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Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

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Appendix C / Axis Transforms<br />

_ _<br />

16.7 Celestial to Satellite LOS Transformations<br />

The Euler triplet defining the transform from the Celestial to each of the<br />

Satellite LOS frames (TRCTOL) located at the missile receiver point (g),<br />

E<br />

L<br />

C<br />

( i , j )<br />

: =<br />

( i : = [ 1(<br />

1 ) 6 ] ) ∧ ( j : = [ 1(<br />

1 ) 4 ] )<br />

⎛<br />

⎜<br />

⎜<br />

⎝<br />

0<br />

,<br />

− tan<br />

−1<br />

16-10<br />

⎛ P<br />

⎜<br />

⎜<br />

⎝<br />

P<br />

ZC<br />

g,<br />

s<br />

hC<br />

g,<br />

s<br />

( i,<br />

j )<br />

( i,<br />

j )<br />

⎞<br />

⎟<br />

⎟<br />

⎠<br />

,<br />

tan<br />

⇒<br />

−1<br />

⎛ P<br />

⎜<br />

⎜<br />

⎝<br />

P<br />

YC<br />

g,<br />

s<br />

XC<br />

g,<br />

s<br />

( )<br />

( ) ⎟ ⎟<br />

i,<br />

j ⎞ ⎞<br />

⎟<br />

i,<br />

j ⎟<br />

⎠ ⎠<br />

Equation 16.7-1<br />

Index (j) refers to a particular satellite in orbital plane (i). When the roll<br />

angle is zero the transformation matrix reduces to,<br />

T<br />

L<br />

C<br />

: =<br />

⎡ L L<br />

cos ΘC<br />

cos ΨC<br />

⎢<br />

⎢<br />

⎢<br />

L<br />

− sin ΨC<br />

⎢<br />

⎢<br />

⎢ L L<br />

⎣ sin ΘC<br />

cos ΨC<br />

16.8 Celestial to Earth Transformation<br />

,<br />

,<br />

,<br />

cos Θ<br />

sin Θ<br />

L<br />

C<br />

cos Ψ<br />

L<br />

C<br />

sin Ψ<br />

L<br />

C<br />

sin Ψ<br />

L<br />

C<br />

L<br />

C<br />

,<br />

,<br />

,<br />

− sin Θ<br />

0<br />

cos Θ<br />

L<br />

C<br />

L<br />

C<br />

⎤<br />

⎥<br />

⎥<br />

⎥<br />

⎥<br />

⎥<br />

⎥<br />

⎦<br />

Equation 16.7-2<br />

Z E rotates clockwise about Z C at 15.041°/hr. At midnight GMT the yaw<br />

angle between X C and X E is 30°. The Euler triplet defining the transform<br />

from Celestial to Earth axes in terms of the time after midnight (tM),<br />

E<br />

E<br />

C<br />

⎛<br />

π ZE<br />

: = ⎜ 0 , 0 , + ωC,<br />

E ⋅ tM<br />

⎝<br />

6<br />

⎞<br />

⎟<br />

⎠<br />

Equation 16.8-1<br />

The transform from the Celestial to Earth frame (TRCTOE) is obtained by<br />

substituting these Euler angles into Equation 16.1-4.<br />

16.9 Earth to Alignment Transformation<br />

The Earth and Alignment frames are fixed with respect to the Earth. The<br />

transform between the two is time invariant and defined by the Euler triplet,<br />

E<br />

A<br />

E<br />

⎛<br />

⎜<br />

⎝<br />

π<br />

− λ<br />

2<br />

π<br />

+ µ<br />

2<br />

= r,<br />

o , 0 , r,<br />

o<br />

:<br />

The geocentric longitude and latitude at point (o) are,<br />

⎞<br />

⎟<br />

⎠<br />

Equation 16.9-1

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