Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: This study investigates the theory of precision satellite orbit propagation and satellite
lifetime prediction and lead to the development of two necessary software tools for
analysis in these fields. Precision propagation was achieved through the implementation
of Cowell's method of special perturbations, considering perturbations due to a 70x70
asymmetrical gravity field, atmospheric drag, Luni-Solar attraction and Solar radiation
pressure. The satellite's perturbed equations of motion were integrated utilizing a seveneighth
order Runge-Kutta-Fehlberg numerical integration procedure, limiting error
propagation by employing adaptive step size control. The MSlS-90 atmospheric density
model, providing for diurnal and semi-annual variations, was employed to determine
atmospheric density. Care was taken in the precision modelling of the motion of the
12000 equator and equinox. Propagation results for this test case proved to be superior to
the SGP4 propagator and a commercial package.
The long-term effects of Earth oblateness and atmospheric drag on a satellite's orbital
elements were investigated and applied to the orbit decay prediction problem. Orbit
decay was predicted by integrating the rates of change of the orbital elements due to Earth
oblateness and atmospheric drag. A semi-analytical technique involving Runge-Kutta
and Gauss-Legendre quadrature was employed in the solution process. Relevant software
was developed to implement the decay theory. Optimum drag coefficients, estimated
from drag analysis using precision propagation, were used in decay prediction. Two test
cases of observed decayed satellites were used to evaluate the theory. Results for both
test cases indicated that the theory fitted observational data well within acceptable limits. / AFRIKAANSE OPSOMMING: 'n Ondersoek is gedoen oor die teorie van presiesie satelliet-wentelbaan vooruitskatting
en satelliet-wentelbaanleeftyd afskatting en het gelei tot die ontwikkeling van twee
analiseprogramme vir gebruik in hierdie vakgebiede. Presiesie vooruitskatting is bereik
deur die gebruik van Cowell se metode van spesiale perturbasies, wat die invloed van 'n
nie-simmetriese 70x070 gravitasieveld, atmosferiese sleur, Son-Maan aantrekkingskragte
en druk van sonradiasie, in ag neem. Die satelliet se versteurde bewegingsvergelykings
is numeries ge-ïntegreer deur gebruik te maak van die sewe-agste orde Runge-Kutta-
Fehlberg metode wat fout-voortplanting inhibeer deur gebruik te maak van 'n aanpasbare
integrasiestaplengte. Die MSIS-90 atmosferies model, wat voorsiening maak vir dag-nag
en half-jaarlikse atmosferiese variasies, is gebruik vir die berekening van atmosferiese
digtheid. Sorg is gedra by die presiesie modellering van die beweging van die J2000
ekwator en ekwinokse. Resultate vir hierdie toetsgeval toon meer voortreflik te wees as
die SPG4 - en 'n kommersieël-beskikbare vooruitskatter.
Die langtermyn effekte van aard-afplatting en atmosferiese sleur op wentelbaanleeftyd is
ondersoek en toegepas op die wentelbaanverval-afskattingsprobleem. Wentelbaanverval
is bereken deur die integrasie van die tydsafgeleides van die wentelbaanelement onder
invloed van aard-afplatting en atmosferiese sleur. Vir die doel is 'n semi-analitiese
tegniek, wat gebruik maak van Gauss-Legendre kwadratuur en Runge-Kutta numeriese
integrasie, gebruik gemaak. Nodige rekenaar programmatuur is ontwi kkeI om die
vervalteorie te implimenteer. Optimale sleur-koëffisiënte is afgeskat deur van presiesie
wentelbaananalise gebruik te maak. Twee gevallestudies van bekende vervalde satelliete
is gebruik om die vervalteorie te evalueer. Resultate vir beide gevallestudies toon aan dat
eksperimentele resultate werklike vervaltye binne aanvaarbare limiete navolg.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53555 |
| Date | 12 1900 |
| Creators | Opperman, B. D. L. |
| Contributors | Milne, G. W., Bredenkamp, B. V., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 1 v. |
| Rights | Stellenbosch University |
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