Use of parameter uncertainty for not estimated parameters

Dear Colleagues,

I am doing the following tests with an Orbit Determination using simulated data.

  1. Estimate only the state vector.
  2. Estimate the state vector plus the station position.

I have seen that in the second case the uncertainty of the state vector is higher as the uncertainty of the station position influences it. Thus I would like to know if it exists the possibility to take into account the station position uncertainty (set to 10 cm in each direction for example) without estimating it.

I have also tried estimating this parameter setting the minimum and maximum possible values to 0 so the value does not change but the uncertainty of the position is estimated in the process and then smaller than the real one.

Many thanks for your help.