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116-575: Vela was the name of a group of satellites developed as the Vela Hotel element of Project Vela by the United States to detect nuclear detonations and monitor Soviet Union compliance with the 1963 Partial Test Ban Treaty . Vela started out as a small budget research program in 1959. It ended 26 years later as a successful, cost-effective military space system, which also provided scientific data on natural sources of space radiation. In
232-591: A Diamant A rocket launched from the CIEES site at Hammaguir , Algeria . With Astérix, France became the sixth country to have an artificial satellite. Early satellites were built to unique designs. With advancements in technology, multiple satellites began to be built on single model platforms called satellite buses . The first standardized satellite bus design was the HS-333 geosynchronous (GEO) communication satellite launched in 1972. Beginning in 1997, FreeFlyer
348-787: A Lissajous orbit ). Earth observation satellites gather information for reconnaissance , mapping , monitoring the weather , ocean, forest, etc. Space telescopes take advantage of outer space's near perfect vacuum to observe objects with the entire electromagnetic spectrum . Because satellites can see a large portion of the Earth at once, communications satellites can relay information to remote places. The signal delay from satellites and their orbit's predictability are used in satellite navigation systems, such as GPS. Space probes are satellites designed for robotic space exploration outside of Earth, and space stations are in essence crewed satellites. The first artificial satellite launched into
464-414: A catalyst . The most commonly used propellant mixtures on satellites are hydrazine -based monopropellants or monomethylhydrazine – dinitrogen tetroxide bipropellants. Ion thrusters on satellites usually are Hall-effect thrusters , which generate thrust by accelerating positive ions through a negatively-charged grid. Ion propulsion is more efficient propellant-wise than chemical propulsion but its thrust
580-456: A standardized bus to save cost and work, the most popular of which are small CubeSats . Similar satellites can work together as groups, forming constellations . Because of the high launch cost to space, most satellites are designed to be as lightweight and robust as possible. Most communication satellites are radio relay stations in orbit and carry dozens of transponders, each with a bandwidth of tens of megahertz. Satellites are placed from
696-409: A transponder ; it creates a communication channel between a source transmitter and a receiver at different locations on Earth . Communications satellites are used for television , telephone , radio , internet , and military applications. Many communications satellites are in geostationary orbit 22,236 miles (35,785 km) above the equator , so that the satellite appears stationary at
812-591: A Satellite Vehicle", by R. R. Carhart. This expanded on potential scientific uses for satellite vehicles and was followed in June 1955 with "The Scientific Use of an Artificial Satellite", by H. K. Kallmann and W. W. Kellogg. The first artificial satellite was Sputnik 1 , launched by the Soviet Union on 4 October 1957 under the Sputnik program , with Sergei Korolev as chief designer. Sputnik 1 helped to identify
928-453: A U.S. Scout rocket from Wallops Island (Virginia, United States) with an Italian launch team trained by NASA . In similar occasions, almost all further first national satellites were launched by foreign rockets. France was the third country to launch a satellite on its own rocket. On 26 November 1965, the Astérix or A-1 (initially conceptualized as FR.2 or FR-2), was put into orbit by
1044-440: A certain amount of meteoroids are shed. The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a "dust trail" (as opposed to a comet's "dust tail" caused by the very small particles that are quickly blown away by solar radiation pressure). The frequency of fireball sightings increases by about 10–30% during the weeks of vernal equinox . Even meteorite falls are more common during
1160-462: A cosmic origin. After reviewing historical records, Heinrich Wilhelm Matthias Olbers predicted the storm's return in 1867, drawing other astronomers' attention to the phenomenon. Hubert A. Newton 's more thorough historical work led to a refined prediction of 1866, which proved correct. With Giovanni Schiaparelli 's success in connecting the Leonids (as they are called) with comet Tempel-Tuttle ,
1276-738: A deviation for any object causing a meteor. Objects smaller than meteoroids are classified as micrometeoroids and interplanetary dust . The Minor Planet Center does not use the term "meteoroid". Almost all meteoroids contain extraterrestrial nickel and iron. They have three main classifications: iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites . Stony meteoroids without these features are called " achondrites ", which are typically formed from extraterrestrial igneous activity; they contain little or no extraterrestrial iron. The composition of meteoroids can be inferred as they pass through Earth's atmosphere from their trajectories and
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#17327902073251392-545: A generic large crater-forming projectile in a manner "to imply that we do not know the precise nature of the impacting body ... whether it is a rocky or metallic asteroid, or an icy comet for example". Meteoroids also hit other bodies in the Solar System. On such stony bodies as the Moon or Mars that have little or no atmosphere, they leave enduring craters. Meteoroid collisions with solid Solar System objects, including
1508-470: A great circle every 60 seconds, and covered the whole sky every 56 hours. Sensitivity to celestial sources was severely limited by the high intrinsic detector background, equivalent to about 80% of the signal from the Crab Nebula , one of the brightest sources in the sky at these wavelengths. The Vela 5B satellite X-ray detector remained functional for over ten years. Like the previous Vela 5 satellites,
1624-418: A meteoroid would be between 100 μm and 10 m (33 ft) across. In 2010, following the discovery of asteroids below 10 m in size, Rubin and Grossman proposed a revision of the previous definition of meteoroid to objects between 10 μm (0.00039 in) and one meter (3 ft 3 in) in diameter in order to maintain the distinction. According to Rubin and Grossman, the minimum size of an asteroid
1740-582: A more rigid definition. It defines a fireball as a meteor that would have a magnitude of −3 or brighter if seen at zenith . This definition corrects for the greater distance between an observer and a meteor near the horizon. For example, a meteor of magnitude −1 at 5 degrees above the horizon would be classified as a fireball because, if the observer had been directly below the meteor, it would have appeared as magnitude −6. Fireballs reaching apparent magnitude −14 or brighter are called bolides . The IAU has no official definition of "bolide", and generally considers
1856-484: A quarter that of ice, to nickel-iron rich dense rocks. The study of meteorites also gives insights into the composition of non-ephemeral meteoroids. Most meteoroids come from the asteroid belt , having been perturbed by the gravitational influences of planets, but others are particles from comets , giving rise to meteor showers . Some meteoroids are fragments from bodies such as Mars or the Moon , that have been thrown into space by an impact. Meteoroids travel around
1972-418: A satellite's lifetime. Resource use is difficult to monitor and quantify for satellites and launch vehicles due to their commercially sensitive nature. However, aluminium is a preferred metal in satellite construction due to its lightweight and relative cheapness and typically constitutes around 40% of a satellite's mass. Through mining and refining, aluminium has numerous negative environmental impacts and
2088-573: A second. Meteors were not known to be an astronomical phenomenon until early in the nineteenth century. Before that, they were seen in the West as an atmospheric phenomenon, like lightning, and were not connected with strange stories of rocks falling from the sky. In 1807, Yale University chemistry professor Benjamin Silliman investigated a meteorite that fell in Weston, Connecticut . Silliman believed
2204-412: A size scale larger than 10 cm (3.9 in) to several meters meteor visibility is due to the atmospheric ram pressure (not friction) that heats the meteoroid so that it glows and creates a shining trail of gases and melted meteoroid particles. The gases include vaporised meteoroid material and atmospheric gases that heat up when the meteoroid passes through the atmosphere. Most meteors glow for about
2320-456: 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), the orbital speeds of meteoroids, and
2436-449: A thin cable called a tether . Recovery satellites are satellites that provide a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth. Biosatellites are satellites designed to carry living organisms, generally for scientific experimentation. Space-based solar power satellites are proposed satellites that would collect energy from sunlight and transmit it for use on Earth or other places. Since
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#17327902073252552-600: A thought experiment by Isaac Newton to explain the motion of natural satellites , in his Philosophiæ Naturalis Principia Mathematica (1687). The first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale , " The Brick Moon " (1869). The idea surfaced again in Jules Verne 's The Begum's Fortune (1879). In 1903, Konstantin Tsiolkovsky (1857–1935) published Exploring Space Using Jet Propulsion Devices , which
2668-400: Is a commercial off-the-shelf software application for satellite mission analysis, design, and operations. After the late 2010s, and especially after the advent and operational fielding of large satellite internet constellations —where on-orbit active satellites more than doubled over a period of five years—the companies building the constellations began to propose regular planned deorbiting of
2784-489: Is called meteoric dust or just meteor dust. Meteor dust particles can persist in the atmosphere for up to several months. These particles might affect climate, both by scattering electromagnetic radiation and by catalyzing chemical reactions in the upper atmosphere. Meteoroids or their fragments achieve dark flight after deceleration to terminal velocity . Dark flight starts when they decelerate to about 2–4 km/s (4,500–8,900 mph). Larger fragments fall further down
2900-610: Is currently unclear. The visibility of man-made objects in the night sky may also impact people's linkages with the world, nature, and culture. At all points of a satellite's lifetime, its movement and processes are monitored on the ground through a network of facilities. The environmental cost of the infrastructure as well as day-to-day operations is likely to be quite high, but quantification requires further investigation. Particular threats arise from uncontrolled de-orbit. Some notable satellite failures that polluted and dispersed radioactive materials are Kosmos 954 , Kosmos 1402 and
3016-399: Is dependent on rocket design and fuel type. The amount of green house gases emitted by rockets is considered trivial as it contributes significantly less, around 0.01%, than the aviation industry yearly which itself accounts for 2-3% of the total global greenhouse gas emissions. Rocket emissions in the stratosphere and their effects are only beginning to be studied and it is likely that
3132-473: Is deployed for military or intelligence purposes, it is known as a spy satellite or reconnaissance satellite. Their uses include early missile warning, nuclear explosion detection, electronic reconnaissance, and optical or radar imaging surveillance. Navigational satellites are satellites that use radio time signals transmitted to enable mobile receivers on the ground to determine their exact location. The relatively clear line of sight between
3248-558: Is given by what can be discovered from Earth-bound telescopes, so the distinction between meteoroid and asteroid is fuzzy. Some of the smallest asteroids discovered (based on absolute magnitude H ) are 2008 TS 26 with H = 33.2 and 2011 CQ 1 with H = 32.1 both with an estimated size of one m (3 ft 3 in). In April 2017, the IAU adopted an official revision of its definition, limiting size to between 30 μm (0.0012 in) and one meter in diameter, but allowing for
3364-517: Is most used in archaeology , cartography , environmental monitoring , meteorology , and reconnaissance applications. As of 2021, there are over 950 Earth observation satellites, with the largest number of satellites operated with Planet Labs . Weather satellites monitor clouds , city lights , fires , effects of pollution , auroras , sand and dust storms , snow cover, ice mapping, boundaries of ocean currents , energy flows, etc. Environmental monitoring satellites can detect changes in
3480-581: Is one of the most carbon-intensive metals. Satellite manufacturing also requires rare elements such as lithium , gold , and gallium , some of which have significant environmental consequences linked to their mining and processing and/or are in limited supply. Launch vehicles require larger amounts of raw materials to manufacture and the booster stages are usually dropped into the ocean after fuel exhaustion. They are not normally recovered. Two empty boosters used for Ariane 5 , which were composed mainly of steel, weighed around 38 tons each, to give an idea of
3596-438: Is quickly overtaken by the expanding atmospheric shock wave composed of ionised gas. Although it emits a considerable amount of light itself it is opaque and prevents the far brighter fireball from shining through. As the shock wave expands, it cools down becoming more transparent allowing the much hotter and brighter fireball to become visible again. No single natural phenomenon is known to produce this signature, although there
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3712-430: Is the chemical propellant used which then releases ammonia , hydrogen and nitrogen as gas into the upper atmosphere. Also, the environment of the outer atmosphere causes the degradation of exterior materials. The atomic oxygen in the upper atmosphere oxidises hydrocarbon-based polymers like Kapton , Teflon and Mylar that are used to insulate and protect the satellite which then emits gasses like CO 2 and CO into
3828-425: Is very small (around 0.5 N or 0.1 lb f ), and thus requires a longer burn time. The thrusters usually use xenon because it is inert , can be easily ionized , has a high atomic mass and storable as a high-pressure liquid. Most satellites use solar panels to generate power, and a few in deep space with limited sunlight use radioisotope thermoelectric generators . Slip rings attach solar panels to
3944-912: The American Rocket Society , the National Science Foundation , and the International Geophysical Year, the Army and Navy worked on Project Orbiter with two competing programs. The army used the Jupiter C rocket , while the civilian–Navy program used the Vanguard rocket to launch a satellite. Explorer 1 became the United States' first artificial satellite, on 31 January 1958. The information sent back from its radiation detector led to
4060-586: The Chinese military shot down an aging weather satellite, followed by the US Navy shooting down a defunct spy satellite in February 2008. On 18 November 2015, after two failed attempts, Russia successfully carried out a flight test of an anti-satellite missile known as Nudol . On 27 March 2019, India shot down a live test satellite at 300 km altitude in 3 minutes, becoming the fourth country to have
4176-471: The Greek βολίς ( bolis ) which can mean a missile or to flash . If the magnitude of a bolide reaches −17 or brighter it is known as a superbolide . A relatively small percentage of fireballs hit Earth's atmosphere and then pass out again: these are termed Earth-grazing fireballs . Such an event happened in broad daylight over North America in 1972 . Another rare phenomenon is a meteor procession , where
4292-574: The Moon or Mars . A meteor or shooting star is the visible passage of a meteoroid, comet, or asteroid entering Earth's atmosphere . At a speed typically in excess of 20 km/s (72,000 km/h; 45,000 mph), aerodynamic heating of that object produces a streak of light, both from the glowing object and the trail of glowing particles that it leaves in its wake. Meteors typically become visible when they are about 100 km (62 mi) above sea level. A series of many meteors appearing seconds or minutes apart and appearing to originate from
4408-565: The Netherlands , Norway , Pakistan , Poland , Russia , Saudi Arabia , South Africa , Spain , Switzerland , Thailand , Turkey , Ukraine , the United Kingdom and the United States , had some satellites in orbit. Japan's space agency (JAXA) and NASA plan to send a wooden satellite prototype called LingoSat into orbit in the summer of 2024. They have been working on this project for few years and sent first wood samples to
4524-509: The Phoenicids can make atmospheric entry at as slow as about 11 km/s. On January 17, 2013, at 05:21 PST, a one-meter-sized comet from the Oort cloud entered Earth atmosphere over California and Nevada . The object had a retrograde orbit with perihelion at 0.98 ± 0.03 AU . It approached from the direction of the constellation Virgo (which was in the south about 50° above
4640-470: The Transit 5-BN-3 . When in a controlled manner satellites reach the end of life they are intentionally deorbited or moved to a graveyard orbit further away from Earth in order to reduce space debris . Physical collection or removal is not economical or even currently possible. Moving satellites out to a graveyard orbit is also unsustainable because they remain there for hundreds of years. It will lead to
4756-576: The White House announced on 29 July 1955 that the U.S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard . On 31 July, the Soviet Union announced its intention to launch a satellite by the fall of 1957. Sputnik 2 was launched on 3 November 1957 and carried the first living passenger into orbit, a dog named Laika . The dog was sent without possibility of return. In early 1955, after being pressured by
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4872-438: The gravity well of Earth. Meteors become visible between about 75 to 120 km (250,000 to 390,000 ft) above Earth. They usually disintegrate at altitudes of 50 to 95 km (160,000 to 310,000 ft). Meteors have roughly a fifty percent chance of a daylight (or near daylight) collision with Earth. Most meteors are, however, observed at night, when darkness allows fainter objects to be recognized. For bodies with
4988-403: The strewn field . The visible light produced by a meteor may take on various hues, depending on the chemical composition of the meteoroid, and the speed of its movement through the atmosphere. As layers of the meteoroid abrade and ionize, the colour of the light emitted may change according to the layering of minerals. Colours of meteors depend on the relative influence of the metallic content of
5104-801: The 1970s, the nuclear detection mission was taken over by the Defense Support Program (DSP) satellites. In the late 1980s, it was augmented by the Navstar Global Positioning System (GPS) satellites. The program is now called the Integrated Operational NuDet (Nuclear Detonation) Detection System ( IONDS ). Twelve satellites were built, six of the Vela Hotel design and six of the Advanced Vela design. The Vela Hotel series
5220-607: The Air Force claimed them to be the world's longest operating satellites. They remained in orbit until their orbits decayed at the end of 1992. The original Vela satellites were equipped with 12 external X-ray detectors and 18 internal neutron and gamma-ray detectors. They were equipped with solar panels generating 90 watts. The Advanced Vela satellites were additionally equipped with two non-imaging silicon photodiode sensors called bhangmeters which monitored light levels over sub-millisecond intervals. They could determine
5336-457: The Earth's vegetation , atmospheric trace gas content, sea state, ocean color, and ice fields. By monitoring vegetation changes over time, droughts can be monitored by comparing the current vegetation state to its long term average. Anthropogenic emissions can be monitored by evaluating data of tropospheric NO 2 and SO 2 . A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via
5452-417: The Earth's orbit was the Soviet Union 's Sputnik 1 , on October 4, 1957. As of December 31, 2022, there are 6,718 operational satellites in the Earth's orbit, of which 4,529 belong to the United States (3,996 commercial), 590 belong to China, 174 belong to Russia, and 1,425 belong to other nations. The first published mathematical study of the possibility of an artificial satellite was Newton's cannonball ,
5568-500: The Earth, called remote sensing . Most Earth observation satellites are placed in low Earth orbit for a high data resolution, though some are placed in a geostationary orbit for an uninterrupted coverage. Some satellites are placed in a Sun-synchronous orbit to have consistent lighting and obtain a total view of the Earth. Depending on the satellites' functions, they might have a normal camera , radar , lidar , photometer , or atmospheric instruments. Earth observation satellite's data
5684-504: The Moon and the Sun. Satellites utilize ultra-white reflective coatings to prevent damage from UV radiation. Without orbit and orientation control, satellites in orbit will not be able to communicate with ground stations on the Earth. Chemical thrusters on satellites usually use monopropellant (one-part) or bipropellant (two-parts) that are hypergolic . Hypergolic means able to combust spontaneously when in contact with each other or to
5800-425: The Moon, Mercury , Callisto , Ganymede , and most small moons and asteroids , create impact craters, which are the dominant geographic features of many of those objects. On other planets and moons with active surface geological processes, such as Earth, Venus , Mars , Europa , Io , and Titan , visible impact craters may become eroded , buried, or transformed by tectonics over time. In early literature, before
5916-444: The Sun in a variety of orbits and at various velocities. The fastest move at about 42 km/s (94,000 mph) through space in the vicinity of Earth's orbit. This is escape velocity from the Sun, equal to the square root of two times Earth's speed, and is the upper speed limit of objects in the vicinity of Earth, unless they come from interstellar space. Earth travels at about 29.6 km/s (66,000 mph), so when meteoroids meet
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#17327902073256032-715: The Vela 6 nuclear test detection satellites were part of a program run jointly by the Advanced Research Projects of the U.S. Department of Defense and the U.S. Atomic Energy Commission, managed by the U.S. Air Force. The twin spacecraft, Vela 6A and 6B, were launched on 8 April 1970. Data from the Vela 6 satellites were used to look for correlations between gamma-ray bursts and X-ray events. At least two good candidates were found, GB720514 and GB740723. The X-ray detectors failed on Vela 6B on 27 January 1972 and on Vela 6A on 12 March 1972. Some controversy still surrounds
6148-544: The Vela program. On 22 September 1979 the Vela 5B satellite (also known as Vela 10 and IRON 6911) detected the characteristic double flash of an atmospheric nuclear explosion near the Prince Edward Islands . Still unsatisfactorily explained, this event has become known as the Vela incident . President Jimmy Carter initially deemed the event to be evidence of a joint Israeli and South African nuclear test , though
6264-478: The XC Detector aboard Vela 5A and 5B also discovered and announced the first X-ray burst ever reported. The announcement of this discovery predated the initial announcement of the discovery of gamma-ray bursts by 2 years. In front of each crystal was a slat collimator providing a full width at half maximum (FWHM) aperture of c. 6.1 × 6.1 degrees. The effective detector area was c. 26 cm. The detectors scanned
6380-460: The atmosphere and hits the ground without being destroyed. Meteorites are sometimes, but not always, found in association with hypervelocity impact craters ; during energetic collisions, the entire impactor may be vaporized, leaving no meteorites. Geologists use the term, "bolide", in a different sense from astronomers to indicate a very large impactor . For example, the USGS uses the term to mean
6496-636: The atmosphere as a meteor and has impacted the ground. In 1961, the International Astronomical Union (IAU) defined a meteoroid as "a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom". In 1995, Beech and Steel, writing in the Quarterly Journal of the Royal Astronomical Society , proposed a new definition where
6612-417: The atmosphere head-on (which only occurs when meteors are in a retrograde orbit such as the Leonids , which are associated with the retrograde comet 55P/Tempel–Tuttle ) the combined speed may reach about 71 km/s (160,000 mph) (see Specific energy#Astrodynamics ). Meteoroids moving through Earth's orbital space average about 20 km/s (45,000 mph), but due to Earth's gravity meteors such as
6728-399: The atmosphere, and thus ionization trails can be found in the upper atmosphere more or less continuously. When radio waves are bounced off these trails, it is called meteor burst communications . Meteor radars can measure atmospheric density and winds by measuring the decay rate and Doppler shift of a meteor trail. Most meteoroids burn up when they enter the atmosphere. The left-over debris
6844-455: The atmosphere. Given the current surge in satellites in the sky, soon hundreds of satellites may be clearly visible to the human eye at dark sites. It is estimated that the overall levels of diffuse brightness of the night skies has increased by up to 10% above natural levels. This has the potential to confuse organisms, like insects and night-migrating birds, that use celestial patterns for migration and orientation. The impact this might have
6960-603: The atmosphere. For example, SpaceX Starlink satellites, the first large satellite internet constellation to exceed 1000 active satellites on orbit in 2020, are designed to be 100% demisable and burn up completely on their atmospheric reentry at the end of their life, or in the event of an early satellite failure. In different periods, many countries, such as Algeria , Argentina , Australia , Austria , Brazil , Canada , Chile , China , Denmark , Egypt , Finland , France , Germany , India , Iran , Israel , Italy , Japan , Kazakhstan , South Korea , Malaysia , Mexico ,
7076-447: The capability to destroy live satellites. The environmental impact of satellites is not currently well understood as they were previously assumed to be benign due to the rarity of satellite launches. However, the exponential increase and projected growth of satellite launches are bringing the issue into consideration. The main issues are resource use and the release of pollutants into the atmosphere which can happen at different stages of
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#17327902073257192-573: The cosmic origin of meteors was firmly established. Still, they remain an atmospheric phenomenon and retain their name "meteor" from the Greek word for "atmospheric". A fireball is a brighter-than-usual meteor that also becomes visible when about 100 km from sea level. The International Astronomical Union (IAU) defines a fireball as "a meteor brighter than any of the planets" ( apparent magnitude −4 or greater). The International Meteor Organization (an amateur organization that studies meteors) has
7308-551: The density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere . The unanticipated announcement of Sputnik 1's success precipitated the Sputnik crisis in the United States and ignited the so-called Space Race within the Cold War . In the context of activities planned for the International Geophysical Year (1957–1958),
7424-546: The discovery of the Earth's Van Allen radiation belts . The TIROS-1 spacecraft, launched on April 1, 1960, as part of NASA's Television Infrared Observation Satellite (TIROS) program, sent back the first television footage of weather patterns to be taken from space. In June 1961, three and a half years after the launch of Sputnik 1, the United States Space Surveillance Network cataloged 115 Earth-orbiting satellites. While Canada
7540-433: The early evening, increasing chances of eyewitness reports. This explains a part, but perhaps not all of the seasonal variation. Research is in progress for mapping the orbits of the meteors to gain a better understanding of the phenomenon. In a range of countries networks of sky observing installations have been set up to monitor meteors. A meteorite is a portion of a meteoroid or asteroid that survives its passage through
7656-484: The earth's climate. After deorbiting 70% of satellites end up in the ocean and are rarely recovered. Using wood as an alternative material has been posited in order to reduce pollution and debris from satellites that reenter the atmosphere. Space debris pose dangers to the spacecraft (including satellites) in or crossing geocentric orbits and have the potential to drive a Kessler syndrome which could potentially curtail humanity from conducting space endeavors in
7772-486: The ecliptic is (in the northern hemisphere) high in the sky in the late afternoon and early evening. This means that fireball radiants with an asteroidal source are high in the sky (facilitating relatively high rates) at the moment the meteoroids "catch up" with Earth, coming from behind going in the same direction as Earth. This causes relatively low relative speeds and from this low entry speeds, which facilitates survival of meteorites. It also generates high fireball rates in
7888-442: The existence of gamma-ray bursts , now recognised as the most violent events in the universe. The scintillation X-ray detector (XC) aboard Vela 5A and its twin Vela 5B consisted of two 1 mm thick NaI(Tl) crystals mounted on photomultiplier tubes and covered by a 0.13 mm thick beryllium window. Electronic thresholds provided two energy channels, 3–12 keV and 6–12 keV. In addition to the x-ray Nova announcement indicated above
8004-419: The final rocket stages that place satellites in orbit and formerly useful satellites that later become defunct. Except for passive satellites , most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope thermoelectric generators (RTGs). Most satellites also have a method of communication to ground stations , called transponders . Many satellites use
8120-444: The further pollution of space and future issues with space debris. When satellites deorbit much of it is destroyed during re-entry into the atmosphere due to the heat. This introduces more material and pollutants into the atmosphere. There have been concerns expressed about the potential damage to the ozone layer and the possibility of increasing the earth's albedo , reducing warming but also resulting in accidental geoengineering of
8236-519: The future. Meteoroid A meteoroid ( / ˈ m iː t i ə r ɔɪ d / MEE -tee-ə-royd ) is a small rocky or metallic body in outer space . Meteoroids are distinguished as objects significantly smaller than asteroids , ranging in size from grains to objects up to a meter 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
8352-514: The generation of these sounds may partially explain them. For example, scientists at NASA suggested that the turbulent ionized wake of a meteor interacts with Earth's magnetic field , generating pulses of radio waves . As the trail dissipates, megawatts of electromagnetic power could be released, with a peak in the power spectrum at audio frequencies . Physical vibrations induced by the electromagnetic impulses would then be heard if they are powerful enough to make grasses, plants, eyeglass frames,
8468-447: The ground). Some imaging satellites chose a Sun-synchronous orbit because they can scan the entire globe with similar lighting. As the number of satellites and space debris around Earth increases, the threat of collision has become more severe. A small number of satellites orbit other bodies (such as the Moon , Mars , and the Sun ) or many bodies at once (two for a halo orbit , three for
8584-457: The hearer's own body (see microwave auditory effect ), and other conductive materials vibrate. This proposed mechanism, although proven plausible by laboratory work, remains unsupported by corresponding measurements in the field. Sound recordings made under controlled conditions in Mongolia in 1998 support the contention that the sounds are real. (Also see Bolide .) A meteor shower is
8700-400: The heat of entry and force of impact. A noted 4-metre (13 ft) asteroid , 2008 TC 3 , was observed in space on a collision course with Earth on 6 October 2008 and entered Earth's atmosphere the next day, striking a remote area of northern Sudan. It was the first time that a meteoroid had been observed in space and tracked prior to impacting Earth. NASA has produced a map showing
8816-516: The horizon at the time), and collided head-on with Earth's atmosphere at 72 ± 6 km/s (161,000 ± 13,000 mph) vaporising more than 100 km (330,000 ft) above ground over a period of several seconds. When meteoroids intersect with Earth's atmosphere at night, they are likely to become visible as meteors . If meteoroids survive the entry through the atmosphere and reach Earth's surface, they are called meteorites . Meteorites are transformed in structure and chemistry by
8932-412: The impact of regulated ozone-depleting substances. Whilst emissions of water vapour are largely deemed as inert, H 2 O is the source gas for HO x and can also contribute to ozone loss through the formation of ice particles. Black carbon particles emitted by rockets can absorb solar radiation in the stratosphere and cause warming in the surrounding air which can then impact the circulatory dynamics of
9048-462: The impacts will be more critical than emissions in the troposphere. The stratosphere includes the ozone layer and pollutants emitted from rockets can contribute to ozone depletion in a number of ways. Radicals such as NO x , HO x , and ClO x deplete stratospheric O 3 through intermolecular reactions and can have huge impacts in trace amounts. However, it is currently understood that launch rates would need to increase by ten times to match
9164-522: The last satellite to be shut down was Vehicle 9 in 1984, which had been launched in 1969 and had lasted nearly 15 years. The Vela series began with the launch of Vela 1A and 1B on 17 October 1963, a flight also marking the maiden voyage of the Atlas-Agena SLV-3 vehicle. The second pair of satellites launched on 17 July 1964, and the third on 20 July 1965. The last launch miscarried slightly when one Atlas vernier engine shut down at liftoff, while
9280-658: The light spectra of the resulting meteor. Their effects on radio signals also give information, especially useful for daytime meteors, which are otherwise very difficult to observe. From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams (see meteor showers ) often associated with a parent comet , others apparently sporadic. Debris from meteoroid streams may eventually be scattered into other orbits. The light spectra, combined with trajectory and light curve measurements, have yielded various compositions and densities, ranging from fragile snowball-like objects with density about
9396-415: The location of a nuclear explosion to within about 3,000 miles. Atmospheric nuclear explosions produce a unique signature, often called a "double-humped curve": a short and intense flash lasting around 1 millisecond, followed by a second much more prolonged and less intense emission of light taking a fraction of a second to several seconds to build up. The effect occurs because the surface of the early fireball
9512-546: The matter particularly urgent, the team at the Los Alamos Scientific Laboratory , led by Ray Klebesadel , filed the data away for investigation. As additional Vela satellites were launched with better instruments, the Los Alamos team continued to find inexplicable gamma-ray bursts in their data. By analyzing the different arrival times of the bursts as detected by different satellites, the team
9628-638: The meteor breaks up into several fireballs traveling nearly parallel to the surface of Earth. A steadily growing number of fireballs are recorded at the American Meteor Society every year. There are probably more than 500,000 fireballs a year, but most go unnoticed because most occur over the ocean and half occur during daytime. A European Fireball Network and a NASA All-sky Fireball Network detect and track many fireballs. The entry of meteoroids into Earth's atmosphere produces three main effects: ionization of atmospheric molecules, dust that
9744-474: The meteor had a cosmic origin, but meteors did not attract much attention from astronomers until the spectacular meteor storm of November 1833. People all across the eastern United States saw thousands of meteors, radiating from a single point in the sky. Careful observers noticed that the radiant , as the point is called, moved with the stars, staying in the constellation Leo. The astronomer Denison Olmsted extensively studied this storm, concluding that it had
9860-413: The meteoroid sheds, and the sound of passage. During the entry of a meteoroid or asteroid into the upper atmosphere , an ionization trail is created, where the air molecules are ionized by the passage of the meteor. Such ionization trails can last up to 45 minutes at a time. Small, sand-grain sized meteoroids are entering the atmosphere constantly, essentially every few seconds in any given region of
9976-569: The meteoroid versus the superheated air plasma, which its passage engenders: The sound generated by a meteor in the upper atmosphere, such as a sonic boom , typically arrives many seconds after the visual light from a meteor disappears. Occasionally, as with the Leonid meteor shower of 2001, "crackling", "swishing", or "hissing" sounds have been reported, occurring at the same instant as a meteor flare. Similar sounds have also been reported during intense displays of Earth's auroras . Theories on
10092-400: The mid-2000s, satellites have been hacked by militant organizations to broadcast propaganda and to pilfer classified information from military communication networks. For testing purposes, satellites in low earth orbit have been destroyed by ballistic missiles launched from the Earth. Russia , United States , China and India have demonstrated the ability to eliminate satellites. In 2007,
10208-413: The most notable asteroid collisions with Earth and its atmosphere from 1994 to 2013 from data gathered by U.S. government sensors (see below). A meteor , known colloquially as a shooting star or falling star , is the visible passage of a glowing meteoroid , micrometeoroid , comet or asteroid through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in
10324-725: The most potent scientific tools of the Twentieth Century." The United States had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy . Project RAND eventually released the report, but considered the satellite to be a tool for science, politics, and propaganda, rather than a potential military weapon. In 1946, American theoretical astrophysicist Lyman Spitzer proposed an orbiting space telescope . In February 1954, Project RAND released "Scientific Uses for
10440-402: The northern hemisphere's spring season. Although this phenomenon has been known for quite some time, the reason behind the anomaly is not fully understood by scientists. Some researchers attribute this to an intrinsic variation in the meteoroid population along Earth's orbit, with a peak in big fireball-producing debris around spring and early summer. Others have pointed out that during this period
10556-451: The now-declassified report of a scientific panel he subsequently appointed while seeking reelection concluded that it was probably not the event of a nuclear explosion. In 2018, a new study confirmed that it is highly likely that it was a nuclear test, conducted by Israel. An alternative explanation involves a magnetospheric event affecting the instruments. An earlier incident occurred when an intense solar storm on 4 August 1972 triggered
10672-557: The older satellites that reached the end of life , as a part of the regulatory process of obtaining a launch license. The largest artificial satellite ever is the International Space Station . By the early 2000s, and particularly after the advent of CubeSats and increased launches of microsats —frequently launched to the lower altitudes of low Earth orbit (LEO)—satellites began to more frequently be designed to get destroyed, or breakup and burnup entirely in
10788-600: The other vernier operated at above-normal thrust levels. This resulted in a slightly lower than normal inclination for the satellites, however the mission was carried out successfully. The problem was traced to a malfunction of the vernier LOX poppet valve. Subsequent Vela satellites were switched to the Titan IIIC booster due to their increased weight and complexity. Three more sets were launched on 28 April 1967, 23 May 1969, and 8 April 1970. The last pair of Vela satellites operated until 1985, when they were finally shut down;
10904-550: The possible use of communications satellites for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet. In May 1946, the United States Air Force 's Project RAND released the Preliminary Design of an Experimental World-Circling Spaceship , which stated "A satellite vehicle with appropriate instrumentation can be expected to be one of
11020-412: The quantity of materials that are often left in the ocean. Rocket launches release numerous pollutants into every layer of the atmosphere, especially affecting the atmosphere above the tropopause where the byproducts of combustion can reside for extended periods. These pollutants can include black carbon , CO 2 , nitrogen oxides (NO x ), aluminium and water vapour , but the mix of pollutants
11136-415: The result of an interaction between a planet, such as Earth, and streams of debris from a comet or other source. The passage of Earth through cosmic debris from comets and other sources is a recurring event in many cases. Comets can produce debris by water vapor drag, as demonstrated by Fred Whipple in 1951, and by breakup. Each time a comet swings by the Sun in its orbit , some of its ice vaporizes and
11252-403: The same fixed point in the sky is called a meteor shower . An estimated 25 million meteoroids, micrometeoroids and other space debris enter Earth's atmosphere each day, which results in an estimated 15,000 tonnes of that material entering the atmosphere each year. A meteorite is the remains of a meteoroid that has survived the ablation of its surface material during its passage through
11368-427: The same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit , where antennas on the ground have to follow the position of the satellites and switch between satellites frequently. When an Earth observation satellite or a communications satellite
11484-409: The satellite; the slip rings can rotate to be perpendicular with the sunlight and generate the most power. All satellites with a solar panel must also have batteries , because sunlight is blocked inside the launch vehicle and at night. The most common types of batteries for satellites are lithium-ion , and in the past nickel–hydrogen . Earth observation satellites are designed to monitor and survey
11600-404: The satellites and receivers on the ground, combined with ever-improving electronics, allows satellite navigation systems to measure location to accuracies on the order of a few meters in real time. Astronomical satellites are satellites used for observation of distant planets, galaxies, and other outer space objects. Tether satellites are satellites that are connected to another satellite by
11716-415: The significance of impact cratering was widely recognised, the terms cryptoexplosion or cryptovolcanic structure were often used to describe what are now recognised as impact-related features on Earth. Molten terrestrial material ejected from a meteorite impact crater can cool and solidify into an object known as a tektite . These are often mistaken for meteorites. Terrestrial rock, sometimes with pieces of
11832-399: The size of a grain of sand, i.e. they are usually millimeter-sized 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
11948-540: The space in 2021 to test the material's resilience to space conditions. Most satellites use chemical or ion propulsion to adjust or maintain their orbit , coupled with reaction wheels to control their three axis of rotation or attitude. Satellites close to Earth are affected the most by variations in the Earth's magnetic , gravitational field and the Sun's radiation pressure ; satellites that are further away are affected more by other bodies' gravitational field by
12064-458: The special conditions of space could be useful for scientific experiments. The book described geostationary satellites (first put forward by Konstantin Tsiolkovsky ) and discussed the communication between them and the ground using radio, but fell short with the idea of using satellites for mass broadcasting and as telecommunications relays. In a 1945 Wireless World article, English science fiction writer Arthur C. Clarke described in detail
12180-459: The stratosphere. Both warming and changes in circulation can then cause depletion of the ozone layer. Several pollutants are released in the upper atmospheric layers during the orbital lifetime of LEO satellites. Orbital decay is caused by atmospheric drag and to keep the satellite in the correct orbit the platform occasionally needs repositioning. To do this nozzle-based systems use a chemical propellant to create thrust. In most cases hydrazine
12296-409: The surface to the orbit by launch vehicles , high enough to avoid orbital decay by the atmosphere . Satellites can then change or maintain the orbit by propulsion , usually by chemical or ion thrusters . As of 2018, about 90% of the satellites orbiting the Earth are in low Earth orbit or geostationary orbit ; geostationary means the satellites stay still in the sky (relative to a fixed point on
12412-589: The system to event mode as if an explosion occurred, but this was quickly resolved by personnel monitoring the data in real-time. Satellite A satellite or artificial satellite is an object, typically a spacecraft , placed into orbit around a celestial body . They have a variety of uses, including communication relay, weather forecasting , navigation ( GPS ), broadcasting , scientific research, and Earth observation. Additional military uses are reconnaissance, early warning , signals intelligence and, potentially, weapon delivery. Other satellites include
12528-473: The term synonymous with "fireball". Astronomers often use "bolide" to identify an exceptionally bright fireball, particularly one that explodes in a meteor air burst . They are sometimes called detonating fireballs. It may also be used to mean a fireball which creates audible sounds. In the late twentieth century, bolide has also come to mean any object that hits Earth and explodes, with no regard to its composition (asteroid or comet). The word bolide comes from
12644-503: The upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake. Although a meteor may seem to be a few thousand feet from the Earth, meteors typically occur in the mesosphere at altitudes from 76 to 100 km (250,000 to 330,000 ft). 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
12760-401: Was able to determine rough estimates for the sky positions of sixteen bursts and definitively rule out a terrestrial or solar origin. Contrary to popular belief, the data was never classified. After thorough analysis, the findings were published in 1973 as an Astrophysical Journal article entitled "Observations of Gamma-Ray Bursts of Cosmic Origin". This alerted the astronomical community to
12876-501: Was about one-third of the distance to the Moon . The first Vela Hotel pair was launched on 17 October 1963, one week after the Partial Test Ban Treaty went into effect, and the last in 1965. They had a design life of six months, but were only actually shut down after five years. Advanced Vela pairs were launched in 1967, 1969, and 1970. They had a nominal design life of 18 months, later changed to seven years. However,
12992-408: Was required for these instruments, and these larger satellites consumed 120 watts generated from solar panels. Serendipitously , the Vela satellites were the first devices ever to detect cosmic gamma ray bursts . On 2 July 1967, at 14:19 UTC, the Vela 4 and Vela 3 satellites detected a flash of gamma radiation unlike any known nuclear weapons signature. Uncertain what had happened but not considering
13108-462: Was speculation that the Velas could record exceptionally rare natural double events, such as a meteoroid strike on the spacecraft that produces a bright flash or triggering on a lightning superbolt in the Earth's atmosphere, as may have occurred in the Vela incident . They were also equipped with sensors which could detect the electromagnetic pulse from an atmospheric explosion. Additional power
13224-426: Was the first academic treatise on the use of rocketry to launch spacecraft. He calculated the orbital speed required for a minimal orbit, and inferred that a multi-stage rocket fueled by liquid propellants could achieve this. Herman Potočnik explored the idea of using orbiting spacecraft for detailed peaceful and military observation of the ground in his 1928 book, The Problem of Space Travel . He described how
13340-483: Was the third country to build a satellite which was launched into space, it was launched aboard an American rocket from an American spaceport. The same goes for Australia, whose launch of the first satellite involved a donated U.S. Redstone rocket and American support staff as well as a joint launch facility with the United Kingdom. The first Italian satellite San Marco 1 was launched on 15 December 1964 on
13456-475: Was to detect nuclear tests in space, while the Advanced Vela series was to detect not only nuclear explosions in space but also in the atmosphere. All spacecraft were manufactured by TRW and launched in pairs, either on an Atlas – Agena or Titan III -C boosters. They were placed in orbits of 118,000 km (73,000 miles) to avoid particle radiation trapped in the Van Allen radiation belts . Their apogee
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