Research on reforming the teaching of satellite communications based on STK

Transcription

1 World Transactions on Enginring and Tchnology Education Vol.11, No., WIETE Rsarch on rforming th taching of satllit communications basd on STK Fijiang Huang, Guangcan Liu, Xiaoyong Li & Wang Shn Changsha Univrsity, Changsha City, Popl s Rpublic of China Zhjiang Univrsity of Scinc and Tchnology, Hangzhou City, Popl s Rpublic of China ABSTRACT: With th aim of improving th fficincy of taching satllit communications, th contnt and faturs of satllit communications ducation hav bn analysd and outlind in this articl. Also prsntd is rsarch carrid out on th faturs of satllit simulation softwar, as wll as th application of such softwar in satllit communications ducation. Advancd is th ida that advantag can b takn of th satllit simulation softwar STK (Systms Tool Kit) to rform th taching of satllit communications, and provid spcific application xampls. Th rsults of this taching rform show that studnts intrst in satllit communications has bn incrasd; and that studnts can bttr grasp th basic knowldg and thoris of satllit communications. This articl provids rfrncs to th rform of taching satllit communications. It is ncssary to rinforc th rsarch on th application of th STK softwar in satllit communications ducation. INTRODUCTION Satllit communications is on of th spcialisd dirction courss for studnts majoring in communication nginring, as wll as an important lctiv cours for studnts majoring in information tchnology at th authors univrsitis. In modrn socity, information tchnology is dvloping rapidly. Satllit communication, which cultivats communication nginrs plays an indispnsabl and ssntial part in communication ducation. To improv th lvl of xprtis and practical skill, to cultivat a rigorous scintific attitud and scintific working mthods, it is of grat significanc for studnts to mastr systmatic and comprhnsiv thoris, as wll as skills rlvant to satllit communications. Satllit communications has abundant contnt, as wll as highly systmatic knowldg and rquirs a larg amount of practic. Thus, it is not adquat that practitionrs just hav a comprhnsion of thortic knowldg [1][]. As a consqunc, it is ncssary to conduct rsarch into th fficincy of taching satllit communications. This articl concrns th rsarch carrid out into making us of th satllit simulation softwar STK (Systms Tool Kit) to promot th practical taching of satllit communications by analysing th faturs of such taching in lin with th currnt status of satllit simulation softwar. THE MAJOR TEACHING CONTENT AND TEACHING FEATURES OF SATELLITE COMMUNICATIONS Major Taching Contnt of Satllit Communications Th contnts of th cours mainly includ basic thory, satllit communication componnts, ky tchnologis, satllit communication ntworks, satllit positioning and th navigation systms. Also, discussd in th cours is th latst businss tchnologis, such as th Intrnt and satllit Intrnt involvd in th satllit communication systm, and th latst dvlopmnts in tchnology. Through this cours, studnts should mastr not only th basic principls, systmatic structur and prformanc faturs of satllit communications, but also hav a solid foundation in th dsign, opration and application of satllit communications, as wll as carry out furthr rsarch on satllit communications. Morovr, studnts also should undrstand th application of modrn communication tchnology and th dvlopmnt status of satllit navigation tchnology [1]. Faturs of Satllit Communications Taching Satllit communications courss hav, as pr-rquisits, courss such as communication thory, lctromagntism, microwav tchnology, lctronic circuits, and so on. Only through mastring th knowldg in thos courss ar studnts abl to larn satllit communications. Many collgs and univrsitis usually arrang thir satllit 108

2 communications courss during th fourth acadmic yar and th class hours ar usually too fw. Th total class hours ar 3, including 8 for larning thory and four for practicals. As can b sn, th total class hours ar rlativly fw and most ar usd for larning thory. Clarly, th tim spnt on practical work is small. Th quipmnt ncssary for th practical taching of satllit communications is costly and, as a rsult, it is difficult to carry out practical taching of satllit communications. Nowadays, most collgs and univrsitis adopt th cramming mthod in taching satllit communications in which studnts passivly listn to lcturs on thory. Howvr, this cours dos rquir considrabl practical larning. Th rlvant thortical knowldg is both abstract and intricat. Taching that dpnds simply on class lcturs will mak studnts fl bord and studnts intrst will not b arousd. Thus, th taching objctivs will not b mt [3]. Hnc, on of th prominnt dirctions for satllit communications ducation is to intnsify th practical taching using a satllit simulation tool. SIMULATION TOOLS IN THE TEACHING OF SATELLITE COMMUNICATIONS Satllit Simulation Tool With th dvlopmnt of satllit communications tchnology, th structur and scal of satllit constllations is bcoming mor complicatd and th application of satllits mor divrsifid. Exprinc alon is not nough to plan and dsign a satllit ntwork. Ntwork simulation tchnology can b adoptd to simulat th bhaviours of a satllit ntworks, so as to valuat and prdict th prformanc of th ntwork. Thrfor, th adoption of ntwork simulation tchnology is an ffctiv way to improv th rliability and accuracy of th planning and dsign of a satllit ntwork. Howvr, in conducting satllit ntwork simulation, th first and most important thing is to slct an appropriat simulation tool. Currntly availabl simulation tools hav diffrnt functions. Thrfor, it is ncssary to comprhnsivly considr all kinds of rquirmnts and to slct appropriat simulation tools. Satllit simulation can b dividd into satllit ntwork constllation simulation and satllit ntwork protocol simulation. Common constllation simulation tools includ SaVi and STK (Systms Tool Kit, formrly calld Satllit Tool Kit). Common ntwork protocol simulation tools includ OPNET NS- (Ntwork Simulator), among othrs [-4]. Th Faturs of STK Satllit Simulation Softwar STK (Systms Tool Kit) is a dsign packag for satllit simulation dvlopd by Amrica s AGI (Analytical Graphics, Incorporatd). At prsnt, STK is th most advancd satllit analysis and visual tool in th arospac industry. STK not only provids th analytical ngin usd for computation, but also can display multiform D maps including satllits, carrir rockts, missils, aroplans, vhicls on th ground, targts, and so on. STK also posssss a 3D visualisation modul, which provids th tool and othr moduls with a lading 3D display nvironmnt. STK is sold as an lmntary or profssional dition, with many typs of componnt. Th lmntary dition of STK offrs mainly cor functions, including th cration and display of a satllit orbit, th dtrmination of satllit visibility and satllit covrag. Th cration of th orbit function handls various typs of orbit, as wll as quickly and accuratly confirming th orbital positions of satllits at any tim. Th visibility analysis function will calculat whthr th satllit is visibl at any tim btwn two arbitrary points. Th covrag rang analysis calculats th covrag of th arth by th satllit, as wll as th position of th satllit itslf. Th profssional dition of STK is an xpansion of th lmntary dition. Th major functions includ orbit prdiction, position adjustmnt, various co-ordinat typs and co-ordinat systms, various rmot snsor typs, visibility rstraint and a databas of citis and ground stations, as wll as of fixd stars [4][5]. Basd on th abov, STK is usd as th simulation softwar in conducting th practical taching of satllit communications. THE APPLICATION OF STK IN THE TEACHING REFORM OF SATELLITE COMMUNICATIONS Application of STK in th Taching of Satllit Orbit Paramtrs To show how an arth-cntrd inrtial co-ordinat systm works and to confirm th position of a satllit in spac at any tim, two groups of Kplrian orbit paramtrs (six in total) ar involvd [1][6]. Ths paramtrs includ thr that dtrmin th position, as wll as dirction of th orbital plan i.. Ω (dxtral ascnding nod right ascnsion), i (orbital inclination), ω (argumnt of prig) and thr paramtrs dtrmining th gomtrical shaps of orbital plan and th kintic charactristics i.. (orbital ccntricity), a (smi-major axis of th orbit) and M (man anomaly) or t p (prig passag tim). Bcaus comprhnsion of th abov paramtrs rquirs studnts to possss a spatial imaging ability, som studnts cannot fully undrstand thm aftr just larning th thory in class. In ordr to hlp studnts to intuitivly and clarly undrstand th paramtrs of a satllit orbit, a satllit constllation was dvlopd using th STK simulation softwar. 109

3 Th constllation consists of satllits in GEO (Gostationary Earth Orbit), IGSO (Inclind Gosynchronous Satllit Orbit) and MEO (Middl Earth Orbit). Th 3D strogram is shown in Figur 1. Figur 1: 3D structur of th satllit constllation. Th D distribution of sub-satllit points of th constllation satllits is shown in Figur. Figur : Th D distribution of sub-satllit points of constllation satllits. Whn any on of th six paramtrs is changd, th corrsponding changs can b clarly sn in th 3D diagram and changs will also happn to rlvant sub-satllit points. Via such dmonstration, studnts can acquir a dpr undrstanding of th knowldg of orbit paramtrs. As wll, during braks in larning, studnts can mak us of th softwar to st thir own orbits and obsrv th changs brought about by th chang of paramtr, in 3D and D diagrams. As a rsult, th thory will bcom mor spcific and clarr, which will b bnficial in nhancing taching fficincy. Application of STK to th Taching of th Visual Modl btwn th Satllit and th Ground Succssful communication btwn th satllit and th ground is basd on th prcondition that th satllits and th ground station should b visibl to ach othr. To xplain th communication btwn th satllit and th ground, it is rasonabl to stablish a visibility calculation modl of th satllit and th ground stations. Factors usd in th calculation modl ar shown in Figur 3 [6]. 1r Satllit φ r 10 α 1 Earth station Tangnt plan r O (Th arth's cor) Th arth R Figur 3: Th visibility calculation modl of th satllit and ground tim synchronisation stations. Rfrring to Figur 3, th visibility function dscribing whthr th satllit and ground stations can b visibl to ach othr is as follows: 110

4 ψ = α1 φ (1) Basd on th calculation rsults of Equation (1), Ψ > 0 signifis that th ground is visibl to th satllit. Th point whr Ψ = 0 is th point whr th satllit riss or falls across th circumscribd horizontal plan. Whn th valu of Ψ shifts from a positiv valu to a ngativ on, th satllit is rising, or vic vrsa. Thus, this dtrmins th visibl tim of th ground tim synchronisation station for th satllit. In trms of th abov modl, th analysis of visibl conditions of th satllit and th ground is conductd in a D plan. Howvr, th authntic visibl conditions of th satllit and th ground should b a 3D strogram. In th taching procss, us is mad of th STK softwar to simulat th visibl tim of Xi an Station for a GEO satllit and an IGSO satllit during 4 hours. Th lowst visibl lvation of th ground station is 5. Th simulation rsults ar shown in Figur 4 and spcific statistical rsults ar shown in Tabl 1. Figur 4: Th visibl tim of Xi an Station for GEO satllit and IGSO satllit. Tabl 1: Statistical tabl of th visibl tim of Xi an Station for GEO satllit and IGSO satllit (simulation priod: 1 Jun 008 1:00: Jun 008 1:00:00.000, unit: hour). GEO01 GEO0 GEO03 IGSO-01 IGSO-0 IGSO According to th rsults shown in Figur 4 and Tabl 1, it is possibl to dtrmin th visibl tim of Xi an Station for satllits. Whn th ground stations or satllits ar diffrnt, th changs of visibl tim can b clarly obsrvd. Such a mthod can hlp studnts to furthr consolidat thir undrstanding of th modl. Application of STK in Taching th Changing Laws of th Links btwn Ground and Satllit Th links btwn satllit and ground ar th foundation for stablishing satllit communication. Th changing laws govrning th links btwn th satllit and th ground dcid th rang of launching powr rquird from th ground for th satllit. In taching, it is possibl to mak us of th basic thory of satllit communication to stablish a modl of distanc btwn th ground and th satllit. Th formula is as follows: d = R (sin E) + h R + h R sin E () Th paramtrs in th formula ar dscribd by Wu t al [1]. From Equation (), it can b sn thr ar many factors affcting th chang of distanc btwn th ground and th satllit. It is difficult to dirctly analys th spcific changs of th distanc from th formula. Aftr stablishing a rlvant modl with th aid of STK, it was asy to simulat th changs of distanc btwn th ground and th satllit. Figur 5 shows th changing laws of distanc btwn Xi an Station and MEO satllit during th visibl priod using th STK simulation. Figur 5: Changing laws of distanc btwn Xi an Station and MEO satllit during th visibl priod. 111

5 From Figur 5, it can b sn that th changs of distanc btwn Xi an Station and an MEO satllit during th visibl priod hav th following laws: as th satllit movs, th distanc rpatdly bcoms smallr and, thn, bcoms largr. Such simulation rsults can mor vividly show th changing laws of th distanc btwn th ground and th satllit. Consquntly, studnts can bttr comprhnd th influnc of distanc changs on launch powr. CONCLUSIONS In th taching of satllit communications, th introduction of Systms Tool Kit softwar into practical taching will hlp studnts to bttr undrstand difficult thortical principls, as wll as abstract, intricat concptions and barly obsrvd phnomna. This is bcaus STK can simulat such aspcts and vividly show th rsults with th aid of D and 3D diagrams, with plntiful figurs and statistics. Th introduction of STK is also hlpful in dpning studnts undrstanding of knowldg rlatd to satllit communications and it boosts thir intrst in larning. This will facilitat th mastring by studnts of th basic principls, systm structur, communication systm and prformanc faturs of satllit communications. By virtu of th advantags of STK, studnts will hav a solid foundation in th dsign, opration and application of satllit communications, as wll as ability to furthr rsarch satllit communications. Th abov rsarch provids rfrncs to rforming th taching of satllit communications. In th futur, it will b ssntial to rinforc th application of STK in rforming th taching of satllit communications. ACKNOWLEDGEMENT This rsarch was supportd by th Hunan Provincial Natural Scinc Foundation of China (No. 11JJ307), th Scintific Rsarch Fund of Hunan Provincial Education Dpartmnt of China (NO.11B015), th Highr Education Taching Rformation Projct of Hunan Provinc of China, and th Scinc and Tchnology Planning Projct of Changsha of China (No. K ). REFERENCES 1. Wu, S., Wu, T. and Zuo, Y., Introduction to Satllit Communications. (nd Edn), Bijing: Publishing Hous of Elctronics Industry (006).. Wang, L. and Hu, T., Rsarch and practic on rform of satllit communication curriculum. J. of Wuhan Univrsity, 58,, (01). 3. Li, R. and Li, B., Application of thr-dimnsional mthod in thory taching of microwav and satllit communication. J. of Wuhan Univrsity, 58,, (01). 4. Kasih, J. and Susanto, S., Prdicting studnts final rsults through discriminant analysis. World Transactions on Engng. and Tchnol. Educ., 10,, (01). 5. Zhang, C., STK and its application in satllit systm simulation. Radio Communications Tchnol., 33, 4, (007). 6. Zhang, G. and Zhang, H., Satllit Mobil Communication Systm. Bijing: Posts & Tlcom Prss (001). 11