------------------------------------------------------------------------------- Transforms the sun vector defined in the ECI xz-plane into the spacecraft whose nominal frame is with the +z axis pointing at the earth, +y along orbit anti-normal and +x completing the right-hand set. The spacecraft rotates about the +z axis with alpha. ------------------------------------------------------------------------------- Form: uB = I2B( q, uI ) ------------------------------------------------------------------------------- ------ Inputs ------ q (4,1) Quaternion from the inertial to the body frame uI (3,1) Sun vector in the I frame ------- Outputs ------- uB (3,1) Sun vector in the B frame -------------------------------------------------------------------------------