 impact was caused by a comet.

The United States Naval Research Laboratory (NRL) and the United States Department of Defense Space Test Program (STP) conducted the Charged Aerosol Release Experiment (CARE) on September 19, 2009, using exhaust particles from a Black Brant XII suborbital sounding rocket launched from NASA's Wallops Flight Facility to create an artificial noctilucent cloud. The cloud was to be observed over a period of weeks or months by ground instruments and the Spatial Heterodyne IMager for MEsospheric Radicals (SHIMMER) instrument on the NRL/STP STPSat-1 spacecraft. The rocket's exhaust plume was observed and reported to news organizations in the United States from New Jersey to Massachusetts.

Observation
Noctilucent clouds are generally colourless or pale blue, although occasionally other colours including red and green occur. The characteristic blue colour comes from absorption by ozone in the path of the sunlight illuminating the noctilucent cloud. They can appear as featureless bands, but frequently show distinctive patterns such as streaks, wave-like undulations, and whirls. They are considered a "beautiful natural phenomenon". Noctilucent clouds may be confused with cirrus clouds, but appear sharper under magnification. Those caused by rocket exhausts tend to show colours other than silver or blue, because of iridescence caused by the uniform size of the water droplets produced.

Noctilucent clouds may be seen by observers at a latitude of 50° to 65°. They seldom occur at lower latitudes (although there have been sightings as far south as Paris, Utah, Italy, Turkey and Spain), and closer to the poles it does not get dark enough for the clouds to become visible. They occur during summer, from mid-May to mid-August in the northern hemisphere and between mid-November and mid-February in the southern hemisphere. They are very faint and tenuous, and may be observed only in twilight around sunrise and sunset when the clouds of the lower atmosphere are in shadow, but the noctilucent cloud is illuminated by the Sun. They are best seen when the Sun is between 6° and 16° below the horizon. Although noctilucent clouds occur in both hemispheres, they have been observed thousands of times in the northern hemisphere, but fewer than 100 times in the southern. Southern hemisphere noctilucent clouds are fainter and occur less frequently; additionally the southern hemisphere has a lower population
impact was caused by a comet. 

 The United States Naval Research Laboratory (NRL) and the United States Department of Defense Space Test Program (STP) conducted the Charged Aerosol Release Experiment (CARE) on September 19, 2009, using exhaust particle from a Black Brant XII suborbital sound rocket launched from NASA's Wallops Flight Facility to create an artificial noctilucent swarm. The cloud was to be observed over a period of week or months by ground instrument and the Spatial Heterodyne IMager for MEsospheric Radicals (SHIMMER) instrument on the NRL / STP STPSat-1 spacecraft. The rocket's exhaust feather was observed and reported to news organizations in the United States from New Jersey to Massachusetts. 

 notice 
 Noctilucent clouds are generally colorless or pale blue, although occasionally other semblance including red and green occur. The characteristic aristocratic colour comes from absorption by ozone in the way of the sunlight illuminating the noctilucent swarm. They can appear as featureless bands, but frequently show distinctive practice such as streaks, wave - like undulations, and whirls. They are considered a " beautiful lifelike phenomenon ". Noctilucent cloud may be confused with cirrus clouds, but appear sharper under magnification. Those caused by rocket exhausts tend to show semblance other than silver or aristocratic, because of iridescence caused by the uniform size of the water droplet produced. 

 Noctilucent cloud may be seen by observers at a latitude of 50 ° to 65 °. They rarely occur at lower latitudes (although there have been sightings as far south as Paris, Utah, Italy, Turkey and Spain), and closer to the pole it does not get dark enough for the clouds to become visible. They occur during summer, from mid - May to mid - August in the northern hemisphere and between mid - November and mid - February in the southern hemisphere. They are very dim and flimsy, and may be watch only in twilight around sunrise and sunset when the clouds of the humble atmosphere are in shadow, but the noctilucent cloud is illuminate by the Sun. They are best seen when the Sun is between 6 ° and 16 ° below the horizon. Although noctilucent clouds occur in both hemisphere, they have been observed thousands of fourth dimension in the northern hemisphere, but few than 100 times in the southern. Southern hemisphere noctilucent clouds are fainter and happen less frequently; additionally the southern hemisphere has a lower population
 imoact was caused by a comtt.

The United Statgs Naval Reseadch Labofatory (NRL) and the United Stetes Depaetment of Defense Spacd Test Prlgram (STP) coiducted the Charjsd Aerosol Remcase Zx'eriment (CARE) ok September 19, 2009, using exhauvt pcrticles from a Black Brant XII subowbital xoknding rocket jaunbhqd fdom NASA's Wallops Flight Facility fo creaue an artificial npctilucent cloud. The cloud was to be observed ovfr a period of rweks or montfs by ground instrumenjs and the Spatial Heterodyne IMxger yor MEsosphgxuc Gddicals (SHINMER) pnstrument on the NRL/VTP STPXat-1 spacecraft. Thx roxket's exhaust plume wes observed and repotted to nefs organizations in tye Unhted Stagws wroj Iew Jersej tk Massachuaetts.

Observqtion
Noctilucent clpuqw are generalmy coljuwless or pale blue, although occasionallj otger colours including rwd and green occur. Thg charactewistic blue colour comes from absorption by ozone in tie pauh of tfw dunlight illuminating the noctilucent cloud. Trsy csn appear as fcatureless bands, bit ftgquently show aistinefibe patterns such ad streahs, wace-like unqulayions, and whirls. They are cinsidered a "yeaytiful natural pheuomenon". Noctnlucenj cloucs may be confused with cirdus clouds, hut appead sharper under mxgnpficdtion. Those caused by rockqt exhausvs teud to shuw cplours other thaj silyar or blue, because of itidescance causef by the uniform size of the wavxr droplets ptodgceg.

Noctilueent ckouds may be feen by observgrs at a jatitjde of 50° to 65°. They veldom occuw at lower ladltudes (althongh there havw bewn sighgkngs as far soith as Pagif, Utqh, Italy, Turkey anv Spxjn), and closer ti tye poles it doex nut den derk egmugh for the clojds yo bezome visiblc. Tfey pccur during summer, xrom mid-May to mid-Auguxt in the borthern hemisphere amd between mid-Novelber end miv-Februsry in the southern hemisphere. Thsy are vegy naint and tentous, and may be pbserved only in twilight around sunrisx and sunset when the coouds of the lower ctkosphere arx in sradow, but the noctilucent cloyd is illuminated by the Sun. They are gest saen wjen the Sun is between 6° and 16° below the horizon. Although noctilucent cloudw occuc yn both hemjsphrres, nhev hcve beeg obdxrved thousands og times in the northern hemisphxre, but fefex than 100 times in the southern. Suuthern hemiskhere noctilucent clouds ade faintrr and occur less frequently; adcitionally the southern memispherw has a lowvt pupulation
impact was caused by a comet. The Naval Laboratory (NRL) the United States Program conducted the Charged Release Experiment (CARE) September 19, 2009, using exhaust particles a Black Brant XII suborbital sounding rocket launched from NASA's Wallops Flight Facility create an artificial noctilucent cloud. The cloud was to be observed over a of or by instruments and the Spatial Heterodyne IMager for MEsospheric Radicals (SHIMMER) instrument on the NRL/STP STPSat-1 spacecraft. rocket's exhaust plume was observed and reported to organizations in the United from New Jersey to Massachusetts. Noctilucent are generally or blue, occasionally other colours red and green occur. The characteristic blue colour comes from absorption by ozone in the path of sunlight illuminating cloud. They appear featureless but frequently show such as streaks, wave-like undulations, and considered a "beautiful natural phenomenon". Noctilucent clouds may confused with clouds, but appear sharper under magnification. caused by rocket exhausts tend to show colours than silver or blue, because of iridescence caused by the uniform size of the water Noctilucent clouds may be by observers at latitude 50° 65°. seldom occur lower latitudes (although there have been sightings as far south as Utah, Italy, Turkey and Spain), and closer to the poles not dark enough for clouds to become visible. occur summer, from mid-May to the hemisphere and in southern hemisphere. They are faint and tenuous, and may observed only in twilight the clouds of the lower atmosphere are in but the noctilucent cloud is illuminated by Sun. They are best seen when the Sun is between 6° and below the noctilucent clouds occur in both hemispheres, they have observed thousands of times the northern hemisphere, but fewer than 100 times in southern. hemisphere noctilucent are fainter and less frequently; additionally southern hemisphere has population
 impact was caused by a comet.

ThE United StaTes NaVal resEaRch LAborAtory (NRL) and the uNiteD States Department of DefEnse SPaCE TesT prOgram (sTP) condUCtED The chArGed aeROsOl RelEasE ExperiMent (CARE) on sepTeMber 19, 2009, using exhAUsT particles FroM a Black Brant xII SuborbItAl sOUndinG roCket lAuncheD From NAsA's WallopS FLIght FaCIlity to CREaTe an Artificial noctiluCEnT Cloud. The cloud wAs to be ObSErVED ovEr a Period of weEkS or moNThs by grOUnD INStrUMents and the SpAtial HeteroDYne iMager FoR MESOspherIc RadIcALs (ShIMMER) instrUmenT on the NRL/sTP STPsAt-1 spaceCRaft. The Rocket'S exHauSt plUMe WaS obSeRVed ANd RepORteD to news oRgAnIzatiOns iN THE unitEd STateS from new Jersey to MaSsaChusETts.

obserVatioN
NocTiLucenT cloudS are gEnErally colourlesS or pAle blue, alThoUgH ocCaSionaLLy otheR coLouRs incluDing red ANd gReEN OCcUr. The characteristiC bLUE cOlour comEs from ABsOrPTion by ozOnE in The pATH of thE sunLIgHt illumiNating THe NoCtiluceNt Cloud. THeY caN apPear aS FeatUrelesS bands, buT freqUEntly show distiNCtive patterns SUcH AS sTReakS, waVe-like undulAtioNS, and WhirLS. THey ARe conSiderEd A "BeAUtiful natural phenomEnOn". NoctIluceNt clouds may be Confused wiTH CIrrus cloUds, bUT aPPear sharper undEr magNification. tHose causEd by rOcket exhAusts tend TO Show coloUrs OthEr tHan SILvEr or blue, becauSE Of irIdEscence CauSed by thE unIfoRm sIze Of The water dRoplets pRoDuCeD.

NOctIluceNT clouds mAy Be sEeN by ObserVErs at a LatitUde oF 50° tO 65°. THEy sEldom ocCUr AT LoweR lAtItudEs (aLtHough TherE HavE been siGhtings as Far SOuth As paRis, Utah, italy, Turkey anD SPain), and cloSeR to The polES It does noT get dark enough for the cloUDs to becOme VisibLe. ThEy occur duRinG summeR, frOM mid-MaY to mid-augusT iN thE NOrtheRN HeMisPhEre and betwEEN miD-NoveMbEr anD mid-FebRuary in the southern HEmiSphere. They are VerY faiNT AnD teNUoUS, anD mAY be OBServed only in twiLight arounD sUNrIse and sunsET whEn The clouDs of the Lower ATmospheRe are in shAdow, but thE nOctiLUCenT cloud is ilLuminateD by the Sun. tHey arE BeSt seeN whEn the SUn Is bEtweeN 6° and 16° beLOw tHe horIzon. AlThOugh noCtiluCeNt clouds Occur in both hemispheres, tHey havE been ObsErved thouSanDS of Times in thE norThern hemisPheRe, bUt fewEr tHAn 100 timEs in THe SouTHern. SOuthERn hemisphERe NocTILuCent clouds aRE FAinTer anD ocCUr less FreqUently; additionallY The southern hemIsphERE haS a lOWer pOpUlation
 impact was caused by a co met.

TheUnite d S tat es  Nav al R esearch Labora t ory(NRL) and the United S tates  D e part m en t ofDefense Sp a c e T es tPro gr a m(STP)  co nducted  the Charg edAe rosol Releas e  E xperiment(CA RE) on Septe mbe r 19,20 09, using  ex haust  parti c les fr om a Blac kB rant X I I subor b i ta l so unding rocket lau n ch e d from NASA'sWallop sF li g h t F aci lity to cr ea te an artific i al n o cti l ucent cloud.The cloud w a s t o be o bs erv e d over  a pe ri o d o f weeks ormont hs by gro und in s trument s  and th e Spat ial  He tero d yn eIMa ge r  fo r  M Eso s phe ric Radi ca ls  (SHI MMER ) i n stru men t on  theNRL/STP STPSa t-1  spa c ecr aft.The r ocke t' s exh aust p lumewa s observed andrepo rted to n ews  o rga ni zatio n s in t heUni ted Sta tes fro m  Ne wJ e r se y to Massachusetts .O bs ervation 
Nocti l uc en t  cloudsar e g ener a l ly co lour l es s or pal e blue ,  a lt hough o cc asiona ll y o the r col o ursinclud ing redand g r een occur. The characteristi c  b l u ec olou r c omes from a bsor p tion  byo zo nei n the  path  o f  t h e sunlight illumina ti ng the  noct ilucent cloud . They can a p pear asfeat u re l ess bands, but  freq uently sho w  distinc tivepatterns  such ass t reaks, w ave -li keund u l at ions, and whi r l s. T he y are c ons idereda " bea uti ful  n atural ph enomenon ".  N oc ti luc ent c l ouds may  b e c on fus ed wi t h cirr us cl ouds ,bu t  ap pear sh a rp e r  und er  m agni fic at ion.Thos e  ca used by  rocket e xha u stste nd  to sho w colours oth er  than silv er  or  blue, b ecause o f iridescence caused by the uni for m siz e of  the wate r d roplet s p r oduced .

Noc tiluc en t c l o uds m a y  b e s ee n by obser v e rsat ala titu de of 5 0° to 65°. They se l dom  occur at low erlati t u de s ( a lt h oug ht her e have been sight ings as fa rs ou th as Pari s , U ta h, Ital y, Turk ey an d  Spain) , and clo ser to th epole s itdoes not g et darkenough fo r  thec lo uds t o b ecomevi sib le. T hey oc c urdurin g summ er , from  mid- Ma y to mid -August in the northern  hemis phere  an d between  mi d -No vember an d mi d-February  in  th e sou the r n hem isph e re . T h ey ar e ve r y faint a n dten u o us , and may b e o bse rvedonl y  in tw ilig ht around sunrise and sunset whe n th e clo uds of t he  lower atmosph ere  a r e  in shad ow , but the n octiluce nt cloud  is il lumina ted byt h eS un. Th ey a rebest seen  wh en the Sun  i sb etween  6°an d 16°belowt he h o r izon. Although n octil u c ent c l oud s occ ur  in bot h  hem ispheres,they have b een ob serv ed th ousands  o f time s i nthe northe r n hemisph ere,but few er  tha n 1 00 tim es i n the s outh er n.Southernh e mi s ph er e  no ctil ucent  c loud s are fai n ter andocc u r lessfr equ e n tly; a d di t i onally the  so uther n hemisphere hasa  l o wer p opulat ion
 impact_was caused_by a comet.

The United_States Naval_Research_Laboratory (NRL)_and_the United States_Department of Defense_Space Test Program (STP)_conducted the Charged_Aerosol_Release Experiment (CARE) on September 19, 2009, using exhaust particles from a Black Brant_XII_suborbital sounding_rocket_launched_from NASA's Wallops Flight Facility_to create an artificial noctilucent_cloud. The_cloud was to be observed over a period_of_weeks or months_by ground instruments and the Spatial Heterodyne IMager for_MEsospheric Radicals (SHIMMER) instrument on the_NRL/STP STPSat-1 spacecraft._The_rocket's_exhaust plume was observed_and reported to news organizations in_the United States from New Jersey_to Massachusetts.

Observation
Noctilucent clouds are generally colourless or_pale blue, although occasionally other colours_including red and green occur._The characteristic_blue colour comes from absorption_by ozone in_the path_of the sunlight_illuminating the noctilucent cloud. They can_appear as featureless_bands, but frequently show distinctive patterns_such_as streaks, wave-like_undulations,_and_whirls. They_are considered a_"beautiful_natural phenomenon"._Noctilucent_clouds may be confused with cirrus_clouds,_but appear sharper under magnification. Those caused_by rocket exhausts tend_to_show colours other than_silver or blue, because of_iridescence caused by the uniform size_of the_water droplets_produced.

Noctilucent clouds may be seen by observers at a latitude of_50° to 65°. They seldom occur_at lower latitudes (although_there have_been_sightings as far_south_as Paris,_Utah, Italy, Turkey and Spain), and closer_to the_poles it does not get dark_enough for the clouds_to_become visible. They occur during summer,_from mid-May to mid-August in the_northern hemisphere and between mid-November_and_mid-February_in the southern hemisphere. They_are very faint and tenuous, and_may be observed_only in twilight around sunrise and sunset_when_the clouds of the lower atmosphere_are_in shadow, but the noctilucent cloud_is_illuminated_by the Sun. They are_best seen when the Sun is_between 6° and 16° below the horizon. Although noctilucent_clouds occur in_both hemispheres, they have been_observed_thousands_of times in the northern hemisphere, but fewer than 100_times in_the southern. Southern_hemisphere noctilucent clouds are fainter and occur less frequently; additionally_the southern hemisphere has a lower population