# Doc1 ```Figure4.3.a: Bi-elliptic transfer
from inner orbit 1 to outer orbit 4.
Occasionally satellites will A circular orbit is
orbit in paths that can be the orbit with a fixed
described as ellipses. In distance around
such cases, the central the barycenter, that is, in
body is located at one of the shape of a circle. Here
the foci of the ellipse the centripetal force is
gravitational force
A Hohmann Transfer is an orbital maneuver that
transfers a satellite or spacecraft from one circular
orbit to another. It was invented by a German scientist
in 1925 and is the most fuel-efficient way to get from
one circular orbit to another circular orbit. Because the
Hohmann Transfer is the most fuel-efficient way to
move a spacecraft, it is a fairly slow process and is used
mostly for transferring spacecraft shorter distances.
Figure4.3.b: Phasing maneuver.
Main orbit (0) and two phasing orbits,
faster (1) and slower (2). T0 is the
period of the main
A phasing maneuver is a two-impulse Hohmann transfer from and back
to the same orbit, used to change the position of a spacecraft in its orbit.
Communications and weather satellites in geostationary earth orbit use
phasing maneuvers to move to new locations above the equator.
Figure4.3.c: Non-Hohmann transfer Figure 4.3.d: Two intersecting orbits whose
apse lines do not coincide.
(3) between two coaxial elliptical
orbits.
illustrates a transfer between two coaxial elliptical orbits in which the
transfer trajectory shares the apse line but is not necessarily tangent to
either the initial, θA and θB are the true anomalies of points A and B
Figure(4.3.d) shows two intersecting orbits which have a common focus,
the opportunity for transfer from one orbit to the other by a single
impulsive maneuver occurs at the intersection points
The bi-elliptical Hohmann transfer uses two coaxial
semi-ellipses, 2 and 3, which extend beyond the outer
orbit. Each of the two ellipses is tangent to circular orbit
Cassini Mission Trajectory Plot
GALILEO Mission Trajectory Plot
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