English thesaurus is mainly derived from The Integral Dictionary (TID). L'appellativo Molnija deriva dal nome dei primi satelliti sovietici che vennero posizionati su orbite di questo tipo nel corso degli anni sessanta; si trattava di una costellazione di tre satelliti in grado di offrire una copertura continua del territorio sovietico, simile a quella che avrebbe avuto un satellite in orbita geostazionaria, ma centrata su regioni situate a latitudini molto alte, non raggiungibili altrimenti. From Russian мо́лния (mólnija, “lightning”) +‎ orbit. As the Earth rotates half a revolution in 12 hours every second apogee will serve one half of the northern hemisphere and every second the other half. Figure 3: View of the Earth four hours before apogee from a Molniya orbit under the assumption that the longitude of the apogee is 90° E. The spacecraft is at an altitude of 24,043 km over the point 92.65° E 47.04° N. Figure 4: View of the Earth from the apogee of a Molniya orbit under the assumption that the longitude of the apogee is 90° E. The spacecraft is at an altitude of 39,867 km over the point 90° E 63.43° N. Figure 5: View of the Earth four hours after apogee from a Molniya orbit under the assumption that the longitude of the apogee is 90° E. The spacecraft is at an altitude of 24,043 km over the point 87.35° E 47.04° N. Figure 6: View of the Earth four hours before apogee from a Molniya orbit under the assumption that the longitude of the apogee is 90° W. The spacecraft is at an altitude of 24,043 km over the point 87.35° W 47.04° N. Figure 7: View of the Earth from the apogee of a Molniya orbit under the assumption that the longitude of the apogee is 90° W. The spacecraft is at an altitude of 39,867 km over the point 90° W 63.43° N. Figure 8: View of the Earth 4 hours after apogee from a Molniya orbit under the assumption that the longitude of the apogee is 90° W. The spacecraft is at an altitude of 24,043 km over the point 92.65° W 47.04° N. Figure 9: A constellation of three Molniya spacecraft providing service for the Northern hemisphere. ○   Lettris For a Molniya orbit the inclination is selected such that as given by the formula above is zero but as given by the other equation will be −0.0742° per orbit. There is some confusion in the existing sources about the naming, with some sources suggesting that all of the satellites on-orbit are of the Molniya-3 type, but referred to as Molniya-1 through -3 depending on their purpose. Most English definitions are provided by WordNet . L'orbita Molnija (dal termine che in lingua russa indica il lampo) è un particolare tipo di orbita utilizzato dai satelliti per comunicazioni militari dell'Unione Sovietica e, attualmente, dalla Russia. The Russian word was used as the name for a series of Soviet/Russian communications satellites, and the orbits which they were placed in. The web service Alexandria is granted from Memodata for the Ebay search. Give contextual explanation and translation from your sites ! The wordgames anagrams, crossword, Lettris and Boggle are provided by Memodata. If for example the apogee longitudes are 90° E and 90° W this means that every second apogee will serve Europe and Asia (see figures 3 to 5) and every second Northern America (see figures 6 to 8). Definition from Wiktionary, the free dictionary, https://en.wiktionary.org/w/index.php?title=Molniya_orbit&oldid=52139320, Creative Commons Attribution-ShareAlike License. These were in turn replaced by the Molniya-3 design. A satellite in a highly eccentric orbit spends most of its time in the neighborhood of apogee which for a Molniya orbit is over the northern hemisphere, the sub-satellite point at apogee having a latitude of 63.4 degrees North. L'orbita Molniya. When one spacecraft has reached the point corresponding to figure 5 (or figure 8) 4 hours after apogee passage the next spacecraft having four hours left to reach apogee and having a right ascension of ascending node 120° larger than the previous spacecraft has the visibility displayed in figure 3 (or figure 6) and the switch-over can take place. All rights reserved. That this is the case follows from equation (28) of the article Orbital perturbation analysis (spacecraft) as the factor, The reason why the orbital period shall be half a sidereal day is that the geometry relative to the ground stations should repeat every 24 hours keeping the longitudes for the apogees passages. Note that the two spacecraft at the time of switch-over only are separated with about 1500 km and that the ground stations therefore only have to move the antennas a few degrees to acquire the new spacecraft. Ro, Cookies help us deliver our services. After two launch failures in 1964, the first successful satellite to use this orbit was Molniya 1-01 launched on April 23, 1965.  | Last modifications, Copyright © 2012 sensagent Corporation: Online Encyclopedia, Thesaurus, Dictionary definitions and more. Molniya orbit is a type of highly elliptical orbit with an inclination of 63.4 degrees, an argument of perigee of −90 degrees and an orbital period of one half of a sidereal day. The orbits are such that the satellite passes close to the earth near the South Pole, travelling fast; and at a great distance from the earth near the North Pole, travelling slowly. The Molniya orbit is a special kind of orbit that achieves precisely these requirements. https://it.wikipedia.org/w/index.php?title=Orbita_Molnija&oldid=108465226, licenza Creative Commons Attribuzione-Condividi allo stesso modo. As the apogee altitude is as high as 40,000 km it will therefore, for a considerable period around apogee, have an excellent visibility from the Northern hemisphere, from Russia but also from northern Europe, Greenland and Canada. The primary use of the Molniya orbit was for the communications satellite series of the same name. In fact, the precise ideal orbital period resulting in a ground track repeating every 24 hours is not precisely half a sidereal day but rather half a "nodal day"! The reason why the inclination should have the value 63.4° is that then the argument of perigee is not perturbed by the J2 term of the gravitational field of the Earth but stays −90°. Molniya definition, one of a series of Soviet communications satellites. The views of the Earth from these 3 points are displayed in figures 3-8. To avoid this expenditure of fuel, the Molniya orbit uses an inclination of 63.4°, for which these perturbations are zero. One such example is the US-KS early-warning satellite which watches for US missile launches, although improvements in these systems have since allowed them to move these to geostationary orbits. A windows (pop-into) of information (full-content of Sensagent) triggered by double-clicking any word on your webpage. Privacy policy In general, the oblateness of the Earth perturbs the argument of perigee, so that even if the apogee started near the north pole, it would gradually move unless constantly corrected with "station keeping" thruster burns. ○   Anagrams Choose the design that fits your site. You can also try the grid of 16 letters. Its replacement, the Molniya-2, provided both military and civilian broadcasting, and was used to create the Orbita television network, spanning the Soviet Union. The English word games are: After two launch failures in 1964, the first successful satellite to use this orbit was Molniya 1-01 launched on April 23, 1965. Questa pagina è stata modificata per l'ultima volta il 25 ott 2019 alle 12:08. This entry is from Wikipedia, the leading user-contributed encyclopedia. The plane of the figure is the longitudinal plane of apogee rotating with the Earth. Get XML access to fix the meaning of your metadata. Disadvantages are that as opposed to a spacecraft in a geostationary orbit the ground station needs a steerable antenna to track the spacecraft and that the spacecraft will pass the Van Allen belt four times per day. Letters must be adjacent and longer words score better. Usually the period from perigee + 2 hours to perigee + 10 hours is used to transmit to the northern hemisphere, Groundtrack of Molniya orbit. By analogy, the equivalent orbit for the southern hemisphere, with the argument of perigee changed to +90 degrees. The Molniya (Russian: Молния, IPA: [ˈmolnʲɪjə] , "Lightning") series satellites are military and communications satellites launched by the Soviet Union from 1965 to 2004. ), Orbital perturbation analysis (spacecraft), JAVA applet animating the orbit of a satellite, Real time satellite tracking for a typical Molniya satellite, illustration of the communication geometry provided by satellites in 12-hour Molniya orbits, http://en.wikipedia.org/w/index.php?title=Molniya_orbit&oldid=500501233. At apogee the green illumination zone applies, three hours before or after apogee the red zone applies, four hours before or after apogee the blue zone applies. Change the target language to find translations. A satellite in a Molniya orbit is better suited to communications in these regions because it looks directly down on them. The orbits of the three spacecraft should then have the same apogee longitudes (for example 90° W and 90° E) but pass the apogee with eight hours shift; i.e., the right ascensions of the ascending nodes should be separated with 120°. Anche alcuni satelliti statunitensi utilizzarono questo tipo di orbita. By analogy, equivalent orbits for other bodies, which provide low apparent motion across the dome of the sky at. The rotational period of the Earth relative the node (i.e., the "nodal day") will therefore be only 86,129 seconds, 35 seconds less than the sidereal day which is 86,164 seconds. In the operational part of the orbit from apogee −3 hours to apogee +3 hours the satellite is north of 55.5° N (latitude of for example central Scotland, Moscow and southern part of Hudson Bay), Figure 2: Illumination zones (at least 10° elevation) from a Molniya orbit. To make squares disappear and save space for other squares you have to assemble English words (left, right, up, down) from the falling squares. Boggle gives you 3 minutes to find as many words (3 letters or more) as you can in a grid of 16 letters. Molniya orbit is a type of highly elliptical orbit with an inclination of 63.4 degrees, an argument of perigee of −90 degrees and an orbital period of one half of a sidereal day. Its replacement, the Molniya-2, provided both military and civilian broadcasting, and was used to create the Orbita television … Much of the area of the former Soviet Union, and Russia in particular, is located at high latitudes. To broadcast to these latitudes from a geostationary orbit would require considerable power due to the low elevation angles. The primary use of the Molniya orbit was for the communications satellite series of the same name. Although geostationary orbits are useful for observing the continental United States, Soviet sensor technology sometimes required high-contrast observing angles which could only be achieved from higher latitudes. This page was last edited on 30 March 2019, at 13:48. Find out more, Figure 1: The Molniya orbit. The Molniya Orbit Russia and its neighboring countries up in the north frequently use the Molniya orbit. These satellites use highly eccentric elliptical orbits known as Molniya orbits , which have a long dwell time over high latitudes. In the eight hours period centered at the apogee passage the longitudinal plane is almost fixed, the longitude of the satellite varies with only ±2.7°. ○   Wildcard, crossword A highly elliptical orbit inclined at an angle of about 65° to the plane of the equator, such as is occupied by the Russian Molniya satellites. an offensive content(racist, pornographic, injurious, etc. L' orbita Molnija (dal termine che in lingua russa indica il lampo ) è un particolare tipo di orbita utilizzato dai satelliti per comunicazioni militari dell' Unione Sovietica e, attualmente, dalla Russia .  |  Company Information The SensagentBox are offered by sensAgent. See if you can get into the grid Hall of Fame ! Contact Us Tips: browse the semantic fields (see From ideas to words) in two languages to learn more.

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