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guidance, flight mechanics and trajectory optimization

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In this form the equations are valid to the second order in the e . It is seen<br />

that the truncation of an infinite series (K) is required in only the radial<br />

<strong>and</strong> the binormal component equations.<br />

As already indicated, however, a linear theory is usually adequate for<br />

rendezvous discussions; therefore, these equations reduce to the following set<br />

of linear equations:<br />

2-<br />

where t7 -/a<br />

-3<br />

. 1.13<br />

Here the independent variable is time; <strong>and</strong> as is customary, the dot indicates<br />

differentiation with respect to time.<br />

The first important point to note is that the out-of-plane motion is<br />

decoupled from the in-plane motion, a feature that is characteristic of all<br />

linear sets. These equations can be changed so that the independent variable<br />

is the mean anomaly, M, since dM = n dt. This step is equivalent to making<br />

the unit of time equal to the time required for a change ofoone radian in mean<br />

anomaly. The resulting equations are (where the open dot is used to indicate<br />

d/dM):<br />

A major simplification occurs if the independent variable is changed to<br />

the true anomaly, (@I, or to the argument of latitude (0 = 8 + 0,). The<br />

transformation makes use of the conservation of angular momentum<br />

8<br />

1.12<br />

1.14a<br />

1.14b

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