<DOC>
<DOCNO>
622
</DOCNO>
<TITLE>
scale height in the upper atmosphere, derived from changes in satellite
orbits .
</TITLE>
<AUTHOR>
king-hele, d.g. and hughes, k.m.
</AUTHOR>
<BIBLIO>
r.a.e. tn space 4, 1962 .
</BIBLIO>
<TEXT>
the'density scale height'h in the upper atmosphere is a measure of the
rate at which air density p varies with height y, being given by
h-p//dp/dy/ . the value of h, although important because/with the
molecular weight of the air/it determines the air temperature, has not
as yet been well determined at heights above 200 km .
this note develops methods for finding h from the decrease in a
satellite's perigee height and from the decrease in the orbital period
of a satellite in a small-eccentricity orbit . these methods are then
applied to all the 14 satellites found suitable for the purpose . the 44
 values of h obtained, for heights of 200-450 km, represent an average
over day and night and probably have errors/s.d./of 5-10( . it is found
that, as solar activity declined between 1957 and 1961, h decreased
greatly ..e.g.at height 275 km, h decreased from 60 km in early 1958 to
height becomes much less rapid above 350 km, and are consistent with the
 supposition that h had low values, near 35 km, at heights near 250 km,
for 1959-61 . the results could be greatly extended in scope and
improved in accuracy if more accurate orbits were available for shortlifetime
satellites .
</TEXT>
</DOC>
