<DOC>
<DOCNO>
618
</DOCNO>
<TITLE>
orbit decay and prediction of the motion of artificial satellites .
</TITLE>
<AUTHOR>
michielsen, h.f.
</AUTHOR>
<BIBLIO>
advances in astronautical science, vol 4 plenum press 1959 . pp 255-310
</BIBLIO>
<TEXT>
the rate of decay of elliptic satellite orbits, due to atmospheric drag,
 is investigated through variation of parameters and through use of an
atmospheric model involving a power function between density and
altitude . this model is shown to fit actual conditions better than an
exponential function .
the effects of the equatorial belt and the rotation of the earth are
investigated . the conclusion is reached that through these anomalies
atmospheric drag substantially affects the orbit elements, especially
those defining the orbit plane .
an alternate approach of variation of parameters is presented, by which
a direct relation between period decay and instantaneous density conditions
is established . this approach, by itself specifically adequate
for prediction work, also opens an avenue for systematic and unified
evaluation of observed decay .
</TEXT>
</DOC>
