Download - National Space Organizations
National Space Organizations
A Comparison of the Capabilities of the National Aeronautics and Space Administration
(NASA) and the European Space Agency (ESA)
by
Glenn Alpaugh
23 April 2006
Regardless of political affiliations, it cannot be denied that many of the
accomplishments in space and triumphs of space research have come about as a result
of the competition between those final two planetary superpowers – the Soviet Union
and the United States. In the final days of the Soviet Union, both nations worked
together on space projects in an effort to rise above their political differences. The
ultimate collapse and fragmentation of the great Soviet power has led to a realignment
of nations. Russia now has its own smaller space program, divested of the other
satellite nations comprising the old union. The new space power of the Old World is a
confederation of 17 European countries – a new union seeking to continue in the bold
tradition of space exploration established by a deceased Soviet superpower. If this new
European Space Agency (ESA) is to step into its role as a world leader in space
programs effectively, it must strive to at least equal the organizational robustness of the
old Soviet space program, while maintaining a world class presence in regard to the
American space program run by the National Aeronautics and Space Administration
(NASA). A comparison of ESA and NASA programs, facilities, research and
development, and contribution to international space projects will show that the new
agency is more than capable of successfully carrying the torch passed to it from the old
Soviet space program, and that it is a worthy contributor to international space projects
that are a necessity if the nations of the Earth are to fulfill their manifest destiny and
reach out to other worlds in search of knowledge.
The ESA is headquartered in Paris, France, and was established in 1973, when
the earlier existing European Launcher Development Organization (ELDO) and the
European Space Research Organization (ESRO) - created in 1953, were combined.1
1
The ESA has expanded from its eleven original founding members to the following
seventeen member states: Austria, Belgium, Denmark, Finland, France, Germany,
Greece, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain, Sweden,
Switzerland and the United Kingdom. Canada, Hungary and the Czech Republic also
participate in some projects under cooperation agreements. 2
The purported mission of the ESA is to shape the development of Europe’s
space capability and ensure that investment in space continues to deliver benefits to the
citizens of Europe.3 This is a far cry from the fallen Soviet Union’s desire to use its
space program for the glory of Communism and the Soviet State, but runs parallel to the
Vision Statement of NASA, which expresses the goal of expanding the frontiers of air
and space to inspire and serve America and to benefit the quality of life on Earth.4
The NASA Mission Statement, however, adopts a more global theme than that of
the ESA statement, expressing a desire to advance and communicate scientific
knowledge and understanding of the earth, the solar system, and the universe, while
advancing the human exploration, use, and development of space.5 In this respect, the
NASA Mission Statement would appear to be more focused on the exploration of space
as a means to advance mankind as a species, rather than focusing on a specific group
of nations, as does the ESA Mission Statement.
2 “Facts & Figures,” ESA. http://www.esa.int/esaCP/GGG4SXG3AEC_index_0.html (accessed 19 April, 2006).
3 Ibid.
4 “NASA Mission Statement,” NACC, http://naccenter.arc.nasa.gov/NASAMission.html (accessed 20 April, 2006).
2
The budgets of the two space agencies differ considerably. The ESA has an
annual budget of almost three billion euros, with a large part of it invested in ESA's
launch vehicles (twenty-two percent - currently the most expensive part of the ESA's
activities), while the NASA budget comes in at around sixteen billion dollars (13 billion
euros).6 An important consideration in comparing the disparity in these budgets is the
fact that some of the member-states belonging to the ESA have their own, independent
space agencies as well. Separate agencies in Germany and France, for example,
budget more than an additional combined two billion euros.7 Add these and the budgets
of other independent national space agencies of Europe to that of the ESA, and the
budgeted amount more than doubles. Additionally, some of the more expensive space
projects in Europe are not funded by the ESA, but rather through special agreements
between members of the European Union; the Galileo global positioning system with a
price tag of four billion euros is one example.8
Based on these factors it would appear that, while NASA has a larger budget
than the ESA, the initial numbers are misleading. Combining the ESA budget with the
expenditures and outlays of individual European nations operating national space
agencies of their own yields a substantial windfall that brings the budgets of the ESA
and NASA within viewing distance of each other. Add to this the funds budgeted by the
Russian space agency and the advantage may, in fact, lay with Europe.
The exploration programs of the ESA include such high profile missions as Giotto
(Figure 1) – its first deep space mission, which was used to study the Comets Halley
and Skejllerup as part of the Halley Armada.9 Other contributors to the Armada include
the Soviet Union, France, and Japan. A planned partner probe to Giotto was to be
3
produced by NASA as an additional part of the Halley Armada, but was scrapped as a
result of budget cuts by the American space agency.10
Figure 1. Artist’s rendition of Deep Space Probe Giotto. (Illustration courtesy of Wikipedia.)
The Giotto project was followed by the star-mapping mission known as
Hipparcos (Figure 2), launched in 1989 and named in honor of Hipparchus, with the
letters of the name taken from the term High Precision Parallax Collecting Satellite.11
Both the Giotto and Hipparcos deep space probe missions were resounding successes.
11 Wikipedia, "European Space Agency."
4
Figure 2. Artist’s rendition of Deep Space Probe Hipparcos. (Illustration courtesy of Wikipedia.)
The plethora of missions undertaken by NASA include deep space missions
comparable to those of the ESA. Such asteroidal and cometary missions as NEAR
Shoemaker, Deep Space 1, Stardust, and Deep Impact have broken new ground in
space research.
The NEAR Shoemaker mission was designed to study the near-Earth asteroid
Eros from close orbit over a period of a year, but included a flyby of Asteroid 253
Mathilde (Figure 3).12 Data obtained from this mission will provide information on
conditions in the early solar system and knowledge about the characteristics of
asteroids, meteorites, and comets.13 This mission was similar to the Giotto mission in
5
complexity and technological sophistication.
1 “A History of the European Space Agency,” ESA. http://www.esa.int/esaCP/ESAQRHPZ9NC_index_0.html (accessed 20 April, 2006).
5 Ibid.
6 Wikipedia contributors, "European Space Agency," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=European_Space_Agency&oldid=49130463 (accessed April 22, 2006).
7 Ibid.
8 Ibid.
9 Wikipedia contributors, "Giotto Mission," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Giotto_mission&oldid=42345953 (accessed April 15, 2006). (accessed April 22, 2006).
10 Ibid.
12 Wikipedia contributors, "NEAR Shoemaker," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=NEAR_Shoemaker&oldid=47120032 (accessed April 20, 2006).
13 Ibid.
6
Figure 3. Trajectory graphic depicting the voyage of the NEAR spacecraft.(Graphic courtesy of NASA.)
The Deep Space 1 spacecraft was launched in 1998 as part of NASA’s New
Millennium Program.14 Similar to the ESA Hipparcos spacecraft, the Deep Space 1 craft
underwent initial failures, but was able to continue with its mission. Undertaken with the
intent of testing new systems with an eye toward utilization in future missions, Deep
Space 1 succeeded in testing most of its new technologies, including its NSTAR
electrostatic Ion engine (Figure 4) – but some of the new systems failed.15
7
Figure 4. Deep Space 1 Ion Engine(Photo courtesy of NASA.)
Overall, the ESA exploration programs are well planned and executed, but seem
to be less numerous than those belonging to NASA. This is partially due to the expertise
cultivated by NASA in its half century of existence.
The ESA has over a dozen satellite projects in place or planned for the near
future. Of those in place, the XMM-Newton (Figure 5) is one of the most impressive.
Containing the most sensitive telescope mirrors ever developed in the world, and
labeled the biggest science satellite ever constructed in Europe, this massive, three-
axis stabilized spacecraft is on a mission to detect and study celestial X-ray sources.16
The telescope derives its name from its X-ray Multi-Mirror design and in honor of Sir
Isaac Newton.
8
Figure 5. Artist’s Rendition of XMM-Newton(Illustration courtesy of D..Ducros and ESA.)
The ESA is also participating in satellite projects with other space agencies. One
such program is known as the TC-2 Double Star – a program run by the Chinese
National Space Administration (CNSA). The ESA was invited to participate in the project
by the CNSA, and accepted a role as a contributor the satellite’s mission – which is to
operate alongside the ESA's Cluster mission, studying the interaction between the solar
wind and Earth's magnetic field.17
The satellite programs of NASA are mature and extensive. Systems for
navigation, communication, defense, meteorology, reconnaissance, and other
applications abound. Satellites placed in orbit over the past fifty years by NASA have
9
spanned a generation of Americans. New and improved systems are being
systematically rotated into aging constellations in a general move toward rejuvenation
and preparation for the demands of a new era of space. Upgrade and enhancement
plans for such satellite systems as the Global Positioning System (GPS) (Figure 6), the
fifth generation of Navstar satellites, are underway – with a first launch expected
sometime in 2012.18
Figure 6. U.S. Navstar Global Positioning System satellite.(Illustration courtesy of CNS.)
The satellite systems of the ESA, those operated solely by the European agency
as well as those shared with other space agencies, are not as numerous as those of
NASA, but they are none the less growing in number. The diversity of satellite types
within the domain of NASA denotes a fully mature and robust satellite program, but the
ESA program is rapidly catching up despite moves by NASA to upgrade and expand.
In regard to military space programs, one has but to follow the money in order to
see the differences between the ESA and NASA. Military space has not traditionally
10
been a priority for European governments, and this stance is reflected in the fact that
only six of these governments have committed to any type of substantial spending on
military space applications.19 As seen in Table-1 below, the disproportion between
European and U.S. military space allocations is not readily apparent when comparing
general defense budgets, but is revealed as significant when viewed as allocations
dedicated to military space spending (1 to 3 versus 1 to 20).20
Table-1. EU / US Ratios (In Billions of Euros for the year 2004).
United States EuropeU.S. to Europe Ratio
Defense Budget Estimated
354 146 <3
Military Space 15.1 0.75 >20
Military Space / Total Defense
4% 0.5%
The concept of military space is not fully mature in Europe, and this is reflected in
the minimal government funding in the only two operational fields - satellite
communications and intelligence imagery.21 The coexistence of multiple national
systems is the closest thing to a European military space program currently in place, but
the ESA is poised to change this according to some reports, which view the ESA in a
new paramilitary role based on its Galileo and GMES (Global Monitoring for
Environment and Security) programs.22
From its inception, NASA has committed itself to a strategic alliance with several
U.S. military organizations. The decades-old relationship was further formalized recently
with the creation of the Partnership Council – a NASA-military alliance created to
11
increase the prowess of U.S. space technology by bringing the agencies of NASA, the
U.S. Strategic Command, the National Reconnaissance Office, Air Force Space
Command, and the Pentagon’s Director of Defense Research and Engineering, to a
common table.23 Some of the technologies likely to benefit as a result of any synergies
achieved from the partnership might include those used in next-generation launch
vehicles, GPS satellite constellations, telecommunications, and radar surveillance from
space, to name only a few.24
In respect to military programs, NASA is clearly the frontrunner when compared
to the ESA. Its tradition of involvement in military applications is part of the NASA
legacy. The ESA, although geared more to commercial programs, is seen to be shifting
to a more paramilitary capability as the nations of Europe awaken to the potential
significance of a military presence in space.
The Research and Development facilities of the ESA are extensive and
widespread throughout the European continent. Expertise in applicable technologies is
apparent in such facilities as the European Space Research and Technology Center
(ESTEC), the European Space Operations Center (ESOC), the European Astronauts
Center (EAC), and the ESA Center for Earth Observation (ESRIN).
The ESTEC is the design hub for most ESA spacecraft and technology
development, and is located in Noordwijk, the Netherlands. The size and capabilities of
some of the ESTEC facilities (for example, the HYDRA high-capacity six-axis hydraulic
(Figure 7)) offer testing opportunities not available elsewhere in Europe.25 Other testing
12
capabilities include a space simulation facility, an acoustic noise testing facility, a
mechanical data handling system, large space simulator (for simulation of in-orbit
environmental conditions), and compact payload test range (for verification of in-orbit
performance of complex radiating systems). Overall, the ESTEC proves to be a
significant and multifaceted test facility.
Figure 7. HYDRA (multi-axis vibration test facility).(Illustration courtesy of ESTEC).
The ESOC is responsible for controlling ESA satellites in orbit and is located in
Darmstadt, Germany. Created in 1967, the ESOC plans missions, operates more than
50 satellites, ensures that ESA spacecraft meet their mission objectives, and maintains
the necessary ground segment infrastructure required to perform these functions.26 The
13
ESOC works closely with the ESA to advance the state of European technology in the
areas of spacecraft operation and communications.27
Located in Cologne, Germany, the EAC is responsible for astronaut training for
future missions. It is the home base of the 13 European astronauts (members of the
European Astronaut Corps), and is where they are trained for a variety of missions -
including those for the International Space Station (ISS).28
The ESRIN is based in Frascati, Italy, and is responsible for the collection,
storage, and distribution of Earth Observation satellite data for partners within the ESA,
and also serves as the ESA’s information technology center.29 Data gleaned through
Earth observation is used to monitor disasters, protect the environment, assist
agriculture and industry, and support European policy goals.30
With liaison offices in Belgium, the United States and Russia; a launch base in
French Guiana; and ground and tracking stations in various areas of the world, the
facilities of the ESA are branched out as a truly global network of cooperative and
cross-functional entities.
As established as the ESA research and development facilities are, those of
NASA are more numerous and have the advantage of a greater historic base to draw
upon. Mercury, Gemini, Apollo, Skylab, Space Shuttle - all names of space programs
providing profound change to the world because of their existence – all children of
NASA research and development.
Each of NASA’s research and development programs and projects support its
four Mission Directorates and are conducted at each of NASA’s Field Centers.31 Typical
of the myriad NASA facilities are:32
14
Ames Research Center - conducting research activities, technology
programs, and flight projects that advance the Nation’s capabilities in civilian
and military aeronautics, space sciences, and space applications
Dryden Flight Research Center - NASA's primary installation for flight
research
Glenn Research Center - designated by NASA as its Lead Center for
Aeropropulsion
Goddard Space Flight Center - lead center for the Earth Observing System,
carries out all aspects of a space-borne science mission from initial concept
to final data archiving, through its six major laboratories
Jet Propulsion Laboratory - engaged in Earth atmosphere and geosciences,
oceanography, planetary studies (including asteroid and comet), and solar,
interplanetary, interstellar, and astrophysical disciplines
Johnson Space Center - lead Center for the Space Shuttle Program,
International Space Station Program, Space Operations, Biomedical
Research and Countermeasures Program, and the Advanced Human Support
Technology Program
Kennedy Space Center - NASA’s primary launch site, also performing design
and development of new payloads, launch vehicles, and new technologies for
future space initiatives
Langley Research Center - develops technology for advanced space
transportation systems and for small spacecraft and instruments by
performing research on analysis/integration/assessment, aerodynamics,
15
aerothermodynamics, hypersonic propulsion, structures, materials,
atmospheric sciences and remote sensing, and airborne systems, including
crew station design and integration
Marshall Space Flight Center - world leader in space propulsion and
transportation systems
Stennis Space Center - primary center for testing and flight certifying rocket
propulsion systems for the Space Shuttle and future generations of space
vehicles
Wallops Flight Facility - operational test site for the next generation of low-
cost launch technologies
White Sands Test Facility - provides a wide variety of test and laboratory
research and development support to all NASA Centers, the Department of
Defense, other Government agencies, and private industry
Center for Space Science - serves as the focal point for civilian space efforts
at Los Alamos National Laboratory, coordinating non-defense space science
and space technology efforts throughout LANL
Each of these facilities exemplify world class organizations dedicated to the
advancement of space research and exploration. Together they form a national brain
trust capable of sustaining a consistent advance in space technology. The ESA
facilities have a long way to go before they can match the capabilities of the NASA
facilities.
In 1998, NASA, Russia, Japan, and the ESA came together to construct the
World’s largest space station in low Earth orbit – the International Space Station
16
(ISS).33 The ESA contribution to the ISS includes the following: 34
Columbus European Laboratory Module (Figure 8) - permanantly
attached to the International Space Station, providing internal payload
accommodation for experiments in the field of multidisciplinary research
into material science, fluid physics and life science
European Automated Transfer Vehicle (ATV) for Servicing and logistics
(Figure 9) - delivers experimental equipment and spare parts as well as
food, air and water for permanent crew of the ESA – scheduled to enter
service in 2007
European Robotic Arm (Figure 10) - able to work with the new Russian
airlock on the ISS, also able to transfer small payloads directly from and to
the interior of the ISS
Data Management System (Figure 11) for the Russian Segment of the ISS
- installed in the Russian Service Module 'Zvezda',as the set of on-board
computers, their avionics and software that provide for the overall control,
mission and failure management of the entire Russian segment of the ISS
Two Connecting Modules (Figure 12) - controls and distributes resources
from the Truss structure and the US laboratory (Destiny) to the other
connected elements
Cupola (Figure 13) - provides a pressurized observation and work area for
ISS crew, giving visibility to support control of the space station remote
manipulator system and general external viewing of Earth, celestial
objects and visiting vehicles
17
Ariane-5 launcher (Figure 14) - used for launches into geostationary orbit,
medium and low-Earth orbits and sun-synchronous orbits
Figure 8. Cut-away of the Columbus European Laboratory Module(Illustration courtesy of ESA).
18
Figure 9. Cut-away of the European Automated Transfer Vehicle(Illustration courtesy of ESA).
Figure 10. European Robotic Arm(Illustration courtesy of ESA).
19
Figure 11. DMS-R: Data Management System for the Russian Segment of the ISS(Illustration courtesy of ESA).
Figure 12. Connecting Module(Illustration courtesy of ESA).
20
Figure 13. Cupola (Illustration courtesy of ESA).
Figure 14. Ariane-5 Launcher(Illustration courtesy of ESA).
21
As documented above, the ESA contributions to the ISS are impressive. When
compared to the contributions of NASA, they remain impressive, but are eclipsed by the
fact that NASA led the project to reality, along with providing critical components such
as connecting modules, a laboratory module, truss segments, four solar arrays, a
habitation module, three mating adapters, a cupola, an unpressurized logistics carrier,
and a centrifuge module:35
As evidenced by this comparison of the ESA and NASA, both agencies are
robust professional organizations representing the culmination of space technology and
expertise of two continents. NASA is the frontrunner of the two when it comes to
funding, infrastructure, longevity, and leadership, but these aspects cannot be
overlooked on the ESA side. The European agency is positioned for growth and is
hungry to capitalize on that position to solidify its role as the dominant force for space
programs in its hemisphere, and eventually, the world. Perhaps, as both agencies
continue to pursue the exploration and exploitation of space, they will capitalize on the
synergies previously experienced in cooperative projects such as the ISS.
22
Illustrations
Figure Page
1. Artist’s Rendition of Deep Space Probe Giotto 42. Artist’s Rendition of Deep Space Probe Hipparcos 43. Trajectory graphic Depicting the Voyage of NEAR Spacecraft 54. Deep Space 1 Ion Engine 65. Artist’s Rendition of XMM-Newton 76. U.S. Navstar Global Positioning System satellite 87. HYDRA (multi-axis vibration test facility) 118. Cut-away of the Columbus European Laboratory Module 129. Cut-away of the European Automated Transfer Vehicle 1710. European Robotic Arm 1711. DMS-R: Data Management System 1812. Connecting Modules 1813. Cupola 1914. Ariane-5 Launcher 19
23
WORKS CITED
Bochinger, Steve. 2005. Europe and Space: The Economic Dimension, EuroConsult, 2005. <http://www.euroconsult-ec.com/pdf_news/Europe%20and%20Space%20the%20Economic%20Dimension.pdf>
David, Leonard. 2002. NASA – U.S. Military Explore Joint Technologies. Space.com News. <http://www.space.com/news/wsc_military_021018.html>
Deep Space 1, 2006. Available from Wikipedia, The Free Encyclopedia. <http://en.wikipedia.org/w/index.php?title=Deep_Space_1&oldid=47375755>
Dinerman, Taylor. 2006. NASA and ESA: A Parting of the Ways?. Available from The Space Review, Essays and Commentary About the Final Frontier. <http://www.thespacereview.com/article/539/1>
ESA, 2005. A History of the European Space Agency, Available from the ESA Website. <http://www.esa.int/esaCP/ESAQRHPZ9NC_index_0.html>.
ESA. 2005. Facilities: Technical and Quality Management. Available from the ESA Website. <http://www.esa.int/techresources/ESTEC-Article-fullArticle_item_selected-2_8_00_par-28_1131951616555.html>
ESA, 2005. Facts and Figures. Available from the ESA Website. <http://www.esa.int/esaCP/GGG4SXG3AEC_index_0.html>
ESA. 2006. International Space Station: Human Spaceflight and Exploration. Available from the ESA Website. <http://www.esa.int/esaHS/ESA7YL0VMOC_iss_0.html>
ESA News Release. 2005. China Launches Second Double Star Satellite. Space Flight Now. Pole Star Publications Ltd. <http://spaceflightnow.com/news/n0407/25doublestar/>
European Space Agency. 2006. Available from Wikipedia, The Free Encyclopedia. <http://en.wikipedia.org/w/index.php?title=European_Space_Agency&oldid=49130463>
Giotto Mission. 2006. Available from Wikipedia, the Free Encyclopedia. <http://en.wikipedia.org/w/index.php?title=Giotto_mission&oldid=42345953>
Hipparcos Mission. 2006. Available from Wikipedia, the Free Encyclopedia. <http://en.wikipedia.org/wiki/Hipparcos>
International Space Station. 1999. Shuttle Press Kit. <http://www.shuttlepresskit.com/ISS_OVR/>
24
Lee, Wayne. 2000. To Rise From Earth, 2nd ed., New York: Checkmark Books.
NACC, NASA Vision. Available from NACC: NASA Mission Statement. <http://naccenter.arc.nasa.gov/NASAMission.html>
NASA Undergraduate Student Research Program. Available from NASA USRP. http://www.vsgc.odu.edu/loc.htm
NEAR Shoemaker. 2006. Available from Wikipedia, the Free Encyclopedia. <http://en.wikipedia.org/wiki/NEAR_Shoemaker>
Satellites/Current Programs. 2006. Available from The Aerospace Corporation. <http://www.aero.org/programs/satellites.html>
XMM-Newton Fact Sheet. 2006. Available from ESA Space Science. <http://www.esa.int/esaSC/SEM14YS1VED_index_0.html>
25
NOTES
14 Wikipedia contributors, "Deep Space 1," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Deep_Space_1&oldid=47375755 (accessed April 19, 2006).
15 Ibid.
16 “XMM-Newton Fact Sheet,” ESA Space Science, http://www.esa.int/esaSC/SEM14YS1VED_index_0.html (accessed 18 April, 2006).
17 “China Launches Second Double Star Satellite,” Space Flight Now, European Space Agency News Release, (Pole Star Publications Ltd, 2006) http://spaceflightnow.com/news/n0407/25doublestar/ (accessed 22 April, 2006).
18 “Satellites/Current Programs,“ The Aerospace Corporation, http://www.aero.org/programs/satellites.html (accessed 23 April, 2006).
19 Steve Bochinger, “Europe and Space: The Economic Dimension,” EuroConsult, (2005), 1. http://www.euroconsult-ec.com/pdf_news/Europe%20and%20Space%20the%20Economic%20Dimension.pdf (accessed 23 April, 2006).
20 Ibid.
21 Ibid.
22 Taylor Dinerman, “NASA and ESA: A Parting of the Ways?” The Space Review, Essays and Commentary About the Final Frontier, (2006), http://www.thespacereview.com/article/539/1 (accessed 23 April, 2006).
23 Leonard David, “NASA – U.S. Military Explore Joint Technologies,” Space.com News, (18 October, 2002), http://www.space.com/news/wsc_military_021018.html (accessed 23 April, 2006).
24 Ibid.
25 “Facilities: Technical and Quality Management,” ESA, (10 October, 2005) http://www.esa.int/techresources/ESTEC-Article-fullArticle_item_selected-2_8_00_par-
26
28_1131951616555.html (accessed 19 April, 2006).
26 Ibid.
27 Ibid.28
? Ibid.29
? Ibid.
30 Ibid.
31 “NASA Undergraduate Student Research Program,” USRP, (2006), http://www.vsgc.odu.edu/loc.htm (accessed 23 April, 2006).
32 Ibid.
33 Wayne Lee, To Rise From Earth, 2nd ed., (New York: Checkmark Books, 2000), 227.
34 “International Space Station: Human Spaceflight and Exploration,” ESA, (21 April, 2006). http://www.esa.int/esaHS/ESA7YL0VMOC_iss_0.html (accessed 23 April, 2006).
35 “International Space Station,” Shuttle Press Kit, (1999). http://www.shuttlepresskit.com/ISS_OVR/ (accessed 23 April, 2006).
27