Astronomija

Službena definicija satelita?

Službena definicija satelita?


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Tako sam se posvađao s prijateljem, a radilo se o tome je li Mjesec planeta ili satelit.

Rezolucija B5 IAU-a 2006 daje definicije onoga što je biti planeta, ali postoji nejasnoća, kako sam shvatio, je da ona ne definira satelite, dok je koristi za definiranje patuljastih planeta.

Postoji dodatni list sa pitanjima i on koristi barycenter da definiramo satelit, ali to je implicirano, ne eksplicitno definirano.

Slijede moja pitanja:

  1. Da li bi se dopunski list sa pitanjima trebao smatrati legitimnom službenom definicijom ili bi se to trebalo smatrati jednim od načina tumačenja Rezolucije B5?
  2. Ako su pitanja i odgovori legitimni, zašto onda definicija satelita nije uključena u Rezoluciju B5? Ako ne, da li službena definicija satelita trenutno ne postoji?
  3. Postoji li izvor ili arhiva službeni ili široko prihvaćene definicije pojmovnika u oblastima astronomije?

Zapravo ne postoji zvanična definicija satelita.

Issac Asimov daje dobar argument da je Mjesec planeta budući da je njegova orbita konveksna oko Sunca za cijelu svoju orbitu, za razliku od ostalih mjeseci Sunčevog sistema koji su udubljeni kada su u suprotnosti i konveksni (u odnosu na Sunce) kada su u konjunkciji.

Pored toga, ideja da je tijelo satelit drugog tijela zasnovanog na tome da je barycenter unutar jednog tijela je pogrešna. Razmislite o premještanju Mjeseca dalje ili bliže sa / na Zemlju. U kojem smjeru biste ga pomaknuli kako biste od njih dvoje napravili "binarni sistem" za razliku od primarnog / mjesečevog sistema. U stvari, iako naivno, uzeli bismo u obzir dva bliže tijela da budu binarni sistem, približavanje Mjeseca približava barycentar središtu Zemlje. Ipak odmičući mjesec dalje pomiče barycentar izvan Zemlje. Da li biste sistem Zemlju / Mjesec smatrali binarnim sistemom da je Mjesec 30% dalje od Zemlje?

Dakle, vidimo da su sve predložene definicije satelita pogrešne i imaju kutne slučajeve koji preciznu definiciju čine spornom. To je isti problem kao i mi kada smo pokušavali definirati planetu. Nijedna definicija neće se lijepo uklopiti u sve kutove koje će nam priroda dati.

Imajte na umu da je ovaj odgovor na engleski preveo moj otac, koji je taj koji ga tipka. Imam osam godina i ne koristim SE bez nadzora. Dobar dio ovih informacija upravo sam sada saznao zbog ovog pitanja, pa hvala OP-u.


Vaša posljednja tri pitanja:

Da li bi se dodatni list sa pitanjima trebao smatrati legitimnim službenim definicijama ili bi se to trebalo smatrati jednim od načina tumačenja Rezolucije B5?

Ta dodatna pitanja i odgovori apsolutno ne bi trebalo smatrati legitimnim službenim definicijama. Ta pitanja i odgovori odnose se na izvorni nacrt rezolucije. Konačna, izglasana verzija predstavlja značajno odstupanje od originala. Konačna verzija je dodala koncept dinamičara "čišćenja susjedstva" definiciji planete, a koncept dvostrukih planeta je nestao. IAU trenutno smatra da je Pluton patuljasta planeta, ali ne i Haron (ali to se može promijeniti). Sa https://www.iau.org/public/themes/pluto/, "Za sada se Charon smatra samo Plutonovim satelitom. Može se razmotriti ideja da bi se Charon mogao kvalificirati da se sam naziva patuljastom planetom kasnije. "

Ako su pitanja i odgovori legitimni, zašto onda definicija satelita nije uključena u Rezoluciju B5? Ako ne, da li službena definicija satelita trenutno ne postoji?

Ovo pitanje je pomalo sporno jer pitanja i odgovori nisu legitimni. Ne postoji zvanična definicija onoga što čini satelit. Prema bilo kojoj razumnoj definiciji koncepta, Pluton nije Haronov satelit, tako da je Pluton status patuljaste planete siguran. Je li Charon satelit Plutona ili nije, pitanje je rasprave, a pretpostavljam da je IAU to ispunio retoričkim raspravama s obzirom na žestoke prigovore na njihovu definiciju pojma "planeta".

Postoje li izvori ili arhiva službenih ili široko prihvaćenih definicija pojmovnika u oblastima astronomije?

Postoji jedna riječ koja ima službeno značenje, a to je "planeta". "Satelit"? Ne. "Zvijezda"? Ne. "Galaksija"? Ne.

Što se tiče debate s vašim prijateljem zbog koje ste postavili ovo pitanje, jedini način na koji se Mjesec može gledati kao planeta je činjenica da je njegova orbita oko Sunca konveksna. To je posljedica gravitacijske sile koju na Mjesec vrši Sunce uvijek je veće veličine od one koju Zemlja na Mjesec vrši. To nije dobra definicija; JUR ga sigurno ne koristi. Zajedno sa Zemljinim Mjesecom, postoji nekoliko vanjskih mjeseci divovskih planeta koji imaju istu karakteristiku i svi su navedeni kao sateliti.


Satelit

Dodatnih 1.280 satelita odobreno je za srednje Zemljine orbite od 8.500 km.

Napor će kombinirati satelitske snimke poljoprivrednih regija sa podsezonskim prognozama do 45 dana.

Neki bi kozmolozi odgovorili da danas sa našim satelitima vršimo potrebna mjerenja.

Kompanija je lansirala više od 600 satelita za Starlink, internetsku mrežu velike brzine koja bi mogla započeti komercijalnu uslugu krajem ove godine za kupce na sjeveru Sjeverne Amerike.

Spremni smo vidjeti više lansiranja satelita svake godine, što znači da se sve više raketnih i svemirskih letjelica oslobađa i zatvara oko 22.000 km / h.

U početku će moći da nosi satelitske navođene bombe od 1000 kilograma ili lasersko navođeno oružje od 500 kilograma.

Za dobavljača aviona Hughes Aircraft to su bili presudni satelitski dijelovi iz Rusije.

Tako je izvještaj o likovima Guya Fawkesa, koji je također preuzeo RT, ruski satelitski kanal na engleskom jeziku.

Kao rezultat, satelit koji prolazi iznad regije veće mase ubrzao bi vrlo malo, a usporio bi se preko niže mase.

Mala vanjska televizijska satelitska antena viri iz visoke trave uz nekoliko gomila drva za ogrjev.

Uhvaćena je prije mnogo godina u pokušaju da sruši vladavinu Wanande na maloj satelitskoj planeti.

Takva vezanost male ili slabe prema velikoj i moćnoj naciji osuđuje prvu da bude satelit druge.

Njegov život sa satelita Boswell drži prvo mjesto među biografijama kao trijumf portreta.

Pozvao je svoj kineski satelit i ležerno prišao vratima.

Rose je požurila sestru i satelit, a zatim pustila veselje.


Tamna energija

Osamdesetih godina astronomi su počeli koristiti supernove tipa Ia kao standardne svijeće. Vjeruje se da se oni javljaju na sljedeći način. Bijela patuljasta zvijezda u binarnoj orbiti sa susjedom može polako izvlačiti materijal, postepeno povećavajući vlastitu masu. Masa bijelog patuljka obično ne bi mogla prijeći granicu Chandrasekhar-a od oko 1,4 Sunčeve mase, ili bi se srušio i formirao neutronsku zvijezdu. Međutim, u slučaju bijelih patuljaka bogatih ugljikom, polaganim nakupljanjem materijala izvučenog iz susjeda, temperatura jezgre raste sve dok nuklearno paljenje ugljika ne izazove odbjeglu eksploziju. Zbog sporog prirasta i ograničenja mase, ove supernove su izuzetno ujednačene po svojoj svjetlini, štoviše, jer su tako sjajne, da ih se može vidjeti na velikim udaljenostima. Ukratko, ujednačena i ekstremna svjetlina super I tipa Ia čine ih izvrsnim standardnim svijećama.

Devedesetih su dvije grupe koristile promatranja supernova tipa Ia u udaljenim galaksijama kako bi utvrdile udaljenost do tih galaksija, a time i kako se brzina širenja svemira mijenjala s vremenom, tačnije nego ikad prije. Projekt kozmologije Supernova, koji su vodili američki fizičar Saul Perlmutter, i tim za pretragu Super-Z Supernova, koji su režirali australijski astronom Brian Schmidt i američki astronom Adam Riess, koristili su opažanja snimljena zemaljskim teleskopima, kao i HST-om. Rezultat je bio najneočekivaniji. Daleko od pronalaska bolje vrijednosti za parametar usporavanja, nakon razdoblja zbunjenosti i kontradikcije, obje su grupe otkrile da se širenje svemira zapravo ubrzava. Direktna zapažanja bila su da se čini da su daleke supernove bile 20-25 posto tamnije od očekivanih. Ta dva tima isključila su takve mogućnosti kao što je prigušivanje prašinom, a njihovi su radovi, objavljeni 1998. i 1999. godine, doveli do istog općeg zaključka. Širenje svemira se ubrzava, a to ubrzanje započelo je tek prije oko pet milijardi ili šest milijardi godina.

Konsenzus koji je proizašao iz projekata supernove Ia bio je da je geometrija svemira u osnovi ravna i stoga prilično blizu kritične gustine, s tim da materija čini samo oko 30 posto ukupne gustine energije, a "tamna energija" čini preostalu 70 posto. (Naknadno istraživanje je malo izmijenilo ove brojke.) Iako su druge mogućnosti otvorene, tamna energija se često identificira sa Ajnštajnovom kosmološkom konstantom koja pruža univerzalnu odbojnu silu, što objašnjava ubrzanje. Priroda tamne energije je nepoznata. Može biti povezano s kvantno-mehaničkom energijom vakuuma, međutim, postoje ozbiljne neriješene poteškoće s ovom mogućnošću. Od otprilike 30 posto svemira koji je materija, samo oko 5 posto može biti obična barionska materija. Od toga je vidljiv samo mali dio u obliku planeta, zvijezda i galaksija.

Predmeti svih astronomskih istraživanja, od vremena starih Grka i Babilonaca do 20. vijeka, predstavljaju samo vrh sante leda. Nakon gotovo 4.000 godina astronomije, svemir nije ništa manje čudan nego što se to Babiloncima moralo činiti.


Sadržaj

Satelitski sistemi, poput planetarnih sistema, proizvod su gravitacione privlačnosti, ali se takođe održavaju fiktivnim silama. Iako je opći konsenzus da je većina planetarnih sistema formirana od akrecionih diskova, formiranje satelitskih sistema je manje jasno. Porijeklo mnogih mjeseci istražuje se od slučaja do slučaja, a smatra se da su veći sustavi nastali kombinacijom jednog ili više procesa.

Stabilnost sistema Uredi

Hill sfera je regija u kojoj astronomsko tijelo dominira privlačnošću satelita. Od planeta Sunčevog sistema, Neptun i Uran imaju najveće brdske sfere, zbog smanjenog gravitacijskog utjecaja Sunca na njihovim dalekim orbitama, međutim svi gigantski planeti imaju brdske sfere u radijusu od oko 100 miliona kilometara. Suprotno tome, brdske sfere Merkura i Cerere, budući da su bliže Suncu, prilično su male. Izvan Hill-ove sfere, Sunce dominira gravitacionim uticajem, osim Lagrangijevih tačaka.

Sateliti su stabilni na L4 i L5 Lagrangijeve tačke. Oni leže na trećim uglovima dvaju jednakostraničnih trokuta u ravni orbite čija je zajednička baza linija između centara dviju masa, tako da tačka leži iza (L5) ili naprijed (L4) manje mase s obzirom na njenu orbitu oko veće mase. Trokutaste točke (L4 i L5) su stabilne ravnoteže, pod uvjetom da omjer M1/ M2 je skoro 24,96. [napomena 1] [4] Kada je tijelo u tim tačkama poremećeno, ono se odmiče od točke, ali će se povećati i faktor suprotan onom koji se povećava ili smanjuje uznemirenjem (ili gravitacija ili brzina izazvana kutnim momentom) ili smanjiti, savijajući put objekta u stabilnu orbitu u obliku zrna bubrega oko tačke (kao što se vidi u korotirajućem referentnom okviru).

Općenito se smatra da bi prirodni sateliti trebali kružiti u istom smjeru u kojem se planeta okreće (poznata kao prograde orbita). Kao takav, za ove orbite koristi se terminološki regularni mjesec. Međutim, moguća je i retrogradna orbita (suprotnog smjera od planete), terminologija nepravilan mjesec koristi se za opis poznatih izuzetaka od pravila, vjeruje se da su nepravilni mjeseci u orbitu umetnuti gravitacijskim hvatanjem. [5]

Teorije prirasta Uredi

Diskovi za akretaciju oko džinovskih planeta mogu se dogoditi na sličan način kao i diskovi oko zvijezda, od kojih planete nastaju (na primjer, ovo je jedna od teorija za formacije satelitskih sistema Urana, [6] Saturn i Jupiter). Ovaj rani oblak plina je vrsta cirkumplanetarnog diska [7] [8] poznat kao proto-satelitski disk (u slučaju sistema Zemlja-Mjesec, proto-lunarni disk). Modeli gasa tokom formiranja planeta podudaraju se sa opštim pravilom za odnos mase planeta i satelita od 10.000: 1 [9] (značajan izuzetak je Neptun). Neke akreciju također predlažu kao teoriju za podrijetlo sistema Zemlja-Mjesec, [10] međutim kutni moment sistema i manje željezno jezgro Mjeseca ne mogu se lako objasniti ovim. [10]

Otpadni diskovi Uredi

Drugi predloženi mehanizam za formiranje satelitskog sistema je nakupljanje ostataka. Znanstvenici teoretiziraju da neki smatraju da su galilejski mjeseci novija generacija mjeseca nastalih raspadanjem ranijih generacija naraslih mjeseci. [11] Prstenasti sustavi su vrsta cirkumplanetarnog diska koji može biti rezultat satelita rastvorenih blizu Rocheove granice. Takvi diskovi bi se s vremenom mogli spojiti i formirati prirodne satelite.

Teorije sudara Uredi

Sudar je jedna od vodećih teorija za formiranje satelitskih sistema, posebno Zemlje i Plutona. Objekti u takvom sistemu mogu biti dio kolizijske porodice i ovo porijeklo se može provjeriti uspoređujući njihove orbitalne elemente i sastav. Kompjuterske simulacije korištene su da bi se pokazalo da su ogromni udari mogli biti porijeklom Mjeseca. Smatra se da je rana Zemlja imala više mjeseci proizašlih iz džinovskog udara. Slični modeli korišteni su za objašnjenje stvaranja plutonskog sistema kao i ostalih objekata Kuiperovog pojasa i asteroida. Ovo je takođe prevladavajuća teorija o porijeklu Marsovih mjeseci. [12] Oba skupa nalaza podupiru porijeklo Fobosa iz materijala izbačenog udarom na Mars koji se ponovno kreirao u Marsovoj orbiti. [13] Sudar se takođe koristi za objašnjavanje posebnosti uranskog sistema. [14] [15] Modeli razvijeni 2018. godine objašnjavaju da neobični zavrtanj planete podržava kosi sudar s objektom dvostruko većim od Zemlje koji bi se mogao ponovo spojiti da bi stvorio ledene mjesece ovog sistema. [16]

Teorije gravitacionog hvatanja Uredi

Neke teorije sugeriraju da je gravitaciono hvatanje porijeklo Neptunovog najvećeg mjeseca Tritona, [17] Marsovih mjeseci, [18] i Saturnovog mjeseca Fibe. [19] [20] Neki naučnici su istakli proširenu atmosferu oko mladih planeta kao mehanizam za usporavanje kretanja objekata koji prolaze da bi pomogli u hvatanju. Hipoteza je postavljena da objasni nepravilne orbite satelita Jupitera i Saturna, na primjer. [21] Signalni znak hvatanja je retrogradna orbita, koja može nastati uslijed približavanja objekta planeti prema kojoj se okreće. [5] Hvatanje je čak predloženo kao ishodište Zemljinog Mjeseca. U slučaju potonjeg, međutim, praktično identični omjeri izotopa pronađeni u uzorcima Zemlje i Mjeseca ne mogu se lako objasniti ovom teorijom. [22]

Privremeno snimanje Uredi

Dokazi o prirodnom procesu satelitskog snimanja pronađeni su u izravnom promatranju objekata koje je uhvatio Jupiter. Primijećeno je pet takvih hvatanja, a najdulje je bilo približno dvanaest godina. Na osnovu računarskog modeliranja, predviđa se da će buduće hvatanje komete 111P / Helin-Roman-Crockett tokom 18 godina započeti 2068. godine. [23] [24] Međutim, privremene zarobljene orbite imaju vrlo nepravilne i nestabilne, teoretizirani procesi iza stabilnog hvatanja mogu biti izuzetno rijetka.

Kontroverzne teorije Uredi

Neke kontroverzne rane teorije, na primjer Teorija Mjeseca svemirskog broda i hipoteza Šupljeg Fobosa Šklovskog sugeriraju da mjeseci uopće nisu nastali prirodno. Te teorije obično podbacuju Occamov brijač. Iako su vještački sateliti danas uobičajena pojava u Sunčevom sustavu, najveći, Međunarodna svemirska stanica najšira je 108,5 metara, malen je u odnosu na nekoliko kilometara najmanjih prirodnih satelita.


Apogee

Tečni apogee motor djeluje kao „konus za hvatanje“ koji pomaže u vođenju sonde koja se nakon prolaska kroz grlo motora širi kako bi uhvatila klijentski satelit.

Raketa Vostok-K poslala je kapsulu, noseći Jurija Gagarina, u nisku orbitu sa apogejem od 327 km.

Zajedno s Galileom, predstavlja Brechta u njegovom epskom apogeju.

Propustili smo da apogee hipi revolucije postane nešto ozbiljnije.

Winehouse je stazu postavila u svom potkrovlju 2009. godine, u apogeju svojih napornih zabava.

Svoj apogej dostiže u Bodrumu, jer nigdje u Turskoj proizvodi i plodovi mora nisu svježi ili obilniji.

Apogej ovog oblačenja dogodio se 23. decembra 1908. godine, kada je osnovao korporaciju Mark Twain.

Kada se dostigne apogej društva, napadi pigmeja izgledaju više znatiželjni nego uvredljivi.

Selo Hatfield dotiče ekstrem bijede, baš kao što Hatfield House obilježava apogej kasnog feudalnog sjaja.

Dostignut je apogej Kompanije: od tada je njen pad bio brz.

Prva renesansa svoj je apogej dobila 1500. godine.

Ovaj navijački incident označio je apogej prve faze Nortove karijere u uredu Zvezde.


ASTRONOMY SATELLITE

Pregled unosa u rječnik: Šta znači astronomski satelit?

ASTRONOMY SATELLITE (imenica)
Imenica ASTRONOMY SATELLITE ima jedno čulo:

1. satelit opremljen teleskopom za posmatranje infracrvenog zračenja

Informacije o poznanstvu: ASTRONOMY SATELLITE koristi se kao imenica vrlo je rijetko.

Detalji unosa u rječnik

ASTRONOMY SATELLITE (imenica)

Satelit opremljen teleskopom za posmatranje infracrvenog zračenja

Imenice koje označavaju umjetne predmete

Hipernimi (& vrsta kvotastronomije satelit & quot je.):

vještački satelit orbiter satelit (umjetna oprema koja kruži oko Zemlje ili Mjeseca)


Prostor kao globalno zajedničko obilježje predaka

Većina učenika astrofizike rano u svojoj karijeri nauče da smo, i ono što svakodnevno konzumiramo ili koristimo, više puta bili u jezgri zvijezda ili stvoreni u smrtnom ropstvu zvijezda. Kada analiziramo podatke o galaksijama udaljenim milijardama svjetlosnih godina, znamo da gledamo u svoju kozmičku prošlost. Ova perspektiva - znajući da je Univerzum u nama i da ćemo se mi i Sunce reciklirati natrag u buduće generacije zvijezda i planeta - nije toliko uklonjena kao što neki mogu vjerovati iz relacijskog pogleda mnogih autohtonih kultura ukorijenjenih u 'Prostoru i mjestu' ili kulturni pogledi na noćno nebo. Svemir je naša prošlost i naša budućnost, ujedinjeni smo u ovom pretku i ovoj krajnjoj sudbini.

Zalažemo se za radikalni pomak u političkom okviru međunarodnih regulatornih tijela prema pogledu na svemir kao globalno zajedništvo predaka koje sadrži nasljeđe i budućnost naučne i kulturne prakse čovječanstva. Ne koristimo izraz radikal olako, ova promjena zahtijeva duboku promjenu u stavu prema tome što prostor znači svima nama i našim urođenim uvjerenjima o ljudskom vlasništvu nad prostorom. Takav stav je u suprotnosti s politikom mnogih nacija i aktera u svemiru danas, na primjer, nedavno je aprila 2020. godine Bijela kuća izdala izvršnu naredbu u kojoj se tvrdi da je „vanjski svemir pravno i fizički jedinstveno područje ljudske aktivnosti, a Sjedinjene Države ne gleda na to kao na zajedničko dobro ”.

Također potičemo savezne i privatne svemirske agencije i korporacije da odmah uspostave ured za kulturnu etiku koji može ponuditi integrativni pristup za kulturnu inteligenciju, podržavajući naučni napredak i kulturne protokole iz zajedničkog etičkog prostora, a ne iz umjetno prešućenih perspektiva, te da izvještaji i nalazi takvih ureda biti u prvom planu donošenja odluka. Ovo će započeti dugo čekani proces uključivanja svih dionika za tamno nebo i svemirski prostor, posebno povijesno marginalizirane i autohtone zajednice, dok razvijamo nove politike za svemirske ugovore i planetarnu zaštitu koje izbjegavaju ponavljanje skupih pogrešaka iz prošlosti. Oduševljenje istraživanjem svemira mora biti utemeljeno na dugoročnom razmišljanju, centriranju autohtonih glasova i održivosti.

Dok se borimo s neviđenim razmjerom i raznovrsnim krizama u 2020. godini, prostor oko Zemlje mijenja se - tiho i trajno. Ono što dalje radimo sa svemirom i za svemir, odrazit će se na nauku i čovječanstvo za generacije koje dolaze. Možemo se odlučiti za pomicanje od obrambenog transakcijskog pogleda na neživi prostor - koji čeka vlasništvo i vađenje - ka relativnijem pogledu na svemir koji sadrži naše znanstveno i kulturno porijeklo, zdrav ekosustav koji drži znanstvene i kulturne prakse iz svih perspektiva. Naše razumijevanje našeg porijekla, kao i naše kolektivne budućnosti, u svemiru ovisi o ovome.


Definicije sumraka

U svom najopštijem smislu, sumrak je vremenski period prije izlaska i nakon zalaska sunca, u kojem je atmosfera djelomično osvijetljena suncem, niti je potpuno mračna niti je potpuno osvijetljena. Međutim, postoje tri kategorije sumraka koje se definiraju prema udaljenosti sunca ispod horizonta.

Građanski sumrak:

  • Počinje ujutro ili završava navečer, kada je geometrijski centar sunca 6 stepeni ispod horizonta. Stoga jutarnji građanski sumrak započinje kada je geometrijski centar sunca 6 stepeni ispod horizonta, a završava se izlaskom sunca. Večernji građanski sumrak započinje zalaskom sunca, a završava kada je geometrijski centar sunca 6 stepeni ispod horizonta. U tim uvjetima bez magle ili drugih ograničenja mogu se vidjeti najsjajnije zvijezde i planete, prepoznati horizont i zemaljski objekti, au mnogim slučajevima nije potrebno umjetno osvjetljenje.

Nautički sumrak:

  • Počinje ujutro ili završava navečer, kada je geometrijski centar sunca 12 stepeni ispod horizonta. Općenito, pojam nautički sumrak odnosi se na mornare koji mogu pouzdano očitavati preko dobro poznatih zvijezda, jer je horizont još uvijek vidljiv, čak i pod uvjetima bez mjeseca. Odsustvo magle ili drugih ograničenja, obrisi kopnenih objekata i dalje se mogu prepoznati, ali detaljne aktivnosti na otvorenom vjerovatno će biti umanjene bez vještačkog osvjetljenja.

Astronomski sumrak:

  • Počinje ujutro ili završava navečer, kada je geometrijski centar sunca 18 stepeni ispod horizonta. U astronomskom sumraku osvjetljenje neba je tako slabo da bi većina slučajnih promatrača nebo smatrala potpuno tamnim, posebno pod urbanim ili prigradskim svjetlosnim zagađenjem. Pod astronomskim sutonom, horizont se ne nazire i umjereno slabe zvijezde ili planete mogu se posmatrati golim okom pod ne svjetlosno zagađenim nebom. Ali da bi se testirale granice posmatranja golim okom, sunce mora biti više od 18 stepeni ispod horizonta. Astronomi u astronomskom sumraku mogu lako proučavati tačkaste izvore svjetlosti poput zvijezda i planeta. Ali difuzne izvore svjetlosti, kao što su galaksije, maglice i kuglasta jata, treba posmatrati pod potpuno tamnim nebom, opet kada je Sunce više od 18 stepeni ispod horizonta.

Donja slika prikazuje civilni, nautički i astronomski sumrak. Imajte na umu da kutovi nisu skalirani kako bi se tri kategorije sumraka prikazale s više jasnoće.


47 CFR § 2.1 - Termini i definicije.

(a) Ako se pojam ili definicija pojavljuje u ovom dijelu Pravila Komisije, to će biti konačni pojam ili definicija i prevladavat će u cijelom Pravilniku Komisije.

(b) Izvor svake definicije naznačen je kako slijedi:

(c) Objavljeni su sljedeći izrazi i definicije:

Prihvaćene smetnje. 1 Ometanje na višem nivou od definisanog kao dozvoljeno ometanje i o kojem su se dogovorile dvije ili više administracija, ne dovodeći u pitanje druge uprave. (RR)

1 Izrazi dopuštene smetnje i prihvaćene smetnje koriste se u koordinaciji dodjele frekvencija između administracija.

Aktivni satelit. Satelit koji nosi stanicu namijenjenu za prijenos ili ponovno emitiranje radiokomunikacijskih signala. (RR)

Aktivni senzor. Merni instrument u satelitskoj službi za istraživanje zemlje ili u službi svemirskih istraživanja pomoću koje se informacije dobijaju prenosom i prijemom radio talasa. (RR)

Adaptivni sistem. Radiokomunikacijski sistem koji svoje radio karakteristike mijenja u skladu s kvalitetom kanala. (RR)

Administracija. Bilo koje vladino odjeljenje ili služba odgovorna za izvršavanje obaveza preuzetih Ustavom Međunarodne unije za telekomunikacije, Konvencijom Međunarodne unije za telekomunikacije i Administrativnim propisima. (CS)

Vazduhoplovna zemaljska stanica. Zemaljska stanica u fiksnoj satelitskoj službi, ili, u nekim slučajevima, u vazduhoplovnoj mobilnoj satelitskoj službi, koja se nalazi na određenoj fiksnoj tački na kopnu kako bi se osigurala napojna veza za vazduhoplovnu mobilnu satelitsku službu. (RR)

Vazduhoplovna fiksna služba. Radiokomunikaciona usluga između određenih fiksnih tačaka pruža se prvenstveno radi sigurnosti vazdušne plovidbe i redovnog, efikasnog i ekonomičnog rada vazdušnog transporta. (RR)

Vazduhoplovna fiksna stanica. Stanica u vazduhoplovnoj fiksnoj službi. (RR)

Aeronautical Mobile Off-Route (OR) usluga. Vazduhoplovna mobilna usluga namijenjena komunikacijama, uključujući one koje se odnose na koordinaciju leta, prvenstveno izvan nacionalnih ili međunarodnih civilnih zračnih ruta. (RR)

Usluga zrakoplovne pokretne rute (R). Vazduhoplovna mobilna usluga rezervirana za komunikaciju koja se odnosi na sigurnost i regularnost leta, prvenstveno duž nacionalnih ili međunarodnih civilnih zračnih linija. (RR)

Vazduhoplovna mobilna satelitska služba (OR). Vazduhoplovna mobilna satelitska služba namijenjena komunikacijama, uključujući one koje se odnose na koordinaciju leta, prvenstveno izvan nacionalnih i međunarodnih civilnih zračnih ruta. (RR)

Usluga vazduhoplovne pokretne satelitske rute (R). Vazduhoplovna mobilna satelitska služba rezervirana za komunikacije u vezi sa sigurnošću i regularnošću letova, prvenstveno duž nacionalnih ili međunarodnih civilnih zračnih linija. (RR)

Vazduhoplovna mobilna satelitska služba. Mobilna satelitska služba u kojoj se mobilne zemaljske stanice nalaze na brodovima za preživljavanje aviona i radio-svjetleće stanice koje pokazuju nužne položaje mogu također sudjelovati u ovoj usluzi. (RR)

Vazduhoplovna mobilna služba. Mobilna usluga između vazduhoplovnih stanica i zrakoplovnih stanica, ili između zrakoplovnih stanica, u kojoj stanice za spasilačke brodove mogu sudjelovati radio-svjetleće stanice koje pokazuju položaj u nuždi, također mogu sudjelovati u ovoj službi na određenim frekvencijama za slučaj nevolje i opasnosti. (RR)

Vazduhoplovna radionavigacijska satelitska služba. Radionavigacijska satelitska služba u kojoj su zemaljske stanice smještene u avionima. (RR)

Služba vazduhoplovne radionavigacije. Radio-navigacijska služba namijenjena dobrobiti i sigurnom radu aviona. (RR)

U određenim slučajevima vazduhoplovna stanica može biti smještena, na primjer, na brodu ili na platformi na moru. (RR)

Avionska zemaljska stanica. Pokretna zemaljska stanica u vazduhoplovnoj mobilnoj satelitskoj službi smještena u zrakoplovu. (RR)

Avionska stanica. Pokretna stanica u vazduhoplovnoj mobilnoj službi, osim stanice za preživljavanje, koja se nalazi u zrakoplovu. (RR)

Dodjela (frekvencijskog opsega). Upis u Tabelu raspodjele frekvencija datog opsega frekvencija u svrhu njegove upotrebe od strane jedne ili više zemaljskih ili svemirskih radiokomunikacionih službi ili radioastronomske službe pod određenim uslovima. Ovaj se izraz također primjenjuje na dotični frekvencijski opseg. (RR)

Dodjela (radio frekvencije ili radio frekvencijskog kanala). Ulazak određenog frekvencijskog kanala u dogovoreni plan, koji je usvojila nadležna konferencija, za upotrebu jedne ili više administracija za zemaljsku ili svemirsku radiokomunikacionu uslugu u jednoj ili više identifikovanih zemalja ili geografskog područja i pod određenim uslovima. (RR)

Nadmorska visina apogeja ili perigeja. Nadmorska visina apogeja ili perigeja iznad određene referentne površine koja služi za predstavljanje površine Zemlje. (RR)

Amaterska satelitska služba. Radiokomunikacijska služba koja koristi svemirske stanice na zemaljskim satelitima u iste svrhe kao i usluge amatera. (RR)

Amaterska usluga. Radiokomunikaciona usluga u svrhu samoobuke, interkomunikacije i tehničkih istraga koju provode amateri, odnosno ovlaštene osobe zainteresirane za radiotehniku ​​isključivo s ličnim ciljem i bez novčanog interesa. (RR)

Amaterska stanica. Stanica u amaterskoj službi. (RR)

Dodijeljena frekvencija. Centar frekvencijskog opsega dodijeljen stanici. (RR)

Dodijeljeni frekvencijski opseg. Frekvencijski opseg unutar kojeg je dozvoljena emisija stanice širina opsega jednaka je potrebnoj širini opsega plus dvostrukoj apsolutnoj vrijednosti tolerancije frekvencije. Što se tiče svemirskih stanica, dodijeljeni frekvencijski opseg uključuje dvostruko veći maksimalni dopler-pomak koji se može dogoditi u odnosu na bilo koju točku Zemljine površine. (RR)

Dodjela (radio frekvencije ili radio frekvencijskog kanala). Ovlaštenje koje je administracija dala radijskoj stanici za upotrebu radio frekvencije ili radio frekvencijskog kanala pod određenim uslovima. (RR)

Osnovna zemaljska stanica. Zemaljska stanica u fiksnoj satelitskoj službi ili, u nekim slučajevima, u kopnenoj mobilnoj satelitskoj službi, koja se nalazi na određenoj fiksnoj točki ili unutar određenog područja na kopnu kako bi osigurala feeder vezu za kopnenu mobilnu satelitsku uslugu. (RR)

Radiodifuzna satelitska služba. Radiokomunikaciona usluga u kojoj su signali koje prenose ili prenose svemirske stanice namijenjeni izravnom prijemu šire javnosti.

U satelitskoj radiodifuznoj službi pojam neposrednog prijema obuhvaćaće i pojedinačni prijem i prijem u zajednici. (RR)

Radiodifuzna služba. Radiokomunikaciona usluga u kojoj su emisije namijenjene direktnom prijemu od strane šire javnosti. Ova usluga može uključivati ​​prijenos zvuka, televizijski prijenos ili druge vrste prijenosa. (CS)

Radiodifuzna stanica. Stanica u radiodifuznoj službi. (RR)

Snaga nosača (radio predajnika). Prosječna snaga koju antenski dalekovod isporučuje predajnik tokom jednog ciklusa radio frekvencija snimljenog pod uslovom da nema modulacije. (RR)

Karakteristična frekvencija. Frekvencija koja se lako može prepoznati i izmjeriti u datoj emisiji.

Noseća frekvencija može se, na primjer, odrediti kao karakteristična frekvencija. (RR)

Klasa emisije. The set of characteristics of an emission, designated by standard symbols, e.g., type of modulation, modulating signal, type of information to be transmitted, and also if appropriate, any additional signal characteristics. (RR)

Coast Earth Station. An earth station in the fixed-satellite service or, in some cases, in the maritime mobile-satellite service, located at a specified fixed point on land to provide a feeder link for the maritime mobile-satellite service. (RR)

Community Reception (in the broadcasting-satellite service). The reception of emissions from a space station in the broadcasting-satellite service by receiving equipment, which in some cases may be complex and have antennae larger than those for individual reception, and intended for use: (1) by a group of the general public at one location or (2) through a distribution system covering a limited area. (RR)

Conterminous United States. The contiguous 48 States and the District of Columbia. (FCC)

Coordinated Universal Time (UTC). Time scale, based on the second (SI), as defined in Recommendation ITU-R TF.460-6.

For most practical purposes associated with the ITU Radio Regulations , UTC is equivalent to mean solar time at the prime meridian (0° longitude), formerly expressed in GMT. (RR)

Coordination Area. When determining the need for coordination, the area surrounding an earth station sharing the same frequency band with terrestrial stations, or surrounding a transmitting earth station sharing the same bidirectionally allocated frequency band with receiving earth stations, beyond which the level of permissible interference will not be exceeded and coordination is therefore not required. (RR)

Coordination Contour. The line enclosing the coordination area. (RR)

Coordination Distance. When determining the need for coordination, the distance on a given azimuth from an earth station sharing the same frequency band with terrestrial stations, or from a transmitting earth station sharing the same bidirectionally allocated frequency band with receiving earth stations, beyond which the level of permissible interference will not be exceeded and coordination is therefore not required. (RR)

Deep Space. Space at distance from the Earth equal to, or greater than, 2 × 10 6 kilometers. (RR)

Differential Global Positioning System (DGPS) Station. A differential RNSS station for specific augmentation of GPS.

Differential Radionavigation Satellite Service (Differential RNSS) Station. A station used for the transmission of differential correction data and related information (such as ionospheric data and RNSS satellite integrity information) as an augmentation to an RNSS system for the purpose of improved navigation accuracy.

Direct Sequence Systems. A spread spectrum system in which the carrier has been modulated by a high speed spreading code and an information data stream. The high speed code sequence dominates the “modulating function” and is the direct cause of the wide spreading of the transmitted signal.

Duplex Operation. Operating method in which transmission is possible simultaneously in both directions of a telecommunication channel. 3 (RR)

3 In general, duplex operation and semi-duplex operation require two frequencies in radiocommunication simplex operation may use either one or two.

Earth Exploration-Satellite Service. A radiocommunication service between earth stations and one or more space stations, which may include links between space stations, in which:

(1) Information relating to the characteristics of the Earth and its natural phenomena, including data relating to the state of the environment, is obtained from active sensors or passive sensors on Earth satellites

(2) Similar information is collected from airborne or Earth-based platforms

(3) Such information may be distributed to earth stations within the system concerned and

(4) Platform interrogation may be included. This service may also include feeder links necessary for its operation. (RR)

Earth Station. A station located either on the earth's surface or within the major portion of earth's atmosphere and intended for communication:

(1) With one or more space stations or

(2) With one or more stations of the same kind by means of one or more reflecting satellites or other objects in space. (RR)

Effective Radiated Power (e.r.p) (in a given direction). The product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given direction. (RR)

Emergency Position-Indicating Radiobeacon Station. A station in the mobile service the emissions of which are intended to facilitate search and rescue operations. (RR)

Emission. Radiation produced, or the production of radiation, by a radio transmitting station.

For example, the energy radiated by the local oscillator of a radio receiver would not be an emission but a radiation. (RR)

End Product. A completed electronic device that has received all requisite FCC approvals and is suitable for marketing.

Equivalent Isotropically Radiated Power (e.i.r.p.). The product of the power supplied to the antenna and the antenna gain in a given direction relative to an isotropic antenna (absolute or isotropic gain). (RR)

Equivalent Monopole Radiated Power (e.m.r.p.) (in a given direction). The product of the power supplied to the antenna and its gain relative to a short vertical antenna in a given direction. (RR)

Equivalent Satellite Link Noise Temperature. The noise temperature referred to the output of the receiving antenna of the earth station corresponding to the radio-frequency noise power which produces the total observed noise at the output of the satellite link excluding the noise due to interference coming from satellite links using other satellites and from terrestrial systems. (RR)

Evaluation Kit. An assembly of components, subassemblies, or circuitry, including software, created by or for a component maker, system integrator, or product developer for the sole purpose of facilitating: (i) End product developer evaluation of all or some of such components, subassemblies, or circuitry, or (ii) the development of software to be used in an end product.

Experimental Station. A station utilizing radio waves in experiments with a view to the development of science or technique.

This definition does not include amateur stations. (RR)

Facsimile. A form of telegraphy for the transmission of fixed images, with or without half-tones, with a view to their reproduction in a permanent form. (RR)

Feeder Link. A radio link from an earth station at a given location to a space station, or vice versa, conveying information for a space radiocommunication service other than for the fixed-satellite service. The given location may be at a specified fixed point, or at any fixed point within specified areas. (RR)

Fixed-Satellite Service. A radiocommunication service between earth stations at given positions, when one or more satellites are used the given position may be a specified fixed point or any fixed point within specified areas in some cases this service includes satellite-to-satellite links, which may also be operated in the inter-satellite service the fixed-satellite service may also include feeder links for other space radiocommunication services. (RR)

Fixed Service. A radiocommunication service between specified fixed points. (RR)

Fixed Station. A station in the fixed service. (RR)

Frequency Assignment Subcommittee (FAS). A subcommittee of the Interdepartment Radio Advisory Committee (IRAC) within NTIA that develops and executes procedures for the assignment and coordination of Federal radio frequencies. (FCC)

Frequency Hopping Systems. A spread spectrum system in which the carrier is modulated with the coded information in a conventional manner causing a conventional spreading of the RF energy about the frequency carrier. The frequency of the carrier is not fixed but changes at fixed intervals under the direction of a coded sequence. The wide RF bandwidth needed by such a system is not required by spreading of the RF energy about the carrier but rather to accommodate the range of frequencies to which the carrier frequency can hop. The test of a frequency hopping system is that the near term distribution of hops appears random, the long term distribution appears evenly distributed over the hop set, and sequential hops are randomly distributed in both direction and magnitude of change in the hop set.

Frequency-Shift Telegraphy. Telegraphy by frequency modulation in which the telegraph signal shifts the frequency of the carrier between predetermined values. (RR)

Frequency Tolerance. The maximum permissible departure by the centre frequency of the frequency band occupied by an emission from the assigned frequency or, by the characteristic frequency of an emission from the reference frequency.

The frequency tolerance is expressed in parts in 10 6 or in hertz. (RR)

Full Carrier Single-Sideband Emission. A single-sideband emission without suppression of the carrier. (RR)

Gain of an Antenna. The ratio, usually expressed in decibels, of the power required at the input of a loss free reference antenna to the power supplied to the input of the given antenna to produce, in a given direction, the same field strength or the same power flux-density at the same distance. When not specified otherwise, the gain refers to the direction of maximum radiation. The gain may be considered for a specified polarization.

Depending on the choice of the reference antenna a distinction is made between:

(1) Absolute or isotropic gain (Gi), when the reference antenna is an isotropic antenna isolated in space

(2) Gain relative to a half-wave dipole (Gd), when the reference antenna is a half-wave dipole isolated in space whose equatorial plane contains the given direction

(3) Gain relative to a short vertical antenna (Gv), when the reference antenna is a linear conductor, much shorter than one quarter of the wavelength, normal to the surface of a perfectly conducting plane which contains the given direction. (RR)

General Purpose Mobile Service. A mobile service that includes all mobile communications uses including those within the Aeronautical Mobile, Land Mobile, or the Maritime Mobile Services.

Geostationary Satellite. A geosynchronous satellite whose circular and direct orbit lies in the plane of the Earth's equator and which thus remains fixed relative to the Earth by extension, a geosynchronous satellite which remains approximately fixed relative to the Earth. (RR)

Geostationary Satellite Orbit. The orbit in which a satellite must be placed to be a geostationary satellite. (RR)

Geosynchronous Satellite. An Earth satellite whose period of revolution is equal to the period of rotation of the Earth about its axis. (RR)

Government Master File (GMF). NTIA's database of Federal assignments. It also includes non-Federal authorizations coordinated with NTIA for the bands allocated for shared Federal and non-Federal use. (FCC)

Harmful Interference. Interference which endangers the functioning of a radionavigation service or of other safety services or seriously degrades, obstructs, or repeatedly interrupts a radiocommunication service operating in accordance with [the ITU] Radio Regulations. (CS)

High Altitude Platform Station (HAPS). A station located on an object at an altitude of 20 to 50 km and at a specified, nominal, fixed point relative to the Earth. (RR)

Hybrid Spread Spectrum Systems. Hybrid spread spectrum systems are those which use combinations of two or more types of direct sequence, frequency hopping, time hopping and pulsed FM modulation in order to achieve their wide occupied bandwidths.

Inclination of an Orbit (of an earth satellite). The angle determined by the plane containing the orbit and the plane of the Earth's equator measured in degrees between 0° and 180° and in counter-clockwise direction from the Earth's equatorial plane at the ascending node of the orbit. (RR)

Individual Reception (in the broadcasting-satellite service). The reception of emissions from a space station in the broadcasting-satellite service by simple domestic installations and in particular those possessing small antennae. (RR)

Industrial, Scientific and Medical (ISM) (of radio frequency energy) Applications. Operation of equipment or appliances designed to generate and use locally radio-frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications. (RR)

Instrument Landing System (ILS). A radionavigation system which provides aircraft with horizontal and vertical guidance just before and during landing and, at certain fixed points, indicates the distance to the reference point of landing. (RR)

Instrument Landing System Glide Path. A system of vertical guidance embodied in the instrument landing system which indicates the vertical deviation of the aircraft from its optimum path of descent. (RR)

Instrument Landing System Localizer. A system of horizontal guidance embodied in the instrument landing system which indicates the horizontal deviation of the aircraft from its optimum path of descent along the axis of the runway. (RR)

Insular area. A jurisdiction that is neither a part of one of the several States nor a Federal district. The U.S. insular areas are listed in 47 CFR 2.105(a) at notes 2 and 3. (FCC)

Interdepartment Radio Advisory Committee (IRAC). A committee of the Federal departments, agencies, and administrations that advises NTIA in assigning frequencies to Federal radio stations and in developing and executing policies, programs, procedures, and technical criteria pertaining to the allocation, management, and use of the spectrum. The IRAC consists of a main committee, subcommittees, and several ad hoc groups that consider various aspects of spectrum management policy. The FCC serves as a member of the Frequency Assignment Subcommittee and as Liaison Representative on the main committee, all other subcommittees and ad hoc groups. (FCC)

Interference. The effect of unwanted energy due to one or a combination of emissions, radiations, or inductions upon reception in a radiocommunication system, manifested by any performance degradation, misinterpretation, or loss of information which could be extracted in the absence of such unwanted energy. (RR)

International Telecommunication Union (ITU). An international organization within the United Nations System where governments and the private sector coordinate global telecom networks and services. The ITU is headquartered in Geneva, Switzerland and its internet address is www.itu.int. (FCC)

Inter-Satellite Service. A radiocommunication service providing links between artificial satellites. (RR)

Ionospheric Scatter. The propagation of radio waves by scattering as a result of irregularities or discontinuities in the ionization of the ionosphere. (RR)

Land Earth Station. An earth station in the fixed-satellite service or, in some cases, in the mobile-satellite service, located at a specified fixed point or within a specified area on land to provide a feeder link for the mobile-satellite service. (RR)

Land Mobile Earth Station. A mobile earth station in the land mobile-satellite service capable of surface movement within the geographical limits of a country or continent. (RR)

Land Mobile-Satellite Service. A mobile-satellite service in which mobile earth stations are located on land. (RR)

Land Mobile Service. A mobile service between base stations and land mobile stations, or between land mobile stations. (RR)

Land Mobile Station. A mobile station in the land mobile service capable of surface movement within the geographical limits of a country or continent.

Land Station. A station in the mobile service not intended to be used while in motion. (RR)

Left-Hand (or Anti-Clockwise) Polarized Wave. An elliptically or circularly-polarized wave, in fixed plane, normal to the direction of propagation, whilst looking in the direction of propagation, rotates with time in a left hand or anti-clockwise direction. (RR)

Line A. Begins at Aberdeen, Washington running by great circle arc to the intersection of 48° N., 120° W., thence along parallel 48° N., to the intersection of 95° W., thence by great circle arc through the southernmost point of Duluth, Minn., thence by great circle arc to 45° N., 85° W., thence southward along meridian 85° W., to its intersection with parallel 41° N., thence along parallel 41° N., to its intersection with meridian 82° W., thence by great circle arc through the southernmost point of Bangor, Maine, thence by great circle arc through the southernmost point of Searsport, Maine, at which point it terminates. (FCC)

Line B. Begins at Tofino, B.C., running by great circle arc to the intersection of 50° N., 125° W., thence along parallel 50° N., to the intersection of 90° W., thence by great circle arc to the intersection of 45° N., 79°30′ W., thence by great circle arc through the northernmost point of Drummondville, Quebec (Lat. 45°52′ N., Long 72°30′ W.), thence by great circle arc to 48°30′ N., 70° W., thence by great circle arc through the northernmost point of Compbellton, N.B., thence by great circle are through the northernmost point of Liverpool, N.S., at which point it terminates. (FCC)

Line C. Begins at the intersection of 70° N., 144° W., thence by great circle arc to the intersection of 60° N., 143° W., thence by great circle arc so as to include all of the Alaskan Panhandle. (FCC)

Line D. Begins at the intersection of 70° N., 138° W., thence by great circle arc to the intersection of 61°20′ N., 139° W. (Burwash Landing), thence by great circle arc to the intersection of 60°45′ N., 135° W., thence by great circle arc to the intersection of 56° N., 128° W., thence south along 128° meridian to Lat. 55° N., thence by great circle arc to the intersection of 54° N., 130° W., thence by great circle arc to Port Clements, thence to the Pacific Ocean where it ends. (FCC)

Maritime Mobile-Satellite Service. A mobile-satellite service in which mobile earth stations are located on board ships survival craft stations and emergency position-indicating radiobeacon stations may also participate in this service. (RR)

Maritime Mobile Service. A mobile service between coast stations and ship stations, or between ship stations, or between associated on-board communication stations survival craft stations and emergency position-indicating radiobeacon stations may also participate in this service. (RR)

Maritime Radionavigation-Satellite Service. A radionavigation-satellite service in which earth stations are located on board ships. (RR)

Maritime Radionavigation Service. A radionavigation service intended for the benefit and for the safe operation of ships. (RR)

Marker Beacon. A transmitter in the aeronautical radionavigation service which radiates vertically a distinctive pattern for providing position information to aircraft. (RR)

Mean Power (of a radio transmitter). The average power supplied to the antenna transmission line by a transmitter during an interval of time sufficiently long compared with the lowest frequency encountered in the modulation taken under normal operating conditions. (RR)

Meteorological Aids Service. A radiocommunication service used for meteorological, including hydrological, observation and exploration. (RR)

Meteorological-Satellite Service. An earth exploration-satellite service for meteorological purposes. (RR)

Mobile Earth Station. An earth station in the mobile-satellite service intended to be used while in motion or during halts at unspecified points. (RR)

Mobile-Satellite Service. A radiocommunication service:

(1) Between mobile earth stations and one or more space stations, or between space stations used by this service or

(2) Between mobile earth stations by means of one or more space stations.

This service may also include feeder links necessary for its operation. (RR)

Mobile Service. A radiocommunication service between mobile and land stations, or between mobile stations. (CV)

Mobile Station. A station in the mobile service intended to be used while in motion or during halts at unspecified points. (RR)

Multi-Satellite Link. A radio link between a transmitting earth station and a receiving earth station through two or more satellites, without any intermediate earth station.

A multisatellite link comprises one up-link, one or more satellite-to-satellite links and one down-link. (RR)

National Telecommunications and Information Administration (NTIA). An agency of the United States Department of Commerce that serves as the President's principal advisor on telecommunications and information policy issues. NTIA manages Federal use of the radio spectrum and coordinates Federal use with the FCC. NTIA sets forth regulations for Federal use of the radio spectrum within its Manual of Regulations & Procedures for Federal Radio Frequency Management (NTIA Manual). (FCC)

Necessary Bandwidth. For a given class of emission, the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specified conditions. (RR)

Non-Voice, Non-Geostationary Mobile-Satellite Service. A mobile-satellite service reserved for use by non-geostationary satellites in the provision of non-voice communications which may include satellite links between land earth stations at fixed locations.

Occupied Bandwidth. The width of a frequency band such that, below the lower and above the upper frequency limits, the mean powers emitted are each equal to a specified percentage β/2 of the total mean power of a given emission.

Unless otherwise specified in an ITU-R Recommendation for the appropriate class of emission, the value of β/2 should be taken as 0.5%. (RR).

On-Board Communication Station. A low-powered mobile station in the maritime mobile service intended for use for internal communications on board a ship, or between a ship and its lifeboats and life-rafts during lifeboat drills or operations, or for communication within a group of vessels being towed or pushed, as well as for line handling and mooring instructions. (RR)

Orbit. The path, relative to a specified frame of reference, described by the centre of mass of a satellite or other object in space subjected primarily to natural forces, mainly the force of gravity. (RR)

Out-of-band domain (of an emission). The frequency range, immediately outside the necessary bandwidth but excluding the spurious domain, in which out-of-band emissions generally predominate. Out-of-band emissions, defined based on their source, occur in the out-of-band domain and, to a lesser extent, in the spurious domain. Spurious emissions likewise may occur in the out-of-band domain as well as in the spurious domain. (RR)

Out-of-band Emission. Emission on a frequency or frequencies immediately outside the necessary bandwidth which results from the modulation process, but excluding spurious emissions. (RR)

Passive Sensor. A measuring instrument in the earth exploration-satellite service or in the space research service by means of which information is obtained by reception of radio waves of natural origin. (RR)

Peak Envelope Power (of a radio transmitter). The average power supplied to the antenna transmission line by a transmitter during one radio frequency cycle at the crest of the modulation envelope taken under normal operating conditions. (RR)

Period (of a satellite). The time elapsing between two consecutive passages of a satellite through a characteristic point on its orbit. (RR)

Permissible Interference. 3 Observed or predicted interference which complies with quantitative interference and sharing criteria contained in these [ITU Radio] Regulations or in ITU-R Recommendations or in special agreements as provided for in these Regulations. (RR)

Port Operations Service. A maritime mobile service in or near a port, between coast stations and ship stations, or between ship stations, in which messages are restricted to those relating to the operational handling, the movement and the safty of ships and, in emergency, to the safety of persons.

Messages which are of a public correspondence nature shall be excluded from this service. (RR)

Power. Whenever the power of a radio transmitter, etc. is referred to it shall be expressed in one of the following forms, according to the class of emission, using the arbitrary symbols indicated:

(1) Peak envelope power (PX or pX)

For different classes of emission, the relationships between peak envelope power, mean power and carrier power, under the conditions of normal operation and of no modulation, are contained in ITU-R Recommendations which may be used as a guide.

For use in formulae, the symbol p denotes power expressed in watts and the symbol P denotes power expressed in decibels relative to a reference level. (RR)

Primary Radar. A radiodetermination system based on the comparison of reference signals with radio signals reflected from the position to be determined. (RR)

Protection Ratio. The minimum value of the wanted-to-unwanted signal ratio, usually expressed in decibels, at the receiver input determined under specified conditions such that a specified reception quality of the wanted signal is achieved at the receiver output. (RR)

Public Correspondence. Any telecommunication which the offices and stations must, by reason of their being at the disposal of the public, accept for transmission. (CS)

Pulsed FM Systems. A pulsed FM system is a spread spectrum system in which a RF carrier is modulated with a fixed period and fixed duty cycle sequence. At the beginning of each transmitted pulse, the carrier frequency is frequency modulated causing an additional spreading of the carrier. The pattern of the frequency modulation will depend upon the spreading function which is chosen. In some systems the spreading function is a linear FM chirp sweep, sweeping either up or down in frequency.

Radar. A radiodetermination system based on the comparison of reference signals with radio signals reflected, or retrainsmitted, from the position to be determined. (RR)

Radar Beacon (RACON). A transmitter-receiver associated with a fixed navigational mark which, when triggered by a radar, automatically returns a distinctive signal which can appear on the display of the triggering radar, providing range, bearing and identification information. (RR)

Radiation. The outward flow of energy from any source in the form of radio waves. (RR)

Radio. A general term applied to the use of radio waves. (RR)

Radio Altimeter. Radionavigation equipment, on board an aircraft or spacecraft or the spacecraft above the Earth's surface or another surface. (RR)

Radio Astronomy. Astronomy based on the reception of radio waves of cosmic origin. (RR)

Radio Astronomy Service. A service involving the use of radio astronomy. (RR)

Radio Astronomy Station. A station in the radio astronomy service. (RR)

Radiobeacon Station. A station in the radionavigation service the emissions of which are intended to enable a mobile station to determine its bearing or direction in relation to radiobeacon station. (RR)

Radiocommunication. Telecommunication by means of radio waves. (CS) (CV)

Radiocommunication Service. A service as defined in this Section involving the transmission, emission and/or reception of radio waves for specific telecommunication purposes.

Radiodetermination. The determination of the position, velocity and/or other characteristics of an object, or the obtaining of information relating to these parameters, by means of the propagation properties of radio waves. (RR)

Radiodetermination-Satellite Service. A radiocommunication service for the purpose of radiodetermination involving the use or one of more space stations. This service may also include feeder links necessary for its own operation. (RR)

Radiodetermination Service. A radiocommunication service for the purpose of radiodetermination. (RR)

Radiodetermination Station. A station in the radiodetermination serviice. (RR)

Radio Direction-Finding. Radiodetermination using the reception of radio waves for the purpose of determining the direction of a station or object. (RR)

Radiolocation. Radiodetermination used for purposes other than those of radionavigation. (RR)

Radiolocation Land Station. A station in the radiolocation service not intended to be used while in motion. (RR)

Radiolocation Mobile Station. A station in the radiolocation service intended to be used while in motion or during halts at unspecified points. (RR)

Radiolocation Service. A radiodetermination service for the purpose of radiolocation. (RR)

Radionavigation. Radiodetermination used for the purposes of navigation, including obstruction warning.

Radionavigation Land Station. A station in the radionavigation service not intended to be used while in motion. (RR)

Radionavigation Mobile Station. A station in the radionavigation service intended to be used while in motion or during halts at unspecified points. (RR)

Radionavigation-Satellite Service. A radiodetermination-satellite service used for the purpose of radionavigation. This service may also include feeder links necessary for its operation. (RR)

Radionavigation Service. A radiod-etermination service for the purpose of radionavigation. (RR)

Radiosonde. An automatic radio transmitter in the meteorological aids service usually carried on an aircraft, free ballon, kite or parachute, and which transmits meteorological data. (RR)

Radiotelegram. A telegram, originating in or intended for a mobile station or a mobile earth station transmitted on all or part of its route over the radiocommunication channels of the mobile service or of the mobile-satellite service. (RR)

Radiotelemetry. Telemetry by means of radio waves. (RR)

Radiotelephone Call. A telephone call, originating in or intended for a mobile station or a mobile earth station, transmitted on all or part of its route over the radiocommunication channels of the mobile service or of the mobile-satellite service. (RR)

Radiotelex Call. A telex call, originating in or intended for a mobile station or a mobile earth station, transmitted on all or part of its route over the radiocommunication channels of the mobile service or the mobile-satellite service. (RR)

Radio Waves or Hertzian Waves. Electromagnetic waves of frequencies arbitrarily lower than 3,000 GHz, propagated in space without aritificial guide. (RR)

Reduced Carrier Single-Sideband Emission. A single-sideband emission in which the degree of carrier suppession enables the carrier to be reconstrituted and to be used for demodulation. (RR)

Reference Frequency. A frequency having a fixed and specified position with respect to the assigned frequency. The displacement of this frequency with respect to the assigned frequency has the same absolute value and sign that the displacement of the characteristic frequency has with respect to the centre of the frequency band occupied by the emission. (RR)

Reflecting Satellite. A satellite intended to reflect radiocommunication signals. (RR)

Right-Hand (or Clockwise) Polarized Wave. An Elliptically or circularly-polarized wave, in which the electric field vector, observed in any fixed plane, normal to the direction of propagation, whilst looking in the direction of propagation, rotates with time in a right-hand or clockwise direction. (RR)

Safety Service. Any radiocommunication service used permanently or temporarily for the safeguarding of human life and property. (RR)

Satellite. A body which revolves around another body of preponderant mass and which has a motion primarily and permanently determined by the force of attraction of that other body. (RR)

Satellite Link. A radio link between a transmitting earth station and a receiving earth station through one satellite. A satellite link comprises one up-link and one down-link. (RR)

Satellite Network. A satellite system or a part of a satellite system, consisting of only one satellite and the cooperating earth stations. (RR)

Satellite System. A space system using one or more artificial earth satellites. (RR)

Secondary Radar. A radiodetermination system based on the comparison of reference signals with radio signals retransmitted from the position to be determined. (RR)

Semi-Duplex Operation. 4 A method which is simplex operation on one end of the circuit and duplex operation at the other. (RR)

Simplex Operation. 4 Operating method in which transmission is made possible alternatively in each direction of a telecommunication channel, for example, by means of manual control.

Ship Earth Station. A mobile earth station in the maritime mobile-satellite service located on board ship. (RR)

Ship Movement Service. A safety service in the maritime mobile service other than a port operations service, between coast stations and ship stations, or between ship stations, in which messages are restricted to those relating to the movement of ships. Messages which are of a public correspondence nature shall be excluded from this service. (RR)

Ship's Emergency Transmitter. A ship's transmitter to be used exclusively on a distress frequency for distress, urgency or safety purposes. (RR)

Ship Station. A mobile station in the maritime mobile service located on board a vessel which is not permanently moored, other than a survival craft station. (RR)

Simplex Operation. Operating method in which transmission is made possible alternatively in each direction of a telecommunication channel, for example, by means of manual control. 5 (RR)

5 (See footnote under Duplex Operations.)

Single-Sideband Emission. An amplitude modulated emission with one sideband only. (RR)

Software defined radio. A radio that includes a transmitter in which the operating parameters of frequency range, modulation type or maximum output power (either radiated or conducted), or the circumstances under which the transmitter operates in accordance with Commission rules, can be altered by making a change in software without making any changes to hardware components that affect the radio frequency emissions. In accordance with § 2.944 of this part, only radios in which the software is designed or expected to be modified by a party other than the manufacturer and would affect the above-listed operating parameters or circumstances under which the radio transmits must be certified as software defined radios.

Spacecraft. A man-made vehicle which is intended to go beyond the major portion of the Earth's atmosphere. (RR)

These functions will normally be provided within the service in which the space station is operating. (RR)

Space Radiocommunication. Any radiocommunication involving the use of one or more space stations or the use of one or more reflecting satellites or other objects in space. (RR)

Space Research Service. A radiocommunication service in which spacecraft or other objects in space are used for scientific or technological research purposes. (RR)

Space Station. A station located on an object which is beyond, is intended to go beyond, or has been beyond, the major portion of the Earth's atmosphere. (RR)

Space System. Any group of cooperating Earth stations and/or space stations employing space radiocommunication for specific purposes. (RR)

Space Telecommand. The use of radiocommunication for the transmission of signals to a space station to initiate, modify or terminate functions of equipment on a space object, incuding the space station. (RR)

Space Telemetry. The use of telemetry for transmission for a space station of results of measurements made in a spacecraft, including those relating to the functioning of the spacecraft. (RR)

Space Tracking. Determination of the orbit, velocity or instanteneous position of an object in space by means of radiodetermination, excluding primary radar, for the purpose of following the movement of the object. (RR)

Special Service. A radiocommunication service, not otherwise defined in this Section, carried on exclusively for specific needs of general utility, and not open to public correspondence. (RR)

Spread Spectrum Systems. A spread spectrum system is an information bearing communications system in which: (1) Information is conveyed by modulation of a carrier by some conventional means, (2) the bandwidth is deliberately widened by means of a spreading function over that which would be needed to transmit the information alone. (In some spread spectrum systems, a portion of the information being conveyed by the system may be contained in the spreading function.)

Spurious domain (of an emission): The frequency range beyond the out-of-band domain in which spurious emissions generally predominate. (RR)

Spurious Emission. Emission on a frequency or frequencies which are outside the necessary bandwidth and the level of which may be reduced without affecting the corresponding transmission of information. Spurious emissions include harmonic emissions, parasitic emissions, intermodulation products and frequency conversion products, but exclude out-of-band emissions. (RR)

Standard Frequency and Time Signal-Satellite Service. A radiocommunication service using space stations on earth satellites for the same purposes as those of the standard frequency and time signal service.

This service may also include feeder links necessary for its operation. (RR)

Standard Frequency and Time Signal Service. A radiocommunication service for scientific, technical and other purposes, providing the transmission of specified frequencies, time signals, or both, of stated high precision, intended for general reception. (RR)

Standard Frequency and Time Signal Station. A station in the standard frequency and time signal service. (RR)

Station. One or more transmitters or receivers or a combination of transmitters and receivers, including the accessory equipment, necessary at one location for carrying on a radiocommunication service, or the radio astronomy service.

Each station shall be classified by the service in which it operates permanently or temporarily. (RR)

Suppressed Carrier Single-Sideband Emission. A single-sideband emission in which the carrier is virtually suppressed and not intended to be used for demodulation. (RR)

Survival Craft Station. A mobile station in the maritime mobile service or the aeronautical mobile service intended solely for survival purposes and located on any lifeboat, life-raft or other survival equipment. (RR)

Telecommand. The use of telecommunication for the transmission of signals to initiate, modify or terminate functions of equipment at a distance. (RR)

Telecommunication. Any transmission, emission or reception of signs, signals, writings, images and sounds or intelligence of any nature by wire, radio, optical or other electromagnetic systems. (CS)

Telegram. Written matter intended to be transmitted by telegraphy for delivery to the addressee. This term also includes radiotelegrams unless otherwise specified. (CS)

In this definition the term telegraphy has the same general meaning as defined in the Convention.

Telegraphy. 5 A form of telecommunication in which the transmitted information is intended to be recorded on arrival as a graphic document the transmitted information may sometimes be presented in an alternative form or may be stored for subsequent use. (CS)

5 A graphic document records information in a permanent form and is capable of being filed and consulted it may take the form of written or printed matter or of a fixed image.

Telemetry. The use of telecommunication for automatically indicating or recording measurements at a distance from the measuring instrument. (RR)

Telephony. A form of telecommunication primarily intended for the exchange of information in the form of speech. (CS)

Television. A form of telecommunication for the transmission of transient images of fixed or moving objects. (RR)

In these [international Radio] Regulations, unless otherwise stated, any station is a terrestrial station. (RR)

Time Hopping Systems. A time hopping system is a spread spectrum system in which the period and duty cycle of a pulsed RF carrier are varied in a pseudorandom manner under the control of a coded sequence. Time hopping is often used effectively with frequency hopping to form a hybrid time-division, multiple-access (TDMA) spread spectrum system.

Transponder. A transmitter-receiver facility the function of which is to transmit signals automatically when the proper interrogation is received. (FCC)

Tropospheric Scatter. The propagation of radio waves by scattering as a result of irregularities or discontinuities in the physical properties of the troposphere. (RR)

Unwanted Emissions. Consist of spurious emissions and out-of-band emissions. (RR)


Galaxies and quasars

Among the biggest cosmic structures we can see are galaxies, which essentially are vast collections of stars. Our own galaxy is called the Milky Way, and is considered a "barred spiral" shape. There are several types of galaxies, ranging from spiral to elliptical to irregular, and they can change as they come close to other objects or as stars within them age.

Often galaxies have supermassive black holes embedded in the center of their galaxies, which are only visible through the radiation that each black hole emanates as well as through its gravitational interactions with other objects. If the black hole is particularly active, with a lot of material falling into it, it produces immense amounts of radiation. This kind of a galactic object is called a quasar (just one of several types of similar objects.)

Large groups of galaxies can form in clusters that are groups as large as hundreds or thousands of galaxies bound together gravitationally. Scientists consider these the largest structures in the universe.