Andrew 9.3-Meter ESA Stereo System User Manual


 
APPENDIX ‘A’
This section contains the formulas for determining the point-
ing capabilities of the modular mount earth station antenna.
Formulas for calculating true azimuth (AZ), true elevation
(EL), relative angle between true azimuth and mount point-
ing angle (dAZ) and strut lengths of the earth station are
given below:
Given the earth station latitude, longitude, azimuth set-
ting of mount (AZm) and satellite longitude (over the equa-
tor), the following calculations can be made:
For earth stations north of the equator:
AZ = 180° + arc tan (tan
θθ
/sin
αα
)
For earth stations south of the equator:
AZ = 360° - arc tan (tan
θθ
/sin |
αα
| )
Where:
AZ = true azimuth to view satellite, in degrees East (clock-
wise) of True North.
αα
= earth station latitude in degrees.
θθ
= satellite longitude minus earth station longitude, in
degrees.
NOTE: Earth station latitude values are positive for sites
located north of the equator and negative for sites south of
the equator. Longitude values are positive for earth station
sites or satellite positions west of Greenwich and negative
east of Greenwich.
dAZ = AZ - AZm
Where:
AZm = azimuth at which mount is set in degrees East
(clockwise) of True North.
dAZ = relative angle between true azimuth angle looking at
satellite and mount pointing direction in degrees.
EL = 90° - T - R
Where:
EL = true elevation angle to view satellite in degrees.
R = arc cos (cos θ cos α)
T = arc tan [sin R/(6.6166 - cos R)]
Pin to pin length of elevation strut in inches:
Equation (1):XEL = 26259.7740 - 14970.1377 [cos(27.0362° + EL)]
For the -90° to +30° dAZ Range:
Pin to pin length of azimuth strut in inches:
Equation (2): LAZ = 7571.2865 - 6181.928 [cos(105° + dAZ)]
For the -60° to +60° dAZ Range:
Pin to pin length of azimuth strut in inches:
Equation (3): LAZ = 7571.2865 - 6181.928 [cos(75° - dAZ)]
For the -30° to +90° dAZ Range:
Pin to pin length of azimuth strut in inches:
Equation (4): LAZ = 7571.2865 - 6181.928 [cos(105° - dAZ)]
NOTE: Azimuth strut pin-to-pin length values are based upon
strut attachment to right portion of structure as viewed from
rear of antenna for -60 to +60° and -30 to +90° azimuth
ranges. Values for -90 to +30° azimuth range are based on
strut attachment to left portion of structure as viewed from rear
of antenna.
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