Space exploration in the context of "Horizon 2000"

The National Aeronautics and Space Administration (NASA /ˈnæsə/) is an independent agency of the US federal government responsible for the United States' civil space program and for research in aeronautics and space exploration. Headquartered in Washington, D.C., NASA operates ten field centers across the United States and is organized into mission directorates for Science, Space Operations, Exploration Systems Development, Space Technology, Aeronautics Research, and Mission Support. Established in 1958, NASA succeeded the National Advisory Committee for Aeronautics (NACA) to give the American space development effort a distinct civilian orientation, emphasizing peaceful applications in space science. It has since led most of America's space exploration programs, including Project Mercury, Project Gemini, the 1968–1972 Apollo program missions, the Skylab space station, and the Space Shuttle.

The agency maintains major ground and communications infrastructure including the Deep Space Network and the Near Space Network. NASA's science division is focused on better understanding Earth through the Earth Observing System; advancing heliophysics through the efforts of the Science Mission Directorate's Heliophysics Research Program; exploring bodies throughout the Solar System with advanced robotic spacecraft such as New Horizons and planetary rovers such as Perseverance; and researching astrophysics topics, such as the Big Bang, through the James Webb Space Telescope, the four Great Observatories (including the Hubble Space Telescope), and associated programs. The Launch Services Program oversees launch operations for its uncrewed launches.

The European Space Agency (ESA), pronounced 'ee-sah', is a 23-member international organisation devoted to space exploration. It has its headquarters in Paris and a staff of around 2,547 people globally as of 2023. ESA was founded in 1975 in the context of European integration. Its 2025 annual budget was €7.7 billion.

The ESA human spaceflight programme includes participation in the International Space Station (ISS) and collaboration with NASA on the Artemis programme, especially manufacturing of the Orion spacecraft's European Service Module (ESM). ESA launches and operates uncrewed missions to the Moon, Mars, Jupiter, Venus, Mercury, the Sun, and various comets and asteroids. Other activities include space telescopes, Earth observation satellites, asteroid impact avoidance, telecommunication and navigation satellites, designing launch vehicles (e.g. Ariane 6 is operated through Arianespace with ESA sharing in the costs), and maintaining Europe's Spaceport (the Guiana Space Centre at Kourou, French Guiana), as well as space safety and commercialisation.

The history of exploration by citizens or subjects of the Russian Federation, the Soviet Union, the Russian Empire, the Tsardom of Russia and other Russian predecessor states forms a significant part of the history of Russia as well as the history of the world. At 17,075,400 square kilometres (6,592,850 sq mi), Russia is the largest country in the world, covering more than a ninth of Earth's landmass. In the times of the Soviet Union and the Russian Empire, the country's share in the world's landmass reached 1/6. Most of these territories were first discovered by Russian explorers (if indigenous peoples of inhabited territories are not counted). Contiguous exploration in Eurasia and the building of overseas colonies in Russian America were some of the primary factors in Russian territorial expansion.

Apart from their discoveries in Alaska, Central Asia, Siberia, and the northern areas surrounding the North Pole, Russian explorers have made significant contributions to the exploration of the Antarctic, Arctic, and the Pacific islands, as well as deep-sea and space explorations.

Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth), celestial bodies (such as moons, asteroids, comets) and planetary systems (in particular those of the Solar System) and the processes of their formation. It studies objects ranging in sizes from micrometeoroids to huge gas giants, with the aim of determining their composition, dynamics, formation, interrelations and history. It is a strongly interdisciplinary field, which originally grew from astronomy and Earth science, and now incorporates many disciplines, including planetary geology, cosmochemistry, atmospheric science, physics, oceanography, hydrology, theoretical planetary science, glaciology, and exoplanetology. Allied disciplines include space physics, when concerned with the effects of the Sun on the bodies of the Solar System, and astrobiology.

There are interrelated observational and theoretical branches of planetary science. Observational research can involve combinations of space exploration, predominantly with robotic spacecraft missions using remote sensing, and comparative, experimental work in Earth-based laboratories. The theoretical component involves considerable computer simulation and mathematical modelling.

The following outline is provided as an overview and topical guide to space science:

Space science – field that encompasses all of the scientific disciplines that involve space exploration and study natural phenomena and physical bodies occurring in outer space, such as space medicine and astrobiology.

Science fiction (often shortened to sci-fi or abbreviated SF) is the genre of speculative fiction that imagines advanced and futuristic scientific or technological progress. The elements of science fiction have evolved over time: from space exploration, extraterrestrial life, time travel, and robotics; to parallel universes, dystopian societies, and biological manipulations; and, most lately, to information technology, transhumanism (and posthumanism), and environmental challenges. Science fiction often specifically explores human responses to the consequences of these types of projected or imagined scientific advances.

The precise definition of science fiction has long been disputed among authors, critics, scholars, and readers. It contains many subgenres, including hard science fiction, which emphasizes scientific accuracy, and soft science fiction, which focuses on social sciences. Other notable subgenres are cyberpunk, which explores the interface between technology and society; climate fiction, which addresses environmental issues; and space opera, which emphasizes pure adventure in a universe in which space travel is common.

A flyby (/ˈflaɪbaɪ/) is a spaceflight operation in which a spacecraft passes in proximity to another body, usually a target of its space exploration mission and/or a source of a gravity assist (also called swing-by) to impel it towards another target. Spacecraft which are specifically designed for this purpose are known as flyby spacecraft, although the term has also been used in regard to asteroid flybys of Earth for example. Important parameters are the time and distance of closest approach.

Government space agencies, established by the governments of countries and regional agencies (groupings of countries) are established as a means for advocating for engaging in activities related to outer space, exploitation of space systems, and/or space exploration. The listings summarize all countries' and regional authorities' space agencies with a comparative summary of demonstrated capabilities.

The objectives include national prestige, exploitation of remote sensing information, communications, education, and economic development. These agencies tend to be civil in nature (vs military) and serve to advance the benefits of exploitation and/or exploration of space. They span the spectrum from old organizations with small budgets to mature national or regional enterprises such as the National Aeronautics and Space Administration (NASA) of the United States, the European Space Agency (ESA) which coordinates for more than 20 constituent countries, the Japan Aerospace Exploration Agency (JAXA), the Roscosmos State Corporation for Space Activities (Roscosmos) of Russia, the Indian Space Research Organisation (ISRO), and the China National Space Administration (CNSA).

A rover (or sometimes planetary rover) is a planetary surface exploration machine designed to move over the rough surface of a planet or other planetary-mass celestial bodies. Some rovers have been designed as land vehicles to transport members of a human spaceflight crew; others have been partially or fully autonomous robots.

Rovers typically landed on an exoplanet (planets other than Earth) or a moon via a lander-style spacecraft, tasked to move around and collect information about the terrain, and to take crust samples such as dust, soil, rocks and even liquids. They are essential astrogeology tools for space exploration.