I am trying to plot the ground tracks of an orbit. But I am having a problem with finding the longitude. The equation for the longitude is shown in the image. Is the Theta GMST initially zero because the greenwich meridian points to the Aries point (x-axis). How do you calculate alpha or vernal equinox? I saw a formula for alpha which is alpha = arctan(ry/rx), but the formula was for Right Ascension angle. Is the right ascension angle the same as vernal equinox. If not, then what is the formula for vernal equinox.
I am trying to plot the ground tracks of an orbit. But I am having a problem with finding the longitude. The equation for the longitude is shown in the image. Is the Theta GMST initially zero because the greenwich meridian points to the Aries point (x-axis). How do you calculate alpha or vernal equinox? I saw a formula for alpha which is alpha = arctan(ry/rx), but the formula was for Right Ascension angle. Is the right ascension angle the same as vernal equinox. If not, then what is the formula for vernal equinox.
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I am trying to plot the ground tracks of an orbit. But I am having a problem with finding the longitude. The equation for the longitude is shown in the image. Is the Theta GMST initially zero because the greenwich meridian points to the Aries point (x-axis). How do you calculate alpha or vernal equinox? I saw a formula for alpha which is alpha = arctan(ry/rx), but the formula was for Right Ascension angle. Is the right ascension angle the same as vernal equinox. If not, then what is the formula for vernal equinox.
Transcribed Image Text:Longitude with respect to the Earth: it can be obtained using the inertial longitude with
respect to the vernal equinox (a), and the Greenwich mean sidereal time (GMST):
λ =α-0GMST
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