Satgen539  Satellite Inclination 1 by GM4IHJ (BID SGEN539) 1999-07-24

Generally speaking, the inclination angle between the plane of a
satellites orbit and the earths equatorial plane , depends on where it
is launched from, and which direction it is launched to. Most launch
sites are on the coast of a large ocean, so that any launch
malfunctions result in a splash in the ocean , rather than a crash on
some urban area.

But it is much cheaper to get into space , if you launch from an
equatorial site. Where a launch to the east to a zero inclination
orbit gets a 1000 mph assist from earth rotation. Any increase in
inclination angle reduces this earth rotation bonus. Such that a 90
degree inclination orbit gets no earth rotation assist , and a launch
to an inclination angle greater than 90 degrees , has to fight against
earth rotation and therefore requires extra rocket thrust to
compensate for this. So if you want a launch with minimum thrust to
orbit, you need an equatorial launch to a low inclination angle.

Very few satellites can take advantage of this situation . The only
satellites going to zero inclination orbits are the geostationaries.
They launch from Florida or from Kouru. With the latter being the best
place to start because it is nearer the equator. Although, this
situation is about to change as Boeing introduce their Sea Launch
platform which is towed complete with rocket to a suitable equatorial
oceanic location for launch.

Most satellites going to low earth orbit cannot take advantage of
earth rotation or an equatorial launch site because they have to start
from countries which have no equatorial launch sites, or, they require
to cover all or most of the earth on each days orbits. Indeed in many
cases both these restrictions apply. The Russians and the Chinese have
no equatorial sites. Up until now it has been convenient for the
Russians to launch to mid latitude orbits from Kazakstan. In Kazakstan
the latitude of the launch site favours a launch trajectory to an
inclination of about 50 degrees. An orbit in which the satellite
regularly overflies the Russian control stations. However the recent
break up of the Soviet Union has left the launch site outside Russia
in independent Kazakstan. Where a recent launch failure in which the
rocket nearly hit a house, has highlighted the dangers of launches
over someone elses land.

Years ago the Russians began to operate a second launch site in the
Russian European Arctic at Plesetsk. From this high latitude site they
can launch satellites out over the Arctic wastes to inclinations of
around 82 to 88 degrees, Where they get no earth rotation assist, but
they do cover all the world in a days orbits. A feature which is
essential for many military applications and is also required for
commercial communication, weather and earth survey satellites. Russian
manned space craft have an additional imperative whereby they should
not be at risk of descent in unoccupied parts of the world such as the
Arctic or Antarctic. So they have always launched from Kazakstan to 
about 52 degrees inclination in order to stay inside the "safety zone"