1.
Earth observation satellite
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Most Earth observation satellites carry instruments that should be operated at a relatively low altitude. Altitudes below 500-600 kilometers are in general avoided, though, because of the significant air-drag at such low altitudes making frequent orbit reboost maneuvres necessary. The Earth observation satellites ERS-1, ERS-2 and Envisat of European Space Agency as well as the MetOp spacecraft of EUMETSAT are all operated at altitudes of about 800 km. The Proba-1, Proba-2 and SMOS spacecraft of European Space Agency are observing the Earth from an altitude of about 700 km, the Earth observation satellites of UAE, DubaiSat-1 & DubaiSat-2 are also placed in Low Earth Orbits orbits and providing satellite imagery of various parts of the Earth. To get global coverage with a low orbit it must be a polar orbit or nearly so, spacecraft carrying instruments for which an altitude of 36000 km is suitable sometimes use a geostationary orbit. Such an orbit allows uninterrupted coverage of more than 1/3 of the Earth, three geostationary spacecraft at longitudes separated with 120 deg can cover the whole Earth except the extreme polar regions. This type of orbit is used for meteorological satellites. A weather satellite is a type of satellite that is used to monitor the weather. These meteorological satellites, however, see more than clouds and cloud systems, weather satellite images helped in monitoring the volcanic ash cloud from Mount St. Helens and activity from other volcanoes such as Mount Etna. 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 NO2 and SO2. These types of satellites are almost always in Sun synchronous and frozen orbits, the Sun synchronous orbit is in general sufficiently close to polar to get the desired global coverage while the relatively constant geometry to the Sun mostly is an advantage for the instruments. The frozen orbit is selected as this is the closest to an orbit that is possible in the gravitational field of the Earth. Terrain can be mapped from space with the use of satellites, such as Radarsat-1 and TerraSAR-X. campevans. org/_CE/html/tiros1-2. html
2.
European Space Agency
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The European Space Agency is an intergovernmental organisation of 22 member states, dedicated to the exploration of space. Established in 1975 and headquartered in Paris, France, ESA has a staff of about 2,000. The main European launch vehicle Ariane 5 is operated through Arianespace with ESA sharing in the costs of launching, after World War II, many European scientists left Western Europe in order to work with the United States. The meeting was attended by representatives from eight countries, including Harrie Massey. The Western European nations decided to have two different agencies, one concerned with developing a system, ELDO, and the precursor of the European Space Agency. The latter was established on 20 March 1964 by an agreement signed on 14 June 1962, from 1968 to 1972, ESRO launched seven research satellites. ESA in its current form was founded with the ESA Convention in 1975, ESA has 10 founding member states, Belgium, Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, Switzerland and the United Kingdom. These signed the ESA Convention in 1975 and deposited the instruments of ratification by 1980, during this interval the agency functioned in a de facto fashion. ESA launched its first major scientific mission in 1975, Cos-B, ESA joined NASA in the IUE, the worlds first high-orbit telescope, which was launched in 1978 and operated very successfully for 18 years. A number of successful Earth-orbit projects followed, and in 1986 ESA began Giotto, its first deep-space mission, to study the comets Halley and Grigg–Skjellerup. Hipparcos, a mission, was launched in 1989 and in the 1990s SOHO, Ulysses. Recent scientific missions in co-operation with NASA include the Cassini–Huygens space probe, as the successor of ELDO, ESA has also constructed rockets for scientific and commercial payloads. Ariane 1, launched in 1979, brought mostly commercial payloads into orbit from 1984 onward, the successor launch vehicle of Ariane 5, the Ariane 6 is already in the definition stage and is envisioned to enter service in the 2020s. The beginning of the new millennium saw ESA become, along with agencies like NASA, JAXA, ISRO, CSA and Roscosmos, one of the major participants in scientific space research. Although ESA had relied on co-operation with NASA in previous decades, especially the 1990s, changed circumstances led to decisions to rely more on itself, a 2011 press issue thus stated, Russia is ESAs first partner in its efforts to ensure long-term access to space. ESA maintains its scientific and research projects mainly for astronomy-space missions such as Corot, launched on 27 December 2006 and this is the reason space exploration is an integral part of overall space activities. It has always been so, and it will be more important in the future. ESA describes its work in two overlapping ways, For the general public the various fields of work are described as Activities, Member states participate to varying degrees in the mandatory and optional space programmes
3.
Astrium
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Astrium was an aerospace manufacturer subsidiary of the European Aeronautic Defence and Space Company that provided civil and military space systems and services from 2006 to 2013. In 2012, Astrium had a turnover of €5.8 billion and 18,000 employees in France, Germany, the United Kingdom, Spain, Astrium was a member of Institute of Space, its Applications and Technologies. In late 2013 Astrium was merged with Cassidian, the division of EADS. EADS itself was reorganized as the Airbus Group, with three divisions that include Airbus, Airbus Defence and Space, and Airbus Helicopters, Astrium Satellites was one of the three business units of Astrium, a subsidiary of EADS. EADS Astrium Satellites employs around 8,348 people on nine sites in the United Kingdom, France, Germany, as of 15 October 2012, the CEO of Astrium is Eric Beranger who took over from Evert Dudok who became Astrium Services. Astrium was formed in 2000 by the merger of Matra Marconi Space with the division of DaimlerChrysler Aerospace AG. Henceforth Astrium was a joint venture between EADS and BAE Systems, on 16 June 2003 the minority shareholder, BAE Systems, sold its 25% share to EADS, making EADS the sole shareholder. Astrium became EADS Astrium Satellites and in a wider restructuring became the constituent of EADS Astrium. Also, Paradigm Secure Communications, initially created by Astrium in the frame of the Skynet 5 contract for the UK Ministry of Defence became the constituent of EADS SPACE Services. CASA Espacio became part of EADS Astrium on 1 January 2004, EADS Astrium is the sole shareholder of Infoterra Ltd. On 1 July 2006, the French subsidiary of EADS Astrium, EADS Astrium SAS, the name of the new company is Astrium SAS. Equivalent mergers have been achieved in 2006 in the other countries, the EADS group does not communicate about these mergers, excepted when required by the law, such as in contractual documents. EADS Astrium Space Transportation was formed in June 2003 from the Space Infrastructure division of Astrium, until July 2006 it was called EADS Space Transportation and was a fully owned subsidiary of EADS Space. In July 2006 the three subsidiaries of EADS Space were reintegrated into one company, EADS Astrium, of which EADS Astrium Space Transportation is a business division, currently 4397 employees work in the launcher segment. The Space Transportation company is the contractor for the Ariane 5 launcher, the Columbus Module of the International Space Station. It also builds launchers for the French nuclear missile program, such as the M51 SLBM and it joined the team led by Lockheed Martin for a bid on NASAs Crew Exploration Vehicle, being in charge of the crafts Mission Module. The team won a contract from NASA in June 2005, in 2005, EADS Astrium Space Transportation started a campaign in favour of a project called LIFE, for astronomy from the Moon surface. The company has facilities in France and in Germany, the facility in Germany is located in Bremen
4.
Ariane 5
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Ariane 5 is a European heavy lift launch vehicle that is part of the Ariane rocket family, an expendable launch system used to deliver payloads into geostationary transfer orbit or low Earth orbit. Ariane 5 rockets are manufactured under the authority of the European Space Agency, airbus Defence and Space is the prime contractor for the vehicles, leading a consortium of other European contractors. Ariane 5 is operated and marketed by Arianespace as part of the Ariane programme, the rockets are launched by Arianespace from the Guiana Space Centre in French Guiana. Ariane 5 succeeded Ariane 4, but was not derived from it directly, Ariane 5 has been refined since the first launch in successive versions, G, G+, GS, ECA, and most recently, ES. ESA originally designed Ariane 5 to launch the Hermes spaceplane, two satellites can be mounted using a SYLDA carrier. Three main satellites are possible depending on size using SPELTRA, up to eight secondary payloads, usually small experiment packages or minisatellites, can be carried with an ASAP platform. As of July 2015 Arianespace has signed contracts for Ariane 5 ECA launches up till 2023, on 14 February 2017, Ariane 5 performed its 77th consecutive successful mission since 2003. Ariane 5’s cryogenic H173 main stage is called the EPC. It consists of a large tank 30.5 metres high with two compartments, one for liquid oxygen and one for hydrogen, and a Vulcain 2 engine at the base with a vacuum thrust of 1,390 kilonewtons. The H173 EPC weighs about 189 tonnes, including 175 tonnes of propellant, after the main cryogenic stage runs out of fuel, it can re-enter the atmosphere for an ocean splashdown. Attached to the sides are two P241 solid rocket boosters, each weighing about 277 tonnes full and delivering a thrust of about 7,080 kilonewtons and they are fueled by a mix of ammonium perchlorate and aluminum fuel and HTPB. They each burn for 130 seconds before being dropped into the ocean, the most recent attempt was for the first Ariane 5 ECA mission. One of the two boosters was successfully recovered and returned to the Guiana Space Center for analysis, prior to that mission, the last such recovery and testing was done in 2003. The French M51 SLBM shares a substantial amount of technology with these boosters, in February 2000 the suspected nose cone of an Ariane 5 booster washed ashore on the South Texas coast, and was recovered by beachcombers before the government could get to it. The second stage is on top of the stage and below the payload. The Ariane 5 G used the EPS, which is fueled by monomethylhydrazine and it also has 10 tonnes of storable propellants. The EPS was improved for use on the Ariane 5 G+, GS, Ariane 5 ECA uses the ESC, which is fueled by liquid hydrogen and liquid oxygen. The EPS upper stage is capable of multiple ignitions, first demonstrated during flight V26 which was launched on 5 October 2007 and this was purely to test the engine, and occurred after the payloads had been deployed
5.
Guiana Space Centre
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The Guiana Space Centre or, more commonly, Centre Spatial Guyanais is a French and European spaceport to the northwest of Kourou in French Guiana. The European Space Agency, the French space agency CNES, and this was the spaceport used by the ESA to send supplies to the International Space Station using the Automated Transfer Vehicle. The location was selected in 1964 to become the spaceport of France, in 1975, France offered to share Kourou with ESA. Commercial launches are bought also by non-European companies, ESA pays two thirds of the spaceports annual budget and has also financed the upgrades made during the development of the Ariane launchers. Since April 4,2017, the centre has been occupied by 30 labor union leaders in the midst of the 2017 social unrest in French Guiana, Kourou is located approximately 500 kilometres north of the equator, at a latitude of 5°10. The near-equatorial launch location provides an advantage for launches to low-inclination Earth orbits compared to launches from spaceports at higher latitude, the proximity to the equator also makes maneuvering satellites for geosynchronous orbits simpler and less costly. Originally built in the 1960s under the name of CECLES, the ELV pad located at 5. 236°N52. 775°W /5.236, one Europa-II was launched from the site, before the programme was cancelled. The pad was demolished, and subsequently rebuilt as the first launch complex for Ariane rockets, renamed ELA, it was used for Ariane 1 and Ariane 2 and 3 launches until being retired in 1989. It was again refurbished for the Vega with the first launch performed on 13 February 2012, the ELA2 pad, located at 5. 232°N52. 776°W /5.232, -52.776 had been used for Ariane 4 launches until 2003. ELA3 has been active for Ariane 5 launches since 1996 and this facility is located at 5. 239°N52. 768°W /5.239, -52.768 and covers an area of 21 square kilometres. ESA has built ELS at 5. 305°N52. 834°W /5.305, the first Soyuz launch from ELS was postponed several times, but launched on October 21,2011. ELS is located on the territory of Sinnamary commune,27 km from Kourou harbor and it is 10 km north of the site used for the Ariane 5 launches. Russia will use the Guiana Space Centre in addition to Baikonur Cosmodrome, the Guiana location has the significant benefit of greatly increased payload capability, owing to the near equatorial position. A Soyuz rocket with a 1.7 tonnes to geostationary transfer orbit performance from Baikonur, the ELS project is being co-funded by Arianespace, ESA, and the European Union, with CNES being the prime contractor. The project has a projected cost of approximately €320 million, where €120 million are allocated for modernizing the Soyuz vehicle, the official opening of the launch site construction occurred on 27 February 2007. Excavation work however, had begun several months beforehand. By October 2010,18 launch contracts had been signed, Arianespace has ordered 24 launchers from Russian industry. On October 21,2011, two Galileo IOV-1 & IOV-2 satellites were launched using a Soyuz-ST rocket, in the first Russian Soyuz vehicle ever launched from Europes Spaceport in French Guiana, astrium assembles each Ariane 5 launcher in the Launcher Integration Building
6.
ELA-3
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ELA-3, short for Ensemble de Lancement Ariane 3, is a launch pad and associated facilities at the Centre Spatial Guyanais in French Guyana. ELA-3 is operated by Arianespace as part of the launch system for Ariane 5 rockets. As of October 2016,88 launches have been carried out from it, ELA-3 is 21 square kilometres in size. As of 5 October 2016, the launch from ELA-3 is scheduled to occur on 17 November 2016
7.
Arianespace
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Arianespace SA is a French multinational company founded in 1980 as the worlds first commercial launch service provider. It undertakes the production, operation, and marketing of the Ariane programme, the main launch vehicles offered by the company are the Ariane 5, the Soyuz-2 as a medium-lift alternative, and the Vega as a lighter one. As of 2008, more than 240 commercial launches have occurred since May 22,1984, Arianespace states that the total number of launch contracts signed since Ariane launches commenced operations in 1984 is 285. Arianespace uses the Centre Spatial Guyanais in French Guiana as a launch site and it has its headquarters in Courcouronnes, Essonne, France, near Évry. On 21 October 2011 Arianespace launched the first Soyuz rocket ever from outside former Soviet territory, the payload was two Galileo navigation satellites. Arianespace primary shareholders are its suppliers, in the nations of the European Union. In 2004, Arianespace held more than 50 percent of the market for boosting satellites to geostationary transfer orbit. According to an Arianespace managing director, Its quite clear theres a significant challenge coming from SpaceX. Therefore things have to change … and the whole European industry is being restructured, consolidated, rationalised and streamlined, in early 2014, Arianespace requested additional subsidies from European governments to face the competition from SpaceX and unfavorable changes in the Euro-Dollar exchange rate. Overall Arianespace signed 11 contracts in 2014 until September, with two additional being in a stage of negotiations. Currently Arianespace operates 3 launch vehicles, including two versions of Ariane 5, Additionally Arianespace offers optional back-up launch service on H-IIA through Launch Services Alliance, new Ariane 6 vehicle is in development. It would be wise in league of Ariane 5 and has tentatively its first test flight in 2020 as of 2016. The Arianes Cup is a competition organized on behalf of the Industrials participating in the Ariane programme. Europa rocket NewSpace Comparable Launch Provider Company United Launch Alliance International Launch Services Space Exploration Technologies Antrix Corporation
8.
Geocentric orbit
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A geocentric orbit or Earth orbit involves any object orbiting the Earth, such as the Moon or artificial satellites. In 1997 NASA estimated there were approximately 2,465 artificial satellite orbiting the Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. Over 16,291 previously launched objects have decayed into the Earths atmosphere, altitude as used here, the height of an object above the average surface of the Earths oceans. Analemma a term in astronomy used to describe the plot of the positions of the Sun on the celestial sphere throughout one year, apogee is the farthest point that a satellite or celestial body can go from Earth, at which the orbital velocity will be at its minimum. Eccentricity a measure of how much an orbit deviates from a perfect circle, eccentricity is strictly defined for all circular and elliptical orbits, and parabolic and hyperbolic trajectories. Equatorial plane as used here, an imaginary plane extending from the equator on the Earth to the celestial sphere, escape velocity as used here, the minimum velocity an object without propulsion needs to have to move away indefinitely from the Earth. An object at this velocity will enter a parabolic trajectory, above this velocity it will enter a hyperbolic trajectory, impulse the integral of a force over the time during which it acts. Inclination the angle between a plane and another plane or axis. In the sense discussed here the reference plane is the Earths equatorial plane, orbital characteristics the six parameters of the Keplerian elements needed to specify that orbit uniquely. Orbital period as defined here, time it takes a satellite to make one orbit around the Earth. Perigee is the nearest approach point of a satellite or celestial body from Earth, sidereal day the time it takes for a celestial object to rotate 360°. For the Earth this is,23 hours,56 minutes,4.091 seconds, solar time as used here, the local time as measured by a sundial. Velocity an objects speed in a particular direction, since velocity is defined as a vector, both speed and direction are required to define it. The following is a list of different geocentric orbit classifications, Low Earth orbit - Geocentric orbits ranging in altitude from 160 kilometers to 2,000 kilometres above mean sea level. At 160 km, one revolution takes approximately 90 minutes, medium Earth orbit - Geocentric orbits with altitudes at apogee ranging between 2,000 kilometres and that of the geosynchronous orbit at 35,786 kilometres. Geosynchronous orbit - Geocentric circular orbit with an altitude of 35,786 kilometres, the period of the orbit equals one sidereal day, coinciding with the rotation period of the Earth. The speed is approximately 3,000 metres per second, high Earth orbit - Geocentric orbits with altitudes at apogee higher than that of the geosynchronous orbit. A special case of high Earth orbit is the elliptical orbit
9.
Polar orbit
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A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited on each revolution. It therefore has an inclination of 90 degrees to the equator, a satellite in a polar orbit will pass over the equator at a different longitude on each of its orbits. Polar orbits are used for earth-mapping, earth observation, capturing the earth as time passes from one point, reconnaissance satellites. The Iridium satellite constellation also uses a polar orbit to provide telecommunications services, the disadvantage to this orbit is that no one spot on the Earths surface can be sensed continuously from a satellite in a polar orbit. Near-polar orbiting satellites commonly choose a Sun-synchronous orbit, meaning each successive orbital pass occurs at the same local time of day. To keep the local time on a given pass, the time period of the orbit must be kept as short as possible. However, very low orbits of a few hundred kilometers rapidly decay due to drag from the atmosphere, commonly used altitudes are between 700 km and 800 km, producing an orbital period of about 100 minutes. The half-orbit on the Sun side then takes only 50 minutes, list of orbits Molniya orbit Vandenberg Air Force Base, a major United States launch location for polar orbits Orbital Mechanics
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Low Earth orbit
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A low Earth orbit is an orbit around Earth with an altitude between 160 kilometers, and 2,000 kilometers. Objects below approximately 160 kilometers will experience very rapid orbital decay, with the exception of the 24 human beings who flew lunar flights in the Apollo program during the four-year period spanning 1968 through 1972, all human spaceflights have taken place in LEO or below. The International Space Station conducts operations in LEO, the altitude record for a human spaceflight in LEO was Gemini 11 with an apogee of 1,374.1 kilometers. All crewed space stations to date, as well as the majority of satellites, have been in LEO, objects in LEO encounter atmospheric drag from gases in the thermosphere or exosphere, depending on orbit height. Due to atmospheric drag, satellites do not usually orbit below 300 km, objects in LEO orbit Earth between the denser part of the atmosphere and below the inner Van Allen radiation belt. The mean orbital velocity needed to maintain a stable low Earth orbit is about 7.8 km/s, calculated for circular orbit of 200 km it is 7.79 km/s and for 1500 km it is 7.12 km/s. The delta-v needed to achieve low Earth orbit starts around 9.4 km/s, atmospheric and gravity drag associated with launch typically adds 1. 3–1.8 km/s to the launch vehicle delta-v required to reach normal LEO orbital velocity of around 7.8 km/s. Equatorial low Earth orbits are a subset of LEO and these orbits, with low inclination to the Equator, allow rapid revisit times and have the lowest delta-v requirement of any orbit. Orbits with an inclination angle to the equator are usually called polar orbits. Higher orbits include medium Earth orbit, sometimes called intermediate circular orbit, orbits higher than low orbit can lead to early failure of electronic components due to intense radiation and charge accumulation. Although the Earths pull due to gravity in LEO is not much less than on the surface of the Earth, people, a low Earth orbit is simplest and cheapest for satellite placement. It provides high bandwidth and low communication time lag, but satellites in LEO will not be visible from any point on the Earth at all times. Earth observation satellites and spy satellites use LEO as they are able to see the surface of the Earth more clearly as they are not so far away and they are also able to traverse the surface of the Earth. A majority of satellites are placed in LEO, making one complete revolution around the Earth in about 90 minutes. The International Space Station is in a LEO about 400 km above the Earths surface, since it requires less energy to place a satellite into a LEO and the LEO satellite needs less powerful amplifiers for successful transmission, LEO is used for many communication applications. Because these LEO orbits are not geostationary, a network of satellites is required to provide continuous coverage, lower orbits also aid remote sensing satellites because of the added detail that can be gained. Remote sensing satellites can also take advantage of sun-synchronous LEO orbits at an altitude of about 800 km, envisat is one example of an Earth observation satellite that makes use of this particular type of LEO. The LEO environment is becoming congested with space debris due to the frequency of object launches and this has caused growing concern in recent years, since collisions at orbital velocities can easily be dangerous, and even deadly
11.
Semi-major and semi-minor axes
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In geometry, the major axis of an ellipse is its longest diameter, a line segment that runs through the center and both foci, with ends at the widest points of the perimeter. The semi-major axis is one half of the axis, and thus runs from the centre, through a focus. Essentially, it is the radius of an orbit at the two most distant points. For the special case of a circle, the axis is the radius. One can think of the axis as an ellipses long radius. The semi-major axis of a hyperbola is, depending on the convention, thus it is the distance from the center to either vertex of the hyperbola. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction. Thus a and b tend to infinity, a faster than b, the semi-minor axis is a line segment associated with most conic sections that is at right angles with the semi-major axis and has one end at the center of the conic section. It is one of the axes of symmetry for the curve, in an ellipse, the one, in a hyperbola. The semi-major axis is the value of the maximum and minimum distances r max and r min of the ellipse from a focus — that is. In astronomy these extreme points are called apsis, the semi-minor axis of an ellipse is the geometric mean of these distances, b = r max r min. The eccentricity of an ellipse is defined as e =1 − b 2 a 2 so r min = a, r max = a. Now consider the equation in polar coordinates, with one focus at the origin, the mean value of r = ℓ / and r = ℓ /, for θ = π and θ =0 is a = ℓ1 − e 2. In an ellipse, the axis is the geometric mean of the distance from the center to either focus. The semi-minor axis of an ellipse runs from the center of the ellipse to the edge of the ellipse, the semi-minor axis is half of the minor axis. The minor axis is the longest line segment perpendicular to the axis that connects two points on the ellipses edge. The semi-minor axis b is related to the axis a through the eccentricity e. A parabola can be obtained as the limit of a sequence of ellipses where one focus is fixed as the other is allowed to move arbitrarily far away in one direction
12.
Orbital eccentricity
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The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is an orbit, values between 0 and 1 form an elliptical orbit,1 is a parabolic escape orbit. The term derives its name from the parameters of conic sections and it is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the galaxy. In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit, the eccentricity of this Kepler orbit is a non-negative number that defines its shape. The limit case between an ellipse and a hyperbola, when e equals 1, is parabola, radial trajectories are classified as elliptic, parabolic, or hyperbolic based on the energy of the orbit, not the eccentricity. Radial orbits have zero angular momentum and hence eccentricity equal to one, keeping the energy constant and reducing the angular momentum, elliptic, parabolic, and hyperbolic orbits each tend to the corresponding type of radial trajectory while e tends to 1. For a repulsive force only the trajectory, including the radial version, is applicable. For elliptical orbits, a simple proof shows that arcsin yields the projection angle of a circle to an ellipse of eccentricity e. For example, to view the eccentricity of the planet Mercury, next, tilt any circular object by that angle and the apparent ellipse projected to your eye will be of that same eccentricity. From Medieval Latin eccentricus, derived from Greek ἔκκεντρος ekkentros out of the center, from ἐκ- ek-, eccentric first appeared in English in 1551, with the definition a circle in which the earth, sun. Five years later, in 1556, a form of the word was added. The eccentricity of an orbit can be calculated from the state vectors as the magnitude of the eccentricity vector, e = | e | where. For elliptical orbits it can also be calculated from the periapsis and apoapsis since rp = a and ra = a, where a is the semimajor axis. E = r a − r p r a + r p =1 −2 r a r p +1 where, rp is the radius at periapsis. For Earths annual orbit path, ra/rp ratio = longest_radius / shortest_radius ≈1.034 relative to center point of path, the eccentricity of the Earths orbit is currently about 0.0167, the Earths orbit is nearly circular. Venus and Neptune have even lower eccentricity, over hundreds of thousands of years, the eccentricity of the Earths orbit varies from nearly 0.0034 to almost 0.058 as a result of gravitational attractions among the planets. The table lists the values for all planets and dwarf planets, Mercury has the greatest orbital eccentricity of any planet in the Solar System. Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion, before its demotion from planet status in 2006, Pluto was considered to be the planet with the most eccentric orbit
13.
Apsis
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An apsis is an extreme point in an objects orbit. The word comes via Latin from Greek and is cognate with apse, for elliptic orbits about a larger body, there are two apsides, named with the prefixes peri- and ap-, or apo- added to a reference to the thing being orbited. For a body orbiting the Sun, the point of least distance is the perihelion, the terms become periastron and apastron when discussing orbits around other stars. For any satellite of Earth including the Moon the point of least distance is the perigee, for objects in Lunar orbit, the point of least distance is the pericynthion and the greatest distance the apocynthion. For any orbits around a center of mass, there are the terms pericenter and apocenter, periapsis and apoapsis are equivalent alternatives. A straight line connecting the pericenter and apocenter is the line of apsides and this is the major axis of the ellipse, its greatest diameter. For a two-body system the center of mass of the lies on this line at one of the two foci of the ellipse. When one body is larger than the other it may be taken to be at this focus. Historically, in systems, apsides were measured from the center of the Earth. In orbital mechanics, the apsis technically refers to the distance measured between the centers of mass of the central and orbiting body. However, in the case of spacecraft, the family of terms are used to refer to the orbital altitude of the spacecraft from the surface of the central body. The arithmetic mean of the two limiting distances is the length of the axis a. The geometric mean of the two distances is the length of the semi-minor axis b, the geometric mean of the two limiting speeds is −2 ε = μ a which is the speed of a body in a circular orbit whose radius is a. The words pericenter and apocenter are often seen, although periapsis/apoapsis are preferred in technical usage, various related terms are used for other celestial objects. The -gee, -helion and -astron and -galacticon forms are used in the astronomical literature when referring to the Earth, Sun, stars. The suffix -jove is occasionally used for Jupiter, while -saturnium has very rarely used in the last 50 years for Saturn. The -gee form is used as a generic closest approach to planet term instead of specifically applying to the Earth. During the Apollo program, the terms pericynthion and apocynthion were used when referring to the Moon, regarding black holes, the term peri/apomelasma was used by physicist Geoffrey A. Landis in 1998 before peri/aponigricon appeared in the scientific literature in 2002
14.
Orbital inclination
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Orbital inclination measures the tilt of an objects orbit around a celestial body. It is expressed as the angle between a plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the equator, the plane of the orbit is the same as the Earths equatorial plane. The general case is that the orbit is tilted, it spends half an orbit over the northern hemisphere. If the orbit swung between 20° north latitude and 20° south latitude, then its orbital inclination would be 20°, the inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planets equator, for planets in the Solar System, the plane of reference is usually the ecliptic, the plane in which the Earth orbits the Sun. This reference plane is most practical for Earth-based observers, therefore, Earths inclination is, by definition, zero. Inclination could instead be measured with respect to another plane, such as the Suns equator or the invariable plane, the inclination of orbits of natural or artificial satellites is measured relative to the equatorial plane of the body they orbit, if they orbit sufficiently closely. The equatorial plane is the perpendicular to the axis of rotation of the central body. An inclination of 30° could also be described using an angle of 150°, the convention is that the normal orbit is prograde, an orbit in the same direction as the planet rotates. Inclinations greater than 90° describe retrograde orbits, thus, An inclination of 0° means the orbiting body has a prograde orbit in the planets equatorial plane. An inclination greater than 0° and less than 90° also describe prograde orbits, an inclination of 63. 4° is often called a critical inclination, when describing artificial satellites orbiting the Earth, because they have zero apogee drift. An inclination of exactly 90° is an orbit, in which the spacecraft passes over the north and south poles of the planet. An inclination greater than 90° and less than 180° is a retrograde orbit, an inclination of exactly 180° is a retrograde equatorial orbit. For gas giants, the orbits of moons tend to be aligned with the giant planets equator, the inclination of exoplanets or members of multiple stars is the angle of the plane of the orbit relative to the plane perpendicular to the line-of-sight from Earth to the object. An inclination of 0° is an orbit, meaning the plane of its orbit is parallel to the sky. An inclination of 90° is an orbit, meaning the plane of its orbit is perpendicular to the sky
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DORIS (geodesy)
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Ground-based radio beacons emit a signal which is picked up by receiving satellites. This is in reverse configuration to other GNSS, in which the transmitters are space-borne, a frequency shift of the signal occurs that is caused by the movement of the satellite. From this observation satellite orbits, ground positions, as well as other parameters can be derived, DORIS is a French system which was initiated and is maintained by the French Space Agency. The ground segment includes about 50-60 ground stations, equally distributed over the earth, for the installation of a beacon only electricity is required because the station only emits a signal but does not receive any information. DORIS beacons transmit to the satellites on two UHF frequencies,401.25 MHz and 2036.25 MHz, the best known satellites equipped with DORIS receivers are the altimetry satellites TOPEX/Poseidon, Jason 1 and Jason 2. They are used to observe the surface as well as currents or wave heights. DORIS contributes to their orbit accuracy of about 2 cm, other DORIS satellites are the Envisat, SPOT, HY-2A and CryoSat-2 satellites. Apart from orbit determination, the DORIS observations are used for positioning of ground stations, the accuracy is a bit lower than with GPS, but it still contributes to the International Terrestrial Reference Frame. AVISO, website which distributes satellite altimeter data IDS, International DORIS Service
16.
Kourou
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Kourou is a commune in French Guiana, an overseas region and department of France located in South America. In addition to being a district in French Guiana, it is also the main town in that district. Within the Kourou district lies the Guiana Space Centre, France, some 60 km northwest of the French Guyanese capital Cayenne the Kourou River empties into the Atlantic Ocean. At the mouth of this sits the town of Kourou. There are three lakes within the city limits, Lake Bois Diable, Lake Marie-Claire, and Lake Bois Chaudat. Long white sand beaches and some rocky outcrops line the towns ocean coast, the town had a fast-growing population of 25,918 inhabitants at the 2007 census. Much of it burned down in a fire in 2006, Guiana in general has a high level of crime compared to the rest of Frances départements, Kourou has an average of two armed robberies a day. A march protesting the high level of insecurity felt by most of the population was held in Kourou on 27 October 2006, shopkeepers of Chinese descent in particular are often targeted by armed robbers, their cash registers emptied and some products stolen. Kourou is the port of departure for those going to the îles du Salut and it is also common for many to go up the river in canoes on weekends to camp in the forest. The Guiana Space Centre, where the European Space Agency starts missions, is located a little behind, part of the town and the islands are closed during rocket launches. Not much is known of the pre-colonial era, the area was mostly populated by Kalina, or Galibi before the arrival of the French in the late 17th century. There is a place not far from the town called les Roches Gravées, vicente Yáñez Pinzón sailed along most of the north coast of South America and passed by the current location of Kourou in 1500. The Society of Jesus was disbanded in 1762, however, the mission at Kourou being abandoned by the Jesuits, the engineers Mentelle and Tugny designed the layout of the future town. This resulted in the called the Bourg, around the Church of Saint Catherine. That same year,1763, as agreed in the Treaty of Paris, having lost their largest and richest colony, the French decided to send a large expedition to Guiana, commanded by Choiseul. Around 10,000 to 12,000 people, mostly Frenchmen, tempted by stories of an El Dorado on the side of the ocean. The small town, surrounded by marshes and rainforest, was unprepared for such an influx of people. Those remaining fled to the îles du Salut, free of mosquitoes due to constant winds, previously they had been known as the îles du Diable, and one of the islands retains the name to this day
17.
French Guiana
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French Guiana, officially called Guiana, is an overseas department and region of France, located on the north Atlantic coast of South America in the Guyanas. It borders Brazil to the east and south, and Suriname to the west. Its 83,534 km2 area has a low population density of only 3 inhabitants per km2, with half of its 244,118 inhabitants in 2013 living in the metropolitan area of Cayenne. By land area, it is the second largest region of France, both the region and the department have been ruled since December 2015 by a single assembly within the framework of a new territorial collectivity, the French Guiana Territorial Collectivity. This assembly, the French Guiana Assembly, has replaced the regional council and departmental council. The French Guiana Assembly is in charge of regional and departmental government, the area was originally inhabited by Native Americans. The first French establishment is recorded in 1503 but the French presence didnt really become durable until 1643, Guiana then became a slave colony and saw its population increase until the official abolition of slavery at the time of the French revolution. During World War II, the Guianan Félix Éboué was one of the first to stand behind General de Gaulle as early as June 18,1940, Guiana officially rallied Free France in 1943. It definitively abandoned its status as a colony and became again a French department in 1946, de Gaulle, who became president, decided to establish the Guiana Space Center in 1965. It is now operated by the CNES, Arianespace and the European Space Agency, several thousand Hmong refugees from Laos migrated to French Guiana in the late 1970s and early 1980s. Nowadays fully integrated in the French central state, Guiana is a part of the European Union, the region is the most prosperous territory in South America with the highest GDP per capita. A large part of Guianas economy derives from the presence of the Guiana Space Centre, as elsewhere in France, the official language is French, but each ethnic community has its own language, of which Guianan Creole is the most widely spoken. Guiana is derived from an Amerindian language and means land of many waters, French Guiana and the two larger countries to the north and west, Guyana and Suriname, are still often collectively referred to as the Guianas and constitute one large shield landmass. French Guiana was originally inhabited by people, Kalina, Arawak, Emerillon, Galibi, Palikur, Wayampi. The French attempted to create a colony there in the 18th century in conjunction with its settlement of some other Caribbean islands, in this penal colony, the convicts were sometimes used as butterfly catchers. During its existence, France transported approximately 56,000 prisoners to Devils Island, fewer than 10% survived their sentence. In addition, in the nineteenth century, France began requiring forced residencies by prisoners who survived their hard labor. A Portuguese-British naval squadron took French Guiana for the Portuguese Empire in 1809 and it was returned to France with the signing of the Treaty of Paris in 1814
18.
Sun-synchronous orbit
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A Sun-synchronous orbit is a geocentric orbit that combines altitude and inclination in such a way that the satellite passes over any given point of the planets surface at the same local solar time. Such an orbit can place a satellite in constant sunlight and is useful for imaging, spy, more technically, it is an orbit arranged in such a way that it precesses once a year. The surface illumination angle will be nearly the same time that the satellite is overhead. This consistent lighting is a characteristic for satellites that image the Earths surface in visible or infrared wavelengths. For example, a satellite in sun-synchronous orbit might ascend across the twelve times a day each time at approximately 15,00 mean local time. This is achieved by having the orbital plane precess approximately one degree each day with respect to the celestial sphere, eastward. Typical sun-synchronous orbits are about 600–800 km in altitude, with periods in the 96–100 minute range, riding the terminator is useful for active radar satellites as the satellites solar panels can always see the Sun, without being shadowed by the Earth. The dawn/dusk orbit has been used for solar observing scientific satellites such as Yohkoh, TRACE, Hinode and PROBA2, Sun-synchronous orbits can happen around other oblate planets, such as Mars. A satellite around the almost spherical Venus, for example, will need an outside push to be in a sun-synchronous orbit.696 deg. Note that according to this approximation cos i equals −1 when the semi-major axis equals 12352 km, the period can be in the range from 88 minutes for a very low orbit to 3.8 hours. If one wants a satellite to fly over some given spot on Earth every day at the same hour, it can do between 7 and 16 orbits per day, as shown in the following table. When one says that a Sun-synchronous orbit goes over a spot on the earth at the local time each time. The Sun will not be in exactly the same position in the sky during the course of the year, very often a frozen orbit is therefore selected that is slightly higher over the Southern hemisphere than over the Northern hemisphere. ERS-1, ERS-2 and Envisat of European Space Agency as well as the MetOp spacecraft of EUMETSAT are all operated in Sun-synchronous, orbital perturbation analysis Analemma Geosynchronous orbit Geostationary orbit List of orbits Polar orbit World Geodetic System Sandwell, David T. The Gravity Field of the Earth - Part 1 Sun-Synchronous Orbit dictionary entry, centennial of Flight Commission NASA Q&A Boain, Ronald J. The A-B-Cs of Sun Synchronous Orbit Design, List of satellites in Sun-synchronous orbit
19.
Orbit
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In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet about a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating path around a body, to a close approximation, planets and satellites follow elliptical orbits, with the central mass being orbited at a focal point of the ellipse, as described by Keplers laws of planetary motion. For ease of calculation, in most situations orbital motion is adequately approximated by Newtonian Mechanics, historically, the apparent motions of the planets were described by European and Arabic philosophers using the idea of celestial spheres. This model posited the existence of perfect moving spheres or rings to which the stars and it assumed the heavens were fixed apart from the motion of the spheres, and was developed without any understanding of gravity. After the planets motions were accurately measured, theoretical mechanisms such as deferent. Originally geocentric it was modified by Copernicus to place the sun at the centre to help simplify the model, the model was further challenged during the 16th century, as comets were observed traversing the spheres. The basis for the understanding of orbits was first formulated by Johannes Kepler whose results are summarised in his three laws of planetary motion. Second, he found that the speed of each planet is not constant, as had previously been thought. Third, Kepler found a relationship between the orbital properties of all the planets orbiting the Sun. For the planets, the cubes of their distances from the Sun are proportional to the squares of their orbital periods. Jupiter and Venus, for example, are respectively about 5.2 and 0.723 AU distant from the Sun, their orbital periods respectively about 11.86 and 0.615 years. The proportionality is seen by the fact that the ratio for Jupiter,5. 23/11.862, is equal to that for Venus,0. 7233/0.6152. Idealised orbits meeting these rules are known as Kepler orbits, isaac Newton demonstrated that Keplers laws were derivable from his theory of gravitation and that, in general, the orbits of bodies subject to gravity were conic sections. Newton showed that, for a pair of bodies, the sizes are in inverse proportion to their masses. Where one body is more massive than the other, it is a convenient approximation to take the center of mass as coinciding with the center of the more massive body. Lagrange developed a new approach to Newtonian mechanics emphasizing energy more than force, in a dramatic vindication of classical mechanics, in 1846 le Verrier was able to predict the position of Neptune based on unexplained perturbations in the orbit of Uranus. This led astronomers to recognize that Newtonian mechanics did not provide the highest accuracy in understanding orbits, in relativity theory, orbits follow geodesic trajectories which are usually approximated very well by the Newtonian predictions but the differences are measurable. Essentially all the evidence that can distinguish between the theories agrees with relativity theory to within experimental measurement accuracy
20.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
21.
Sentinel (satellite)
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Copernicus is the worlds largest single earth observation programme and directed by the European Commission in partnership with the European Space Agency. It aims at achieving a global, continuous, autonomous, high quality and it follows and greatly expands on the work of the previous 2.3 billion euros European Envisat program which operated from 2002 to 2012. In other words, it will pull together all the information obtained by the Copernicus environmental satellites, air, the geo-spatial information services offered by Copernicus can be grouped into six main interacting themes, land, ocean, emergency response, atmosphere, security and climate change. Over the last decades, European and national institutions have made substantial R&D efforts in the field of Earth observation and these efforts have resulted in tremendous achievements, but the services and products developed during this period had limitations that were inherent to R&D activities. In 2014-2015 Copernicus is moving towards an operational phase, the key to providing operational Copernicus services is to have an appropriate governance and business model structure in place that supports provisioning of these services. February 2004, the Commission Communication GMES, Establishing a GMES capacity by 2008 introduces an Action Plan aimed at establishing a working GMES capacity by 2008. In 2004, a Framework Agreement is also signed between EC and ESA, thus providing the basis for a component of GMES. Later services, also known as Pilot Services, are expected to address atmosphere monitoring, security, June 2006, the EC establishes the GMES Bureau, with the primary objective of ensuring the delivery of the priority services by 2008. Other objectives of the GMES Bureau are to address the issues of the GMES governance structure, may 2007, adoption of the European Space Policy Communication, recognising GMES as a major flagship of the Space Policy. September 2008, official launch of the three FTS services and two Pilot services in their version at the occasion of the GMES Forum held in Lille. November 2008, the Commission Communication GMES, We care for a Safer Planet establishes a basis for discussions on the financing, operational infrastructure. November 2010, the regulation on the European Earth Observation Programme, June 2011, the Commission presents its proposal for the next multiannual financial framework corresponding to the period 2014-2020. In this document, the Commission proposes to foresee the funding of the GMES programme outside the financial framework after 2014. December 2012, the Commission announces the change to Copernicus. October 2014, ESA and European Commission have established a budget for Copernicus Programme covering years 2014-2020 within Multiannual Financial Framework. Budget provided a total of 4.3 billion €, including 3.15 billion € for ESA to cover operations of the satellite network, ESA is currently developing seven missions under the Sentinel programme. The Sentinel missions include radar and super-spectral imaging for land, ocean, each Sentinel mission is based on a constellation of two satellites to fulfill and revisit the coverage requirements for each mission, providing robust datasets for all Copernicus services. The Sentinel missions will have the objectives, Sentinel-1 will provide all-weather, day and night radar imaging for land
22.
Sentinel-1
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Sentinel-1 is a space mission funded by the European Union and carried out by the ESA within the Copernicus Programme, consisting of a constellation of two satellites. The payload of Sentinel-1 is a Synthetic Aperture Radar in C band that provides continuous imagery, on 12 March 2010, the European Space Agency and Thales Alenia Space signed a contract worth €270 million to build the second satellite of the Sentinel-1 pair. First Sentinel 1A arrived at launch site in Kourou, French Guiana on 25 February, sentinel-1A satellite was launched on 3 April 2014, by a Soyuz Rocket. Sentinel-1 will provide continuity of data from ERS and Envisat missions, with enhancements in terms of revisit, coverage, timeliness. A summary of applications are, Monitoring sea ice zones and the Arctic environment, the Sentinel-1 satellites are expected to make analysis of earthquakes using InSAR techniques quicker and simpler. Prime contractor of mission is Thales Alenia Space Italy, with whole system integration and also production of platform Spacecraft Management Unit and payload Data Storage. SAR instrument on payload is the responsibility of Astrium Gmbh, the Ground Segment prime contractor is Astrium with subcontractors Telespazio, WERUM, Advanced Computer Systems and Aresys
23.
European Remote-Sensing Satellite
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European remote sensing satellite was the European Space Agencys first Earth-observing satellite programme using a polar orbit. The first satellite was launched on 17 July 1991 into a Sun-synchronous polar orbit at an altitude of 782–785 km, ERS-1 carried an array of earth-observation instruments that gathered information about the Earth using a variety of measurement principles. These included, RA is a single frequency nadir-pointing radar altimeter operating in the Ku band, aTSR-1 is a 4 channel infrared radiometer and microwave sounder for measuring temperatures at the sea-surface and the top of clouds. SAR operating in C band can detect changes in surface heights with sub-millimeter precision, Wind Scatterometer used to calculate information on wind speed and direction. MWR is a Microwave Radiometer used in measuring atmospheric water, as well as providing a correction for the water for the altimeter. To accurately determine its orbit, the satellite included the PRARE, the PRARE became non-operational shortly after launch. The Retroreflector was used for calibrating the Radar Altimeter to within 10 cm, ERS-1 had various mission phases using 3-day, 35-day and a 336-day repeat cycle. The 336-day mission allowed for mapping of the Earths bathymetry. ERS-1 failed on 10 March 2000, far exceeding its expected lifespan and its successor, ERS-2, was launched on 21 April 1995, on an Ariane 4, from ESAs Guiana Space Centre near Kourou, French Guiana. Largely identical to ERS-1, it added additional instruments and included improvements to existing instruments including, GOME is a nadir scanning ultraviolet, aTSR-2 included 3 visible spectrum bands specialized for Chlorophyll and Vegetation When ERS-2 was launched, ERS-1 shared the same orbital plane. This allowed a tandem mission, with ERS-2 passing the point on the ground 1 day later than ERS-1. ERS-2 has a cycle of 35 days. ERS-2 has been operating without gyroscopes since February 2001, resulting in degradation of the data provided by the instruments. The tape drive aboard failed on 22 June 2003, leaving the instruments operating only within visibility of a ground station, since the tape drive failure additional ground stations have been brought online to increase the data gathering abilities of the satellite. The Wind Scatterometer and GOME were the instruments of their kind until the launches of MetOp-A and Envisat. The successor to ERS-2 is Envisat containing improved versions of many of the instruments onboard ERS-2, however, over a series of burns in July, August and September, ERS-2 was finally depleted of all fuel on 5 September 2011. In the final stages of emptying the fuel tanks, it was estimated that they would be empty after a 40-minute burn on 2 September 2011, however, the spacecraft survived both this maneuver and a second 40-minute burn on 3 September. On 5 September a third burn was initiated and the tanks were finally drained
24.
Atmospheric chemistry
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Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earths atmosphere and that of other planets is studied. It is an approach of research and draws on environmental chemistry, physics, meteorology, computer modeling, oceanography, geology and volcanology. Research is increasingly connected with other arenas of such as climatology. The composition and chemistry of the Earths atmosphere is of importance for several reasons, the composition of the Earths atmosphere changes as result of natural processes such as volcano emissions, lightning and bombardment by solar particles from corona. It has also changed by human activity and some of these changes are harmful to human health, crops. Examples of problems which have been addressed by atmospheric chemistry include acid rain, ozone depletion, photochemical smog, greenhouse gases, notes, the concentration of CO2 and CH4 vary by season and location. The mean molecular mass of air is 28.97 g/mol, Ozone is not included due to its high variability. The ancient Greeks regarded air as one of the four elements, in the late 19th and early 20th centuries interest shifted towards trace constituents with very small concentrations. One particularly important discovery for atmospheric chemistry was the discovery of ozone by Christian Friedrich Schönbein in 1840, further studies on ozone issues led to the 1995 Nobel Prize in Chemistry award shared between Paul Crutzen, Mario Molina and Frank Sherwood Rowland. In the 21st century the focus is now shifting again, Atmospheric chemistry is increasingly studied as one part of the Earth system. Instead of concentrating on atmospheric chemistry in isolation the focus is now on seeing it as one part of a system with the rest of the atmosphere, biosphere and geosphere. Observations, lab measurements, and modeling are the three elements in atmospheric chemistry. Progress in atmospheric chemistry is driven by the interactions between these components and they form an integrated whole. For example, observations may tell us more of a chemical compound exists than previously thought possible. This will stimulate new modelling and laboratory studies which will increase our scientific understanding to a point where the observations can be explained, observations of atmospheric chemistry are essential to our understanding. Routine observations of chemical composition tell us about changes in composition over time. One important example of this is the Keeling Curve - a series of measurements from 1958 to today which show a rise in of the concentration of carbon dioxide. Observations of atmospheric chemistry are made in such as that on Mauna Loa and on mobile platforms such as aircraft, ships
25.
Ozone depletion
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The latter phenomenon is referred to as the ozone hole. In addition to these well-known stratospheric phenomena, there are also springtime polar tropospheric ozone depletion events, the details of polar ozone hole formation differ from that of mid-latitude thinning but the most important process in both is catalytic destruction of ozone by atomic halogens. The main source of these atoms in the stratosphere is photodissociation of man-made halocarbon refrigerants, solvents, propellants. These compounds are transported into the stratosphere by winds after being emitted at the surface, both types of ozone depletion were observed to increase as emissions of halocarbons increased. CFCs and other substances are referred to as ozone-depleting substances. Three forms of oxygen are involved in the cycle, oxygen atoms, oxygen gas. Ozone is formed in the stratosphere when oxygen molecules photodissociate after intaking an ultraviolet photon whose wavelength is shorter than 240 nm and this converts a single O2 into two atomic oxygen radicals. The atomic oxygen radicals then combine with separate O2 molecules to create two O3 molecules and these ozone molecules absorb ultraviolet light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom then joins up with a molecule to regenerate ozone. This is a process that terminates when an oxygen atom recombines with an ozone molecule to make two O2 molecules. 2 O3 →3 O2 The overall amount of ozone in the stratosphere is determined by a balance between production and recombination. Ozone can be destroyed by a number of free radical catalysts, the dot is a common notation to indicate that all of these species have an unpaired electron and are thus extremely reactive. Cl and Br atoms destroy ozone molecules through a variety of catalytic cycles, in the simplest example of such a cycle, a chlorine atom reacts with an ozone molecule, taking an oxygen atom to form chlorine monoxide and leaving an oxygen molecule. The ClO can react with a molecule of ozone, releasing the chlorine atom. More complicated mechanisms have been discovered that lead to destruction in the lower stratosphere as well. On a per atom basis, bromine is more efficient than chlorine at destroying ozone. As a result, both chlorine and bromine contribute significantly to overall ozone depletion, Laboratory studies have shown that fluorine and iodine atoms participate in analogous catalytic cycles. On average, a chlorine atom is able to react with 100,000 ozone molecules before it is removed from the catalytic cycle
26.
Biological oceanography
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Biological oceanography is the study of how organisms affect and are affected by the physics, chemistry, and geology of the oceanographic system. Biological oceanography mostly focuses on the microorganisms within the ocean, looking at how they are affected by their environment and how that affects larger marine creatures, biological oceanography is similar to marine biology, but is different because of the perspective used to study the ocean. Biological oceanography takes a bottom up approach, while marine biology studies the ocean from a top down perspective, biological oceanography also investigates the role of microbes in food webs, and how humans impact the ecosystems in the oceans. The Challenger Expedition was pivotal to biological oceanography and oceanography in general, the Challenger Expedition was headed by Charles Wyville Thomson in 1872-1876 The expedition also included two other naturalists, Henry N. Moseley and John Murray. They also brought the equipment to collect data about the biological, chemical and they mapped the oceanic sediment and collected data The data collected in this voyage proved that there was life in deep waters and that the composition of water in the ocean is consistent
27.
Wind wave
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In fluid dynamics, wind waves, or wind-generated waves, are surface waves that occur on the free surface of bodies of water. They result from the wind blowing over an area of fluid surface, Waves in the oceans can travel thousands of miles before reaching land. Wind waves on Earth range in size from small ripples, to waves over 100 ft high, when directly generated and affected by local winds, a wind wave system is called a wind sea. After the wind ceases to blow, wind waves are called swells, more generally, a swell consists of wind-generated waves that are not significantly affected by the local wind at that time. They have been generated elsewhere or some time ago, wind waves in the ocean are called ocean surface waves. Wind waves have an amount of randomness, subsequent waves differ in height, duration. The key statistics of wind waves in evolving sea states can be predicted with wind wave models, although waves are usually considered in the water seas of Earth, the hydrocarbon seas of Titan may also have wind-driven waves. The great majority of large breakers seen at a result from distant winds. Water depth All of these work together to determine the size of wind waves. Further exposure to that wind could only cause a dissipation of energy due to the breaking of wave tops. Waves in an area typically have a range of heights. For weather reporting and for analysis of wind wave statistics. This figure represents an average height of the highest one-third of the waves in a time period. The significant wave height is also the value a trained observer would estimate from visual observation of a sea state, given the variability of wave height, the largest individual waves are likely to be somewhat less than twice the reported significant wave height for a particular day or storm. Wave formation on a flat water surface by wind is started by a random distribution of normal pressure of turbulent wind flow over the water. This pressure fluctuation produces normal and tangential stresses in the surface water and it is assumed that, The water is originally at rest. There is a distribution of normal pressure to the water surface from the turbulent wind. Correlations between air and water motions are neglected, the second mechanism involves wind shear forces on the water surface
28.
Hydrology
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Hydrology is the scientific study of the movement, distribution, and quality of water on Earth and other planets, including the water cycle, water resources and environmental watershed sustainability. A practitioner of hydrology is a hydrologist, working within the fields of earth or environmental science, physical geography, geology or civil, Hydrology subdivides into surface water hydrology, groundwater hydrology, and marine hydrology. Domains of hydrology include hydrometeorology, surface hydrology, hydrogeology, drainage-basin management and water quality, oceanography and meteorology are not included because water is only one of many important aspects within those fields. Hydrological research can inform environmental engineering, policy and planning, the term hydrology comes from Greek, ὕδωρ, hýdōr, water, and λόγος, lógos, study. Chemical hydrology is the study of the characteristics of water. Ecohydrology is the study of interactions between organisms and the hydrologic cycle, hydrogeology is the study of the presence and movement of groundwater. Hydroinformatics is the adaptation of technology to hydrology and water resources applications. Hydrometeorology is the study of the transfer of water and energy between land and water surfaces and the lower atmosphere. Isotope hydrology is the study of the signatures of water. Surface hydrology is the study of processes that operate at or near Earths surface. Drainage basin management covers water-storage, in the form of reservoirs, water quality includes the chemistry of water in rivers and lakes, both of pollutants and natural solutes. Determining the water balance of a region, mitigating and predicting flood, landslide and drought risk. Real-time flood forecasting and flood warning, designing irrigation schemes and managing agricultural productivity. Part of the module in catastrophe modeling. Designing dams for water supply or hydroelectric power generation, designing sewers and urban drainage system. Analyzing the impacts of antecedent moisture on sanitary sewer systems, predicting geomorphologic changes, such as erosion or sedimentation. Assessing the impacts of natural and anthropogenic environmental change on water resources, assessing contaminant transport risk and establishing environmental policy guidelines. Hydrology has been a subject of investigation and engineering for millennia, for example, about 4000 BC the Nile was dammed to improve agricultural productivity of previously barren lands
29.
Humidity
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Humidity is the amount of water vapor present in the air. Water vapor is the state of water and is invisible. Humidity indicates the likelihood of precipitation, dew, or fog, higher humidity reduces the effectiveness of sweating in cooling the body by reducing the rate of evaporation of moisture from the skin. This effect is calculated in an index table or humidex. The amount of vapor that is needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of water becomes lower it will not reach the point of saturation without adding or losing water mass. The differences in the amount of vapor in a parcel of air can be quite large. For example, a parcel of air that is near saturation may contain 28 grams of water per cubic meter of air at 30 °C, there are three main measurements of humidity, absolute, relative and specific. Absolute humidity is the content of air expressed in gram per cubic meter. Relative humidity, expressed as a percent, measures the current absolute humidity relative to the maximum for that temperature, specific humidity is the ratio of the mass of water vapor to the total mass of the moist air parcel. Absolute humidity is the mass of water vapor present in a given volume of air. It does not take temperature into consideration, absolute humidity in the atmosphere ranges from near zero to roughly 30 grams per cubic meter when the air is saturated at 30 °C. Absolute humidity is the mass of the vapor, divided by the volume of the air and water vapor mixture. The absolute humidity changes as air temperature or pressure changes and this makes it unsuitable for chemical engineering calculations, e. g. for clothes dryers, where temperature can vary considerably. Mass of water per unit volume as in the equation above is defined as volumetric humidity. Because of the confusion, British Standard BS1339 suggests avoiding the term absolute humidity. Units should always be carefully checked, many humidity charts are given in g/kg or kg/kg, but any mass units may be used. The field concerned with the study of physical and thermodynamic properties of mixtures is named psychrometrics
30.
Flood
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A flood is an overflow of water that submerges land which is usually dry. The European Union Floods Directive defines a flood as a covering by water of land not normally covered by water, in the sense of flowing water, the word may also be applied to the inflow of the tide. Floods can also occur in rivers when the flow exceeds the capacity of the river channel. Floods often cause damage to homes and businesses if they are in the flood plains of rivers. Some floods develop slowly, while others such as floods, can develop in just a few minutes. Additionally, floods can be local, impacting a neighborhood or community, or very large, the word flood comes from the Old English flod, a word common to Germanic languages. Deluge myths are stories of a great flood sent by a deity or deities to destroy civilization as an act of divine retribution. Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths, surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience flooding during periods when precipitation exceeds evaporation. Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the worlds largest rivers. When overland flow occurs on tilled fields, it can result in a flood where sediments are picked up by run off. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, the cause may be localized convective precipitation or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. In one instance, a flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the rate increased from about 50 to 1,500 cubic feet per second in just one minute. Two larger floods occurred at the site within a week
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Digital elevation model
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A digital elevation model is a digital model or 3D representation of a terrains surface — commonly for a planet, moon, or asteroid — created from terrain elevation data. There is no usage of the terms digital elevation model, digital terrain model. In most cases the term digital surface model represents the earths surface, in contrast to a DSM, the digital terrain model represents the bare ground surface without any objects like plants and buildings. DEM is often used as a term for DSMs and DTMs. Other definitions equalise the terms DEM and DTM, or define the DEM as a subset of the DTM, there are also definitions which equalise the terms DEM and DSM. On the Web definitions can be found which define DEM as a regularly spaced GRID, most of the data providers use the term DEM as a generic term for DSMs and DTMs. All datasets which are captured with satellites, airplanes or other flying platforms are originally DSMs and it is possible to compute a DTM from high resolution DSM datasets with complex algorithms. In the following the term DEM is used as a term for DSMs and DTMs. A DEM can be represented as a raster or as a vector-based triangular irregular network, the TIN DEM dataset is also referred to as a primary DEM, whereas the Raster DEM is referred to as a secondary DEM. The DEM could be acquired through techniques such as photogrammetry, lidar, IfSAR, land surveying, DEMs are commonly built using data collected using remote sensing techniques, but they may also be built from land surveying. DEMs are used often in information systems, and are the most common basis for digitally produced relief maps. Mappers may prepare digital elevation models in a number of ways, the SPOT1 satellite provided the first usable elevation data for a sizeable portion of the planets landmass, using two-pass stereoscopic correlation. The HRS instrument on SPOT5 has acquired over 100 million square kilometers of stereo pairs, older methods of generating DEMs often involve interpolating digital contour maps that may have been produced by direct survey of the land surface. This method is used in mountain areas, where interferometry is not always satisfactory. Note that contour line data or any other sampled elevation datasets are not DEMs, a DEM implies that elevation is available continuously at each location in the study area. The quality of a DEM is a measure of how accurate elevation is at each pixel, the limitation with the GTOPO30 and SRTM datasets is that they cover continental landmasses only, and SRTM does not cover the polar regions and has mountain and desert no data areas. SRTM data, being derived from radar, represents the elevation of the first-reflected surface — quite often tree tops, so, the data are not necessarily representative of the ground surface, but the top of whatever is first encountered by the radar. Submarine elevation data is generated using ship-mounted depth soundings, when land topography and bathymetry is combined, a truly Global Relief Model is obtained
32.
Interferometry
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Interferometry is a family of techniques in which waves, usually electromagnetic waves, are superimposed causing the phenomenon of interference in order to extract information. Interferometers are widely used in science and industry for the measurement of small displacements, refractive index changes, in an interferometer, light from a single source is split into two beams that travel different optical paths, then combined again to produce interference. The resulting interference fringes give information about the difference in path length, waves which are not completely in phase nor completely out of phase will have an intermediate intensity pattern, which can be used to determine their relative phase difference. Most interferometers use light or some form of electromagnetic wave. Typically a single incoming beam of coherent light will be split into two beams by a beam splitter. Each of these beams travels a different route, called a path, the path difference, the difference in the distance traveled by each beam, creates a phase difference between them. It is this phase difference that creates the interference pattern between the initially identical waves. If a single beam has been split along two paths, then the difference is diagnostic of anything that changes the phase along the paths. This could be a change in the path length itself or a change in the refractive index along the path. As seen in Fig. 2a and 2b, the observer has a view of mirror M1 seen through the beam splitter. The fringes can be interpreted as the result of interference between light coming from the two virtual images S1 and S2 of the original source S, the characteristics of the interference pattern depend on the nature of the light source and the precise orientation of the mirrors and beam splitter. In Fig. 2a, the elements are oriented so that S1 and S2 are in line with the observer. Use of white light will result in a pattern of colored fringes, the central fringe representing equal path length may be light or dark depending on the number of phase inversions experienced by the two beams as they traverse the optical system. Interferometers and interferometric techniques may be categorized by a variety of criteria, In homodyne detection, the phase difference between the two beams results in a change in the intensity of the light on the detector. The resulting intensity of the light after mixing of two beams is measured, or the pattern of interference fringes is viewed or recorded. Most of the interferometers discussed in this article fall into this category, the heterodyne technique is used for shifting an input signal into a new frequency range as well as amplifying a weak input signal. A weak input signal of frequency f1 is mixed with a reference frequency f2 from a local oscillator. The nonlinear combination of the input signals creates two new signals, one at the sum f1 + f2 of the two frequencies, and the other at the difference f1 − f2 and these new frequencies are called heterodynes
33.
Atmospheric dispersion modeling
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Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. It is performed with programs that solve the mathematical equations. They can also be used to predict future concentrations under specific scenarios, therefore, they are the dominant type of model used in air quality policy making. They are most useful for pollutants that are dispersed over large distances, for pollutants that have a very high spatio-temporal variability and for epidemiological studies statistical land-use regression models are also used. Dispersion models are important to governmental agencies tasked with protecting and managing the ambient air quality, the models also serve to assist in the design of effective control strategies to reduce emissions of harmful air pollutants. During the late 1960s, the Air Pollution Control Office of the U. S. EPA initiated research projects that would lead to the development of models for the use by urban and transportation planners. A major and significant application of a dispersion model that resulted from such research was applied to the Spadina Expressway of Canada in 1971. Air dispersion models are used by public safety responders and emergency management personnel for emergency planning of accidental chemical releases. Appropriate protective actions may include evacuation or shelter in place for persons in the downwind direction, at industrial facilities, this type of consequence assessment or emergency planning is required under the Clean Air Act codified in Part 68 of Title 40 of the Code of Federal Regulations. Source term and temperature of the material Emissions or release parameters such as location and height, type of source and exit velocity, exit temperature. Terrain elevations at the location and at the receptor location, such as nearby homes, schools, businesses. The location, height and width of any obstructions in the path of the emitted gaseous plume, the plots of areas impacted may also include isopleths showing areas of minimal to high concentrations that define areas of the highest health risk. The isopleths plots are useful in determining protective actions for the public, the atmospheric dispersion models are also known as atmospheric diffusion models, air dispersion models, air quality models, and air pollution dispersion models. Discussion of the layers in the Earths atmosphere is needed to understand where airborne pollutants disperse in the atmosphere, the layer closest to the Earths surface is known as the troposphere. It extends from sea-level to a height of about 18 km, the stratosphere is the next layer and extends from 18 km to about 50 km. The third layer is the mesosphere which extends from 50 km to about 80 km, there are other layers above 80 km, but they are insignificant with respect to atmospheric dispersion modeling. The lowest part of the troposphere is called the boundary layer or the planetary boundary layer. The air temperature of the boundary layer decreases with increasing altitude until it reaches what is called the inversion layer that caps the atmospheric boundary layer
34.
Cartography
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Cartography is the study and practice of making maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively, the fundamental problems of traditional cartography are to, Set the maps agenda and select traits of the object to be mapped. This is the concern of map editing, traits may be physical, such as roads or land masses, or may be abstract, such as toponyms or political boundaries. Represent the terrain of the object on flat media. This is the concern of map projections, eliminate characteristics of the mapped object that are not relevant to the maps purpose. This is the concern of generalization, reduce the complexity of the characteristics that will be mapped. This is also the concern of generalization, orchestrate the elements of the map to best convey its message to its audience. This is the concern of map design, modern cartography constitutes many theoretical and practical foundations of geographic information systems. The earliest known map is a matter of debate, both because the term map isnt well-defined and because some artifacts that might be maps might actually be something else. A wall painting that might depict the ancient Anatolian city of Çatalhöyük has been dated to the late 7th millennium BCE, the oldest surviving world maps are from 9th century BCE Babylonia. One shows Babylon on the Euphrates, surrounded by Assyria, Urartu and several cities, all, in turn, another depicts Babylon as being north of the world center. The ancient Greeks and Romans created maps since Anaximander in the 6th century BCE, in the 2nd century AD, Ptolemy wrote his treatise on cartography, Geographia. This contained Ptolemys world map – the world known to Western society. As early as the 8th century, Arab scholars were translating the works of the Greek geographers into Arabic, in ancient China, geographical literature dates to the 5th century BCE. The oldest extant Chinese maps come from the State of Qin, dated back to the 4th century BCE, in the book of the Xin Yi Xiang Fa Yao, published in 1092 by the Chinese scientist Su Song, a star map on the equidistant cylindrical projection. Early forms of cartography of India included depictions of the pole star and these charts may have been used for navigation. Mappa mundi are the Medieval European maps of the world, approximately 1,100 mappae mundi are known to have survived from the Middle Ages. Of these, some 900 are found illustrating manuscripts and the remainder exist as stand-alone documents, the Arab geographer Muhammad al-Idrisi produced his medieval atlas Tabula Rogeriana in 1154
35.
Snow
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Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime. As snow accumulates into a snowpack, it may blow into drifts, over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form, otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture. In the Southern Hemisphere, snow is confined primarily to mountainous areas, Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds that themselves are part of a weather system. The physics of snow crystal development in clouds results from a set of variables that include moisture content. The resulting shapes of the falling and fallen crystals can be classified into a number of shapes and combinations. Occasionally, some plate-like, dendritic and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Two additional and locally productive sources of snow are lake-effect storms and elevation effects, miid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemispheres fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall, in the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side, a cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, in cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air, often, snow transitions to rain in the warm sector behind the front. The same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the air mass is uplifted by the orographic influence of higher elevations on the downwind shores
36.
Ice
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Ice is water frozen into a solid state. Depending on the presence of such as particles of soil or bubbles of air. In the Solar System, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far as away the Oort cloud objects, beyond the Solar System, it occurs as interstellar ice. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes, Ice molecules can exhibit up to sixteen different phases that depend on temperature and pressure. When water is cooled rapidly, up to three different types of ice can form depending on the history of its pressure and temperature. When cooled slowly correlated proton tunneling occurs below 20 K giving rise to macroscopic quantum phenomena, virtually all the ice on Earths surface and in its atmosphere is of a hexagonal crystalline structure denoted as ice Ih with minute traces of cubic ice denoted as ice Ic. The most common phase transition to ice Ih occurs when water is cooled below 0°C at standard atmospheric pressure. It may also be deposited directly by water vapor, as happens in the formation of frost, the transition from ice to water is melting and from ice directly to water vapor is sublimation. Ice is used in a variety of ways, including cooling, winter sports, as a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered a mineral. It possesses a regular crystalline structure based on the molecule of water, an unusual property of ice frozen at atmospheric pressure is that the solid is approximately 8. 3% less dense than liquid water. The density of ice is 0.9167 g/cm3 at 0 °C, liquid water is densest, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid, density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm³ at −180 °C. When water freezes, it increases in volume and it is also a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes. The result of this process is that ice floats on liquid water, sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weather extremes such as wind chill. This creates an environment for bacterial and algal colonies. When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 °C, during the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the bonds between ice molecules. Energy becomes available to increase the thermal energy only after enough hydrogen bonds are broken that the ice can be considered liquid water, the amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the heat of fusion
37.
Photovoltaic system
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A photovoltaic system, also PV system or solar power system, is a power system designed to supply usable solar power by means of photovoltaics. It may also use a tracking system to improve the systems overall performance and include an integrated battery solution. Strictly speaking, a solar array only encompasses the ensemble of solar panels, the part of the PV system. Moreover, PV systems convert light directly into electricity and shouldnt be confused with other technologies, such as concentrated solar power or solar thermal, used for heating and cooling. PV systems range from small, rooftop-mounted or building-integrated systems with capacities from a few to tens of kilowatts. Nowadays, most PV systems are grid-connected, while off-grid or stand-alone systems only account for a portion of the market. A rooftop system recoups the energy for its manufacturing and installation within 0.7 to 2 years. Due to the growth of photovoltaics, prices for PV systems have rapidly declined in recent years. However, they vary by market and the size of the system, a photovoltaic system converts the suns radiation into usable electricity. It comprises the solar array and the balance of system components, other distinctions may include, systems with microinverters vs. central inverter, systems using crystalline silicon vs. thin-film technology, and systems with modules from Chinese vs. About 99 percent of all European and 90 percent of all U. S. solar power systems are connected to the grid, while off-grid systems are somewhat more common in Australia. PV systems rarely use battery storage and this may change soon, as government incentives for distributed energy storage are being implemented and investments in storage solutions are gradually becoming economically viable for small systems. A solar array of a typical residential PV system is rack-mounted on the roof, rather than integrated into the roof or facade of the building, utility-scale solar power stations are ground-mounted, with fixed tilted solar panels rather than using expensive tracking devices. Crystalline silicon is the predominant material used in 90 percent of worldwide produced solar modules, about 70 percent of all solar cells and modules are produced in China and Taiwan, leaving only 5 percent to European and US-manufacturers. S. Which are less opposed to ground-mounted solar farms and cost-effectiveness is more emphasized by investors, driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics is declining continuously. There are several million PV systems distributed all over the world, mostly in Europe, in exceptionally irradiated locations, or when thin-film technology is used, the so-called energy payback time decreases to one year or less. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have greatly supported installations of PV systems in many countries. As of 2015, the fast-growing global PV market is approaching the 200 GW mark – about 40 times the installed capacity of 2006
38.
Water
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Water is a transparent and nearly colorless chemical substance that is the main constituent of Earths streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that its molecule contains one oxygen, Water strictly refers to the liquid state of that substance, that prevails at standard ambient temperature and pressure, but it often refers also to its solid state or its gaseous state. It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, Water covers 71% of the Earths surface. It is vital for all forms of life. Only 2. 5% of this water is freshwater, and 98. 8% of that water is in ice and groundwater. Less than 0. 3% of all freshwater is in rivers, lakes, and the atmosphere, a greater quantity of water is found in the earths interior. Water on Earth moves continually through the cycle of evaporation and transpiration, condensation, precipitation. Evaporation and transpiration contribute to the precipitation over land, large amounts of water are also chemically combined or adsorbed in hydrated minerals. Safe drinking water is essential to humans and other even though it provides no calories or organic nutrients. There is a correlation between access to safe water and gross domestic product per capita. However, some observers have estimated that by 2025 more than half of the population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in developing regions of the world. Water plays an important role in the world economy, approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a source of food for many parts of the world. Much of long-distance trade of commodities and manufactured products is transported by boats through seas, rivers, lakes, large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a variety of chemical substances, as such it is widely used in industrial processes. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, Water is a liquid at the temperatures and pressures that are most adequate for life. Specifically, at atmospheric pressure of 1 bar, water is a liquid between the temperatures of 273.15 K and 373.15 K
39.
Atmosphere
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An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is likely to be retained if the gravity it is subject to is high. The atmosphere of Earth is mostly composed of nitrogen, oxygen, argon with carbon dioxide, the atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of modification of the paleoatmosphere by living organisms. The term stellar atmosphere describes the region of a star. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere, Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the recognized standard atmosphere. It is measured with a barometer, the pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above. The height at which the pressure from an atmosphere declines by a factor of e is called the height and is denoted by H. For such an atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the determination of the atmospheric pressure at any particular altitude is more complex. Surface gravity, the force that holds down an atmosphere, differs significantly among the planets, for example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from objects with lower gravity. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite their relatively low gravities, rogue planets, theoretically, may also retain thick atmospheres. Since a collection of gas molecules may be moving at a range of velocities. Lighter molecules move faster than ones with the same thermal kinetic energy. It is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, Earths magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the polar regions due to auroral activity
40.
ERS 1
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European remote sensing satellite was the European Space Agencys first Earth-observing satellite programme using a polar orbit. The first satellite was launched on 17 July 1991 into a Sun-synchronous polar orbit at an altitude of 782–785 km, ERS-1 carried an array of earth-observation instruments that gathered information about the Earth using a variety of measurement principles. These included, RA is a single frequency nadir-pointing radar altimeter operating in the Ku band, aTSR-1 is a 4 channel infrared radiometer and microwave sounder for measuring temperatures at the sea-surface and the top of clouds. SAR operating in C band can detect changes in surface heights with sub-millimeter precision, Wind Scatterometer used to calculate information on wind speed and direction. MWR is a Microwave Radiometer used in measuring atmospheric water, as well as providing a correction for the water for the altimeter. To accurately determine its orbit, the satellite included the PRARE, the PRARE became non-operational shortly after launch. The Retroreflector was used for calibrating the Radar Altimeter to within 10 cm, ERS-1 had various mission phases using 3-day, 35-day and a 336-day repeat cycle. The 336-day mission allowed for mapping of the Earths bathymetry. ERS-1 failed on 10 March 2000, far exceeding its expected lifespan and its successor, ERS-2, was launched on 21 April 1995, on an Ariane 4, from ESAs Guiana Space Centre near Kourou, French Guiana. Largely identical to ERS-1, it added additional instruments and included improvements to existing instruments including, GOME is a nadir scanning ultraviolet, aTSR-2 included 3 visible spectrum bands specialized for Chlorophyll and Vegetation When ERS-2 was launched, ERS-1 shared the same orbital plane. This allowed a tandem mission, with ERS-2 passing the point on the ground 1 day later than ERS-1. ERS-2 has a cycle of 35 days. ERS-2 has been operating without gyroscopes since February 2001, resulting in degradation of the data provided by the instruments. The tape drive aboard failed on 22 June 2003, leaving the instruments operating only within visibility of a ground station, since the tape drive failure additional ground stations have been brought online to increase the data gathering abilities of the satellite. The Wind Scatterometer and GOME were the instruments of their kind until the launches of MetOp-A and Envisat. The successor to ERS-2 is Envisat containing improved versions of many of the instruments onboard ERS-2, however, over a series of burns in July, August and September, ERS-2 was finally depleted of all fuel on 5 September 2011. In the final stages of emptying the fuel tanks, it was estimated that they would be empty after a 40-minute burn on 2 September 2011, however, the spacecraft survived both this maneuver and a second 40-minute burn on 3 September. On 5 September a third burn was initiated and the tanks were finally drained
