Statistical Conjunction Analysis and Modeling of Low-Earth-Orbit Catalogued Objects

Thenumber of space debris objects in the low Earth orbits,especially in the sun synchronous orbits,is increasing, and the breakups in 2007 have added more risk to the satellites in this region. It is necessary to study the risk of conjunctions in these orbits to plan a future course of action regarding the control and mitigation of space debris objects. A statistical approach to obtain the number of conjunctions in a prescribed altitude bin considering various inclinationbandsispresentedinthispaper.ThelowEarthorbits,whichareaffectedthemostbytheaccumulationof space debris objects, are analyzed with special emphasis on sun synchronous orbits. The study is based on the cataloguedobjectsfromthetwolineelementsets.Itisobservedthat,afterthemajorbreakupsin2007,thenumberof conjunctionsinthesunsynchronousorbitalregionishighlysignificant.Thesecondpartofthestudyconcentrateson themodelingaspectsofspatialdensityandbringsoutastochasticmodelbasedonamixtureofLaplacedistributions. ItisnotedfromthemodelthatthefragmentationeventsinlowEarthorbitduring2007haveredefinedthepatternof spatial density distribution in the region below 1100 km. Nomenclature a = area parameter in the modified Laplace distribution di = half-range of the inclination band under consideration, deg