STEP 1: ORBIT ELEMENTS

aW




Variable Symbol Value
R.A. 1 a1 290.29484
R.A. 2 a2 293.03953
Change in R.A. Da 2.74467
Change in Dec. Dd -2.94401
Average Declination dav 45.04611
Orbit Inclination i 67.13


Now that we have determined the semi-major axis and inclination of the satellite's orbit, we can use this knowledge to determine the orbit's right ascension of ascending node (RAAN). This value denotes the point at which the satellite's orbit plane crosses the Earth's equatorial plane as the satellite crosses (ascends) from the southern to the northern hemisphere.

First, we need the average right ascension of the satellite streak:

aav = [ a1 + a2 ] / 2

aav = 291.66717

Next, we can calculate the RAAN. Be very careful when considering the conditions or the determined orbit can have the wrong plane!

If Da>0 and Dd>0 then aW = aav - sin-1 [ tandav / tan(i) ]

If Da>0 and Dd<0 then aW = aav - 180 + sin-1 [ tandav / tan(i) ]

If Da<0 and Dd>0 then aW = aav + sin-1 [ tandav / tan(i) ]

If Da<0 and Dd<0 then aW = aav + 180 - sin-1 [ tandav / tan(i) ]

Da > 0 and Dd < 0

aW = 136.66

RAAN is normally expressed in degrees, not hours. The RAAN indicates the right ascension of the node created by the intersection of the equatorial plane of the Earth and the satellite's orbit as the satellite ascends (moves from south to north).

 

GO BACK TO STEP #5

PROCEED TO STEP #7



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ZENITH METHOD

 

Step 6: Right Ascension of Ascending Node Was Last Modified On December 31, 2013