STEP 9: FINDING THE GEOCENTRIC COORDINATES

ag, dg



 
Element Symbol Value
Epoch to 05:54:21.171 UTC December 16, 2007
Inclination i 51o.9970
R.A. of the Ascending Node aW0 251o.0219
Eccentricity e 0.0001492
Argument of Perigee w0 33o.8641
Mean Anomaly at TLE Epoch Mo 326o.2322
Mean Motion n 12.62256095 orbits / solar day
Propagation Time Dt 1.7677141 solar days
Mean Anomaly at Time t M(t) 1.37777389 radians (78o.940629)
True Anomaly at Time t n(t) 78o.95065818
Semi-major Axis a 7791.787473 km
Perigee Distance P 7790.624938 km
Geocentric Distance r(t) 7791.564499 km
Precessed R.A. of Asc. Node aW(t) 245o.6400244
Precessed Arg. of Perigee w(t) 37o.77767416
Argument of Latitude m(t) 116o.7283323
R.A. Difference Da 129o.278845


The R.A. Difference is the difference between the Geocentric Right Ascension of the satellite and its (precessed) R.A. of Ascending Node:

Da = ag - aW(t)

Rearranging the terms, the Geocentric Right Ascension (ag) coordinate of the Satellite can be found by using the following equation:

ag = Da + aW(t) - 360o { INTEGER [ (Da + aW(t)) / 360o ] }

ag = 14o.9188694

The Geocentric Declination (dg) coordinate of the satellite can be determined by using the following equation:

dg = [SIGN (sinm(t))] cos-1 [ cosm(t) / cosDa ]

IMPORTANT NOTE: When using this equation, please keep in mind that the SIGN (sinm(t)) term means that only the sign of the result is to be used (+1 or -1) and not the value of the sine itself. SIGN (sinm(t)) is used only to determine the sign of the geocentric declination (above or below the celestial equator).

dg = +44o.73125163
 

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Step 9: Finding the Geocentric Coordinates Was Last Modified On April 01, 2014