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Standard gravitational parameter

In celestial mechanics, the standard gravitational parameter μ of a celestial body is the product of the gravitational constant G and the mass M of the body. Μ = G M For several objects in the Solar System, the value of μ is known to greater accuracy than either G or M. The SI units of the standard gravitational parameter are m3 s−2. However, units of km3 s−2 are used in the scientific literature and in spacecraft navigation; the central body in an orbital system can be defined as the one whose mass is much larger than the mass of the orbiting body, or M ≫ m. This approximation is standard for planets orbiting the Sun or most moons and simplifies equations. Under Newton's law of universal gravitation, if the distance between the bodies is r, the force exerted on the smaller body is: F = G M m r 2 = μ m r 2 Thus only the product of G and M is needed to predict the motion of the smaller body. Conversely, measurements of the smaller body's orbit only provide information on the product, μ, not G and M separately.

The gravitational constant, G, is difficult to measure with high accuracy, while orbits, at least in the solar system, can be measured with great precision and used to determine μ with similar precision. For a circular orbit around a central body: μ = r v 2 = r 3 ω 2 = 4 π 2 r 3 T 2 where r is the orbit radius, v is the orbital speed, ω is the angular speed, T is the orbital period; this can be generalized for elliptic orbits: μ = 4 π 2 a 3 T 2 where a is the semi-major axis, Kepler's third law. For parabolic trajectories rv2 is constant and equal to 2μ. For elliptic and hyperbolic orbits μ = 2a | ε |. In the more general case where the bodies need not be a large one and a small one, e.g. a binary star system, we define: the vector r is the position of one body relative to the other r, v, in the case of an elliptic orbit, the semi-major axis a, are defined accordingly μ = Gm1 + Gm2 = μ1 + μ2, where m1 and m2 are the masses of the two bodies. Then: for circular orbits, rv2 = r3ω2 = 4π2r3/T2 = μ for elliptic orbits, 4π2a3/T2 = μ for parabolic trajectories, rv2 is constant and equal to 2μ for elliptic and hyperbolic orbits, μ is twice the semi-major axis times the negative of the specific orbital energy, where the latter is defined as the total energy of the system divided by the reduced mass.

GM⊕, the gravitational parameter for the Earth as the central body, is called the geocentric gravitational constant. It equals ×1014 m3 s−2; the value of this constant became important with the beginning of spaceflight in the 1950s, great effort was expended to determine it as as possible during the 1960s. Sagitov cites a range of values reported from 1960s high-precision measurements, with a relative uncertainty of the order of 10−6. During the 1970s to 1980s, the increasing number of artificial satellites in Earth orbit further facilitated high-precision measurements, the relative uncertainty was decreased by another three orders of magnitude, to about 2×10−9 as of 1992. Measurement involves observations of the distances from the satellite to Earth stations at different times, which can be obtained to high accuracy using radar or laser ranging. GM☉, the gravitational parameter for the Sun as the central body, is called the heliocentric gravitational constant or geopotential of the Sun and equals ×1020 m3 s−2.

The relative uncertainty in GM☉, cited at below 10−10 as of 2015, is smaller than the uncertainty in GM⊕ because GM☉ is derived from the ranging of interplanetary probes, the absolute error of the distance measures to them is about the same as the earth satellite ranging measures, while the absolute distances involved are much bigger. Astronomical system of units Planetary mass

Ordos City

Ordos is one of the twelve major subdivisions of Inner Mongolia, China. It lies within the Ordos Plateau of the Yellow River. Although rural, Ordos is administered as a prefecture-level city. Ordos is known for its large scale government projects undertaken including most prominently the new Kangbashi District, an urban district planned as a massive civic mall with abundant monuments, cultural institutions, other showpiece architecture, it was the venue for the 2012 Miss World Final. When it was newly built, the streets of the new Kangbashi district didn't have much activity, the district was described as a "ghost city" by several western media outlets. However, by 2017, Kangbashi had become more populated with a resident population of 153,000 and around one-third of apartments occupied. In a Forbes article, Wade Shepard noted that "Of the 40,000 apartments, built in the new district since 2004, only 500 are still on the market; the area had been administered under the Ih Ju League spelled Ikh Juu since the 17th century, was redesignated a prefecture-level city and renamed to Ordos on 26 February 2001.

"Ordos" means "palaces" in the Mongolian language. Ordos referred to a tribe belonging to the Yeke Juu league and included the tribe's area, hence the Ordos, or Ordus, the area within the big bend of the Yellow River. Mongolian ordu, ord ` residence of a ruler. According to Ramstedt -s is a plural suffix; the name is sometimes claimed to be related to the eight white yurts of Genghis Khan. Linguistically, the Ordos dialect of Mongolian is quite different from neighboring Chakhar Mongolian. At the southern end of the Ordos grassland, there is a river originating from Dingbian County in northwestern Shaanxi, flowing through the Otog Banner and Uxin Banner in Inner Mongolia, flowing from the east of Batuwan Village into the territory of northern Shanxi, after converging with Xiangshui River, it flows into a tributary of the Yellow River, to the southeast. In the loose Mu Us Sandyland, a “U” shaped river valley is washed out; this river is known as the Sarawusu River. Sara Wusu, Mongolian means yellow water, which means that the river here is yellow all the year round.

It is in this river. In 1922, the French Catholic priest Sang Zhihua first discovered a fossil of the "Hetao People" here. Since Chinese archaeologists have visited the site many times. A large number of cultural relics have been discovered, as early as 35,000 years ago, "Hetao people" lived here; the material culture created by the “Hetao People” is now called “Salawusu Culture”. After a comprehensive analysis of geology, animal fossils and stone tools, the Sarawusu culture was identified as the late Paleolithic culture. Hetao civilization is the product of the integration of grassland culture and Yellow River civilization, its long-term development and complex transmutation process the relationship with Urad and Ordos Mongolian culture illustrates the relationship between Hetao civilization and Yellow River civilization. Hetao culture is one of the important components of the mainstream culture of the northern grasslands. In the grassland culture, the Hetao culture is both a stream; as a source, Hetao culture has a historical accumulation of symbiosis with the northern grassland culture.

As a stream, it is different from the Mongolian classic culture in the eastern part of Inner Mongolia, such as Hongshan culture and Khorchin Mongols culture. It has its unique development trend. In the origin of grassland culture, it is a source of the late Paleolithic period, which originated from the prosperity of ancient ethnic minorities, it was formed in the Qin, Han and Qing Dynasties, it is a cultural system of modern and contemporary civilization. It is an independent unit culture circle of grassland culture and a complete regional cultural system, which plays an important role in the composition of grassland culture. Before the Zhou Dynasty, it was a nomadic area such as the Lin Hu. In the Warring States Period, it was the Yunzhong County of the Zhao State Territory, belonged to the Qin State. At the beginning of the Han Dynasty, it was the front line of the Han wars. Emperor Wu of Han Dynasty set up the Shuofang County here; when Emperor Xuan of Han called the Huxie Chanyu to come, he became the residence of the Southern Xiongnu.

Hu Han lived in harmony, the Uprising of the Five Barbarians broke out in the Western Jin Dynasty. Sixteen Kingdoms were the post-Qin territory; the Northern Dynasties belonged to the Northern Wei Dynasty, the Western Wei Dynasty, the Northern Zhou Dynasty. In the Sui and Tang Dynasties, they were all territories. In the Tang Dynasty, they were placed in the party, the famous General Guo Ziyi once held this position. During the Anshi Rebellion, Emperor Suzong of Tang fled to this place. Qin Zhidao was an important military road for Qin Shihuang to be supervised by Meng Tian from 212 BC to 210 BC. Qinzhidao starts from Yunyang Linguang Palace in the Xianyang military site, goes to Jiuyuan County in the north. Qinzhidao passes through Ordos City, three Banners and one district, the Qinzhidao site protection unit is established in Ordos City. One of the northern border counties of the Han Dynasty, the Sufang County was set

Bilbao Exhibition Centre

The Bilbao Exhibition Centre is an exhibition centre in Barakaldo, Basque Country, Spain. The current headquarters of the Feria de Muestras de Bilbao, its facilities are located on land occupied by the Basque iron company Altos Hornos de Vizcaya in the neighbourhood of Ansio in Barakaldo, in the Greater Bilbao area; these facilities, opened in April 2004, allow for high capacity international fairs with better services and connections than the previous facilities in central Bilbao. The Bilbao Exhibition Centre is jointly owned by the Basque Government, the Provincial Council of Biscay, Bilbao Municipal Council, Barakaldo Municipal Council and the Bilbao Chamber of Commerce; the Bilbao Exhibition Centre covers an area of 251,055 square metres, of which 246,457 square metres are distributed in six pavilions without any columns intended for exhibitions, while the rest houses a shopping mall and a hotel. In addition to the exhibition halls, the complex has a VIP hall, a conference centre, 6,500 square feet dedicated to office space, a large atrium.

It has an underground car park with capacity for 4,000 vehicles. On the roof, a photovoltaic solar energy park has been installed, it has become one of the largest the Basque Country; the park has 628 solar photovoltaic panels and achieves an output of 100 kW in an area of 1,000 square metres. The BEC Tower, at 92.83 metres high, was the tallest building the Basque Country when it opened, higher than the BBVA Tower in central Bilbao, at 88 metres in height. In 2009, the title of tallest building went to the Iberdrola Tower, finished in 2011 and has a height of 165 metres. A restaurant and the offices of the BEC company are located in the tower. Bizkaia Arena is the largest multi-purpose hall in Spain, since it can accommodate up to 26,000 people, 18,640 for most indoor sports, it forms part of Bilbao Exhibition Centre complex. The venue hosts basketball matches. Between 2009 and 2010, it was the home arena of Bilbao Basket; the arena was the venue of the final stage of the 2010 Copa del Rey de Baloncesto, was one of the sites of 2014 FIBA Basketball World Cup, hosted by Spain.

The arena hosted the annual MTV Europe Music Awards in 2018 as the awards show was held in Spain for the third time and the first time in Bilbao. Several national and international fairs are held in the BEC facilities, including Ferroforma, the Biennial Machine-Tool Fair, the Euskal Encounter. In the Bizkaia Arena, basketball games, motocross races, music concerts are held; the main political parties in the region hold campaign events and sometimes their congresses there. Several labour unions and business organisations hold a variety of meetings and conventions; the Jehovah's Witnesses have held their December meetings there for several years. Alongside the construction of the BEC, the Ansio station on Line 2 of Metro Bilbao was built; the station deals with heavy passenger traffic when there is some event at the BEC, so Metro Bilbao offers special services for such events, such as delaying the closing time and stepping up frequencies. Opposite the main entrance of the BEC, there are two Bizkaibus stops: one for the 3142 line, line 3136.

Around the centre are other Bizkaibus stops. Media related to Bilbao Exhibition Centre at Wikimedia Commons Official website Virtual Tour

The Final Showdown

Star Wars: The Jedi Quest – The Final Showdown is the tenth and final novel set in the Jedi Quest series, set in the Star Wars galaxy. It is written by Jude Watson, was released on November 1, 2004; the book was published by Scholastic, first in hardcover in paperback. The cover art is by David Mattingly. Granta Omega is an evil mastermind. Now, Omega has escaped to the planet of Korriban, graveyard of the ancient Sith and home to their most powerful secrets. It's up to Obi-Wan Kenobi and Anakin Skywalker to intercept this madman before his sinister power grows out of control. Accompanying the pair on this mission is Anakin's rival, Ferus Olin; the competitive Anakin sees the search for Omega as a contest to be won. But such thoughts are unbecoming of a Jedi, as the quest plunges deeper into the dark side, Jedi disciplines may be all that stave off the inevitable outcome of this showdown: Death. Listing Official CargoBay Listing

Oklahoma State Highway 89

State Highway 89 is a state highway in the southern part of the U. S. state of Oklahoma. It runs from the Taovayas Indian Bridge at the Texas state line to State Highway 53, a distance of 30.3 miles. SH-89 was designated on July 26, 1944, it has no lettered spur routes. State Highway 89 begins at the Taovayas Indian Bridge on the Illinois Bend of the Red River, continuing Farm to Market Road 677 from Texas. One mile north of the river, it intersects SH-32 at Courtney. SH-89 overlaps SH-32 for 6.1 miles headed due west, but curving around to the northwest and the north, crossing into Jefferson County and passing through unincorporated Petersburg. SH-32 angles off to the northwest while SH-89 continues on a due north course. After splitting off to the north, SH-89 travels through eastern Jefferson County for 13.4 miles paralleling the county line. The highway continues along a rough northerly heading, though it heads northwest at times. SH-89 runs to the east of the town of Cornish, intersects US-70 as it enters Ringling.

After passing through the town, it curves northwest. SH-89 turns back to a due north course, which it will maintain for the rest of its existence; the highway comes to an end 9.8 miles north of Ringling at SH-53 east of Loco. State Highway 89 was first added to the Oklahoma state highway system on July 26, 1944; the original extent of the highway was from the current northern junction with SH-32 to US-70 in Ringling. These remained the route's termini until January 21, 1957, when it was extended north through Ringling to SH-53, setting its northern terminus at its present location. Minor realignments would take place during the next two years, after which the highway would remain the same for three decades. On September 6, 1994, the highway was extended south. SH-89 now overlapped SH-32 to Courtney, where it split away towards its new southern terminus at the Texas state line; the highway has undergone no further changes since this extension. SH-89 at Roadklahoma


Airspace is the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more any specific three-dimensional portion of the atmosphere. It is not the same as aerospace, the general term for Earth's atmosphere and the outer space in its vicinity. Within the United States: Controlled airspace exists where it is deemed necessary that air traffic control has some form of positive executive control over aircraft flying in that airspace. Airspace may be further subdivided into a variety of areas and zones, including those where there are either restrictions on flying activities or complete prohibition of flying activities. By international law, a state "has complete and exclusive sovereignty over the airspace above its territory", which corresponds with the maritime definition of territorial waters as being 12 nautical miles out from a nation's coastline. Airspace not within any country's territorial limit is considered international, analogous to the "high seas" in maritime law.

However, a country may, by international agreement, assume responsibility for controlling parts of international airspace, such as those over the oceans. Such airspace in respect of which a country is responsible under the International Civil Aviation Organisation for operational control is called a Flight Information Region. For a coastal state, the FIR consists of the airspace above its land and sea territory plus any international airspace in respect of which ICAO has assigned responsibility to that state. For instance, the United States provides air traffic control services over a large part of the Pacific Ocean though the airspace is international. There is no international agreement on the vertical extent of sovereign airspace, with suggestions ranging from about 30 km —the extent of the highest aircraft and balloons—to about 160 km —the lowest extent of short-term stable orbits; the Fédération Aéronautique Internationale has established the Kármán line—at an altitude of 100 km —as the boundary between the Earth's atmosphere and outer space, while the United States considers anyone who has flown above 80 kilometres to be an astronaut.

Indeed, descending space shuttles have flown closer than 80 km over other nations, such as Canada, without requesting permission first. Nonetheless, both the Kármán line and the U. S. definition are working benchmarks, without any real legal authority over matters of national sovereignty. The boundary between public airspace and private air rights is defined by local law. Controlled airspace is a generic term that covers the different classifications of airspace and defined dimensions within which air traffic control service is provided in accordance with the airspace classification. Controlled airspace consists of: Class A Class B Class C Class D Class E Class A airspace is the airspace from 18,000 feet mean sea level up to and including flight level 600, including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous states and Alaska. Unless otherwise authorized, all operation in Class A airspace is conducted under instrument flight rules. Class B airspace is airspace from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of airport operations or passenger enplanements.

The configuration of each Class B airspace area is individually tailored, consists of a surface area and two or more layers, is designed to contain all published instrument procedures once an aircraft enters the airspace. An ATC clearance is required for all aircraft to operate in the area, all aircraft that are so cleared receive separation services within the airspace. Class C airspace is airspace from the surface to 4,000 feet above the airport elevation surrounding those airports that have an operational control tower, are serviced by a radar approach control, have a certain number of IFR operations or passenger enplanements. Although the configuration of each Class C area is individually tailored, the airspace consists of a surface area with a five NM radius, an outer circle with a ten NM radius that extends from 1,200 feet to 4,000 feet above the airport elevation, an outer area; each aircraft must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while within the airspace.

Class D airspace is airspace from the surface to 2,500 feet above the airport elevation surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored and when instrument procedures are published, the airspace is designed to contain the procedures. Arrival extensions for instrument approach procedures may be Class E airspace. Unless otherwise authorized, each aircraft must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while in the airspace. If the airspace is not Class A, B, C, or D, is controlled airspace it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace; when designated as a surface area, the airspace is configured to contain all instrument procedures. In this class are federal airways, airspace beginning at either 700 or 1,200 feet