Chapter 5. Space exploration and the pursuit of scientific knowledge

This chapter reviews recent developments in space exploration and space sciences, the progress made in human spaceflight missions, as well as the growing challenges posed by space debris. It presents some of the main missions planned in the next decade and highlights specific trends, such as the rise of citizen science and crowdsourcing.


The statistical data for Israel are supplied by and under the responsibility of the relevant Israeli authorities. The use of such data by the OECD is without prejudice to the status of the Golan Heights, East Jerusalem and Israeli settlements in the West Bank under the terms of international law.


Space exploration is a key driver for investments in innovation and science, and it constitutes an intensive activity for space agencies, research institutes, academia and industry. Space science and planetary missions have seen an influx of new actors and new opportunities enabled by digital technologies. Human spaceflight is also developing steadily, also here with new government and private actors and with capabilities on the horizon developed by industry. A crucial challenge for the future will be the handling of space debris.

Space sciences and robotic space exploration

Space sciences and planetary missions have developed markedly over the years, with new actors joining in. Space-based science and exploration missions consist of a wide range of spacecrafts such as flyby spacecraft, orbiters, landers, rovers exploring the sun, planets and celestial bodies in the solar system, and objects and events beyond our solar system. These missions contribute to furthering human knowledge in different scientific fields (e.g. bio-chemistry, climate) and provide invaluable insights into the origins of the universe and to how planets could harbour and sustain life.

While the principal objectives of these activities are scientific to benefit communities of researchers, there may also be significant derived socio-economic impacts, such as technology development and knowledge transfers to sectors beyond the space industry. Space science and exploration activities are also characterised historically by a high degree of international co-operation, not only because of the significant costs of such missions, but also because of the need for deep space monitoring systems based on networks of giant radio antennas installed in different countries (e.g. Australia, Chile, South Africa, the United States) that communicate with the spacecraft.

Space science missions orbiting the earth

Earth-orbiting space science spacecraft, several of which are international missions, are generally dedicated to the study the universe and the sun (without the distortions from the earth’s atmosphere) and fundamental physics.

Three of the largest space observatories in extended operation, capturing light and radiation in different regions of the electromagnetic spectrum are supported by the United States. They include 1) the Hubble Space Telescope (a joint mission with the European Space Agency (ESA) launched in 1990), optimised mainly for observations in the ultraviolet and visible regions of the electromagnetic spectrum (NASA, 2018[1]); 2) the Chandra X-Ray Observatory, launched in 1999 and capturing x-rays (Harvard-Smithsonian Center for Astrophysics, 2016[2]); and 3) the Spitzer Space Telescope, a cryogenically cooled infrared telescope, launched in 2003 (NASA, 2017[3]).

Europe operates three operational observatories for high-energy observations (gamma- and x-rays): Gaia, Integral and XMM-Newton (ESA, 2018[4]; ESA, 2018[5]). The Solar and Heliospheric Observatory (SOHO) is a joint US-European mission, dedicated to sun physics and space weather.

A highly anticipated forthcoming mission is the James Webb Space Telescope for infrared and near-infrared observations, currently scheduled for launch in the next couple of years (NASA, 2018[1]). NASA has the overall primary responsibility for the mission, with ESA and Canada contributing several instruments. ESA also provides the Ariane 5 launch vehicle.

The United States and the European Union also have other space science satellites in orbit, in addition to those of other countries, in particular Japan and the Russian Federation. India and the People’s Republic of China (hereafter “China”) each also recently launched their first dedicated astronomical satellites, ASTROSAT (India) launched in 2015, and the Hard X-Ray Modulation Telescope, HXMT (China), launched in 2017 (Chinese Academy of Sciences, 2018[6]; ISRO, 2017[7]).

In quantum physics, the Chinese experimental quantum communications satellite Micius successfully transmitted entangled photon pairs between ground stations in Beijing and Graz in Austria, over a distance of more than 1 200 km (Yin et al., 2017[8]). This is a potentially groundbreaking discovery for future long-distance secure encrypted communications.

Robotic extra-planetary missions

The last decade has seen some extraordinary firsts in extra-planetary space exploration, including the first landing on a comet (Rosetta/Philae mission); the first high-resolution close-ups of the dwarf planet Pluto; the first soft landing on the far side of the Moon and India’s successful low-cost orbiter mission to Mars, to name just a few. Missions are increasingly ambitious and complex, and there are more participating countries than ever before. Table 5.1 shows the most popular extra-planetary destinations of the last 60 years.

Table 5.1. Popular extra-planetary destinations, 1958-2018
As of November 2018

Planet / celestial body

Number of missions

Number of planned future missions



Selected missions



2 (USA)

1 (carrying 2 orbiters, (ESA, JPN)

Latest: 2004-15 (USA)


The 2018 BepiColombo mission is to take seven years to get to Mercury (ESA, JPN).



+40 (ESA, JPN, USA, former USSR)

1 (RUS planned for 2026)

2 flybys by BepiColombo in early 2020

1 current orbiter (JPN)

Latest: 1984 (RUS)

Venera 3 (RUS) was the first spacecraft to reach the surface of another planet in 1966. In 2015, the Akatsuki (JPN) orbiter was successfully inserted into orbit.



+10 000 satellites launched since 1957


+1 000 operational satellites


Satellites used for communications, navigation, meteorology, climate and space science. An increasing number of commercial constellations and very small satellites.


Earth’s moon



3 current orbiters (USA, CHN)

1 current rover and lander (CHN)

The 2019 Chinese Chang’e-4 probe, consisting of a lander and a rover, is the first mission to land on the far side of the moon.



+40 (USA, former USSR, ESA, IND)


6 current orbiters (USA, ESA, RUS, IND)

2 current rovers, 1 lander (USA)

India’s 2013 first Mars orbiter mission (Mangalyaan) was a technical and scientific success. The US company SpaceX is planning a cargo mission to Mars in the early 2020s.


Phobos (Mars’ moon)





The Japanese Martian Moons Exploration (MMX) mission is planned for launch in the early 2020s. MMX will visit Phobos and Deimos, land on the surface of Phobos, and collect a surface sample.




1 (ESA)

1 current orbiter (USA)


Several flybys, making Jupiter the most visited of the Solar System’s outer planets. The Juno orbiter (NASA) reached Jupiter in 2016.





Latest: 2004-17 (USA)


Several flybys by NASA probes since 1979 (Pioneer 11, Voyager 1 and 2).

The 13-year Cassini mission (USA) ended in 2017, when it deliberately plunged into Saturn’s upper atmosphere.


Titan (Saturn’s moon)



Latest: 2005 (USA, EUR/ITA)

Latest: 2005 (USA, EUR/ITA)

The Huygens probe landed on Titan, Saturn’s largest moon, in 2005.



1 (USA)




Flyby of the Voyager 2 probe (1986, NASA).



1 (USA)




Flyby of the Voyager 2 probe (1989, NASA).


Pluto (dwarf planet)

1 (USA)




NASA’s New Horizons space probe conducted a flyby in 2015. The mission provided unprecedented high-resolution images of Pluto’s surface.


Asteroids and comets

+20 (EUR, JPN, USA)

2 (USA)

1 current orbiter (USA)

Latest: 2018 (JPN, EUR)

ESA’s Philae (on the Rosetta spacecraft), the first mission designed to orbit and land on a comet, made a partially successful landing on Comet 67P Churyumov-Gerasimenko in 2014. NASA’s Dawn space probe entered into the dwarf planet Ceres’ orbit in 2015 and was still orbiting it in 2018.

Note: Includes only successful missions (flybys, orbiters, landers and rovers).

As of early 2019, there were orbiters on three of Earth’s nearest neighbours (Earth’s moon, Venus and Mars). Mars has a total six orbiters from four countries/agencies (India, the Russian Federation, the United States and the ESA) two rovers and one lander (United States) (NASA, 2018[1]). NASA had another two operational orbiters exploring Jupiter (Juno) and the dwarf planet Ceres (Dawn), with the New Horizon probe continuing its journey through the Kuiper Belt after its flyby with the object 2014 MU69 (nicknamed Ultima Thule) in January 2019. In refining its course towards Ultima Thule, the New Horizons spacecraft carried out the most distant course-correction manoeuvre ever conducted (NASA, 2018[9]). The radio signals confirming the manoeuvre travelled more than 6.1 billion km and took 5 hours and 41 minutes to reach the Deep Space Network station in California (Johns Hopkins Applied Physics Laboratory, 2017[10]).

In terms of planned missions, at least 15 missions are foreseen to Earth’s moon by 2025 period, from eight countries/space agencies (China, India, Israel, Japan, Korea, the Russian Federation, the United States and ESA), with a few commercial missions from American and Japanese startups planned, including flybys and moon rovers. In parallel, several long-term proposals call for setting up permanent scientific and commercial outposts on the Moon’s surface (e.g. ESA’s suggestion for a Moon Village by 2040).

The early 2020s are also set to be an eventful period for Mars exploration. The most favourable alignment of the Mars and Earth orbits takes place every 18 months or so and ensures the shortest travel time between the two planets. At least six missions are planned (China, Europe, India, Japan, the United Arab Emirates and the United States) targeting the launch windows in 2020 and 2022. Japan is also preparing an ambitious mission to Mars’ moons Deimos and Phobos, including a lander and sample return mission (International Space Exploration Coordination Group, 2018[11]). Going further, a Jupiter mission should be launched in 2022 with the ESA JUICE spacecraft, which will travel to this large planet and look for traces of ice and water on its moons (ESA, 2018[12]). India is considering a mission to Venus. There are also several planned asteroid missions. The Japanese Hayabusa 2 spacecraft (Peregrine falcon) became in September 2018 the first to land moving rovers on the surface of an asteroid. Before it leaves the Ryugu asteroid in 2019, the Hayabusa 2 mothership should release two more landers and touch the asteroid surface itself to collect a sample to bring back to Earth.

Considering the major achievements of recent missions such as the Indian Mangalyaan mission to Mars, the European Rosetta/Philae landing on an asteroid or the NASA New Horizons mission to Pluto, it is easy to forget the inherent challenges of space exploration. Mission success rates for Mars missions are only about 42% (47% if including partially successful missions) and for the lunar missions some 55% (NASA, 2018[13]; OECD, 2014[14]). Indeed, the Google Lunar XPRIZE for privately funded robotic spacecraft to land and travel across the lunar surface expired without a winner in 2018, after several deadline extensions (Diamandis and Shingles, 2018[15]).

The rise of citizen science and crowdsourcing

Institutional missions create enormous amounts of scientific data, and innovative methods have been put in place to make maximal use of the datasets from these and other space science spacecraft and terrestrial telescopes. One example is crowdsourcing, which has seen an increasing number of space science projects appearing in the last years.

Crowdsourcing refers to the “outsourcing” of tasks to large groups of people, often amateur volunteers, generally by means of the Internet, which allow things to be conducted at a much larger scale, and ideally process data and information better and more quickly (OECD, 2017[16]). Some of these tasks could be automated in the near future, via advances in artificial intelligence, but at this stage, the human eye is still the best detector. In 2017, for the first time a multi-planet system was discovered entirely through crowdsourcing, in a project called Exoplanet Explorers, available on the online citizen science platform Zooniverse (NASA, 2018[17]). In only 48 hours, a star with four orbiting exoplanets was detected, after some 10 000 volunteers had combed through data from NASA’s Kepler space telescope. The method of detection was the so-called transit method - i.e. the brightness of a host star dips when planets pass in front of them. Volunteers had access to a field guide showing good and bad exoplanet candidates and could also discuss with the responsible researchers or fellow volunteers (Zooniverse, 2018[18]).

The Zooniverse platform, based at the University of Oxford, hosts another 16 active space science projects (as of June 2018), for instance Galaxy Zoo, Planet Four and Solar Stormwatch. The projects, shown in Table 5.2 are mostly supported and funded by space agencies, national and international research agencies and other academic organisations.

Table 5.2. Selected citizen science projects for space science (solar system, sun and universe)
Active projects as of June 2018


Volunteer tasks

Data source

Number of volunteers (rounded to nearest hundred)

Backyard Worlds: Planet 9

Scan the realm beyond Neptune and distinguish real celestial objects (brown dwarfs and low-mass stars) from image artefacts.

Wide-field Infrared Survey Explorer (WISE) mission (NASA)

47 600

Exoplanet Explorers

Detect exoplanets by looking for a dip in a star’s brightness as a planet crosses (transits) in front of it.

Kepler Space Telescope (NASA)

20 000

Planet Hunters

Find planets around stars.

Kepler (K2) Space Telescope (NASA)


Project Our Planet from Solar Storms

Classify clouds of solar matter by their complexity (by analysing and ranking pairs of imagery).

STEREO spacecraft (NASA)


Solar Stormwatch II

Make detailed traces of the outer edge of each solar storm. This contributes to refining and improving estimates of each storm’s arrival time at Earth.

STEREO spacecraft (NASA)

3 500

Galaxy Zoo

Classify galaxies according to their shapes.

Dark Energy Camera Legacy Survey (DECaLS) and Sloan Digital Sky Survey

9 200

Gravity Spy

Classify and characterise glitches (instrumental and environmental noise) in the dataset.

Laser Interferometer Gravitational-wave Observatory (LIGO) (National Science Foundation)

12 500

Milky Way Project

Detect objects and structures in the Milky Way (e.g. bubbles, bow shocks, star clusters, galaxies).

Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) (NASA)

11 300

Radio Meteor Zoo

Identify meteor echoes during meteor showers. Automatic detection algorithms try to detect specific shapes associated with meteor echoes. However, none of them can perfectly mimic the human eye which remains the best detector.

Belgian RAdio Meteor Stations (BRAMS) network (Belgian Institute for Space Aeronomy)

6 500

Supernova Hunters

Filter night-time multi-galaxy data to detect supernovae.

Panoramic Survey Telescope and Rapid Response System (University of Hawaii)

7 800

Source: Adapted from Zooniverse (2018[21]), Projects website, (accessed on 06 June 2018).

In some of these projects, the efforts of volunteers contribute directly to identifying objects or areas of interest, which can be subject to more detailed investigation by researchers. For instance, in the Planet Four project for Mars terrains, volunteers identify terrain structures using low-resolution imagery from the CTX imager on-board the NASA Mars MRO orbiter, which can then be studied in greater detail on the higher resolution images provided by the HiRISE imager, another instrument on the orbiter (Zooniverse, 2018[19]). In other cases, the most important contribution of volunteers is probably the labelling of datasets for algorithm training and improved machine detection of objects.

While crowdsourcing clearly can make important contributions to science, projects need to be carefully designed to be successful, and volunteers need to be trained. The assigned tasks need to be simple and well explained, and in projects with low participation, the quality of the results may be an issue (Mazumdar et al., 2016[20]). Participation rates vary quite significantly across projects, from hundreds to tens of thousands (in part dependant on the duration of the project, but not only).

Paving the way for new human spaceflight missions beyond Earth’s orbit

More countries than ever are investing in indigenous human spaceflight capabilities, with strong policy support in the United States, China and the Russian Federation. In many parts of the world, governments and industry are developing new technical capabilities for human exploration of the cislunar space, i.e. the region between the earth and the Moon, the lunar surface, and eventually Mars. In early 2019, human spaceflight activities take place in the low-earth orbit via stays in the International Space Station (ISS) and the Chinese Tiangong-2 experimental space station. However, this is likely to dramatically change in the coming decade, if current plans hold. Table 5.3 summarises current and planned spaceflight capabilities.

Table 5.3. Human spaceflight capabilities in selected parts of the world
As of 2019, including planned programmes for 2020-29

Orbital capabilities

Human-rated launcher/crew capsule capabilities





United States

International Space Station (ISS)

ISS, Gateway

Space Shuttle2

Space Launch System/Orion capsule

Potential commercial contracts with:

  1. – Boeing Atlas V/CST-100

  2. – SpaceX Falcon 9/Dragon crew capsule







Tiangong-11 and Tiangong-2

Chinese Space Station

Long March/Shenzhou capsule

Long March/Shenzhou second generation

Russian Federation



Soyuz launcher and capsule

Soyuz/Soyuz-5 launchers and Soyuz capsule/PTK Federatsiya capsule

1. Tiangong-1 was deorbited in 2018.

2. The space shuttle programme stopped in 2011.

The ISS has continuously supported astronauts in orbit since 2000. There are 15 countries involved in this partnership: Canada, Japan, the Russian Federation and the United States and 11 participating ESA country members (Belgium, Denmark, France, Germany, Italy, the Netherlands, Norway, Spain, Sweden, Switzerland and the United Kingdom). The ISS has served as a catalyzer for commercial spaceflight development. Already, there are several available space vehicles for delivering cargo and crew supplies to the ISS: three government capsules from the ESA, Japan and the Russian Federation; and two US commercial capsules, provided by SpaceX and ATK Orbital. A third US commercial capsule by Sierra Nevada Corporation should fly at least six resupply missions by 2024, with its first mission in 2019. The only way for crews to reach the station is by using the Russian Soyuz capsules, but US companies Boeing and SpaceX, contracted by NASA, are developing commercial crew capsules, with the first crew test flights scheduled in 2019-20 (NASA, 2018[22]).

Planning human presence beyond Earth’s orbit, the United States plans to deploy a manned outpost orbiting the moon (the Gateway) in the 2020s, with the first manned mission by 2023 (NASA, 2018[23]). This project will be collaborative, including possible contributions from other governments and the private sector (NASA, 2017[24]). NASA is finalising work on its new heavy-lift launcher, the Space Launch System (SLS), and the human-rated capsule (Orion), which will play a key role in the plans for the Lunar-Orbital Platform-Gateway and subsequent Mars exploration. The first launch, currently scheduled for 2019-20, will be an unmanned mission with the Orion capsule flying several thousand kilometers beyond the Moon and back to Earth (NASA, 2018[23]).

While existing Chinese space-based installations include the Tiangong-2 test bed space station, work continues on the permanent Chinese Space Station, which should be operational in 2022. Furthermore, the China Academy of Space Technology is working on successors to the current Shenzhou crew capsule. The new-generational capsule would be reusable and bigger, holding four to six taikonauts, compared to the current three, and come in two different versions: one 14-tonne version for trips to the Chinese Space Station, near-Earth asteroids and Mars; and a 20-tonne version (Jones, 2018[25]). China’s longest manned space mission to date is the Shenzhou-11 mission, a 32-day visit to the Tiangong-2 space station in 2016 (Griffiths, 2016[26]).

The Russian Federation is equally working on a next-generation crew vehicle, called Federatsiya (Federation), replacing the current Soyuz capsule. The first unmanned flight is scheduled for 2022, with a manned flight scheduled the following year, in 2023 (TASS, 2017[27]). The capsule is set to fly on top a new launcher, the Soyuz-5 (TASS, 2017[27]).

In parallel to these government-led initiatives, SpaceX, a US company, is developing a fully reusable super-heavy-lift launcher (currently labelled BFG) for cargo and crew missions to Mars. The first manned mission to Mars could take place within the next decade. Other private companies, such as Virgin Galactic and Blue Orbital, continue to develop space tourism activities, aiming to offer zero-gravity/parabolic flights, sub-orbital flights and orbital space travel to private consumers (see also Chapter 4).

Many science and exploration missions are by definition highly complex, with space agencies managing multiple actors, objectives and suppliers while also having to adhere to tight cost and time schedules. A case in point is the challenging development of the James Webb Space Telescope, currently two and half years behind schedule, with delays caused by human errors, excessive contractor optimism, use of new untested technologies and the shear complexity of the project.

Space agencies aim to carry out their activities as cost-efficiently as possible while avoiding failures and malfunctions, and there have been several recent developments in specific project management and procurement procedures for science and exploration. A common thread is an increased sharing of risk between space agencies and private sector contractors.

  • In Japan, JAXA has recently restructured its procurement and programme control mechanisms, after malfunctions in the 2016 ASTRO-H X-ray astronomy mission (Kinoshita, 2018[28]). The ASTRO-H mission, which took nine years to develop, lost communications with ground control only 40 days after launch. While the malfunction had multiple causes, it was found that several risks had been underestimated in the early phases of the project. This triggered a review of JAXA’s overall project management and procurement mechanisms. As a result, the very early, explorative stages in the project cycle have been strengthened and extended, to eliminate potential R&D risks as early as possible. Responsibilities between the space agency and its supplying companies have also been reshuffled, with contractors taking on more independent responsibility from the preliminary design phase onwards. These changes are being applied to the management of the forthcoming Martian Moons exploration mission (MMX) and the X-ray astronomy recovery mission (XARM).

  • Both ESA and NASA are considering different types of public-private partnerships for space exploration, with the private partner contributing more funding and covering more risks than what has previously been the case. For ESA, this would build on already existing partnerships in earth observation and satellite communications (Germes, 2018[29]). In the 2018-2030 NASA Exploration Campaign, the agency foresees to use commercial robotic lunar payload service contracts for surface delivery. Service contracts are also under consideration for the mid-to-large (500-1 000kg) lunar lander (Tawney, 2018[30])

The challenges and opportunities of space debris

The number of objects in space is expected to grow exponentially over the next decades, in part due to the ongoing small satellite revolution and an increase in the number of space actors. Space objects include not only spacecraft of various sizes and functions, but increasingly also space debris. Space debris refer to inactive, manmade objects and their fragments, that are orbiting Earth and eventually re-entering the atmosphere (ESA, 2017[31]). They include everything from discarded lens caps to large spent rocket stages (or even space stations), with the majority of objects smaller than 1 cm.

The uncontrolled presence of space debris in orbit can pose severe risks to functional satellites and other spacecraft. Several satellite failures have already been attributed to space debris collisions and commercial satellite operators and the International Space Station partners have had to repeatedly use space debris avoidance manoeuvres over the past years (UNOOSA, 2018[32]).

Still, the growing risks of space debris and the need to act cooperatively to protect congested orbits may contribute to opening the way for new technological solutions.

The space debris challenges

Space debris have been accumulating since the launch of the first satellite in 1957, both as a result of routine space operations and accidents and explosions. Since 1957, almost 9 000 satellites have been placed in orbit, with about 5 000 satellites still in orbit in early 2019 (1 200 of which are operational). In the last 60 years, there have been more than 500 break-ups, collisions and explosions, so-called fragmentation events.

Due to orbital decay – the process that leads to gradual decrease of the distance between two orbiting bodies – debris accumulation is uneven among different orbits. The highest concentrations of objects are found in the low–earth orbit between 800 and 1 000 kilometres of altitude and towards 1 400 kilometres. Other debris belts are close to the orbit of navigation satellite constellations, between 19 000 and 23 000 kilometres of altitude, and in the geostationary orbit at around 36 000 kilometres.

The amount of objects accumulated in Earth orbits, as reported by the European Database and Information System Characterising Objects in Space (DISCOS) database, has significantly grown over time. In particular, there has been a marked increase of objects in the low-earth orbit over the last decade. More than 13 000 objects tracked by DISCOS were located in the low-earth orbit at the end of 2017.

This accumulation of space debris constitutes a considerable and growing collision hazard for both satellites in orbit and satellites travelling through the space debris belt during orbit-raising and lowering. Given that the velocity of objects can reach up to 10 kilometres/second in low-earth orbit (LEO), eventual impacts involving larger objects may lead to the destruction of an entire spacecraft (ESA, 2017[31]). It has been argued that the increased use of electric propulsion for orbit-raising increases the length of exposure for satellites during orbit-raising.

Furthermore, people and installations on Earth can be at risk. While the majority of objects burn when entering the atmosphere, estimates suggest that, due to their size, 10 to 20% of big objects reach the earth’s surface (CNES, 2017[33]). Several large spacecraft have been safely deorbited over the years, including the controlled deorbit of the 120 metric tonnes Mir space station over the South Pacific Ocean in 2001. But several large structures have also fallen back to Earth in an uncontrolled manner, most recently the Chinese spacelab Tiangong 1, which burnt up over the Pacific Ocean in 2018.

Table 5.4. Space debris in numbers

Number of launches since the start of the space age in 1957

About 5 400

Number of satellites placed into Earth’s orbit

About 8 900

Number of satellites in Earth’s orbit

About 5 000

Number of operational satellites

About 1 900

Number of debris objects regularly tracked by the US Space Surveillance Network and maintained in their catalogue

About 23 200

Estimated number of break-ups, explosions and collision events resulting in fragmentation

More than 500

Total mass of all space objects in Earth’s orbit

About 8 400 tonnes

Number of debris objects estimated by statistical models to be in orbit

34 000 objects >10 cm

900 000 objects from 1 cm to 10 cm

128 million objects from 1 mm to 1 cm

Source: Adapted from ESA (2019[31]), Space debris: the ESA approach,

The way forward: International cooperation and private initiatives

Mitigation efforts include the systematic surveillance and tracking of existing objects and preventive regulations and guidelines to reduce the future amount of debris. Possible technical solutions for active debris removal are being explored by space agencies and some private companies.

Several public and private actors make efforts to identify, map and track debris objects in different orbits. The US Department of Defence’s Space Surveillance Network (SSN) is a global network of ground- and space-based radars, lasers and telescopes that currently track some 23 000 orbiting pieces of debris larger than 10 cm in low-earth orbit (LEO) and 30 cm in geostationary orbit (GEO). More than half of the catalogued items, some 56%, are fragments from the more than 500 recorded fragmentation events. Around 38% of the SSN`s catalogue include large space debris such as derelict spacecraft and upper stages of launch vehicles, carriers for multiple payloads and mission-related items. Functional satellites account only for 6% of catalogued items. A new surveillance and tracking system, the Space Fence, is currently under development and testing, and should be able to identify and track much smaller objects than currently possible (Lockheed Martin, 2019[34]).

Other countries and organisations also track and classify space objects, The European DISCOS database collects information on space objects, including launch information, object registration, launch vehicle descriptions, etc. The dataset comprises more than 40 000 identifiable items (ESOC, 2018[35]). The European Union supports space surveillance and tracking capabilities and services in the EUSST project, funded by Horizon 2020. Japan is planning to update and extend national capabilities and Korea is developing the OWL-Net network of robotic optical telescopes (Yoshitomi, 2018[36]; Choi et al., 2018[37])

Existing catalogues cover only a fraction of actual collision-prone objects. Estimates from debris environment modelling exercises indicate that around 166.8 million debris objects bigger than 1 millimetre may currently be circling the earth (ESA, 2017[31]). Of these objects, 166 million would be smaller than 1 cm.

This is opening the market for commercial products and services collecting, processing and analysing data. One example is the US start-up LeoLabs, which proposes space debris mapping services via radars located in different parts of the world to public and private satellite operators. The main innovation lies in the data platform made available to operators and developers, which addresses the fundamental shortage of space situational awareness data in the sector and provides datasets that can be used to train and perfect object-detecting algorithms and develop applications. The company plans to have six low-cost radars up and running by the end of 2019.

An important avenue of action is the sharing of data. The US Strategic Command has data-sharing agreements with some 20 countries (Australia, Belgium, Brazil, Canada, Denmark, France, Germany, Italy, Israel, Japan, Korea, the Netherlands, New Zealand, Norway, Poland, Romania, Spain, Thailand, the United Arab Emirates and United Kingdom), the European Space Agency, EUMETSAT and almost 80 commercial satellite owners, operators and launch providers (US Strategic Command, 2018[38]). In 2017, the US Strategic Command issued hundreds of warnings to their partners, with more than 80 confirmed collision manoeuvres from satellite operators (Weeden, 2018[39]).

The problem of space debris and the challenges it poses require coordinated efforts from both public and private actors at the global level. Discussion are currently taking place at the Inter-Agency Space Debris Co-ordination Committee (IADC) and the United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS). Private actors also have an important role to play as satellite operators and developers of technological solutions.

  • The Inter-Agency Space Debris Co-ordination Committee includes 13 major space agencies which exchange information on space debris research activities. The main goal is to foster cooperation in space debris research, review the progress of ongoing cooperative activities, and identify potential debris mitigation options (IADC, 2018[40]). The IADC have produced several guidelines and draft plans over the last decade, including the 2007 “Space Debris Mitigation Guidelines”, which were later endorsed by a United Nations’ General Assembly resolution (see Table 5.5). Later, in 2015, during its 33rd meeting, the IADC underlined the necessity of a concrete plan to mitigate the effects of the fast-appearing large constellations of small satellites in LEO (IADC, 2017[41]).

  • The IADC also participates in and contributes to the United Nations space debris activities via the Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space (UN COPUOS). The Committee offers governments and organisations a platform to facilitate the exchange of information in the area of space debris research. Recently, the outcomes of these interactions led to the publication of a compendium of space debris mitigation standards (UN COPUOS, 2018[42]).

Table 5.5. Selected international cooperation mechanisms in the area of space debris





Inter-Agency Space Debris Coordination Committee (IADC)

IADC Statement on Large Constellations of Satellites in low-earth Orbit


United Nations Committee on the Peaceful Uses of Outer Space (COPUOS)

Compendium of space debris mitigation standards adopted by states



Space Debris Mitigation Policy for Agency Projects



Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer Space


International Telecommunications Union (ITU)

Recommendation ITU-R S.1003.2, “Environmental protection of the geostationary-satellite orbit”



Space Debris Mitigation Guidelines


ASI, British National Space Centre, CNES, DLR, ESA

European Code of Conduct for Space Debris Mitigation

In addition to the work of the IADC and of the UN COPUOS, several other international cooperation mechanisms exist. First, the European Code of Conduct for Space Debris Mitigation was developed and formally adopted in 2004 by the Italian Space Agency (ASI), the British National Space Centre (the current UK Space Agency), the French Space Agency (CNES), the German Aerospace Agency (DLR) and the European Space Agency (ESA). The Code defines measures to reduce on-orbit break-ups and collisions of spacecraft, facilitate debris removal and limit the number of objects released during normal spacecraft operations. Second, ESA’s Space Debris Mitigation Policy for Agency Projects, launched in 2014, sets the technical requirements on space debris mitigation for projects run by agencies and defines the associated internal responsibilities. Finally, the International Telecommunications Union (ITU) Recommendation ITU-R S.1003.2 of 2010 establishes guidelines about disposal orbits for satellites in the geostationary satellite orbit to decrease debris accumulation locally.

ESA is currently developing new models to analyse space debris and their dynamics over time and evaluate the effectiveness of mitigation practices, such as the Debris Environment Long-Term Analysis (DELTA) tool (ESOC, 2016[43]). The model forecasts future trends on the basis of different possible individual mitigation actions implemented in the present. Scenarios can be built for the low, medium and geosynchronous Earth orbits, over a number of years and for all objects larger than a user-defined size. Several conditions can be selected to characterise the predictions, including, among the others, future traffic profiles and the enforcement of debris mitigation and active debris removal measures. However, even in case of full compliance with existing rules, long term debris proliferation will continue (ESA, 2017[44]). International cooperation guidelines trying to mitigate the creation of space debris may slow down the accumulation of space objects, but will not resolve the problem and eliminate the risks. For this, active debris removal would be necessary.

For this reason, several public and private actors are working to identify potential space debris removal solutions. ESA’s Clean Space initiative is looking at the required technology developments, including advanced image processing, complex guidance, navigation and control and innovative robotics to capture debris. In 2018-19, the European RemoveDebris mission is testing several active debris removal technologies on-orbit.

Meanwhile, private sector actors are developing products and services to meet the demand for space debris removals. The goal is to develop commercially affordable debris removal solutions adopting innovative technics to capture and then destroy large debris objects, while monitoring smaller objects. As an example, Astroscale is developing deorbit services using small satellites, capable of docking with big debris objects and bringing them to the atmosphere to be burnt. Both Airbus and Thales Alenia Space are developing on-orbit servicing vehicles with debris removal functionalities (Lamigeon, 2018[45]).

International cooperation is necessary to mitigate the problem of debris accumulation in Earth’s orbits. Timely and coherent international coordination and shared agreements on the “rules of the game” will be crucial. Regulations and guidelines need to adapt to the evolving nature of space activities, and innovation. Public authorities and governments in general must make sure that directives are well received and then respected by space users in every country. This approach does not have to come at the cost of limitations in private actors’ initiative in the space sector. One of the most important roles of governments is still to support commercial activities in space. Creating the right institutional framework and incentives for private business is essential to promote the role of space as a provider of socio-economic benefits. Governments should advocate the importance of respecting debris mitigation rules in order to reduce the risks associated to investments in space.

Promoting and sustaining space surveillance activities is another key area for policy intervention. This entails supporting existing space surveillance and tracking (SST) systems which make it possible to detect and catalogue space debris and predict their orbits (ESA, 2017[44]). It is also important to develop improved analytical tools to derive applications and services, as it is the case for collision warning systems. Both public and private actors can turn these space debris uncertainties into opportunities for collaboration and new technological developments.


[6] Chinese Academy of Sciences (2018), Space missions of IHEP website, (accessed on 7 June 2018).

[37] Choi, J. et al. (2018), “Optical tracking data validation and orbit estimation for sparse observations of satellites by the OWL-Net.”, Sensors, Vol. 18/6,

[33] CNES (2017), “Débris spatiaux: où en est-on?”, Media releases website, 24 November, (accessed on 22 May 2018).

[15] Diamandis, P. and M. Shingles (2018), An important update from Google Lunar XPRIZE, 23 January, (accessed on 7 June 2018).

[12] ESA (2018), ESA Missions website, (accessed on 6 June 2018).

[4] ESA (2018), Orbiting observatories website, (accessed on 8 June 2018).

[5] ESA (2018), Solar system operations website, (accessed on 8 June 2018).

[44] ESA (2017), ESA space debris website, (accessed on 15 May 2018).

[31] ESA (2019), Space debris: the ESA approach, March,

[35] ESOC (2018), ESA’s Annual Space Environment Report: Produced with the DISCOS Database, European Space Operations Centre, Darmstadt,

[43] ESOC (2016), “DELTA (debris environment long term analysis)”, European Space Operations Centre, Darmstadt,

[29] Germes, F. (2018), “Changes in ESA procurement: Next decade of space activities”, presentation at the OECD Space Forum Workshop:The Transformation of the Space Industry: Linking Innovation and Procurement, 27 April 2018, Paris.

[26] Griffiths, J. (2016), “Shenzhou-11 astronauts return home after China’s longest-ever space mission”, CNN, 18 November, (accessed on 11 June 2018).

[2] Harvard-Smithsonian Center for Astrophysics (2016), Chandra X-Ray observatory website, (accessed on 8 June 2018).

[40] IADC (2018), “An overview of IADC’s annual activities”, 55th Session of the Scientific and Technical Subcommittee United Nations Committee on the Peaceful Uses of Outer Space, Inter-Agency Space Debris Coordination Committee,

[41] IADC (2017), IADC statement on large constellations of satellites in low Earth orbit, Issued by the Inter-Agency Space Debris Coordination Committee Steering Group, November,

[11] International Space Exploration Coordination Group (2018), The Global Exploration Roadmap, (accessed on 7 June 2018).

[7] ISRO (2017), ASTROSAT website, (accessed on 7 June 2018).

[10] Johns Hopkins Applied Physics Laboratory (2017), “New Horizons corrects its course in the Kuiper Belt”, News releases website, 9 December, (accessed on 7 June 2018).

[25] Jones, A. (2018), “China is developing a new crewed spacecraft for Moon and deep space missions”, GB Times, 13 March, (accessed on 11 June 2018).

[28] Kinoshita, A. (2018), “Adaptation to a new space sector: Innovation in procurement mechanisms”, presentation at the OECD Space Forum Workshop:The Transformation of the Space Industry: Linking Innovation and Procurement, 27 April, Paris.

[45] Lamigeon, V. (2018), “Le ravitailleur spatial, nouveau pari de Thales Alenia Space”, in Challenges, 15 November, (accessed on 9 May 2019).

[34] Lockheed Martin (2019), Space Fence website, (accessed on 15 January 2019).

[20] Mazumdar, S. et al. (2016), Crowd4Sat: Executive summary, (accessed on 7 June 2018).

[13] NASA (2018), Historical log: Mars exploration program, webpage, (accessed on 13 November 2018).

[17] NASA (2018), “Multi-planet system found through crowdsourcing”, Media releases website, 11 January, (accessed on 6 June 2018).

[22] NASA (2018), “NASA commercial crew program mission in sight for 2018”, Media releases website, 4 January, (accessed on 11 June 2018).

[23] NASA (2018), “NASA’s lunar outpost will extend human presence in deep space”, Media releases website, 13 February, (accessed on 11 June 2018).

[9] NASA (2018), “New Horizons captures record-breaking images in the Kuiper Belt”, Media releases website, 8 February, (accessed on 7 June 2018).

[1] NASA (2018), Solar system exploration missions website, (accessed on 6 June 2018).

[24] NASA (2017), “Roscosmos sign joint statement on researching, exploring space”, Media releases website, 27 September, (accessed on 11 June 2018).

[3] NASA (2017), Spitzer space telescope website, (accessed on 8 June 2018).

[16] OECD (2017), Fostering Innovation in the Public Sector, OECD Publishing, Paris,

[14] OECD (2014), The Space Economy at a Glance 2014, OECD Publishing, Paris,

[27] TASS (2017), “Federatsiya spacecraft’s first flight may be rescheduled to 2022”, TASS, 27 May, (accessed on 11 June 2018).

[30] Tawney, T. (2018), “NASA exploration campaign”, presentation at the OECD Space Forum Workshop: The Transformation of the Space Industry: Linking Innovation and Procurement, 27 April 2018, Paris.

[42] UN COPUOS (2018), Compendium of space debris mitigation standards adopted by states, United Nations Office for Outer Space Affairs (UNOOSA),

[32] UNOOSA (2018), Space debris website, (accessed on 16 May 2018).

[38] US Strategic Command (2018), “Thailand sign agreement to share space services, data”, Press releases website, 11 October, (accessed on 14 January 2019).

[39] Weeden, B. (2018), “Promoting cooperative solutions for space sustainability: US perspectives on SSA”, presentation at the symposium “The SSA Strategic Challenges for India”, 14-15 June, Bengaluru, (accessed on 15 January 2019).

[8] Yin, J. et al. (2017), “Satellite-based entanglement distribution over 1200 kilometers”, Science, Vol. 356/6343, pp. 1140-1144,

[36] Yoshitomi, S. (2018), “The SSA Strategic Challenges for India: Japanese Perspective”, presentation at the symposium “The SSA Strategic Challenges for India”, 14-15 June, Bengaluru, (accessed on 14 January 2019).

[18] Zooniverse (2018), “Exoplanet explorers”, Projects website, (accessed on 6 June 2018).

[19] Zooniverse (2018), “Planet four: Terrains”, Projects website, (accessed on 7 June 2018).

[21] Zooniverse (2018), Projects website, (accessed on 6 June 2018).

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