Analog mission
Human analog missions are experiences carried out on Earth in environments that simulate those beyond our planet, such as the Moon or Mars. In these remote and often extreme environments, participants conduct research projects to better understand our universe. Additionally, these environments provide a context for examining and experiencing the social and psychological dynamics that would arise in a closed extraterrestrial civilization.

The point in the orbit of the Moon or a satellite at which it is furthest from the Earth. Apogee is also used for our purposes to reference the highest point in a suborbital flight or balloon ride to space.

A person who is trained to travel as a commander or crew member on a spacecraft. Until the emergence of commercial space programs in 2004, astronauts were trained only by governments, through either the military or civilian space agencies. Individuals that are not sponsored and / or trained by government agencies are sometimes referred to as commercial or private astronauts.

Astronaut Experiences
Experiences taking place in or above the stratosphere.

Baikonur Cosmodrome
A spaceport located in Kazakhstan, leased to Russia, and jointly managed by the Roscosmos State Corporation and the Russian Aerospace Forces. The Baikonur Cosmodrome is the world’s first spaceport for human launches and launch location for all crewed Russian spaceflights. The Cosmodrome was originally built in the late 1950s as the operations base for the Soviet space program.

Russia’s name for an astronaut fielded by Russia or, previously, the Soviet Union.

A layer or set of layers of gases surrounding a planet or other body that is held in place by that body’s gravity. Earth’s atmosphere provides oxygen that most living organisms use for respiration and helps protect organisms from ultraviolet radiation, solar wind, and cosmic rays.

Earthrise is an influential photograph of Earth peeking out from beyond the lunar surface that was taken from lunar orbit by astronaut William Anders on December 24, 1968, during the Apollo 8 mission.

European Space Agency (ESA)
An intergovernmental organization of 22 member states established in 1975 and dedicated to space exploration. The ESA is headquartered in Paris, France. 

Fédération Aéronautique Internationale (FAI)
A non-governmental and non-profit international organization dedicated to furthering aeronautical and astronautical activities. FAI is the world’s governing body for air sports and steward of definitions regarding human spaceflight. 

Free-return trajectory
A concept in orbital mechanics that describes the trajectory of a spacecraft traveling away from a primary body that is influenced by the gravity of a secondary body in such a way that the spacecraft returns to the primary body without requiring additional propulsion. For example, a spacecraft traveling from Earth to the Moon and returning to the Earth without needing additional propulsive maneuvers. 

Hypobaric chamber
A hypobaric chamber, or altitude chamber, simulates the effects of high altitude on the human body, such as hypoxia (low oxygen) and hypobaria (low ambient air pressure). It is used in aerospace training and high terrestrial altitude training and research.

International Space Station (ISS)
A multinational space station located in low Earth orbit with five participating space agencies - NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada) - and governed by international agreements. The ISS functions as a microgravity research laboratory for fields such as astronomy, meteorology, physics, and astrobiology. Since its completion in 2011, the ISS has a 100% safety record.

Kármán Line
The Kármán line, defined as an altitude of 100 km (62 miles) above Earth’s main sea level, is recognized by some organizations as the boundary between Earth’s atmosphere and outer space. The Fédération Aéronautique Internationale (FAI) uses this metric while other organizations, such as NASA and the US Air Force, use different definitions (NASA defines the edge of space as 50 miles above sea level). There is no international law defining the edge of space.

Kennedy Space Center
The John F. Kennedy Space Center (KSC) is one of NASA’s 10 field centers, and the space agency’s primary launch center for human spaceflight since 1968. KSC is located on the east coast of Florida close to Cape Canaveral Space Force Station. The two entities work closely together.

Low Earth Orbit (LEO)
An Earth-centred orbit close to the planet, often specified as an orbital period of 128 minutes or less. “LEO region” describes the area of space below an altitude of 2,000 km (1,200 mi), or ⅓ Earth’s radius. All crewed space stations, including the ISS to date have been in LEO. No human has been beyond LEO since the Apollo program ended in 1972.

Lunar gravity
Lunar gravity describes the acceleration due to gravity, often referred to as gravitational force, that exists on the Moon’s surface. The Moon has significantly less mass than the Earth which contributes to a difference in gravitational acceleration. The result is that objects on the Moon weigh 16.6% (about 1/6) of what they weigh on Earth.

Martian gravity
Martian gravity describes the acceleration due to gravity, often referred to as gravitational force, that exists on the surface of Mars. Mars has less mass than the Earth which contributes to a difference in gravitational acceleration. The result is that objects on the Moon weigh about 38% (about 1/3) of what they weigh on Earth.

The mesosphere is the third major layer of the Earth's atmosphere, above the stratosphere and below the thermosphere, between about 30 and 50 miles (50 and 80 km) in altitude. The mesosphere is the coldest part of the Earth’s atmosphere. Meteors tend to burn up in the mesosphere.

The National Aeronautics and Space Administration (NASA) is an independent agency of the U.S. Federal Government responsible for the civilian space program, as well as aeronautics and space research. NASA was established in 1958.

Orbital spaceflight
A spaceflight in which a spacecraft is placed on a trajectory where it can remain in space for at least one orbit. To reach Earth’s orbit, the spacecraft must be on a free trajectory which has an altitude at closest approach around 80 kilometers (50 mi). To remain in orbit at this altitude requires an orbital speed of ~7.8 km/s. Axiom Space, SpaceX, and Space Adventures all offer orbital spaceflight experiences.

Overview effect
The overview effect describes a psychological reaction, or cognitive shift in awareness, that some astronauts report when they view Earth from outer space. Many astronauts describe the experience as a shift in perspective, as they realize how small and fragile their home planet and atmosphere is against the vast backdrop of outer space. “From space, national boundaries vanish, the conflicts that divide people become less important, and the need to create a planetary society with the united will to protect this ‘pale blue dot’ becomes both obvious and imperative.” - Author Unknown 

Parabolic flight
A flight that simulates microgravity by flying along a parabolic trajectory.

The part of a satellite or aircraft that performs the flight’s main mission - collecting and producing data, communications, and revenue.
RoscosmosThe Roscosmos State Corporation for Space Activities (Roscosmos or Роскосмос), is a state corporation of the Russian Federation responsible for space flights, cosmonautics programs, and aerospace research.

Any trip to space, whether through a rocket launch or a space balloon. There is some debate over what is considered spaceflight. The Fédération Aéronautique Internationale (FAI) Sporting Code only recognizes flights above the Kármán line (62 miles / 100 km) above Earth’s average sea level, while the US (including NASA)  recognizes spaceflight at an altitude of 50 miles (80 km).

The stratosphere is the second major layer of the Earth's atmosphere. It extends from the top of the troposphere to about 30 miles (50 kilometers) above the surface. Clouds rarely form in the stratosphere. Unlike in the troposphere, the stratosphere is colder closer to Earth and warmer at higher altitudes. Weather / space balloons and some spy planes fly in the stratosphere. 

Soyuz spacecraft
The Soyuz spacecraft were designed for the Soviet space program in the 1960s and remain in service today, having taken 140+ flights. The Soyuz spacecraft is launched on a Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan. After the retirement of the US Space Shuttle in 2011, the Soyuz served as the only means to make crewed space flights and the only means to reach the ISS until the first flight of SpaceX Crew Dragon Demo 2 in 2020. 

Suborbital spaceflight
A spaceflight in which the spacecraft reaches outer space, but its trajectory and speed is such that it will not complete one orbital rotation or escape the gravitational force of the body from which it was launched. Examples of suborbital spacecraft are Blue Origin’s New Shepard and Virgin Galactic’s VSS Imagine. A flight that does not reach space is still sometimes called suborbital, but is not a 'suborbital spaceflight.'

The layer of Earth’s atmosphere directly above the mesosphere and below the exosphere. The thermosphere is home to the International Space Station and LEO satellites. The thermosphere can reach up to 4,500 degrees Fahrenheit. 

The troposphere is the lowest layer of Earth's atmosphere, with an average height of 13 km (varying by latitude and season). 75% of our atmosphere’s mass is contained in the troposphere. Almost all weather occurs in the troposphere. Commercial airplanes fly in the troposphere.