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Computation procedure

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 - cf. fig. 6.2) the computation is repeated with the more protecting configurations (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 and, 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.

Lorenzo Zago,, Sun Feb 26 22:57:31 GMT+0100 1995