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Klaus Wittmann, Willi Hallmann and Nicolaus Hanowski 1

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The launch of Sputnik 1 in October 1957 marks the Following the initial period of non-military space beginning of the space age. Since 1957 more than flight, important commercial space activities evol- 3 5000 satellites and human spacecraft have entered ved. These include rocket systems, spacecraft and space and about 850 of them are still operational. payloads in the areas of communication, navigation, The utilization of a spacecraft ends when important remote sensing and meteorology. subsystems fail or with its controlled or uncontrolled Space missions are performed not only by single reentry through the Earth’s atmosphere. Every year nations, but also by international companies and 4 more new spacecraft are launched than old satellites multinational institutions such as the European Space return to Earth. Thus, the number of satellites in Agency (ESA). space has been continuously growing in the past and Cooperation between public entities and com- is expected to continue to grow in the future. Space mercial companies is gaining importance in space flight was initiated by the USA and the former Soviet flight projects. These cooperative projects are termed Union. Since then space projects have been conducted public–private partnerships or PPPs. An example of a 5 by all major industrialized countries. In addition, a PPP space project is the German mission TerraSAR-X number of developing countries have implemented (Figure 1.2) [1.2] with a high-resolution X-band radar space programs. On a global scale the USA are still the as the main payload. dominant spacefaring nation according to the number of active spacecraft (see Figure 1.1). 6

500 450 400 350 7 300 250 200 150 100 50 8 0 USA Russia Asia Europe Others Figure 1.2: The satellite TerraSAR-X, an example of a PPP mission, Figure 1.1: National distribution of operating spacecraft is operated by the German Space Operations Centre (GSOC) (Source: (2007). ASTRIUM). 9 Handbook of Space Technology W. Ley, K. Wittmann, W. Hallmann © 2008, Carl Hanser Verlag. This edition published 2009 by John Wiley & Sons, Ltd

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reduce threats and hardship by supporting regional environmental protection and through disaster ma- nagement. Analysis of effects and identification of the 1 rescue options after natural disasters as well as their prediction increasingly relies on the use of satellites. The potential of space missions for these purposes has not yet been fully exploited. In economic, commercial and transportation areas as well as for individuals, the 2 use of satellites is also gaining importance. The uti- lization of satellite communication and navigation has already become an integral part of our society, growing even more important as the capacity and quality of satellite services continuously improve. 3 The fascination with space flight also stems from the high visibility of the technical performance needed to develop a space system. Thus, in addition to the direct utilization of space missions, innovation and spin-off products are linked to space flight. 4 Figure 1.3: The European planetary probe Mars Express which was The objective of this book is to provide insight into launched in June 2003 (Source: ESA). space systems and the related methods and processes for their development, operation and utilization. During the past few decades characteristic uti- Based on practical experience, the state of space flight lization areas have evolved in space flight. They technology should become apparent. The book also include the exploration of our planetary system (see provides an overview of the subsystems typically 5 Figure 1.3) as well as astronomy and basic research constituting a space system. In addition the book tho- in physics. Observation of the Earth by satellites is roughly describes the integration of those subsystems carried out for scientific, commercial and military into the complete space system. By describing the state purposes. Communication and navigation missions of the art, this book also indicates the basis for the have gained high commercial value. In technology development of new concepts and ideas. 6 missions, new systems and components are tested. Stimulated by the implementation of large space Human space flight provides a unique environment projects such as Galileo, an increase in space activities for research programs including, for instance, experi- in Europe can be observed. With new applications and ments in reduced gravity. In addition, exploration of increasing integration of the technical fields involved, the planetary system by astronauts is in preparation. a vast development potential for companies has been 7 The importance of satellite missions for military or generated. Academic institutions such as universities civil security purposes is recognized by a growing are increasingly able to conduct their own satellite number of nations including the member states of missions in order to train their students and to ex- the European Union. ploit the potential of new technologies. Together with The potential of space missions has been demons- commercial and public space flight activities, this is trated over the decade. For the scientific community providing an inspiring and attractive environment 8 new fundamental knowledge was gained and new for young engineers. fields of research have been opened [1.3]. Space Despite the fascination with space flight, well- telescopes have improved our knowledge of the Uni- trained space technology-oriented engineers are verse because observation became possible in those lacking in many European countries. Thus, the ed- areas of the electromagnetic spectrum which are not ucation programs in space technology need to be 9 visible from the ground due to atmospheric blocking. optimized and broadened in order to attract more By observing the Earth, satellites have also helped to young people. 10

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A considerable number of European universities – Mobile Rocket Base (MoRaBa) in Oberpfaf- and high schools are offering curricula in space flight fenhofen technology. A detailed list would exceed the intended – Astronaut Center in Cologne size of this chapter. An excellent entry point for – Microgravity User Support Centre (MUSC) in 1 more information is provided by national organiza- Cologne tions representing the professional community in the • Institute of Space Propulsion Systems in Lampolds- aerospace domain. These are, for example: hausen

AAAF Association Aéronautique et Astronautique CNES Centre National d’Etudes Spatiales (center 2 de France (3AF) (center in Paris, France) in Paris, France) AIAE Asociación de Ingenieros Aeonáuticos de ASI Agenzia Spaziale Italiana (center in Rome, España (center in Madrid, Spain) Italy) AIDAA Associazione Italiana di Aeronautica e BNSC British National Space Centre (center in Astronautica (center in Rome, Italy) London, United Kingdom) 3 DGLR Deutsche Gesellschaft für Luft- und Raum- CDTI Centro para el Desarrollo Tecnológico fahrt (German Society for Aeronautics and Industrial (center in Madrid, Spain) Astronautics; center in Bonn, Germany) FTF Flygtekniska Föreningen (Swedish Society Most of these space agencies combine an agency for Aeronautics and Astronautics; center in function with research and development functions 4 Solana, Sweden) in order to make new technologies available for their HAES Hellenic Aeronautical Engineers Society space programs. (center in Athens, Greece) ESA, with its head office in Paris, maintains the NVvL Nederlandse Vereniging voor Luchtvaart- following research, management and operation fa- techniek (center in Amsterdam, the Ne- cilities: therlands) 5 RAeS The Royal Aeronautical Society (center in European Space Research & Technology Centre London, United Kingdom) (ESTEC) in Noordwijk, the Netherlands SVFW Schweizerische Vereinigung für Flugwissen- European Space Research Institute (ESRIN) in schaften (Swiss Association of Aeronautical Frascati, Italy Sciences; center in Emmen, Switzerland) European Space Operations Centre (ESOC) in Darm- 6 stadt, Germany These organizations have founded a European associ- European Astronaut Centre (EAC) in Cologne, ation, CEAS (Confederation of European Aerospace Germany Sciences), which offers conventions, literature and European Space Astronomy Centre (ESAC) in expert consultancy in the field of space flight and Villafranca, Spain 7 aeronautics. Further organizations or companies like EUMETSAT Public space programs in Europe are initiated and (European Organization for the Exploitation of Me- implemented by national space agencies or by ESA. teorological Satellites) in Darmstadt, Germany, and Examples of national space agencies are: EUTELSAT, SES ASTRA, INMARSAT, HISPASAT (Communications), are conducting public and/or 8 DLR German Aerospace Centre (center in Cologne, commercial space programs. A broad range of com- Germany): 29 research institutes and units panies in the space industry is supplying the necessary in 13 locations in Germany including space development potential on system and subsystem scales. operations and test sites, for example: Some examples of such European companies are: • Space Operations and Astronaut Training: – German Space Operations Centre (GSOC) in EADS (European Aeronautic Defence and 9 Space Company) 10

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Headquarters: Schiphol Rijk (the 1.1 Historical Overview Netherlands) Within EADS space-related activities Willi Hallmann 1 are performed by: • Astrium Satellites • Astrium Space Transportation 1.1.1 Introduction • Astrium Services The history of space flight is also the history of the 2 Thales Alenia Space rocket. Only a rocket is able to overcome Earth’s Headquarters: Cannes, Toulouse (France) gravity and travel upward into air-free space. This Telespazio was not always obvious, as a quote from Max Valier Headquarters: Rome (Italy) (1895–1930) indicates: OHB (Orbitale Hochtechnologie Bremen) Just one year ago the problem of rocket propulsion 3 Bremen (Germany) was considered a fairy tale and everyone who fought Surrey Satellite Technology Limited for it with conviction was derided as a dreamer and Guildford (United Kingdom) laughed at. However, today after the first successful Arianespace runs of a rocket-propelled vehicle the public is Evry-Courcouronnes (France) becoming impatient since there is no in the advance into space. 4 The significance of space technology in research and industrial applications has been recognized by an Badische Zeitung, Karlsruhe, 1929 increasing number of countries all over the world. It is expected that this trend will continue, further in- Hermann Ganswindt (1856–1934), born in Seeburg, creasing the potential of international space programs East Prussia, may have been one of the first who was 5 and providing fascinating new jobs for a worldwide convinced about the technical realism of a spacecraft community of scientists and engineers. and presented an elaborate construction scheme. He made his first public presentation on May 27, 1891 in the Berlin Philharmonie about his idea of a “world- craft” and explained how space flight might be realized Bibliography 6 by means of the propulsion principle. [1.1] TerraSAR-X. Das deutsche Radar-Auge im All. DLR- In the twentieth century these visions became rea- Missionsbroschüre. Deutsches Zentrum für Luft- und lity. Space flight pioneers created the theoretical basis Raumfahrt, 2005. and took the first practical steps. While Konstantin E. [1.2] Feuerbacher, B., Stoewer, H. Utilization of Space. Tsiolkovsky (1857–1935) is called the “father of cos- Basics, Fields of Usage, Future Developments: Today and Tomorrow. Heidelberg: Springer Verlag, 2005. monautics” in Russia, the Americans refer to Robert 7 [1.3] 7 Gründe warum Deutschland Raumfahrt braucht. H. Goddard (1882–1945) as the “father of rocket tech- Berlin: Bundesverband der Deutschen Luft- und Raum- nology.” Hermann Oberth (1894–1989) is considered fahrtindustrie, 2006. a “pioneer of space flight” in Europe, while Wernher [1.4] Studienangebote Raumfahrt. www.studienwahl.de, von Braun (1912–1977) as his ablest student surely 2007. [1.5] Hallmann, W. Ingenieure, Wegbereiter der Zukunft. did a great deal of the pioneering work as well (see 8 Düren: Hahne & Schloemer Verlag, 2006. Figure 1.1.1). Not only were technicians excited by the idea of space flight, but also movie makers and artists. Fritz Lang, director of the first space movie Lady in the moon (premiered in 1928), introduced the launch countdown, which is still customary today. Born 1857 in Izhevskoye, Russia, Konstantin 9 E. Tsiolkovsky presented his fundamental ideas for space flight in “The conquest of space with propulsion 10

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Technical Data for the A4/V2 Height: 14.03 m 1 Diameter: 1.68 m

Take-off mass: 12.8 t

Max. velocity: 5.760 km/h Flight time (fueled): 70 s 2 Thrust: approx. 25 t at 2000 m/s exhaust velocity

Max. altitude: 96 km Range: 330 km 3 Figure 1.1.2: Overview of characteristics of A4/V2 rocket used in World War II. (Source: Bundesarchiv).

The creation of a rocket launch area in Berlin 4 (1930), led by Rudolf Nebel (1894–1978), and the use of rockets with liquid fuel were important steps. The foundation of modern space flight was laid in the years 1935 to 1955. As has been the case se- veral times in the past, technical development was 5 stimulated by war, first by World War II, then by the Figure 1.1.1: Portraits of space flight pioneers: Tsiolkovsky (top Cold War. left), Goddard (top right), Oberth (bottom left) and von Braun Military developments in the Soviet Union led (lower right) (Source [1.1.10]). to the construction of a two-stage intercontinental vehicle to transport warheads. This development became known as the R7 or “Semyorka.” Its further 6 devices”; in 1911 he described an inhabited satellite. development finally led to the reliable Soyuz rocket, He laid the theoretical groundwork of astronautics, today still Russia’s only vehicle for human flights. and between 1925 and 1932 generated more than 60 This launcher and the Progress spacecraft trace back papers on that topic. to Sergey P. Korolyov. Born 1882 in Worcester, Massachusetts, Robert In May 1945 Wernher von Braun and six colle- 7 H. Goddard published a book entitled About a agues were taken into custody by the Americans. In method to reach greatest altitudes. In 1926 he laun- February 1946, 118 engineers and technicians from ched the world’s first successful liquid-fueled Germany were working in White Sands, New Mexico. rocket (petrol–liquid oxygen). While commercially At the beginning von Braun developed the American available rockets were able to produce an emission medium-range rocket C and its derivatives, 8 velocity of 300 m/s, he managed to produce an the Redstone and Jupiter prototypes. The foundation emission velocity of approximately 2400 m/s with for both Russian as well as American rocket develop- petrol–liquid oxygen. ment was originally the German V2 rocket of World Hermann Oberth was born 1894 in Hermann- War II (Figure 1.1.2). It has been forgotten today stadt, Siebenbürgen. In his book of 1923, The rocket that there were considerations in 1950 about using towards the planet regions, he described his theory of nuclear energy for rocket propulsion [1.1.5], [1.1.6], 9 rocket propulsion in a vacuum. [1.1.7]. The interested reader is referred to the chapter 10

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In 1962 a modest sum of DM 11 million was al- located for space flight activities. This was not due to the “Sputnik shock” of 1957, but due to the creation 1 of ESRO (European Space Research Organization) and ELDO (European Launcher Development Orga- nization), which Germany joined in 1963. The most important research institutes were in Belgium and the Netherlands. 2 In Germany a national space flight program was set up under the responsibility of an agency originally called the GFW (Society for Space Research). This agency was integrated into the DFVLR (German Aerospace Research and Experiment Institute). At 3 the end of the 1980s this integration was reversed by the founding of DARA (German Agency for Space Figure 1.1.3: With the launch of the first artificial satellite Sputnik Affairs) and in 1997 it was reintegrated as part of 1 on October 4, 1957 the Soviet Union also launched the space DLR (German Aerospace Centre). Important satellite age (Source: ESA). missions and human missions (, D-1, D-2, 4 etc.) have been conducted as part of the national space “Historical overview of the beginnings of space flight,” program. The technical basis of space flight activities by Ants Kutzer, in the second edition of this handbook in the German aerospace industry was established in [1.1.2] and to [1.1.13], as well as to Ron Miller’s inte- the 1960s, 1970s and 1980s. The resulting knowledge resting publication [1.1.8]. on the component, subsystem and system levels ini- The age of operational space flight began in 1957, tially led to national satellite missions, contributions 5 when an aluminum sphere with a mass of 83 kg and to launcher development and human missions. Today a diameter of 58 cm excited the world with its signals DLR institutes, partially in cooperation with industry, (Figure 1.1.3). After more than 50 years of experience, develop new sensors, technologies and operation con- space flight is not questioned by anyone. cepts, and are integrated into execution tasks of both the German and international programs. 6 From 1981 on, the East German Institute for 1.1.2 The Development of Unmanned Cosmos Research (IFK) that emerged from a number German and European Space of institutes was also heavily occupied with the deve- Flight lopment of space flight systems and components. In 1992 the institute was merged with the newly formed 7 This historic part of the book has been written from DLR site at Berlin-Adlershof. a distinctly German perspective. However, some Independent planning and execution of space aspects of the following paragraphs exemplify deve- flight missions in Germany started in the late 1960s. lopmental steps in countries comparable to Germany But especially with respect to launchers, Germany or even have general implications on how space flight continued to be dependent on the availability of Ame- developed. rican types. Many of the satellite missions conducted 8 Initial steps in Germany were the first research were joint projects in which Germany was able to projects and experiments for space flight applications establish itself as a competent partner. starting as early as 1951, when the North German Important milestones in unmanned space flight Society for Space Flight was founded. This society were the missions shown in Figures 1.1.4–1.1.17. launched two test rockets under allied oversight in As early as 1962 the development of a launcher 9 1952. In 1954 a German “Aerospace Center” was system (EUROPE rocket) commenced on a Euro- founded [1.1.3]. pean level with the objective of creating a European 10

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AZUR DIAL/WIKA Launch: November 8, 1969 Launch: March 11, 1970 Mass 72 kg, electric power 27 W Mass 63 kg, electric power 10 W 1 First German satellite mission German–French mission

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Figure 1.1.5: In the DIAL/WIKA mission (science capsule) four ex- 5 periments (among others identifying electron density) were put into an equatorial orbit. The satellite could not be commanded actively. The mission ended after a little more than two months. The mission was launched by a Diamant-B rocket (Source: EADS). Figure 1.1.4: AZUR was intended to explore Earth’s radiation belt under the system leadership of the Bölkow GmbH company. The satellite was launched by a US Scout rocket into a polar orbit. A Finally, European access to space has been assured 6 special requirement was that all materials had to be nonmagnetic by the Ariane rocket family (Ariane 5 at the moment). (Source: DLR). And Ariane has now also proven to be economically successful. Important steps were: capacity to transport a 100 kg payload into a 300 km orbit. The first stage was built by the United King- 1979: The first Ariane rocket (Ariane 1) is successful- 7 dom, the second by France and the third by Germa- ly launched from the Kourou space center in ny. Due to several launch failures and for political French Guiana (Figure 1.1.18). The companies reasons, the EUROPE rocket program was cancelled Aerospatiale, MATRA, ENRO, MBB and CASA in 1972. participated significantly in the development In 1975 ELDO and ESRO merged into the newly and construction of this European satellite founded (ESA). Since then launcher. 8 many highly complex projects have been prepared 1984: The 49 m high Ariane 3 is launched for the and conducted under ESA’s responsibility. In that first time. A version of this rocket without program a large number of German contributions a solid rocket booster became known as were involved. The German budgetary contributions Ariane 2. invested in European space flight are distinctly larger 1990: Aerospatiale receives an order from Arianes- 9 than the corresponding national space budgets. pace to deliver 50 Ariane 4 rockets. 10

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Aeros A and B Helios A and B Launch: December 16, 1972 and July 16, 1974 Launch: December 10, 1974 and January 15, 1976 Mass 126 kg, electric power 55 W Mass 371 kg, electric power 216/1000 W 1 German atmospheric physics missions German–American solar research mission

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4 Figure: 1.1.7: With the solar probe Helios A, which came within 0.3 astronomical units of the Sun, the interplanetary medium in this region was analyzed for the first time. The probe was built in Germany and used by German and American scientists. Launcher: 5 Titan IIIE-Centaur (Source: DLR). 4.7 t in total. Up to then, 116 Ariane launchers had put more than 400 t of satellite payload into orbit from Kourou. Three launches failed. 2005: Ariane 5 is launched with the new upper stage 6 ECA and a 10 t payload. This was the 164th Figure 1.1.6: The Aeros satellite had a cylindrical structure with Ariane launch. a diameter of 0.9 m. One mission objective was to identify the 2006: A new launch with a heavy-duty version ECA conditions and behavior of the top layers of the atmosphere. In takes place. A French and a Japanese satellite total five experiments were accommodated in each of the satel- are deployed. lites. Launch was accomplished by a Scout rocket into a polar orbit 7 (Source: DLR) Significant and ambitious European space programs in the areas of astronomy and exploration of the 1996: The maiden flight of the new European Ariane planetary system, Earth observation, navigation and 5 takes place but is aborted after 40 seconds communications are being implemented by ESA. because of a software failure. Table 1.1.1 gives an overview of the most important 8 1997: The 100th flight of an Ariane rocket takes past and current unmanned ESA missions. With the place. In total 134 satellites and 26 piggyback European Galileo satellite navigation system, ESA is payloads have been put into orbit. engaged in a program of considerable magnitude. To 1999: The first commercial use of the Ariane 5 takes implement this navigation system consisting of 30 place with the launch of the X-ray satellite satellites requires an extensive synthesis of public and XMM. industrial competence in Europe. In 2003 the Galileo 9 2003: The last launch of Ariane 4 (version 44L) takes project was given the go-ahead. In December 2005 the place with Intelsat 907 as its payload weighing first test satellite for Galileo was launched into orbit 10

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Symphony A and B AMPTE/IRM Launch: December 19, 1974 and August 27, 1975 Launch: August 16, 1984 Mass approx. 400 kg, electric power 300 W Mass approx. 705 kg, electric power 60 W 1 German–French communications satellite German–American–British research mission

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Figure 1.1.8: Symphony A, the first German–French experimental communications satellite, was originally planned to transmit the 4 Olympic Games in Munich. The Symphony satellite was three-axis stabilized in geostationary orbit. It was alternately operated by a German and a French control center. Launcher: Thor–Delta (Source: DLR).

and the second followed in spring 2008. From 2013, 5 after a prior so-called in-orbit validation with four satellites, 30 navigation satellites will provide Europe with an independent global satellite navigation system. It is expected that up to 140 000 new jobs will be cre- Figure 1.1.9: AMPTE/IRM (Ion Release Module) was the German ated in Europe by Galileo. Ariane 5 will put up to six contribution to three simultaneously launched satellites for research 6 Galileo satellites at a time into orbit (Figure 1.1.19). on the magnetosphere. The satellite deployed barium and lithium and analyzed the behavior of the ion cloud generated. The launch Galileo is supposed to ensure Europe’s independence took place with a Delta rocket (Source: NASA). but will also be compatible with GPS. Aldrin were the first men to stand on the Moon. The Soviet Union confined itself to the robotic return of 7 1.1.3 The Development of Human lunar samples. Space Flight in Europe Until the end of 1972, 12 astronauts landed on the Moon as part of the Apollo missions. During this Human space flight in Europe is built upon the great period the two superpowers were already actively ini- experience of the Russians and Americans from the tiating the operation of large space stations occupied 8 1960s and 1970s. After the first space flight of the Rus- by humans. Important milestones on the way toward sian Yuri Gagarin (1934–1968) in 1961, efforts by the a station in orbit for extensive research were: Soviet Union and the USA were soon directed toward Salyut 6/7: In April 1971 the Soviet Union put the a human Moon landing. With resolute preparation, first space station with two main coupling starting with the Mercury program, the USA were able ports into space. Thus the ISS can be viewed to reach this goal via the Gemini and finally the Apollo as the grandchild of Salyut 6/7. On August 26, 9 programs. In July 1969 Neil Armstrong and Edwin 1978 Sigmund Jähn, a citizen of the German 10

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TV-Sat 1 and 2 ROSAT Launch: November 21, 1987 and August 8, 1989 Launch: June 1, 1990 Mass 2077 kg and 1027 kg respectively, electric power 3 kW Mass 2421 kg, electric power 900 W 1 German communications satellite German–American–British X-ray telescope

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Figure 1.1.10: TV-Sat 1 and 2 are direct transmitting satellites whose television and radio signals are strong enough to be received with 50 cm dish antennas. After the deployment of an antenna 4 failed, TV-Sat 1 was placed into a graveyard orbit. Launches took place with Ariane rockets (Source: Aerospatiale).

DFS-Copernicus 1, 2 and 3 Launch: June 5, 1989, July 24, 1990 and October 12, 1992 5 Mass 645, 850 and 1400 kg respectively, electric power 1.5 kW German communications satellite

Figure 1.1.12: On the ROSAT mission a complete survey of the sky for X-ray sources as well as their detailed analysis was conducted. The satellite was three-axis stabilized and operated successfully for almost 10 years. The launch took place with a Delta II rocket 6 (Source: MPG).

Democratic Republic, was sent aboard Soyuz 31 together with cosmonaut Valery F. Bykovsky to Salyut 6. 7 Skylab: This US station was placed into an orbit of 432 km altitude and 50° inclination on May 14, 1973. The station comprised a modified third Saturn 5 stage. In the time between May 25, 1973 and February 8, 1974 Skylab was vi- 8 sited by three Apollo command modules with three astronauts each for 28, 59 and 84 days. In July 1979, after more than six years, Skylab reentered the atmosphere and came down over Figure 1.1.11: The DFS-Copernicus communications satellites were Australia as debris. built in Bremen for the German federal postal service. After the launch : This was a modular space station composed 9 and early operation phase, conducted by the German Aerospace Cen- tre, the satellites were transferred to Usingen for routine operations. of different station parts which were launched Launchers: Ariane 4 44L and Delta II (Source: MBB/ERNO). one after another. The assembly started in 10

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EXPRESS CHAMP Launch: January 15, 1995 Launch: July 15, 2000 Mass 765 kg Mass 522 kg, electric power 140 W 1 German–Japanese reentry capsule German Earth observation satellite

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Figure 1.1.13: Comprising a service and a reentry module, the probe only carried out three Earth orbits due to a launcher failure. 4 Nevertheless, telemetry was received and the reentry vehicle was Figure 1.1.15: With the CHAMP satellite the gravitational field recovered in Africa. The launch took place with a Japanese M-3SII of the Earth, as well as physical and chemical properties of the rocket (Source: DLR). Earth’s atmosphere, are being determined. The payload consists of accelerometers, magnetometers, a GPS receiver, laser retro-reflec- tors and an ion-drift meter. The launcher rocket was a Cosmos-3M (Source: Astrium/DLR/GFZ). 5 EQUATOR-S Launch: December 2, 1997 February 1986 with the basis module, followed Mass 250 kg, electric power 80 W German research satellite by the Kvant 1 docking module (March 1987), Kvant 2 (November 1989), Kristall (Kvant 3) (May 1990), Spektr (May 1995, docking module 6 for the US docking in November 1995) and Priroda (April 1996). Except for Kvant 1 the mass of each module was 19 t. In July 1995 the first shuttle docked with the MIR station after the first US astronaut had flown to 7 MIR from Baikonur on a Soyuz spacecraft. The space station was visited by 96 cosmonauts. The longest time on-board was spent by Valeriy V. Polyakov with a total of 679 days, of which 438 days were spent on one mission. The German 8 astronauts Ulf Merbold, Klaus-Dieter Flade, and visited the MIR station in the course of the German– Figure 1.1.14: The EQUATOR-S satellite was a contribution to the Russian missions MIR 92 and MIR 97 and the International Solar–Terrestrial-Physics Program (ISTP). It was used ESA missions MIR 94 and MIR 95. On April 4, to survey plasma, magnetic field and electric field properties at dif- 9 ferent altitudes. System leadership lay with the Max-Planck Institute 2000 the last crew were sent to MIR. On March for Extraterrestrial Physics. Launcher: Ariane 4 (Source: MPG). 23, 2001 the 15-year-old station largely burned 10

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BIRD Launch: October 22, 2001 1 Mass 92 kg, electric power 40 W German technology satellite

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4 Figure 1.1.16: With the DLR BIRD satellite numerous new satellite components could be tested. For instance, the infrared cameras provided extraordinary data for detecting and examining fires, volcanic activity and thermal signatures of the Earth’s surface. The 5 launcher was an Indian PSLV rocket (Source: DLR). Figure 1.1.18: Ariane 1. First successful rocket launch on December GRACE 1 and 2 24, 1979 in Kourou (Source: ESA). Launch: March 17, 2002 Mass 490 kg each, electric power 620 W German–American Earth observation satellites 6 up in Earth’s atmosphere after a controlled reentry. However, 19 t of the total 124 t mass cra- shed unburned into the Pacific Ocean. During its history the MIR space station, which was originally designed for a lifetime of seven years, 7 orbited the Earth 86 325 times at an altitude of 390 km [1.1.12].

With the Space Shuttle (first launched in April 1981) a partially reusable and very capable system 8 became available for the USA. The shuttle played an important role in the transport of heavy satellites and laboratory modules and later in the transport of large components to the ISS. High costs and the loss of the Figure 1.1.17: Flying with a separation of approx. 200 km the Challenger (1986) and Columbia (2003) shuttles from two satellites are used for precise measurements of the Earth’s a fleet comprising a total of five shuttles led to the 9 gravitational field. This is achieved by determining variations in the distance between both satellites on a micrometer scale. Launcher: decision to phase out the shuttle program by 2010 or Rokot (Source: Astrium/DLR). shortly thereafter. 10

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Table 1.1.1: Important ESA missions.

Year Mission name Mission application 1968 HEOS 1 Space physics 1 1975 COS-B Gamma radiation astronomy 1978 IUE Ultraviolet space telescope 1978 GEOS 2 Magnetosphere survey 1983 EXOSAT X-ray astronomy 2 1985 Giotto Comet fly-by 1989 Olympus Experimental communication 1989 Hipparcos Astrometry Figure 1.1.20: Spacelab, built by MBB/ERNO in Bremen, flew on- 1990 Ulysses Solar research board the Space Shuttle Columbia for the first time. As the first 1991 ERS-1 Earth observation astronaut of the Federal Republic of Germany, Ulf Merbold was on 3 1992 EURECA Experiment platform this European mission which featured 38 experiments. The launch took place in November 1983 (Source: NASA). 1995 ISO Infrared space telescope 1995 SOHO Solar research 1997 Huygens Titan landing probe on Cassini In Europe the Spacelab, SPAS and EURECA 4 1999 XMM-Newton X-ray astronomy platforms were developed by MBB for ESA as contri- 2000 Cluster Magnetosphere research butions to the shuttle program around 1980. 2002 INTEGRAL Gamma radiation astronomy For human space flight ESA facilities work clo- sely with national institutions. German astronauts 2002 ENVISAT Earth observation have been part of important missions, especially for 2003 SMART-1 Moon exploration the Spacelab FSLP (1983, Figure 1.1.20), D1 (1985, 5 2003 Mars Express Mars exploration Figure 1.1.21), D2 (1993) and SRTM (2000) missions 2004 Rosetta Comet rendezvous which were conducted in cooperation with the USA. 2005 Venus Express Venus exploration

1.1.3.1 The International Space 6 Station

A little more than 40 years after the first space flight, the first of the basic elements for the assembly of the future International Space Station (ISS) (Figure 1.1.22) 7 was launched on November 20, 1998 from Baikonur in Kazakhstan. The corresponding plans date back to the 1980s. At that time the space station was referred to as “Freedom” or “Alpha.” The project became a co- operative effort among several nations. In addition to 8 NASA and the Russian space flight agency Roskosmos, Europe is also participating. ESA signed a contract to cooperate in the station’s construction in 1998. Moreover, the Canadian and Japanese space agencies have also signed contracts. Figure 1.1.19: Artist’s impression of the planned Ariane 5 upper 9 stage with eight Galileo satellites prior to separation (Source: As a partner of the USA, Russia, Japan and Canada, ESA). Europe operates the Columbus laboratory module as 10

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Table 1.1.2: European astronauts and cosmonauts with space experience (as at June 2008). 1 Name Country Aleksandar Panayotov Bulgaria Alexsandrov Anatoly Artsebarsky Ukraine Patrick Baudry France 2 Ivan Bella Slovakia Italy Jean-Loup Chrétien France Jean-François Clervoy France Belgium Spain 3 Reinhold Ewald Germany Figure 1.1.21: The Spacelab D1 mission was launched with two German scientists on-board (Ernst Messerschmid and Reinhard Fur- Léopold Eyharts France rer). Mission management and payload operations were a German Bertalan Farkas Hungary responsibility. The launch took place on October 30, 1985 with the Jean-Jacques Favier France Space Shuttle Challenger (Source: MBB/ERNO). Klaus-Dietrich Flade Germany 4 Dirk Frimout Belgium Sweden Reinhard Furrer Germany Italy Claudie Haigneré France 5 Jean-Pierre Haigneré France Miroslaw Hermaszewski Poland Georgi Ivanov Bulgaria Sigmund Jähn Germany (GDR and FRG) Leonid Kadenyuk Ukraine André Kuipers Netherlands 6 Franco Malerba Italy Ulf Merbold Germany Ernst Messerschmid Germany Italy Figure 1.1.22: Artist’s impression of the ISS (Source: ESA). Switzerland 7 Netherlands France part of the ISS and provides an automated transfer Dumitru Prunariu Romania vehicle (ATV) for supplying the station. In 2006 the Thomas Reiter Germany Columbus module was handed over to NASA by Vladimir Remek Czechoslovakia/Czech Germany for integration into the Space Shuttle in order Republic 8 to transport it to the ISS (launched February 2008). Germany Even in an unfinished state (construction should Helen Sharman United Kingdom be finished by 2010) the station has been occupied Anatoly Solovyev Lithuania by astronauts and cosmonauts or tourists from the Germany beginning (see also Table 1.1.2). After completion it France will reach a size of approx. 110 m × 90 m × 30 m and Franz Viehböck Austria 9 will stay in operation at least until 2016. At the moment Italy it is the biggest human-built object in Earth orbit. Ulrich Walter Germany 10

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1

2

3 Figure 1.1.24: The Columbus module attached to the ISS (Source: ESA).

The Columbus program was initiated in 1986 at an EU Council of Ministers conference to be imple- mented by ESA in addition to the Hermes and Ariane 4 5 programs. Columbus (Figure 1.1.24) was originally meant to be a laboratory docked to the US Space Sta- tion Freedom (SSF) or a free-flying device. The name Columbus was chosen because the discovery of Ame- Figure 1.1.23: The ATV for supplying the ISS (Source: ESA). rica by Columbus had its 500th anniversary in 1992. 5 Thus hope was expressed that Columbus would dock with the SSF in 1992. However, Columbus was initially The station is circling at an altitude of 350 km with also intended to be able to be launched by an Ariane an inclination of 51.6°. At the end of 2006 astronaut 5. The launch of Columbus and docking with the ISS Thomas Reiter completed a long-term stay on the ISS became a reality in 2008. Operation of the Columbus 6 which had begun in July 2006 in the course of the module is conducted by the Columbus Control Centre Astrolab mission. at DLR/GSOC Oberpfaffenhofen. Beginning in 2008 Europe is also contributing On a personal note, it is unrealistic to illustrate the to the supply of the space station. This is being ac- history of space flight over the last 50 years within 10 complished by the ATV (Figure 1.1.23), according to pages. Everything stated above has been chosen subjec- the same principle as for the Russian Progress space tively and must therefore be incomplete. During pre- 7 transporter. In summer 2004 production of six such paration, the journals SGLR-Luft- und Raumfahrt and ESA transporters was initiated under a contract with Planet Aerospace as well as [1.1.14] were of great help. EADS Space Transportation. The contract lasts until 2013. The ATV comprises three main elements: a propulsion system, a control unit with an on-board Bibliography 8 computer, and the payload. Its task is to keep the ISS alive and to supply materials (food/water, oxygen, fuel, [1.1.1] Puttkamer, J. v. Von Apollo zur ISS. Munich: Herbig experimental equipment, etc.). Its technical data is as Verlag, 2001. follows: overall length, 10.3 m; diameter, 4.48 m; max. [1.1.2] Hallmann, W., Ley, W. Handbuch Raumfahrttechnik, 2. take-off mass, 20.75 t; payload, 7.6 t; mission duration, Auflage. Munich: Carl Hanser Verlag, 1999. [1.1.3] Krieger, W. Technologiepolitik der Bundesrepublik 9 max. six months docked to ISS; power supply, four Deutschland (1949–1990), Band IX, S. 242. Düsseldorf: solar panels and eight rechargeable batteries. VDI Verlag, 1992. 10

CCH01.inddH01.indd SSec1:15ec1:15 22/26/09/26/09 99:45:05:45:05 AMAM 0 16 1 Introduction

[1.1.4] Hornschild, K., Neckermann, G. Die deutsche Luft- und Raumfahrtindustrie, Stand und Perspektiven. Frankfurt a.M.: Campus Verlag, 1988. 1 [1.1.5] Reichel, R.H. Die heutigen Grenzen des Raketenan- triebes und ihre Bedeutung für den Raumfahrtgedanken. VDI-Z, 92 (32), 1950. [1.1.6] Reichel, R.H. Raketenantriebe. VDI-Z, 102 (12), 1960. [1.1.7] Micheley, W. Bericht über den IX Internationalen 2 Astronautischen Kongress 1958 in Amsterdam. VDI-Z, 100 (36), 1958. [1.1.8] Miller, R. The Dream Machines. Molabor, FL: Krieger, 1993. [1.1.9] Zeit im Flug: Eine Chronologie der EADS. Hamburg: EADS Edition, 2003. [1.1.10] Gierson, R. et al. DESK CALENDAR 1988, General 3 Dynamics, Space System Division, 1988. [1.1.11] Messerschmid, E., Bertrand, R. Space Station Systems and Utilization. Berlin: Springer Verlag, 1999. [1.1.12] Gilbert, L., Rebrow, M. Das Thomas Reiter Kosmosbuch. Klitzschen: Elbe-Dnjepr Verlag, 1996. [1.1.13] Engelhardt, W. Enzyklopädie der Raumfahrt. Frankfurt 4 a.M.: Harry Deutsch Verlag, 2001. [1.1.14] Reinke, N. Geschichte der deutschen Raumfahrtpolitik. Munich: Oldenbourg Verlag, 2004. 5 1.2 Space Missions 6 Klaus Wittmann and Nicolaus Hanowski 1.2.1 Space System Segments

A typical space flight system comprises three system segments, which are coordinated according to the 7 mission objectives (Figure 1.2.1). The design of the system segments and consideration of their mutual dependencies is the central challenge for successfully preparing and conducting space flight missions. Figure 1.2.1: The three segments comprising a space system: the space segment with the space vehicle (top), the transfer segment The space segment comprises the spacecraft and with the launcher (center) and the ground segment with control 8 its payload in orbit. The transfer segment provides center and ground station (bottom) (Source: ESA/DLR). the transport of the spacecraft and its payload into space by a launcher (typically a rocket). In order to control and monitor the spacecraft and its payload parameters of the spacecraft and the payload. In turn, as well as to distribute and process the payload data, these depend essentially on the mission objective and a ground segment is required. The design of ground the mission duration. The three system segments can 9 and transfer segments and the costs connected with be split up further into so-called system elements their realization are mainly influenced by the physical (Figure 1.2.2). 10

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TerraSAR-X system elements the additional task of providing life support for the crew. Space vehicle Astrium “Flexbus” System Element: Orbit 1 This system element is essential for conceptualizing a Payload Primary: SAR space flight system. The orbit of a spacecraft is defined Secondary: LCT Space segment by the mission objective. More than 95% of all space Secondary: GPS mission orbits are orbits around the Earth. Low Earth Orbit orbits between 300 and 1500 km are often used, for 2 Polar example, for Earth observation satellites and human Solar synchronous space flight, and the so-called geostationary orbit at Launcher: approx. 36 000 km altitude for communications sat- Transfer segment DNEPR-1 ellites (Figure 1.2.3). Orbits at intermediate altitudes, such as so-called medium Earth orbits (MEOs), are 3 Operation used for instance for navigation satellites (GPS, Ga- Mission operations system (DLR-GSOC ) lileo). The relatively small number of interplanetary Payload ground system (DLR-DFD ) Instrument operation calibration system (DLR-HR ) missions on which spacecraft are sent beyond an Earth orbit into planetary orbits are often characterized by Ground stations and networks several years of flight time until the spacecraft reach TM/TC: DLR Weilheim ground station 4 Payload data: DLR and user stations their target object or orbit (see Table 1.2.2). With the Launch and early orbit phase: polar stations exception of the Apollo missions to the Moon, which were concluded in 1972, planetary missions are still Mission products limited to unmanned endeavors. Science (DLR-DFD ) Ground segment Commercial (Infoterra) Unmanned spacecraft flying in Earth orbit are referred to as satellites. When flying in orbits beyond 5 Earth’s orbit they are termed space probes. Space- Figure 1.2.2: Organization of a space flight system in system ele- craft carrying humans are referred to according to ments, exemplified by the German radar remote sensing satellite their functions as space shuttles, space ships or space TerraSAR-X (SAR = Synthetic Aperture Radar, LCT = Laser Communica- stations. Objects with ballistic trajectories which tion Terminal, GPS = Global Positioning System). can reach altitudes in excess of 1000 km are called 6 suborbital rockets or sounding rockets. They are not discussed in this book. 1.2.1.1 The Space Segment System Element: Spacecraft System Element: Payload With ever-expanding areas of application, spacecraft As the central application element the payload is at have evolved in their development over more than 50 7 the heart of a space flight mission. Successful payload years into a huge variety of types with a wide range operations open the door to mission success or put it of characteristics. However, in order to work proper- in doubt, even if all other subsystems of a spacecraft ly the spacecraft has to perform an invariable set of work flawlessly. The payload’s proximity to the appli- functions. The corresponding functional structure cation and therefore to the actual motivation for the of subsystems represents the common basis for de- 8 mission justify an extraordinary position for it within sign, production and operation of all spacecraft. In the whole system design process (Table 1.2.1). particular, the complexity of subsystems has drama- The payload with its characteristic parameters tically increased over the decades. Nevertheless, the of mass, geometry, power and communication functional logic of each subsystem as well as aspects requirements determines the properties of the car- of its compatibility have not changed significantly. rying satellite platform, which is often referred to The following spacecraft subsystems are generally 9 as the satellite bus. In human space flight there is distinguished (see also Figure 1.2.4). 10

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Table 1.2.1: Payload overview with examples of their applications on spacecraft.

Payload Application Characteristic Mission example 1 • Cameras (UV/Vis./IR) • Earth observation • Payload: from • EnMAP • Radar • Weather monitoring global overview • SAR-Lupe • Planetary exploration down to high • Meteosat • Astronomy resolution of • Mars Express selected spots • 2 • Sensors (nonimaging) • Earth exploration • Great variety of • CHAMP • Atmospheric research payloads • GRACE 1 and 2 • Planetary exploration • ENVISAT • Experimental components, spacecraft • Validating new technology • Passive, robotic • BIRD components • TerraSAR-X 3 • ROCVISS on ISS • Repeater/transponder • Television • Large satellites, • EUTELSAT • Internet often in • ASTRA • Telephony geostationary • Iridium orbit • Signal transmitter • Navigation • Typically in • GPS 4 • Atomic clock • Positioning medium to high • Galileo orbits • Glonass • Lander • Analyses of planet • Highly complex • Apollo • In-situ analysis instruments surfaces systems • Viking • Rover for human • Giotto • Mars Express 5 • Philae/Rosetta

Structure 400 Numerous immediate characteristics of a spacecraft 350 are determined by its mechanical structure, which 300 6 accommodates all other subsystems. As well as the 250 pure static properties of the structure there are often 200 dynamic aspects, such as deployment, rotation and 150 100 swing functions, with frequent and considerable 50 effects on other subsystems. 7 0 Power Supply The focus of this subsystem is on assuring an efficient

distribution of electrical energy within the spacecraft >36000 km 300–1000 km 1000–1500 km

and its components. Power sources can be for instance: 1500–15000 km 8 solar generators, batteries, fuel cells or so-called radio- 15000–20000 km 20000–25000 km 25000–35000 km 35000–36000 km isotopic thermoelectric generators (RTGs). Figure 1.2.3: Number of operating satellites at various orbital altitudes (average orbit altitude). Thermal Subsystem The temperature of spacecraft components has to under certain temperature conditions. The ther- be kept within a defined range. Not only are tem- mal subsystem provides an optimized equilibrium 9 perature-related tolerances crucial, but so too is the between heat absorption and dissipation by passive efficiency of components (solar panel, sensors, etc.) and/or active regulation. 10

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Table 1.2.2: Overview of orbits for space flight missions.

Orbit• Application • Characteristic • Mission example • LEO (Low Earth Orbit) • Earth observation • Altitude of 300 up to • CHAMP 1 • Weather monitoring 1500 km • SAR-Lupe • Technology • BIRD • Astronomy • ROSAT • MEO (Medium Earth • Communications • Altitude of several • Globalstar Orbit) • Navigation thousand km • GPS • Galileo 2 • HEO (High Elliptical • Communications • Altitude of a few hundred • Molniya Orbit) • Astronomy up to 100 000 km • GTO (Geostationary • Injection orbit • Altitude of a few hundred • EUTELSAT Transfer Orbit) for launchers of up to 35 786 km • ASTRA communications satellites • GEO (Geostationary • Communications • Altitude of 35 786 km • EUTELSAT 3 Orbit) • ASTRA • Lagrange points • Astronomy • Distance > 1 million km • SOHO • Fundamental research • JWST • Interplanetary orbits • Planetary exploration • Distance up to several • Mars Express billion km • Rosetta 4 control components. Especially, activities such as the Structure and mechanisms use of reaction thrusters or the acceleration of reaction wheels require a good understanding of the orientati- Thermal subsystem on and dynamic properties of the spacecraft. 5 Data processing Communications Central components of this subsystem are transmit- Energy supply ters, receivers and antennas. There are different types of data sets to be transmitted to and from Earth or Communications between individual spacecraft: so-called telemetry 6 for spacecraft monitoring, commands for control, Attitude regulation Space vehicle and payload data. platform (bus) Propulsion Data Processing In this subsystem the processing and formatting of (Life support subsystem) data generated on the spacecraft are carried out. 7 Central elements are corresponding on-board com- puters and peripheral equipment. In contrast to the + Payload data system hardware, on-board software can still be modified after launch by so-called software uploads. Figure 1.2.4: Differentiation of spacecraft system elements into 8 subsystems. Propulsion This subsystem allows the spacecraft’s orbit to be Attitude Control changed by firing thrusters. With the application of The attitude control subsystem monitors and controls electric propulsion it has become necessary to master the orientation of the spacecraft in space. In many long-lasting propulsion maneuvers. In contrast, typical cases this is the most complex subsystem with a huge propulsion phases with chemical thrusters last only 9 number of parameters, sensors, and active and passive minutes or hours. 10

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Life Support System communications satellites, there is a trend toward This system evolved from the special requirements rather heavy satellites (Figure 1.2.5). 1 of human space flight. It is limited to this area and guarantees physical integrity and appropriate living 1.2.1.3 The Ground Segment conditions for humans in space. In addition to the function and capability of each In addition to the spacecraft with its payload and subsystem it is very important to consider their com- orbit, the ground segment shapes the space flight patibility and the properties of the complete system. mission scenario. Similar to the spacecraft, the ground 2 System engineers and other system experts hold segment also provides a large set of degrees of freedom a key position in the design and production phase as in the design with a high potential of optimization well as with regard to operations. Only by systematic with regard to efficiency. In contrast to the spacecraft, design that focuses on the interaction between space considerable changes can still be applied to the ground and ground segments, corresponding adaptations on segment after launch. These changes can sometimes 3 the spacecraft system and subsystem levels, and the be quite extensive and often decide the success of a payload can an optimized space mission be realized. mission. Mostly, however, late changes translate into significant additional work and costs. 1.2.1.2 Transfer Segment The ground segment can be divided into two system elements: mission operations and the ground Another system segment in space missions involves station network. 4 the launcher that transports the spacecraft into space. Numerous rockets have become available on the System Element: Mission Operations commercial market over the years. With the Ariane For the most part, mission operations are designed 5 rocket Europe has a powerful and internationally and conducted at a control center. With this system competitive product at its disposal. the spacecraft is monitored and controlled and the Significant factors in choosing a specific laun- 5 data traffic organized. In addition, the control center cher are the orbit to be reached as well as the mass contains all necessary interfaces to the spacecraft and dimensions of the spacecraft. Due to the high manufacturer as well as to its users. The control center development and modification costs of rockets, the routes all relevant data to them. variety of relevant types for a mission profile is often The central part of mission operations is flight very limited. This also means that the rocket offers operations, which are conducted from a control room 6 fewer variables for mission optimization than do the spacecraft and the ground segment. However, multiple launches of several spacecraft at the same time and additional boost stages on the spacecraft to reach 250 certain orbits offer some additional flexibility. It is also 200 7 possible for one or more small satellites to be launched “piggyback” together with the main payload. 150 For spacecraft with a mass under 2 t and LEOs 100 there are a large number of launchers available. At present these are built and launched also by develop- 50 8 ing countries, such as Brazil or India. On the other 0 hand, there are only a few models available at the upper end of the scale. Satellites with a mass of more than 8 t can only be launched into geostationary orbit <10 kg >5000 kg 10–100 kg

by the Ariane 5 ECA as well as by the US Atlas V and 100–500 kg 500-5000 kg 500-1000 kg 9 Delta IV rockets. For extreme launch masses in the 1000-2500 kg 2 area of 25 t into LEO there is only the Space Shuttle Figure 1.2.5: Number of operating satellites according to their available. Because of the growing use of powerful launch mass (fueled). 10

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(Figure 1.2.6). Flight operations activities include the determination and prediction as well as other aspects management of the actual flight tasks and the mainte- of navigation. The latter provides the tools necessary nance of the spacecraft in all mission phases in order to generate and handle timelines, schedules, etc., to use it optimally and as long as possible. Operation and considers user priorities as well as physical and 1 specialists for the subsystems are organized in a flight technical constraints. Ground data processing, flight team. Under the lead of a responsible system engineer dynamics and mission planning are highly interlinked and by means of telemetry from the space segment, with flight operations and coordinated by the mission their analyses include considering the status and management. In complex missions the aim is to grant trends in the mission, working through procedures, all mission participants easy access to relevant data, 2 generating command sequences and conducting flight information and products on electronic platforms. maneuvers. Mission management is carried out from Increasingly, close cooperation between so-cal- or in close coordination with flight operations. led user ground centers and mission operations is Operations activities vary profoundly with the required. In commercial Earth observation missions different phases of preparation and execution of a these centers take care of tasks such as processing raw 3 mission. The most intense phase of mission operations user data into finished information products. Data is the so-called launch and early operation phase refining, thematic editing and archiving are some of (LEOP), in which the spacecraft is activated after the relevant aspects. Sometimes necessary payload injection and its survival secured under the extreme activities, including instrument calibration and con- conditions of space with respect to temperature, figuration changes, are also prepared. Other services 4 vacuum, radiation, etc. Compared to the following include interface adaptations for routine operations. phases of in-orbit testing (IOT) and especially routine operations, this flight phase is by far the most deman- System Element Ground Station Network ding in terms of personnel and resources. The antennas (Figure 1.2.7) located at ground stations Flight operations use the ground data proces- are the most visible element of the transmission path 5 sing facilities and equipment at the control center. from and to the spacecraft. Various frequency bands These facilities assure the correct configuration and can be used whose allocation is subjected to inter- availability of all telemetry data required for opera- national coordination. Ground stations receive the tions. Additional contributions to flight operations data for spacecraft control from an associated control are made by the flight dynamics group and by mission center. On the other side, status and user data from the planning. The former is especially responsible for orbit spacecraft are routed to the control center from the 6 ground station. In addition, a ground station provides orbit determination (tracking) data. The mission profile of a ground station is also highly dependent on the mission phase. During mis- sion preparation, compatibility with communication 7 components of the spacecraft and configuration of data interfaces have a high priority. With separation from the launcher and the beginning of the LEOP, detection of spacecraft position as well as frequent and long-lasting contacts with the spacecraft are especially 8 important. Visibility of satellites in LEO typically lasts only a few minutes for one ground station. After that the spacecraft is without contact to the ground for periods from 90 minutes up to several hours, if no Figure 1.2.6: Control room of the Columbus control center as part other ground stations are employed. In order to assure of the flight operations at DLR in Oberpfaffenhofen. From this 9 room European activities on the ISS are coordinated and monitored more frequent or even around-the-clock contact with (Source: DLR). the spacecraft, especially in the critical LEOP, global 10

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orbits are visible only four to six times a day when they reach a sufficient height above the horizon (Figure 1.2.9). For ground stations near the terres- 1 trial poles, however, there is visibility with sufficient elevation for every orbit. In addition to the availability of communication resources the control loop time (latency) also affects the mission concept. This latency is defined as the 2 overall time for signal transmission and processing in the loop: telemetry generation – telemetry transmis- sion – telemetry processing – command generation – command transmission – command implementati- on. If the control loop time is longer than the necessary 3 reaction time, autonomous operation of functions becomes mandatory. Figure 1.2.7: Large (30 m) S-band antenna at DLR’s ground station in Weilheim. (Source: DLR)

ground station networks are established (Figure 1.2.8). 1.2.2 Design of System Segments 4 These take over the necessary data traffic in sequence so for Space Flight Missions that gaps between passes over the antenna and resulting gaps in monitoring and control do not get too large. The starting point for the design of the complete For ground stations at medium latitudes (e.g., system of a space flight mission is the planned ob- 5 DLR’s Weilheim ground station), satellites in polar jective and the spacecraft’s application, as well as the

6

7

8

Figure 1.2.8: Global ground track of the polar orbiting DLR satellite BIRD during the LEOP. Also illustrated are visibility areas of the central 9 DLR ground station in Weilheim and further ground stations belonging to the BIRD-LEOP network at high latitudes (Kiruna, Sweden and Fairbanks, Alaska). With their help the satellite is visible at least once every 90 minutes. Thus telemetry can be downloaded and the satellite controlled by commands 15 times per day (Source: DLR). 10

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90 90 80 80 70 70 WHM 1 WHM 1 1 60 60 50 50 40 40 WHM 1 WHM 1 30 30 Elevation [deg] 20 20 10 10 2 0 0 6h 12h 18h Figure 1.2.9: Elevation for four BIRD contacts during one day with the DLR Weilheim ground station (corresponding to the two successive passages in Figure 1.2.8). Contacts last less than 10 minutes each. Failure-free data exchange is only possible at an elevation over 5° (Source: DLR). 3

resulting requirements (Figure 1.2.10). There is no Requirements fixed procedure for the design of a space flight system. Application Goal Important aspects beyond those described here are 4 covered in Chapter 8. Moreover, the standard publi- cations [1.2.2] to [1.2.6] describe relevant methods Mission concept Design to the of systems engineering. Orbit/payload system element level The mission objective determines the mission. Thus the description of the payload often stands at Ground segment Space segment Preliminary choice 5 the beginning of the full system description. During concept concept of launcher payload design, quantitative properties of the payload, such as optical resolution (Earth observation), trans- Budget mission capacity (communications) or signal accuracy (cost, feasibility) (navigation) are the center of attention. However, lifetime as well as the interaction of components Concept 6 assessment and operational manageability are also important aspects. Depending on the payload requirements, OK characteristic parameters (mass, volume, energy de- Mission Orbit/payload Design to the mand, communication demand, etc.) are estimated architecture subsystem level and further requirements for the spacecraft and its 7 orbit (pointing accuracy, ground track and times, Ground segment Space segment Launcher measurement geometry) are determined. architecture architecture architecture The system engineer often works initially in a so-called top-down design approach within the hi- System budget erarchical structure of a system (Figure 1.2.11) on 8 the concepts for the upper levels (beginning with the System system elements). In the course of the design process assessment

more details become clarified and the lower system OK levels are defined. Using mission objectives and payload characteris- Conclusion of project phase A 9 tics it is possible to define an optimum orbit applying Figure 1.2.10: Flow chart for defining a space flight mission an adequate mission analysis. This can be a suitable (project phase A). 10

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After the first estimation of feasibility and costs System segments the mission concept is revised. If a stable mission con- 1 cept (or several apparently equal mission concepts) System elements is obtained after a number of iterations, the mission architecture can be built up by developing the sub- system design from the subsystem requirements. This Subsystems Space system enables detailed cost and feasibility analyses. This basis is often followed by further iterations of the mission 2 Components architecture until a number of stable alternatives are defined. Within a system analysis the favored alterna- Parts tive is chosen for subsequent realization. The two essential conditions for the design to converge into an optimized complete system are Figure 1.2.11: Hierarchical structure of a space flight mission. 3 transparency of the design process and completeness of the system and subsystem aspects. Today, both Earth orbit as well as an interplanetary orbit or even conditions can be supported by the new methods an orbit around another celestial body. Despite the and tools of concurrent engineering, especially for potential to create optimal solutions in the orbit complex missions. Specialists in all relevant domains 4 selection process, further options are helpful, as rea- work on the design process simultaneously, which sons might emerge during the actual system design increases efficiency. Only a clear solution which for choosing a nonoptimal orbit. Typical examples of includes the ground segment and launcher and all such reasons are ground station availability or aspects their critical aspects can confirm the feasibility of a of the spacecraft’s energy supply. mission. For the launcher, primarily the orbit to be When visions concerning payload and orbit lay- reached, the mass and volume of the spacecraft and 5 out have converged, one can start by describing the its availability, reliability and costs are of outstanding spacecraft. At first the spacecraft can be described importance. by defining subsystem requirements. A first set of Following the determination of the mission archi- characteristic parameters for the spacecraft and orbit tecture, which is the subject of a Phase A study, typi- can be defined. cally a Phase B study or definition study is conducted 6 Knowing these characteristic spacecraft data in order to define the components and individual (volume, mass, etc.) and orbit (propulsion demand, parts of all subsystems. This is followed by the final location of launch place, etc.) a first selection of an cost and feasibility analysis. Design, construction, appropriate launcher becomes possible. At the same integration, test and qualification are combined in time spacecraft (communication demand, degree of Phase C/D, which is followed by operations (Phase 7 autonomy, etc.) and orbit (antenna visibility) parame- E) and, finally, secure shutdown and disposal of the ters are used to design the ground segment. space flight system. This initial rough knowledge of payload, orbit In creating a mission concept, useful experience and spacecraft permits the determination of a sui- can be formulated as the following rules of thumb: table launcher and the design of the ground segment, resulting in a preliminary mission concept for the 1. The feasibility of a mission is often dependent on 8 space system. the compatibility of a mission with a financial The first mission concept also enables a rough budget. Ground segment costs and the range of check of superior mission constraints to be made, such operation tasks are dominated by the required as costs and technical feasibility. This presupposes a infrastructure. The cost of the transfer segment preliminary understanding of the properties and costs is primarily dominated by spacecraft mass and 9 of the potential system segments including spacecraft, geometry as well as propulsion demand. Space launcher and ground segment. segment costs are influenced by the complexity 10

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of the spacecraft and the payload. Minimizing 1.2.3 Space Flight Mission mass leads in general to an increase of complexity. Classification Therefore optimization is also necessary here. In 1 all domains experience (available operation pro- The decisive factor for the properties of a spacecraft, cesses, experience with launchers, serial produc- the corresponding ground segment and the mission tion of satellites and payloads) results in distinct is its application and the corresponding requirements. cost reductions. In addition to standard systems for the spacecraft, 2. The mass of the spacecraft platform is three to such as standard platforms with different payloads, ten times the mass of the payload. For large com- there are also standardized components for ground 2 munications satellites this mass ratio is often be- tween three and five. On planetary and in earlier missions the mass ratio favored the platform even Example TerraSAR-X: German radar Earth observation satellite more. (Figure 1.2.12) 3. The mass of the satellite subsystems is dominated Launch: June 2007 3 by the power supply and the structure. Together Mass: 1200 kg both mass subsystems comprise between one-third Altitude: 520 km and one-half of a spacecraft’s dry mass. Propulsion Inclination: 97° Launch site: Baikonur and attitude control are next with regard to the Payload: High-resolution X-band radar proportion of mass. 4 4. The operation effort varies strongly over the life- time of a mission. The greatest effort is required during the few days of the launch and early opera- tion phase during which the subsystems are ad- justed to the extreme environmental conditions of space after ascent and separation from the launcher. 5 After stabilizing the spacecraft’s condition there is a commissioning and test phase during which atten- tion is mostly on the configuration of the payload. In this phase the operation effort is still rather high compared to the subsequent routine operations 6 phase. In this phase, sometimes lasting several years, only a fraction of the initial operations crew of the first two phases is required, especially if operation takes place in a so-called multimission environment, in which several spacecraft are con- 7 trolled simultaneously. With increasing mission duration the operation effort also increases again after a few years as components and subsystems subject to deterioration fail. Typically, attitude control and power are affected most seriously. In general, the number of unpredictable failures 8 increases with lifetime, which can lead to the de- stabilization of the entire spacecraft. The operation effort increases dramatically again and often stays Figure: 1.2.12: TerraSAR-X satellite during acceptance tests before at a relative high level until the end of the mission. transport to the launch site. The payload (X-band radar) is inte- grated into the main body of the satellite. Communication occurs 9 This operations profile from launch to end of life via a boom antenna, which can be seen on the right in its folded is termed an asymmetric “bathtub profile.” state (Source: DLR). 10

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segment equipment and the launcher. There are nine Example characteristic areas of application for space flight MetOp-A: European weather satellite 1 missions, as follows. (Figure 1.2.13) Launch: October 2006 Mass: 4093 kg 1.2.3.1 Earth Observation Altitude: 820 km Inclination: 99° Earth observation missions are conducted with Launch site: Baikonur small as well as medium and large satellites. Earth Payload: 13 instruments for weather observation 2 observation comprises data acquisition with cameras and sensors which work at different wavelengths over infrared, visible and ultraviolet ranges. Both passive optical observation techniques and active sampling (radar) are used. Moreover, a variety of different 3 measuring methods are applied to determine the electric, magnetic, optic or gravimetric properties of the Earth and its atmosphere. Orbits for Earth observation are often rather low (< 1000 km) and have a high inclination in order to be able to observe 4 the Earth with high resolution and from pole to pole. Sometimes a target is to be imaged at a certain time of the day (to achieve equivalent shadowing condi- tions). That requires a rotation of the orbital plane of approx. 1° around the Earth’s axis every day (Sun- synchronous orbit). This rotation can be generated by 5 an orbit disturbance caused by the Earth’s oblateness. It requires that the orbit is not exactly above the poles, but slightly inclined (as in the TerraSAR-X mission). In case the target is to be reanalyzed under the same observation angle, the satellite has to be brought 6 onto the original track after a few orbits (repeat ground track).

Figure 1.2.13: The European MetOp-A satellite is in a Sun-synchronous 1.2.3.2 Weather Observation LEO. The satellite operates together with the American NOAA weather observation satellites. This suits the purpose of optimizing the 7 A special case of Earth observation is weather obser- coverage of relevant observation areas (Source: ESA). vation. Since the beginning of space flight missions weather observation has been a continuously expan- 1.2.3.3 Technology Testing ding area of application with numerous satellites in low as well as geostationary orbits. Central aspects Technology testing missions are used for testing and 8 are the local, regional and global analysis of weather validating technical components and procedures un- conditions, the generation of data as input for der space conditions. On the one hand this can be done weather forecast models, and the characterization for satellite components and payloads for operational of the atmosphere regarding properties and changes applications as well as new materials or robotic com- in regional and global climate. Imaging instruments ponents. On the other hand new communication and are often used on the satellites. Commercial user navigation procedures can be tested. Technology tests 9 scenarios in weather observation are also gaining in are intensively conducted also in the context of human importance. missions. Since the 1970s space laboratory modules 10

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Example Example BIRD: German technology testing satellite ROSAT: German X-ray telescope satellite (Figure 1.2.15) (Figure 1.2.14) Launch: June 1990 1 Launch: October 2001 Mass: 2426 kg Mass: 92 kg Altitude: 570 km Altitude: 580 km Inclination: 58° Inclination: 97° Launch site: Cape Canaveral Launch site: Sriharikota Payload: Four-times nested Wolter telescope Payload: Infrared detectors, WAOSS camera system, GPS navigation system, etc. 2

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Figure 1.2.15: Complete image of the sky in X-ray light (0.1– 2.0 keV) from ROSAT; observation of the first half year of almost 10 operating years (Source: MPG).

1.2.3.5 Communication 5 Figure 1.2.14: BIRD payload: a two-channel infrared camera as part of an extensive technology test package on the DLR satellite Communication is by far the greatest area of applica- (Source: DLR). tion for the commercial operation of satellites. The required electrical power and the typical propulsion requirements for the positioning of these satellites in have been used. Beside platforms such as the ISS, small geostationary orbit lead to great dimensions and seve- 6 spacecraft and sometimes microsatellites with a mass ral tonnes of total mass. These satellites are launched of less than 100 kg in low orbits are also employed. into a so-called geostationary transfer orbit (perigee approx. 500 km, apogee approx. 36 000 km) by the most powerful launchers available. The adaptation of 1.2.3.4 Fundamental Research this orbit into the final geostationary orbit occurs by 7 Fundamental research missions typically suit the so-called apogee boost maneuvers with the satellite’s purpose of studying astronomical objects or physical main engine in the first few days of the mission. Due phenomena in the context of cosmology or analyses to the large number of satellites in geostationary orbit in relativistic physics. The range of instruments used with its subdivision into discrete control boxes, the for that purpose covers the complete electromagnetic demand on flight dynamics is continuously high. The 8 spectrum as well as precise experimental arrangements. density caused by having hundreds of communica- Space telescopes are also used and can be extremely tions satellites located in this orbital region makes it large and complex. Interlinked systems comprising se- necessary to put the satellite into a so-called graveyard veral satellites gain more and more importance. Orbits orbit some hundreds of kilometers beyond at the end for such missions are very diverse, and in some cases of its service life (nominally about 15 years). There have extreme altitudes (100 000 km), for example to are also communications satellites, for example as 9 avoid magnetospheric disturbances. constellations (Iridium), in lower orbits. 10

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Example Example EUTELSAT W5: Communication satellite of the European Galileo: European navigation satellite system 1 operator EUTELSAT (Figure 1.2.16) (Figure 1.2.17) Launch: November 2002 Launch: 2010–2013 Mass: 3170 kg Mass: 680 kg Altitude: 35 000 km Altitude: 23 600 km Inclination: 0° Inclination: 56° Launch site: Cape Canaveral Launch site: Kourou Payload: 24 Ku-band transponder Payload: Navigation signal transmitter and 2 high-precision clock

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Figure 1.2.16: Schematic illustration of the so-called antenna map- ping output of a geostationary communications satellite. The irregular 5 form of the lines of equal irradiation intensity is exactly controlled by an appropriate antenna design. At the end of the positioning Figure 1.2.17: Schematic illustration of the Galileo constellation with procedure the satellite’s radiation power profile is measured on the 27 operating satellites and three spare satellites on standby. Monitor- ground by changing the orientation of the satellite. Subsequently, the ing and control of the satellites are carried out at control centers in satellite is transferred into routine operations (Source: DLR). Germany (Oberpfaffenhofen) and Italy (Fucino) (Source: ESA).

6 1.2.3.6 Navigation Earth observation, technology testing and weather With increasing utilization of the US global position- observation. However, the employed spacecraft differ ing system (GPS) since the 1970s, the significance in data protection (encoding), general secrecy and in of this application has grown rapidly. Navigation many cases hardening against electromagnetic inter- satellites provide a permanent signal by which, using ference. In addition, there may be a small number of 7 at least four satellites at the same time, any position satellites with interfering or destructive functions. on Earth can be determined. Orbits are typically me- This huge variety of military spacecraft results in an dium high; in the case of GPS, 20 183 km. In order equally high variety of spacecraft and orbits. In the to provide a global navigation service, there have to area of high-resolution Earth observation, very low or- be more than 20 identical satellites in a constellation. bits dominate and result in relatively short lifetimes for 8 In addition to other systems the European Galileo the satellites. In Germany satellite missions are being navigation system will gain outstanding significance conducted in this area of application for the first time as a commercial system. with the SAR-Lupe reconnaissance constellation.

1.2.3.7 Military Missions 1.2.3.8 Planetary Exploration 9 Military missions comprise mission types with appli- To this day planetary exploration has remained an cations in the areas of communication, navigation, activity of unmanned space flight except for the Apollo 10

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Example Example SAR-Lupe: German radar intelligence satellite Rosetta: European comet probe (Figure 1.2.19) constellation (Figure 1.2.18) Launch: March 2004 1 Launch: December 2006 Mass: 3100 kg Mass: 770 kg Altitude: In planetary orbit with several Earth, Mars Altitude: 490 km and asteroid fly-bys Inclination: 98° Launch site: Kourou Launch site: Plesetsk Payload: Lander with drill, cameras, spectrometer, Payload: High-resolution X-band radar etc. 2

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Figure 1.2.19: Conceptual illustration of a successful landing Figure 1.2.18: The satellites of the German SAR-Lupe constellation maneuver on the comet 67P/Churyumov–Gerasimenko in 2014 used for radar intelligence (Source: OHB System). (Source: ESA). 6

missions to the Moon. Over the decades dozens of flight. Basically one has to distinguish between trans- space probes have flown to all planets (except Pluto) port systems like the Space Shuttle or Soyuz spacecraft as well as to many asteroids and comets. In many cases and long-term orbiting systems like the ISS. One these were not only fly-bys but even orbiting and strives to reduce the flight and maintenance effort in 7 landing missions. For instance, robotic vehicles have favor of science and experiment time. Human space been deployed on Mars, or cometary material has been flight in Earth orbit is typically realized with medium returned to Earth. Special challenges of interplanetary inclinations at relatively low altitudes. The spacecraft space flight are significant signal latency (up to hours typically have much more mass than the satellites. in the outer Solar System), long flight time, and navi- 8 gation. Moreover, a sufficient power supply is one of the greatest problems in the outer Solar System. Bibliography

[1.2.1] Union of Concerned Scientist Satellite Database. http:// 1.2.3.9 Human Space Flight www.ucsusa.org/global_security/space_weapons/satel- lite_database.html, 2007. 9 The unique requirements of life support mean a [1.2.2] Brown, Ch. Elements of Spacecraft Design, AIAA Educa- considerably higher effort in the area of human space tion Series. Reston, VA: AIAA, 2002. 10

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[1.2.3] Fortescue, P.W., Stark, J.P.W., Swinerd, G. Spacecraft Systems Engineering. Chichester: John Wiley & Sons, Ltd, 2003. 1 [1.2.4] Griffin, M.D., French, J.R. Space Vehicle Design, AIAA Education Series. Reston, VA: AIAA, 2004. [1.2.5] Pisacane, V.L. Fundamentals of Space Systems, Johns Hopkins University/Applied Physics Laboratory Series. New York: Oxford University Press, 2005. [1.2.6] Wertz, J.R., Larson, W.J. Space Mission Analysis and 2 Design, Space Technology Library. Dordrecht: Springer Netherland, 1999.

Example 3 Columbus: European space laboratory on the ISS (Figure 1.2.20) Launch: February 2008 Mass: 10 275 kg Altitude: 350 km Inclination: 51° Launch site: Cape Canaveral 4 Payload: Internal and external experiment modules, racks and crew 5

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9 Figure 1.2.20: The European Columbus laboratory module on the ISS operated from Oberpfaffenhofen (Source: ESA). 10

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