In the simulation each record of the wind/seeing data set is associated with a random orientation of the telescope. These data, together with the status of the windscreen and louvers of the enclosure, are used as input for a computation of mirror buffeting, mirror seeing and guiding error.
The model includes a parameterizations of the flow parameters (elaborated from the wind tunnel test data) for the main venting configurations of the enclosure
In the example described here below
the initial criterion for the operation of the windscreen and louvers
of the enclosure will be dictated by the requirement to limit the
wind buffeting on the primary mirror.
Starting with
the all-open configuration of the enclosure (A),
the rms
slope error
of the wavefront aberration 
and then the corresponding
CIR factor 
are computed.
If 
is lower than the budget value (in this case 0.99 -
see fig. 6.4) the
computation is repeated with the more protecting configuration (B)
and, if required, (C) and (D).
Then the guiding error is also computed for the identified
configuration.
The computation is done for each data record. If the set of site data is large, one will then obtain a statistically reliable distribution of the different configurations of the enclosure and of all the key quantities which determine the performance of the telescope.