ncall= -1  calculate forces for equations of motion
= -2  calculate partial derivatives
solcon = pep solar radiation pressure constant for gps
satellites (assumes cross section of 6.0088 sq m)
x(6) =  sbcor(6) = s/c w.r.t. earth (au)
rmag= rsb = magnitude of x
bcor(6) = s/c w.r.t. sun (au)
rsmag= rsb = magnitude of bcor
radcon(3)= con(9), con(10), con(11) in ertorb
radcon(1)= oi39 = coefficient of radiation presssure in
direction perpendicular to solar panels
radcon(2)= oi40 = coef. of rad. press. in y-axis direction
radcon(3)= oi41 = angle between panel axis and y-axis (rad)
shape= lambda = fraction of sun not occulted by earth
fi(3) =  output force along inertial x,y,z axes
qrad(3,3)= explicit partials of fi w.r.t. radcon
q(3,3)= partials of fi w.r.t. coordinates ( x )

substitute the following two cards to remove the factor
"shape*1e-12" from the y axis force model.
pak(1,2) = COS(oi41)
pak(2,2) = SIN(oi41)