The term apsis refers to an extreme point in the orbit of an object. It denotes either the respective distance of the bodies; the word comes via Latin from Greek, there denoting a whole orbit, is cognate with apse. Except for the theoretical possibility of one common circular orbit for two bodies of equal mass at diametral positions, there are two apsides for any elliptic orbit, named with the prefixes peri- and ap-/apo-, added in reference to the body being orbited. All periodic orbits are, according to Newton's Laws of motion, ellipses: either the two individual ellipses of both bodies, with the center of mass of this two-body system at the one common focus of the ellipses, or the orbital ellipses, with one body taken as fixed at one focus, the other body orbiting this focus. All these ellipses share a straight line, the line of apsides, that contains their major axes, the foci, the vertices, thus the periapsis and the apoapsis; the major axis of the orbital ellipse is the distance of the apsides, when taken as points on the orbit, or their sum, when taken as distances.
The major axes of the individual ellipses around the barycenter the contributions to the major axis of the orbital ellipses are inverse proportional to the masses of the bodies, i.e. a bigger mass implies a smaller axis/contribution. Only when one mass is sufficiently larger than the other, the individual ellipse of the smaller body around the barycenter comprises the individual ellipse of the larger body as shown in the second figure. For remarkable asymmetry, the barycenter of the two bodies may lie well within the bigger body, e.g. the Earth–Moon barycenter is about 75% of the way from Earth's center to its surface. If the smaller mass is negligible compared to the larger the orbital parameters are independent of the smaller mass. For general orbits, the terms periapsis and apoapsis are used. Pericenter and apocenter are equivalent alternatives, referring explicitly to the respective points on the orbits, whereas periapsis and apoapsis may refer to the smallest and largest distances of the orbiter and its host.
For a body orbiting the Sun, the point of least distance is the perihelion, the point of greatest distance is the aphelion. The terms become apastron when discussing orbits around other stars. For any satellite of Earth, including the Moon, the point of least distance is the perigee and greatest distance the apogee, from Ancient Greek Γῆ, "land" or "earth". For objects in lunar orbit, the point of least distance is sometimes called the pericynthion and the greatest distance the apocynthion. Perilune and apolune are used. In orbital mechanics, the apsides technically refer to the distance measured between the barycenters of the central body and orbiting body. However, in the case of a spacecraft, the terms are used to refer to the orbital altitude of the spacecraft above the surface of the central body; these formulae characterize the pericenter and apocenter of an orbit: Pericenter Maximum speed, v per = μ a, at minimum distance, r per = a. Apocenter Minimum speed, v ap = μ a, at maximum distance, r ap = a.
While, in accordance with Kepler's laws of planetary motion and the conservation of energy, these two quantities are constant for a given orbit: Specific relative angular momentum h = μ a Specific orbital energy ε = − μ 2 a where: a is the semi-major axis: a = r per + r ap 2 μ is the standard gravitational parameter e is the eccentricity, defined as e = r ap − r per r ap + r per = 1 − 2 r ap r per + 1 Note t
The kilometre, or kilometer is a unit of length in the metric system, equal to one thousand metres. It is now the measurement unit used for expressing distances between geographical places on land in most of the world. K is used in some English-speaking countries as an alternative for the word kilometre in colloquial writing and speech. A slang term for the kilometre in the US and UK military is klick. There are two common pronunciations for the word; the former follows a pattern in English whereby metric units are pronounced with the stress on the first syllable and the pronunciation of the actual base unit does not change irrespective of the prefix. It is preferred by the British Broadcasting Corporation and the Australian Broadcasting Corporation. Many scientists and other users in countries where the metric system is not used, use the pronunciation with stress on the second syllable; the latter pronunciation follows the stress pattern used for the names of measuring instruments. The problem with this reasoning, however, is that the word meter in those usages refers to a measuring device, not a unit of length.
The contrast is more obvious in countries using the British rather than American spelling of the word metre. When Australia introduced the metric system in 1975, the first pronunciation was declared official by the government's Metric Conversion Board. However, the Australian prime minister at the time, Gough Whitlam, insisted that the second pronunciation was the correct one because of the Greek origins of the two parts of the word. By the 8 May 1790 decree, the Constituent assembly ordered the French Academy of Sciences to develop a new measurement system. In August 1793, the French National Convention decreed the metre as the sole length measurement system in the French Republic; the first name of the kilometre was "Millaire". Although the metre was formally defined in 1799, the myriametre was preferred to the "kilometre" for everyday use; the term "myriamètre" appeared a number of times in the text of Develey's book Physique d'Emile: ou, Principes de la science de la nature, while the term kilometre only appeared in an appendix.
French maps published in 1835 had scales showing myriametres and "lieues de Poste". The Dutch gave it the local name of the mijl, it was only in 1867 that the term "kilometer" became the only official unit of measure in the Netherlands to represent 1000 metres. Two German textbooks dated 1842 and 1848 give a snapshot of the use of the kilometre across Europe - the kilometre was in use in the Netherlands and in Italy and the myriametre was in use in France. In 1935, the International Committee for Weights and Measures abolished the prefix "myria-" and with it the "myriametre", leaving the kilometre as the recognised unit of length for measurements of that magnitude. In the United Kingdom, road signs show distances in miles and location marker posts that are used for reference purposes by road engineers and emergency services show distance references in unspecified units which are kilometre-based; the advent of the mobile phone has been instrumental in the British Department for Transport authorising the use of driver location signs to convey the distance reference information of location marker posts to road users should they need to contact the emergency services.
In the US, the National Highway System Designation Act of 1995 prohibits the use of federal-aid highway funds to convert existing signs or purchase new signs with metric units. The Executive Director of the US Federal Highway Administration, Jeffrey Paniati, wrote in a 2008 memo: "Section 205 of the National Highway System Designation Act of 1995 prohibited us from requiring any State DOT to use the metric system during project development activities. Although the State DOT's had the option of using metric measurements or dual units, all of them abandoned metric measurements and reverted to sole use of inch-pound values." The Manual on Uniform Traffic Control Devices since 2000 is published in both metric and American Customary Units. Some sporting disciplines feature 1000 m races in major events, but in other disciplines though world records are catalogued, the one kilometre event remains a minority event; the world records for various sporting disciplines are: Conversion of units, for comparison with other units of length Cubic metre Metric prefix Mileage Odometer Orders of magnitude Square kilometre Media related to Distance indicators at Wikimedia Commons
Jet Propulsion Laboratory
The Jet Propulsion Laboratory is a federally funded research and development center and NASA field center in La Cañada Flintridge, United States, though it is referred to as residing in Pasadena, because it has a Pasadena ZIP Code. Founded in the 1930s, the JPL is owned by NASA and managed by the nearby California Institute of Technology for NASA; the laboratory's primary function is the construction and operation of planetary robotic spacecraft, though it conducts Earth-orbit and astronomy missions. It is responsible for operating NASA's Deep Space Network. Among the laboratory's major active projects are the Mars Science Laboratory mission, the Mars Reconnaissance Orbiter, the Juno spacecraft orbiting Jupiter, the NuSTAR X-ray telescope, the SMAP satellite for earth surface soil moisture monitoring, the Spitzer Space Telescope, it is responsible for managing the JPL Small-Body Database, provides physical data and lists of publications for all known small Solar System bodies. The JPL's Space Flight Operations Facility and Twenty-Five-Foot Space Simulator are designated National Historic Landmarks.
JPL traces its beginnings to 1936 in the Guggenheim Aeronautical Laboratory at the California Institute of Technology when the first set of rocket experiments were carried out in the Arroyo Seco. Caltech graduate students Frank Malina, Qian Xuesen, Weld Arnold, Apollo M. O. Smith, along with Jack Parsons and Edward S. Forman, tested a small, alcohol-fueled motor to gather data for Malina's graduate thesis. Malina's thesis advisor was engineer/aerodynamicist Theodore von Kármán, who arranged for U. S. Army financial support for this "GALCIT Rocket Project" in 1939. In 1941, Parsons, Martin Summerfield, pilot Homer Bushey demonstrated the first jet-assisted takeoff rockets to the Army. In 1943, von Kármán, Malina and Forman established the Aerojet Corporation to manufacture JATO rockets; the project took on the name Jet Propulsion Laboratory in November 1943, formally becoming an Army facility operated under contract by the university. During JPL's Army years, the laboratory developed two deployed weapon systems, the MGM-5 Corporal and MGM-29 Sergeant intermediate-range ballistic missiles.
These missiles were the first US ballistic missiles developed at JPL. It developed a number of other weapons system prototypes, such as the Loki anti-aircraft missile system, the forerunner of the Aerobee sounding rocket. At various times, it carried out rocket testing at the White Sands Proving Ground, Edwards Air Force Base, Goldstone, California. In 1954, JPL teamed up with Wernher von Braun's engineers at the Army Ballistic Missile Agency's Redstone Arsenal in Huntsville, Alabama, to propose orbiting a satellite during the International Geophysical Year; the team lost that proposal to Project Vanguard, instead embarked on a classified project to demonstrate ablative re-entry technology using a Jupiter-C rocket. They carried out three successful sub-orbital flights in 1956 and 1957. Using a spare Juno I, the two organizations launched the United States' first satellite, Explorer 1, on January 31, 1958. JPL was transferred to NASA in December 1958, becoming the agency's primary planetary spacecraft center.
JPL engineers designed and operated Ranger and Surveyor missions to the Moon that prepared the way for Apollo. JPL led the way in interplanetary exploration with the Mariner missions to Venus and Mercury. In 1998, JPL opened the Near-Earth Object Program Office for NASA; as of 2013, it has found 95% of asteroids that are a kilometer or more in diameter that cross Earth's orbit. JPL was early to employ female mathematicians. In the 1940s and 1950s, using mechanical calculators, women in an all-female computations group performed trajectory calculations. In 1961, JPL hired Dana Ulery as the first female engineer to work alongside male engineers as part of the Ranger and Mariner mission tracking teams. JPL has been recognized four times by the Space Foundation: with the Douglas S. Morrow Public Outreach Award, given annually to an individual or organization that has made significant contributions to public awareness of space programs, in 1998; when it was founded, JPL's site was west of a rocky flood-plain – the Arroyo Seco riverbed – above the Devil's Gate dam in the northwestern panhandle of the city of Pasadena.
While the first few buildings were constructed in land bought from the city of Pasadena, subsequent buildings were constructed in neighboring unincorporated land that became part of La Cañada Flintridge. Nowadays, most of the 177 acres of the U. S. federal government-owned NASA property that makes up the JPL campus is located in La Cañada Flintridge. Despite this, JPL still uses a Pasadena address as its official mailing address; the city of La Cañada Flintridge was incorporated in 1976, well after JPL attained international recognition as a Pasadena institution. There has been occasional rivalry between the two cities over the issue of which one should be mentioned in the media as the home of the laboratory. There are 6,000 full-time Caltech employees, a few thousand additional contractors working on any given day. NASA has a resident office at the facility staffed by federal managers who oversee JPL's activities and work for NASA. There are some Caltech graduate students, college student interns and co-op students.
The JPL Education Office serves educators and students by providi
The Flora family is a prominent family of stony asteroids located in the inner region of the asteroid belt. It is one of the largest families with more than 13,000 known members, or 3.5% of all main-belt asteroids. The origin and properties of this family are poorly understood, it is a broad family which fades into the surrounding background population. While the largest members, 8 Flora and 43 Ariadne, are located near the edge, there are several distinct groupings within the family created by secondary collisions. Due to this complex internal structure and the poorly defined boundaries, the Flora family has been described as an asteroid clan. Only few interlopers have been identified; this family may be the source of the impactor that formed the Chicxulub crater, the culprit in the extinction of the dinosaurs. The largest member is 8 Flora, which measures 140 km in diameter, comprises about 80% of the total family mass; the parent body was certainly disrupted by the impact/s that formed the family, Flora is a gravitational aggregate of most of the pieces.
43 Ariadne makes up much of the remaining mass. Because of the family's poorly defined boundaries, the location of Flora itself near the edge, it has been called the "Ariadne family", when Flora did not make it into the group during an analysis; the remaining family members being small, below 30 km in diameter. A noticeable fraction of the parent body has been lost from the family since the original impact due to processes such as e.g. secondary collisions. For example, it has been estimated that Flora contains only about 57% of the parent body's mass, but about 80% of the mass in the present family; the Flora family is broad and fades into the background population in such a way that its boundaries are poorly defined. There are several non-uniformities or lobes within the family, one cause of which may have been secondary collisions between family members. Hence, it is a classical example of a so-called asteroid clan. Curiously, the largest members, 8 Flora and 43 Ariadne, are located near the edge of the family.
The reason for this unusual mass distribution within the family is unknown at present. 951 Gaspra, a medium-sized core family member, was visited by the Galileo spacecraft on its way to Jupiter, is one of the most extensively studied asteroids. Studies of Gaspra suggests that the family's age is of the order of 200 million years, that the parent body was at least differentiated; the Flora family members are considered good candidates for being the parent bodies of the L chondrite meteorites, which contribute about 38% of all meteorites impacting the Earth. This theory is supported by the family's location close to the unstable zone of the ν 6 secular resonance, because the spectral properties of family members are consistent with being the parent bodies of this meteorite type; the Flora family was one of the five original Hirayama families. It has a high number of early discovered members both because S-type asteroids tend to have high albedo, because it is the closest major asteroid grouping to Earth.
A HCM numerical analysis by Vincenzo Zappalà in 1995 determined a large group of'core' family members, whose proper orbital elements lie in the approximate ranges The boundaries of the family are, however indistinct. At the present epoch, the range of osculating orbital elements of these core members is Zappalà's 1995 analysis found 604 core members, 1027 in a wider group. A search of a recent proper element database for 96944 minor planets in 2005 yielded 7438 objects lying within the rectangular-shaped region defined by the first table above. However, this includes parts of the Vesta and Nysa families in the corners so that a more membership estimate is 4000–5000 objects; this means. Because of the high background density of asteroids in this part of space, one might expect that a great number of interlopers would be present. However, few have been identified; this is because interlopers are hard to distinguish from family members because the family is of the same spectral type that dominates the inner main belt overall.
The few interlopers that have been identified are all small They include 298 Baptistina, 422 Berolina, 2093 Genichesk, 2259 Sofievka, 2952 Lilliputia, 453 Tea, 3533 Toyota, 3850 Peltier, 3875 Staehle, 4278 Harvey, 4396 Gressmann, 4750 Mukai. Zappalà, Vincenzo. PDS asteroid taxonomy data set Bus, Schelte J.. Data set online here. Nesvorný, D. et al.. AstDys site. Proper element
906 Repsolda is a minor planet orbiting the Sun. It is named for the German astronomer and fireman Johann Georg Repsold, who founded and ran Hamburg Observatory. 906 Repsolda at AstDyS-2, Asteroids—Dynamic Site Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info 906 Repsolda at the JPL Small-Body Database Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters
An hour is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3,599–3,601 seconds, depending on conditions. The hour was established in the ancient Near East as a variable measure of 1⁄12 of the night or daytime; such seasonal, temporal, or unequal hours varied by latitude. The hour was subsequently divided into each of 60 seconds. Equal or equinoctial hours were taken as 1⁄24 of the day. Since this unit was not constant due to long term variations in the Earth's rotation, the hour was separated from the Earth's rotation and defined in terms of the atomic or physical second. In the modern metric system, hours are an accepted unit of time defined as 3,600 atomic seconds. However, on rare occasions an hour may incorporate a positive or negative leap second, making it last 3,599 or 3,601 seconds, in order to keep it within 0.9 seconds of UT1, based on measurements of the mean solar day. The modern English word hour is a development of the Anglo-Norman houre and Middle English ure, first attested in the 13th century.
It displaced the Old English "tide" and "stound". The Anglo-Norman term was a borrowing of Old French ure, a variant of ore, which derived from Latin hōra and Greek hṓrā. Like Old English tīd and stund, hṓrā was a vaguer word for any span of time, including seasons and years, its Proto-Indo-European root has been reconstructed as *yeh₁-, making hour distantly cognate with year. The time of day is expressed in English in terms of hours. Whole hours on a 12-hour clock are expressed using the contracted phrase o'clock, from the older of clock. Hours on a 24-hour clock are expressed as "hundred" or "hundred hours". Fifteen and thirty minutes past the hour is expressed as "a quarter past" or "after" and "half past" from their fraction of the hour. Fifteen minutes before the hour may be expressed as "a quarter to", "of", "till", or "before" the hour; the ancient Egyptians began dividing the night into wnwt at some time before the compilation of the Dynasty V Pyramid Texts in the 24th century BC. By 2150 BC, diagrams of stars inside Egyptian coffin lids—variously known as "diagonal calendars" or "star clocks"—attest that there were 12 of these.
Clagett writes that it is "certain" this duodecimal division of the night followed the adoption of the Egyptian civil calendar placed c. 2800 BC on the basis of analyses of the Sothic cycle, but a lunar calendar long predated this and would have had twelve months in each of its years. The coffin diagrams show that the Egyptians took note of the heliacal risings of 36 stars or constellations, one for each of the ten-day "weeks" of their civil calendar; each night, the rising of eleven of these decans were noted, separating the night into twelve divisions whose middle terms would have lasted about 40 minutes each. The original decans used by the Egyptians would have fallen noticeably out of their proper places over a span of several centuries. By the time of Amenhotep III, the priests at Karnak were using water clocks to determine the hours; these were filled to the brim at sunset and the hour determined by comparing the water level against one of its twelve gauges, one for each month of the year.
During the New Kingdom, another system of decans was used, made up of 24 stars over the course of the year and 12 within any one night. The division of the day into 12 hours was accomplished by sundials marked with ten equal divisions; the morning and evening periods when the sundials failed to note time were observed as the first and last hours. The Egyptian hours were connected both with the priesthood of the gods and with their divine services. By the New Kingdom, each hour was conceived as a specific region of the sky or underworld through which Ra's solar barge travelled. Protective deities were used as the names of the hours; as the protectors and resurrectors of the sun, the goddesses of the night hours were considered to hold power over all lifespans and thus became part of Egyptian funerary rituals. Two fire-spitting cobras were said to guard the gates of each hour of the underworld, Wadjet and the rearing cobra were sometimes referenced as wnwt from their role protecting the dead through these gates.
The Egyptian for astronomer, used as a synonym for priest, was wnwty, "One of the Hours" or "Hour-Watcher". The earliest forms of wnwt include one or three stars, with the solar hours including the determinative hieroglyph for "sun". Ancient China divided its day into 100 "marks" running from midnight to midnight; the system is said to have been used since remote antiquity, credited to the legendary Yellow Emperor, but is first attested in Han-era water clocks and in the 2nd-century history of that dynasty. It was measured with sundials and water clocks. Into the Eastern Han, the Chinese measured their day schematically, adding the 20-ke difference between the solstices evenly throughout the year, one every nine days. During the night, time was more commonly
For the quarter and the train station, see Bergedorf and Hamburg-Bergedorf station. Bergedorf is the largest of the seven boroughs of Hamburg, named after a quarter within this borough. In 2016 the population of the borough was 126,395; the city of Bergedorf received town privileges in 1275 a part of the younger Duchy of Saxony, partitioned by its four co-ruling dukes in 1296 into the branch duchies of Saxe-Lauenburg and Saxe-Wittenberg. Bergedorf became part of the former; this was only to last until 1303, when Lauenburg's three co-ruling dukes, Albert III, Eric I, John II partitioned their branch duchy into three smaller duchies. Eric held Bergedorf and Lauenburg and inherited the share of his childless brother Albert III, Saxe-Ratzeburg, after he was deceased in 1308 and a retained section from Albert's widow Margaret of Brandenburg-Salzwedel on her death. However, his other brother, John II claimed a part, so in 1321 Eric conceded Bergedorf to him, whose share thus became known thereafter as Saxe-Bergedorf-Mölln while Eric's was known as Saxe-Ratzeburg-Lauenburg.
In 1370, John's fourth successor Eric III pawned the Herrschaft of Bergedorf, the Vierlande, half the Saxon Wood and Geesthacht to Lübeck in return for a credit of 16,262.5 Lübeck marks. This acquisition included much of the trade route between Hamburg and Lübeck, thus providing a safe passage for freight between the cities. Eric III only retained a life tenancy; the city of Lübeck and Eric III further stipulated, that upon his death, Lübeck would be entitled to take possession of the pawned areas until his successors repaid the credit and exercised the repurchase of Mölln, altogether amounting to the enormous sum of 26,000 Lübeck Marks. In 1401, Eric III died without issue and was succeeded by his second cousin Eric IV of Saxe-Ratzeburg-Lauenburg. In the same year, Eric IV, supported by his sons Eric and John, forcefully captured the pawned areas without making any repayment, before Lübeck could take possession of them. Lübeck acquiesced for the time being. In 1420, Eric V attacked Prince-Elector Frederick I of Brandenburg and Lübeck allied with Hamburg in support of Brandenburg.
Armies of both cities opened a second front and conquered Bergedorf, Riepenburg castle and the Esslingen river toll station within weeks. This forced Eric V to agree with Hamburg's burgomaster Hein Hoyer and Burgomaster Jordan Pleskow of Lübeck to the Peace of Perleberg on 23 August 1420, which stipulated that all the pawned areas, which Eric IV, Eric V and John IV had violently taken in 1401, were to be irrevocably ceded to the cities of Hamburg and Lübeck; the cities transformed the acquired areas into the "Beiderstädtischer Besitz", ruled by bailiffs in four year terms, alternately staffed by one of the cities. In 1446 the bailiffs' terms were increased to six years, in 1620 to life terms. In 1542 bailiff Ditmar Koel introduced the Protestant Reformation in the co-governed municipalities; the area was formally annexed to the First French Empire as part of Bouches de l'Elbe département between 1811 and 1813. Thereafter, the area was restored to both sovereign states; the first railway in Northern Germany was opened between Hamburg and Bergedorf by the Hamburg-Bergedorf Railway Company in 1842.
In the 1860s the Condominium issued its own postage stamps. Effective of 1 January 1868 Lübeck sold its share in the bi-urban condominium to the Free and Hanseatic City of Hamburg for 200,000 Prussian thaler. Hamburg integrated the area into its state territory, forming there the Landherrenschaft Bergedorf comprising the cities of Bergedorf and Geesthacht and a number of rural municipalities not integrated into the city of Hamburg proper. By the Greater Hamburg Act of 1937 the exclave of Geesthacht was ceded to Schleswig-Holstein. On 1 April 1938 Bergedorf city and the other municipalities became the Borough of Bergedorf, an integrated part of the city of Hamburg. Bergedorf is known by its nickname Garden of Hamburg; the borough of Bergedorf consists of the quarters Allermöhe, Bergedorf, Curslack, Lohbrügge, Neuallermöhe. Neuengamme, Reitbrook and Tatenberg. In 2017 the city of Hamburg started planning the new quarter Oberbillwerder, located in today's Billwerder. In 2006, according to the statistical office of Hamburg and Schleswig-Holstein, the borough of Bergedorf has a total area of 154.8 square kilometres.
Today's quarter is the old city Bergedorf, located on the river Bille, a right tributary of the Elbe. In 2006, 118,942 people were living in Bergedorf borough; the population density was 769 inhabitants per square kilometre. 19.3% were children under the age of 18, 18.2% were 65 years of age or older. 9.6% were immigrants. 6,027 people were registered as unemployed. In 1999 there were 51,752 households and 34.6% of all households were made up of individuals. According to the Department of Motor Vehicles, there were 48,003 private cars registered in the borough of Bergedorf. There were 22 elementary schools, 16 secondary schools, 184 physicians in private practice, 23 pharmacies in the borough of Bergedorf; these numbers include the Bergedorf quarter. The Bezirksversammlung is elected as representatives of the citizens with elections to the state parliament, it consists of 47 representatives. Elections were held in Hamburg on 15 February 2015. Voter participation was 52.7% in Bergedorf. B