For the spherical solar radiation pressure model in STK, acceleration due to solar pressure is given by:
where:
= acceleration vector in inertial coordinates
Cr = coefficient of reflectivity
A = area of spacecraft
m = mass of spacecraft
K = percentage of the sun, as seen from the spacecraft, that is not eclipsed (usually 1.0)
= solar flux at 1 AU
c = speed of light
RAU = distance from the spacecraft to the sun in AU
= the unit position vector of the sun as seen from the spacecraft. You may opt to use the true or apparent position of the sun for this parameter.