During this period of typically 2-3 weeks, the PI is primarily responsible for demonstrating to the Instrument Responsible that the instrument performance at the telescope conforms to its specification. During the commissioning phase the final versions of these programs will be formally delivered to and accepted by the Instrument Responsible.
The DFS products will be interfaced with the instrument during this period, or during the following performance evaluation period. For the necessary knowhow transfer it appears indispensable that the DFIR be at Paranal during this period.
An Engineering Version of the data reduction software must be available during commissioning of the instrument. It allows to check baseline performance and verify the optical configurations. It may be more interactive and not so fast as the procedures prepared for the pipeline. The engineering version will not be distributed to users outside the observatory.