this should be it

mission/controller/acs/Guidance.cpp

@@ -418,6 +418,7 @@ void Guidance::comparePtg(double currentQuat[4], double currentSatRotRate[3], do
                           double targetSatRotRate[3], double refQuat[4], double refSatRotRate[3],
                           double errorQuat[4], double errorSatRotRate[3], double &errorAngle) {
   // First calculate error quaternion between current and target orientation
+  QuaternionOperations::inverse(targetQuat, targetQuat);
   QuaternionOperations::multiply(currentQuat, targetQuat, errorQuat);
   // Last calculate add rotation from reference quaternion
   QuaternionOperations::multiply(refQuat, errorQuat, errorQuat);