ESTEC, Keplerlaan 1, 2201AZ, Noordwijk, The Netherlands

138 Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany

139 SISSA (Scuola Internazionale Superiore di Studi Avanzati), via Bonomea 265, 34136 Trieste, Italy

140 Instituto Nacional de Pesquisas Espaciais/Ministério da Ciencia Tecnologia, Avenida dos Astronautas 1758, São José Dos Campos, SP 12227-010, Brazil

141 Argelander Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

142 European Southern Observatory (ESO), Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany

143 Laboratory of Optics, Lasers and Systems, Faculty of Sciences, University of Lisbon, Campus do Lumiar, Estrada do Paço do Lumiar, 22, 1649-038 Lisboa, Portugal

144 Department of Physics and Astronomy, Notre Dame University, Louaize, PO Box 72, Zouk Mikaël, Lebanon

145 University of Nova Gorica, Vipavska 13, 5000 Nova Gorica, Slovenia

146 Max Planck Institute for Extraterrestrial Physics, OPINAS, Gießenbachstraße, 85741 Garching, Germany

147 NASA/IPAC Infrared Science Archive, California Institute of Technology, Mail Code 100-22, 770 South Wilson Avenue, Pasadena, CA, 91125, USA

148 Center of Applied Space Technology and Microgravity (ZARM), c/o Universität Bremen, Am Fallturm 1, 28359 Bremen, Germany

149 RHEA System for ESA/ESOC, Robert Bosch Straße 5, 64293 Darmstadt, Germany

150 Tartu Observatory, 61602 Tõravere, Estonia

151 Sydney Institute for Astronomy, School of Physics A28, The University of Sydney, NSW 2006, Australia

152 Slovak Organisation for Space Activities, Zamocka 18, 85101 Bratislava, Slovak Republic

153 National Astronomical Observatories, CAS, 100012 Beijing, PR China

154 US Naval Observatory, Astrometry Department, 3450 Massachusetts Ave. NW, Washington DC 20392-5420 D.C., USA

155 European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001 Santiago de Chile, Chile

156 EJR-Quartz BV for ESA/ESTEC, Keplerlaan 1, 2201AZ, Noordwijk, The Netherlands

157 The Server Labs for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

158 Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, ul. Sloneczna 36, 60-286 Poznań, Poland

159 CS Systèmes d’Information for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France

160 Praesepe BV for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
161 Sorbonne Universités UPMC et CNRS, UMR7095, Institut d'Astrophysique de Paris, 75014 Paris, France

162 GMV for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

163 Institute of Theoretical Physics and Astronomy, Vilnius University, Sauletekio al. 3, 10222 Vilnius, Lithuania

164 S[&]T Corporation, PO Box 608, 2600 AP, Delft, The Netherlands

165 Department of Space Studies, Southwest Research Institute (SwRI), 1050 Walnut Street, Suite 300, Boulder, Colorado 80302, USA

166 Deutsches Zentrum für Luft- und Raumfahrt, Institute of Space Systems, Am Fallturm 1, 28359 Bremen, Germany

167 University of Applied Sciences Munich, Karlstr. 6, 80333 Munich, Germany

168 Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Rome, Italy

169 Department of Physics and Astronomy, University of the Western Cape, Robert Sobukwe Road, 7535 Bellville, Cape Town, South Africa

170 INAF-Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy

171 Department of Physics, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA

172 Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
## Appendix A: Acronyms

The following table has been generated from the online Gaia acronym list.

<table><caption>**Table A.1.** Acronyms used in this paper.</caption><thead><tr><td>Acronym</td><td>Description</td></tr></thead><tbody><tr><td>AC</td><td>ACross-scan (direction)</td></tr><tr><td>ADC</td><td>Analogue-to-Digital Converter</td></tr><tr><td>AF</td><td>Astrometric Field</td></tr><tr><td>AGIS</td><td>Astrometric Global Iterative Solution</td></tr><tr><td>AL</td><td>ALong-scan (direction)</td></tr><tr><td>AOCS</td><td>Attitude and Orbit Control Subsystem</td></tr><tr><td>ASD</td><td>Auxiliary Science Data (VPU)</td></tr><tr><td>AVM</td><td>AVionics Model</td></tr><tr><td>BAM</td><td>Basic Angle Monitor</td></tr><tr><td>BP</td><td>Blue Photometer</td></tr><tr><td>CCD</td><td>Charge-Coupled Device (detector)</td></tr><tr><td>CDB</td><td>Configuration DataBase</td></tr><tr><td>CDU</td><td>Clock Distribution Unit</td></tr><tr><td>CPS</td><td>Chemical Propulsion Subsystem (orbit maintenance)</td></tr><tr><td>CTI</td><td>Charge-Transfer Inefficiency</td></tr><tr><td>CU</td><td>Coordination Unit (in DPAC)</td></tr><tr><td>DCS</td><td>De-compression and Calibration Services</td></tr><tr><td>Δ-DOR</td><td>Delta Differential One-way Range</td></tr><tr><td>DIB</td><td>Diffuse Interstellar Band</td></tr><tr><td>DPAC</td><td>Data Processing and Analysis Consortium</td></tr><tr><td>DPC</td><td>Data Processing Centre</td></tr><tr><td>DR1</td><td>(Gaia) Data Release 1 (September 2016)</td></tr><tr><td>DS</td><td>(Airbus) Defence and Space</td></tr><tr><td>EAR</td><td>Event Anomaly Report</td></tr><tr><td>EIRP</td><td>Equivalent Isotropic Radiated Power</td></tr><tr><td>EO</td><td>Extended Object</td></tr><tr><td>EPSL</td><td>Ecliptic Poles Scanning Law</td></tr><tr><td>ESA</td><td>European Space Agency</td></tr><tr><td>ESAC</td><td>European Space Astronomy Centre (ESA)</td></tr><tr><td>ESO</td><td>European Southern Observatory</td></tr><tr><td>ESOC</td><td>European Space Operations Centre (ESA)</td></tr><tr><td>ESTRACK</td><td>ESA Tracking Stations Network</td></tr><tr><td>E-SVM</td><td>Electrical Service Module</td></tr><tr><td>FL</td><td>First Look</td></tr><tr><td>GAIA</td><td>Global Astrometric Interferometer for Astrophysics (obsolete; now spelled as Gaia)</td></tr><tr><td>GBOT</td><td>Ground-Based Optical Tracking</td></tr><tr><td>GMSK</td><td>Gaussian Minimum Shift Keying</td></tr><tr><td>GOST</td><td>Gaia Observation Scheduling Tool</td></tr><tr><td>GSR</td><td>Global Sphere Reconstruction</td></tr><tr><td>ICRF</td><td>International Celestial Reference Frame</td></tr><tr><td>ICRS</td><td>International Celestial Reference System</td></tr><tr><td>IDT</td><td>Initial Data Treatment</td></tr><tr><td>IDU</td><td>Intermediate Data Update</td></tr><tr><td>IGSL</td><td>Initial Gaia Source List</td></tr><tr><td>INPOP</td><td>Intégrateur Numérique Planétaire de l'Observatoire de Paris (ephemerides)</td></tr><tr><td>M2MM</td><td>M2 Mirror Mechanism (focus)</td></tr><tr><td>MDB</td><td>Main DataBase</td></tr><tr><td>MIT</td><td>MOC Interface Task</td></tr><tr><td>MMH</td><td>Mono-Methyl Hydrazine</td></tr><tr><td>MOC</td><td>Mission Operations Centre (ESOC)</td></tr><tr><td>MP</td><td>Metal-Poor (star)</td></tr><tr><td>MPS</td><td>Micro-Propulsion Subsystem (science mode)</td></tr></tbody></table>
<table><caption>**Table A.1.** continued.</caption><thead><tr><td>Acronym</td><td>Description</td></tr></thead><tbody><tr><td>M-SVM</td><td>Mechanical Service Module</td></tr><tr><td>NSS</td><td>Non-Single Star</td></tr><tr><td>NTO</td><td>(di-)Nitrogen TetrOxide</td></tr><tr><td>OBMT</td><td>OnBoard Mission Timeline</td></tr><tr><td>OBT</td><td>OnBoard Time (realised in CDU)</td></tr><tr><td>ODAS</td><td>One-Day Astrometric Solution</td></tr><tr><td>OGA-1</td><td>First On-Ground Attitude determination (in IDT)</td></tr><tr><td>OGA-2</td><td>Second (and improved) On-Ground Attitude determination (in ODAS/FL)</td></tr><tr><td>PAA</td><td>Phased-Array Antenna</td></tr><tr><td>PDHU</td><td>Payload Data-Handling Unit</td></tr><tr><td>PEM</td><td>Proximity-Electronics Module (CCD)</td></tr><tr><td>PLM</td><td>PayLoad Module</td></tr><tr><td>PO</td><td>(DPAC) Project Office</td></tr><tr><td>PSF</td><td>Point Spread Function</td></tr><tr><td>QSO</td><td>Quasi-Stellar Object</td></tr><tr><td>RAFS</td><td>Rubidium Atomic Frequency Standard (part of CDU)</td></tr><tr><td>RMS</td><td>Root-Mean-Square</td></tr><tr><td>RP</td><td>Red Photometer</td></tr><tr><td>RVS</td><td>Radial-Velocity Spectrometer</td></tr><tr><td>SEA</td><td>Source Environment Analysis</td></tr><tr><td>SED</td><td>Spectral Energy Distribution</td></tr><tr><td>SIF</td><td>Service Interface Function (VPU)</td></tr><tr><td>SM</td><td>Sky Mapper (detector)</td></tr><tr><td>SOC</td><td>Science Operations Centre (ESAC)</td></tr><tr><td>SP</td><td>Star Packet (VPU)</td></tr><tr><td>SSO</td><td>Solar System Object</td></tr><tr><td>TCB</td><td>Barycentric Coordinate Time</td></tr><tr><td>TDI</td><td>Time-Delayed Integration (CCD)</td></tr><tr><td>TMA</td><td>Three-Mirror Anastigmat (telescope)</td></tr><tr><td>TODCOR</td><td>Two-Dimensional CORrelation</td></tr><tr><td>UTC</td><td>Coordinated Universal Time</td></tr><tr><td>VPA</td><td>Video Processing Algorithms (run on the VPU)</td></tr><tr><td>VPU</td><td>Video Processing Unit (runs the VPAs)</td></tr><tr><td>WFS</td><td>Wave-Front Sensor</td></tr><tr><td>XP</td><td>Shortcut for BP and/or RP (generic name for Blue and Red Photometer)</td></tr></tbody></table>