Space debris in the context of Re-entry

A meteoroid (/ˈmiːtiərɔɪd/ MEE-tee-ə-royd) is a small body in outer space.Meteoroids are distinguished as objects significantly smaller than asteroids, ranging in size from grains to objects up to one meter (3.28 feet) wide. Objects smaller than meteoroids are classified as micrometeoroids or space dust. Many are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.

The visible passage of a meteoroid, comet, or asteroid entering Earth's atmosphere is called a meteor, and a series of many meteors appearing seconds or minutes apart and appearing to originate from the same fixed point in the sky is called a meteor shower.

Space environment is a branch of astronautics, aerospace engineering and space physics that seeks to understand and address conditions existing in space that affect the design and operation of spacecraft. A related subject, space weather, deals with dynamic processes in the solar-terrestrial system that can give rise to effects on spacecraft, but that can also affect the atmosphere, ionosphere and geomagnetic field, giving rise to several other kinds of effects on human technologies.

Effects on spacecraft can arise from radiation, space debris and meteoroid impact, upper atmospheric drag and spacecraft electrostatic charging. Various mitigation strategies have been adopted.

A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake. Meteors typically occur in the mesosphere at altitudes from 76–100 kilometres (47–62 miles). The root word meteor comes from the Greek meteōros, meaning "high in the air".

Millions of meteors occur in Earth's atmosphere daily. Most meteoroids that cause meteors are about the size of a grain of sand, i.e. they are usually 1 mm (1⁄25 in) or smaller. Meteoroid sizes can be calculated from their mass and density which, in turn, can be estimated from the observed meteor trajectory in the upper atmosphere.Meteors may occur in showers, which arise when Earth passes through a stream of debris left by a comet, or as "random" or "sporadic" meteors, not associated with a specific stream of space debris. A number of specific meteors have been observed, largely by members of the public and largely by accident, but with enough detail that orbits of the meteoroids producing the meteors have been calculated. The atmospheric velocities of meteors result from the movement of Earth around the Sun at about 30 km/s (67,000 mph; 110,000 km/h), the orbital speeds of meteoroids, and the gravity well of Earth.

Atmospheric entry (sometimes listed as V_impact or V_entry) is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. Atmospheric entry may be uncontrolled entry, as in the entry of astronomical objects, space debris, or bolides. It may be controlled entry (or reentry) of a spacecraft that can be navigated or follow a predetermined course. Methods for controlled atmospheric entry, descent, and landing of spacecraft are collectively termed as EDL.

Objects entering an atmosphere experience atmospheric drag, which puts mechanical stress on the object, and aerodynamic heating—caused mostly by compression of the air in front of the object, but also by drag. These forces can cause loss of mass (ablation) or even complete disintegration of smaller objects, and objects with lower compressive strength can explode.

A geocentric orbit, Earth-centered orbit, or Earth orbit involves any object orbiting Earth, such as the Moon or artificial satellites. In 1997, NASA estimated there were approximately 2,465 artificial satellite payloads orbiting Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. More than 16,291 objects previously launched have undergone orbital decay and entered Earth's atmosphere.

A spacecraft enters orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the horizontal component of its velocity. For a low Earth orbit, this velocity is about 7.8 km/s (28,100 km/h; 17,400 mph); by contrast, the fastest crewed airplane speed ever achieved (excluding speeds achieved by deorbiting spacecraft) was 2.2 km/s (7,900 km/h; 4,900 mph) in 1967 by the North American X-15. The energy required to reach Earth orbital velocity at an altitude of 600 km (370 mi) is about 36 MJ/kg, which is six times the energy needed merely to climb to the corresponding altitude.

Human presence in space (also anthropogenic presence in space or humanity in space) is the direct and mediated presence or telepresence of humans in outer space, and in an extended sense across space including astronomical bodies. Human presence in space, particularly through mediation, can take many physical forms from space debris, uncrewed spacecraft, artificial satellites, space observatories, crewed spacecraft, art in space, to human outposts in outer space such as space stations.

While human presence in space, particularly its continuation and permanence can be a goal in itself, human presence can have a range of purposes and modes from space exploration, commercial use of space to extraterrestrial settlement or even space colonization and militarisation of space. Human presence in space is realized and sustained through the advancement and application of space sciences, particularly astronautics in the form of spaceflight and space infrastructure.

The Space Safety Programme (S2P), formerly the Space Situational Awareness (SSA) programme, is an initiative by the European Space Agency (ESA) to monitor hazards from space, determine their risk, make this data available to the appropriate authorities, and where possible, mitigate the threat. The programme focuses on 3 areas: space weather forecasting and nowcasting, asteroid impact prediction and prevention, and space debris mitigation. S2P is being implemented as an optional ESA programme with financial participation by 14 Member States.

A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun itself are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits, as they orbit their respective planet (although the Moon has a convex orbit around the Sun).

The barycenter of the Solar System, while always very near the Sun, moves through space as time passes, depending on where other large bodies in the Solar System, such as Jupiter and other large gas giants, are located at that time. A similar phenomenon allows the detection of exoplanets by way of the radial-velocity method.

Satellite laser ranging (SLR) is a method to measure the distance to satellites in a geocentric orbit. It consists of an astronomical observatory equipped with a laser that sends ultrashort pulses of light. The pulses hit the satellite and bounce back to be caught by the station, which measure the round trip time with the speed of light formula. These measurements are instantaneous and with millimeter level precision, which can be accumulated to provide accurate measurement of orbits and a host of important scientific data. Some satellites have retroreflectors, but the method also works on space debris.

Satellite laser ranging is a proven geodetic technique with significant potential for important contributions to scientific studies of the earth/atmosphere/ocean system. It is the most accurate technique currently available to determine the geocentric position of an Earth satellite, allowing for the precise calibration of radar altimeters and separation of long-term instrumentation drift from secular changes in ocean topography.

This is a list of uncrewed spacecraft which have been intentionally destroyed at their objects of study, typically by hard landings or crash landings at the end of their respective missions and/or functionality. This list only includes spacecraft specifically instructed to crash into the surface of an astronomical body other than the Earth, and also does not include unintentionally crashed spacecraft, derelict spacecraft, or spacecraft designed as landers. Intentionally crashing spacecraft not only removes the possibility of orbital space debris and planetary contamination, but also provides the opportunity (in some cases) for terminal science given that the transient light released by the kinetic energy may be available for spectroscopy; the physical ejecta can be used for further study.

Even after soft landings had been mastered, NASA used crash landings to test whether Moon craters contained ice by crashing space probes into craters and testing the debris that got thrown out. Several rocket stages utilized during the Apollo space program were intentionally crashed on the Moon to aid seismic research, and four of the ascent stages of Apollo Lunar Modules were intentionally crashed onto the Moon after they had fulfilled their primary mission. In total at least 47 NASA rocket bodies have impacted the Moon.

Bradbury Landing is the August 6, 2012, landing site within Gale crater on planet Mars of the Mars Science Laboratory (MSL) Curiosity rover. On August 22, 2012, on what would have been his 92nd birthday, NASA named the site for author Ray Bradbury, who had died on June 5, 2012. The coordinates of the landing site on Mars are: 4°35′22″S 137°26′30″E / 4.5895°S 137.4417°E / -4.5895; 137.4417.

The rover drove away from this specific landing location in the summer of 2012, but because of the nature of landing there is no actual lander there. The track prints and blast marks are slowly blowing away in the Martian wind, as recorded by Mars orbiters.