52-499: TIROS-N satellite is the first of the TIROS-N series. It is a weather satellite launched on 13 October 1978. It was designed to become operational during 2 years. Its mass is 734 kilograms. Its perigee to Earth is 829 kilometers. Its apogee is 845 kilometers away from Earth. Its inclination is 98.70°. It was managed by the U.S. National Oceanic and Atmospheric Administration (NOAA); designed and launched by NASA . The spacecraft
104-590: A generic two-body model ) of the actual minimum distance to the Sun using the full dynamical model . Precise predictions of perihelion passage require numerical integration . The two images below show the orbits, orbital nodes , and positions of perihelion (q) and aphelion (Q) for the planets of the Solar System as seen from above the northern pole of Earth's ecliptic plane , which is coplanar with Earth's orbital plane . The planets travel counterclockwise around
156-447: A higher heart rate, and adjusting its blood chemistry. It can take days or weeks to adapt to high altitude. However, above 8,000 metres (26,000 ft), (in the " death zone "), altitude acclimatization becomes impossible. There is a significantly lower overall mortality rate for permanent residents at higher altitudes. Additionally, there is a dose response relationship between increasing elevation and decreasing obesity prevalence in
208-610: A reference datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometry, geographical survey, sport, or atmospheric pressure). Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage. In aviation, altitude is typically measured relative to mean sea level or above ground level to ensure safe navigation and flight operations. In geometry and geographical surveys, altitude helps create accurate topographic maps and understand
260-525: A story published in 1998, thus appearing before perinigricon and aponigricon (from Latin) in the scientific literature in 2002. The suffixes shown below may be added to prefixes peri- or apo- to form unique names of apsides for the orbiting bodies of the indicated host/ (primary) system. However, only for the Earth, Moon and Sun systems are the unique suffixes commonly used. Exoplanet studies commonly use -astron , but typically, for other host systems
312-468: Is -gee , so the apsides' names are apogee and perigee . For the Sun, the suffix is -helion , so the names are aphelion and perihelion . According to Newton's laws of motion , all periodic orbits are ellipses. 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, compared to the larger mass,
364-435: Is 236 years early, less accurately shows Eris coming to perihelion in 2260. 4 Vesta came to perihelion on 26 December 2021, but using a two-body solution at an epoch of July 2021 less accurately shows Vesta came to perihelion on 25 December 2021. Trans-Neptunian objects discovered when 80+ AU from the Sun need dozens of observations over multiple years to well constrain their orbits because they move very slowly against
416-414: Is always qualified by explicitly adding a modifier (e.g. "true altitude"), or implicitly through the context of the communication. Parties exchanging altitude information must be clear which definition is being used. Aviation altitude is measured using either mean sea level (MSL) or local ground level (above ground level, or AGL) as the reference datum. Pressure altitude divided by 100 feet (30 m)
468-434: Is always set to standard pressure (29.92 inHg or 1013.25 hPa ). On the flight deck, the definitive instrument for measuring altitude is the pressure altimeter , which is an aneroid barometer with a front face indicating distance (feet or metres) instead of atmospheric pressure . There are several types of altitude in aviation: These types of altitude can be explained more simply as various ways of measuring
520-473: Is currently about 1.016 71 AU or 152,097,700 km (94,509,100 mi). The dates of perihelion and aphelion change over time due to precession and other orbital factors, which follow cyclical patterns known as Milankovitch cycles . In the short term, such dates can vary up to 2 days from one year to another. This significant variation is due to the presence of the Moon: while the Earth–Moon barycenter
572-410: Is due to two competing physical effects: gravity, which causes the air to be as close as possible to the ground; and the heat content of the air, which causes the molecules to bounce off each other and expand. The temperature profile of the atmosphere is a result of an interaction between radiation and convection . Sunlight in the visible spectrum hits the ground and heats it. The ground then heats
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#1732791327122624-472: Is known as the adiabatic lapse rate , which is approximately 9.8 °C per kilometer (or 5.4 °F [3.0 °C] per 1000 feet) of altitude. The presence of water in the atmosphere complicates the process of convection. Water vapor contains latent heat of vaporization . As air rises and cools, it eventually becomes saturated and cannot hold its quantity of water vapor. The water vapor condenses (forming clouds ), and releases heat, which changes
676-432: Is moving on a stable orbit around the Sun, the position of the Earth's center which is on average about 4,700 kilometres (2,900 mi) from the barycenter, could be shifted in any direction from it—and this affects the timing of the actual closest approach between the Sun's and the Earth's centers (which in turn defines the timing of perihelion in a given year). Because of the increased distance at aphelion, only 93.55% of
728-456: Is the flight level , and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions). So when the altimeter reads the country-specific flight level on the standard pressure setting the aircraft is said to be at "Flight level XXX/100" (where XXX is the transition altitude). When flying at a flight level, the altimeter
780-452: Is the farthest or nearest point in the orbit of a planetary body about its primary body . The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values . Apsides pertaining to orbits around the Sun have distinct names to differentiate themselves from other apsides; these names are aphelion for the farthest and perihelion for
832-444: Is the process of convection . Convection comes to equilibrium when a parcel of air at a given altitude has the same density as its surroundings. Air is a poor conductor of heat, so a parcel of air will rise and fall without exchanging heat. This is known as an adiabatic process , which has a characteristic pressure-temperature curve. As the pressure gets lower, the temperature decreases. The rate of decrease of temperature with elevation
884-483: The First Point of Aries not in terms of days and hours, but rather as an angle of orbital displacement, the so-called longitude of the periapsis (also called longitude of the pericenter). For the orbit of the Earth, this is called the longitude of perihelion , and in 2000 it was about 282.895°; by 2010, this had advanced by a small fraction of a degree to about 283.067°, i.e. a mean increase of 62" per year. For
936-622: The Galactic Center respectively. The suffix -jove is occasionally used for Jupiter, but -saturnium has very rarely been used in the last 50 years for Saturn. The -gee form is also used as a generic closest-approach-to "any planet" term—instead of applying it only to Earth. During the Apollo program , the terms pericynthion and apocynthion were used when referring to orbiting the Moon ; they reference Cynthia, an alternative name for
988-463: The comets , and the asteroids of the Solar System . There are two apsides in any elliptic orbit . The name for each apsis is created from the prefixes ap- , apo- (from ἀπ(ό) , (ap(o)-) 'away from') for the farthest or peri- (from περί (peri-) 'near') for the closest point to the primary body , with a suffix that describes the primary body. The suffix for Earth
1040-428: The precession of the axes .) The dates and times of the perihelions and aphelions for several past and future years are listed in the following table: The following table shows the distances of the planets and dwarf planets from the Sun at their perihelion and aphelion. These formulae characterize the pericenter and apocenter of an orbit: While, in accordance with Kepler's laws of planetary motion (based on
1092-435: The troposphere (up to approximately 11 kilometres (36,000 ft) of altitude) in the Earth's atmosphere undergoes notable convection; in the stratosphere , there is little vertical convection. Medicine recognizes that altitudes above 1,500 metres (4,900 ft) start to affect humans, and there is no record of humans living at extreme altitudes above 5,500–6,000 metres (18,000–19,700 ft) for more than two years. As
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#17327913271221144-526: The Earth reaches perihelion in early January, approximately 14 days after the December solstice . At perihelion, the Earth's center is about 0.983 29 astronomical units (AU) or 147,098,070 km (91,402,500 mi) from the Sun's center. In contrast, the Earth reaches aphelion currently in early July, approximately 14 days after the June solstice . The aphelion distance between the Earth's and Sun's centers
1196-434: The Earth's distance from the Sun. In the northern hemisphere, summer occurs at the same time as aphelion, when solar radiation is lowest. Despite this, summers in the northern hemisphere are on average 2.3 °C (4 °F) warmer than in the southern hemisphere, because the northern hemisphere contains larger land masses, which are easier to heat than the seas. Perihelion and aphelion do however have an indirect effect on
1248-584: The Greek Moon goddess Artemis . More recently, during the Artemis program , the terms perilune and apolune have been used. Regarding black holes, the term peribothron was first used in a 1976 paper by J. Frank and M. J. Rees, who credit W. R. Stoeger for suggesting creating a term using the greek word for pit: "bothron". The terms perimelasma and apomelasma (from a Greek root) were used by physicist and science-fiction author Geoffrey A. Landis in
1300-404: The Sun and for each planet, the blue part of their orbit travels north of the ecliptic plane, the pink part travels south, and dots mark perihelion (green) and aphelion (orange). The first image (below-left) features the inner planets, situated outward from the Sun as Mercury, Venus, Earth, and Mars. The reference Earth-orbit is colored yellow and represents the orbital plane of reference . At
1352-452: The Sun. The words are formed from the prefixes peri- (Greek: περί , near) and apo- (Greek: ἀπό , away from), affixed to the Greek word for the Sun, ( ἥλιος , or hēlíos ). Various related terms are used for other celestial objects . The suffixes -gee , -helion , -astron and -galacticon are frequently used in the astronomical literature when referring to the Earth, Sun, stars, and
1404-597: The United States. In addition, the recent hypothesis suggests that high altitude could be protective against Alzheimer's disease via action of erythropoietin, a hormone released by kidney in response to hypoxia. However, people living at higher elevations have a statistically significant higher rate of suicide. The cause for the increased suicide risk is unknown so far. For athletes, high altitude produces two contradictory effects on performance. For explosive events (sprints up to 400 metres, long jump , triple jump )
1456-414: The air at the surface. If radiation were the only way to transfer heat from the ground to space, the greenhouse effect of gases in the atmosphere would keep the ground at roughly 333 K (60 °C; 140 °F), and the temperature would decay exponentially with height. However, when air is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward. This
1508-441: The altitude increases, atmospheric pressure decreases, which affects humans by reducing the partial pressure of oxygen . The lack of oxygen above 2,400 metres (8,000 ft) can cause serious illnesses such as altitude sickness , high altitude pulmonary edema , and high altitude cerebral edema . The higher the altitude, the more likely are serious effects. The human body can adapt to high altitude by breathing faster, having
1560-439: The altitude: The Earth's atmosphere is divided into several altitude regions. These regions start and finish at varying heights depending on season and distance from the poles. The altitudes stated below are averages: The Kármán line , at an altitude of 100 kilometres (62 mi) above sea level , by convention defines represents the demarcation between the atmosphere and space . The thermosphere and exosphere (along with
1612-437: The background stars. Due to statistics of small numbers, trans-Neptunian objects such as 2015 TH 367 when it had only 8 observations over an observation arc of 1 year that have not or will not come to perihelion for roughly 100 years can have a 1-sigma uncertainty of 77.3 years (28,220 days) in the perihelion date. Altitude Altitude is a distance measurement, usually in the vertical or "up" direction, between
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1664-422: The conservation of angular momentum ) and the conservation of energy, these two quantities are constant for a given orbit: where: Note that for conversion from heights above the surface to distances between an orbit and its primary, the radius of the central body has to be added, and conversely. The arithmetic mean of the two limiting distances is the length of the semi-major axis a . The geometric mean of
1716-409: The distance of the line that joins the nearest and farthest points across an orbit; it also refers simply to the extreme range of an object orbiting a host body (see top figure; see third figure). In orbital mechanics , the apsides technically refer to the distance measured between the barycenter of the 2-body system and the center of mass of the orbiting body. However, in the case of a spacecraft ,
1768-405: The extreme range—from the closest approach (perihelion) to farthest point (aphelion)—of several orbiting celestial bodies of the Solar System : the planets, the known dwarf planets, including Ceres , and Halley's Comet . The length of the horizontal bars correspond to the extreme range of the orbit of the indicated body around the Sun. These extreme distances (between perihelion and aphelion) are
1820-401: The generic suffix, -apsis , is used instead. The perihelion (q) and aphelion (Q) are the nearest and farthest points respectively of a body's direct orbit around the Sun . Comparing osculating elements at a specific epoch to those at a different epoch will generate differences. The time-of-perihelion-passage as one of six osculating elements is not an exact prediction (other than for
1872-465: The higher parts of the mesosphere) are regions of the atmosphere that are conventionally defined as space. Regions on the Earth 's surface (or in its atmosphere) that are high above mean sea level are referred to as high altitude . High altitude is sometimes defined to begin at 2,400 meters (8,000 ft) above sea level. At high altitude, atmospheric pressure is lower than that at sea level. This
1924-563: The lapse rate from the dry adiabatic lapse rate to the moist adiabatic lapse rate (5.5 °C per kilometer or 3 °F [1.7 °C] per 1000 feet). As an average, the International Civil Aviation Organization (ICAO) defines an international standard atmosphere (ISA) with a temperature lapse rate of 6.49 °C per kilometer (3.56 °F per 1,000 feet). The actual lapse rate can vary by altitude and by location. Finally, only
1976-907: The letter "A". Athletes also can take advantage of altitude acclimatization to increase their performance. The same changes that help the body cope with high altitude increase performance back at sea level. These changes are the basis of altitude training which forms an integral part of the training of athletes in a number of endurance sports including track and field, distance running, triathlon, cycling and swimming. Decreased oxygen availability and decreased temperature make life at high altitude challenging. Despite these environmental conditions, many species have been successfully adapted at high altitudes . Animals have developed physiological adaptations to enhance oxygen uptake and delivery to tissues which can be used to sustain metabolism. The strategies used by animals to adapt to high altitude depend on their morphology and phylogeny . For example, small mammals face
2028-465: The lines of apsides of the orbits of various objects around a host body. Distances of selected bodies of the Solar System from the Sun. The left and right edges of each bar correspond to the perihelion and aphelion of the body, respectively, hence long bars denote high orbital eccentricity . The radius of the Sun is 0.7 million km, and the radius of Jupiter (the largest planet) is 0.07 million km, both too small to resolve on this image. Currently,
2080-413: The nearest point in the solar orbit. The Moon 's two apsides are the farthest point, apogee , and the nearest point, perigee , of its orbit around the host Earth . Earth's two apsides are the farthest point, aphelion , and the nearest point, perihelion , of its orbit around the host Sun. The terms aphelion and perihelion apply in the same way to the orbits of Jupiter and the other planets ,
2132-503: The orbit of the Earth around the Sun, the time of apsis is often expressed in terms of a time relative to seasons, since this determines the contribution of the elliptical orbit to seasonal variations. The variation of the seasons is primarily controlled by the annual cycle of the elevation angle of the Sun, which is a result of the tilt of the axis of the Earth measured from the plane of the ecliptic . The Earth's eccentricity and other orbital elements are not constant, but vary slowly due to
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2184-588: The perihelion passage. For example, using an epoch of 1996, Comet Hale–Bopp shows perihelion on 1 April 1997. Using an epoch of 2008 shows a less accurate perihelion date of 30 March 1997. Short-period comets can be even more sensitive to the epoch selected. Using an epoch of 2005 shows 101P/Chernykh coming to perihelion on 25 December 2005, but using an epoch of 2012 produces a less accurate unperturbed perihelion date of 20 January 2006. Numerical integration shows dwarf planet Eris will come to perihelion around December 2257. Using an epoch of 2021, which
2236-409: The perturbing effects of the planets and other objects in the solar system (Milankovitch cycles). On a very long time scale, the dates of the perihelion and of the aphelion progress through the seasons, and they make one complete cycle in 22,000 to 26,000 years. There is a corresponding movement of the position of the stars as seen from Earth, called the apsidal precession . (This is closely related to
2288-504: The radiation from the Sun falls on a given area of Earth's surface as does at perihelion, but this does not account for the seasons , which result instead from the tilt of Earth's axis of 23.4° away from perpendicular to the plane of Earth's orbit. Indeed, at both perihelion and aphelion it is summer in one hemisphere while it is winter in the other one. Winter falls on the hemisphere where sunlight strikes least directly, and summer falls where sunlight strikes most directly, regardless of
2340-630: The reduction in atmospheric pressure signifies less atmospheric resistance, which generally results in improved athletic performance. For endurance events (races of 5,000 metres or more) the predominant effect is the reduction in oxygen which generally reduces the athlete's performance at high altitude. Sports organizations acknowledge the effects of altitude on performance: the International Association of Athletic Federations (IAAF), for example, marks record performances achieved at an altitude greater than 1,000 metres (3,300 ft) with
2392-417: The seasons: because Earth's orbital speed is minimum at aphelion and maximum at perihelion, the planet takes longer to orbit from June solstice to September equinox than it does from December solstice to March equinox. Therefore, summer in the northern hemisphere lasts slightly longer (93 days) than summer in the southern hemisphere (89 days). Astronomers commonly express the timing of perihelion relative to
2444-401: The smaller mass is negligible (e.g., for satellites), then the orbital parameters are independent of the smaller mass. When used as a suffix—that is, -apsis —the term can refer to the two distances from the primary body to the orbiting body when the latter is located: 1) at the periapsis point, or 2) at the apoapsis point (compare both graphics, second figure). The line of apsides denotes
2496-415: The terms are commonly used to refer to the orbital altitude of the spacecraft above the surface of the central body (assuming a constant, standard reference radius). The words "pericenter" and "apocenter" are often seen, although periapsis/apoapsis are preferred in technical usage. The words perihelion and aphelion were coined by Johannes Kepler to describe the orbital motions of the planets around
2548-416: The terrain's elevation. For high-altitude trekking and sports, knowing and adapting to altitude is vital for performance and safety. Higher altitudes mean reduced oxygen levels, which can lead to altitude sickness if proper acclimatization measures are not taken. Vertical distance measurements in the "down" direction are commonly referred to as depth . The term altitude can have several meanings, and
2600-412: The time of vernal equinox, the Earth is at the bottom of the figure. The second image (below-right) shows the outer planets, being Jupiter, Saturn, Uranus, and Neptune. The orbital nodes are the two end points of the "line of nodes" where a planet's tilted orbit intersects the plane of reference; here they may be 'seen' as the points where the blue section of an orbit meets the pink. The chart shows
2652-491: The two distances is the length of the semi-minor axis b . The geometric mean of the two limiting speeds is which is the speed of a body in a circular orbit whose radius is a {\displaystyle a} . Orbital elements such as the time of perihelion passage are defined at the epoch chosen using an unperturbed two-body solution that does not account for the n-body problem . To get an accurate time of perihelion passage you need to use an epoch close to
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#17327913271222704-403: Was 3-axis stabilized . TIROS-N was operated for 868 days until deactivated by NOAA on 27 February 1981. This spacecraft or satellite related article is a stub . You can help Misplaced Pages by expanding it . Apsis An apsis (from Ancient Greek ἁψίς ( hapsís ) 'arch, vault'; pl. apsides / ˈ æ p s ɪ ˌ d iː z / AP -sih-deez )
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