In order to identify the center of the NI mirror, we switched on the NI RH at 15 W.

To perform this measurement the ITF was set in DOWN. The reference wavefront has been acquired with CH and DAS ON. 

The acquisition started at 15.15 UTC, and the RH has been switched ON at 15.20 UTC.

The curvature induced by the RH has been identified in the HWS maps (see fig. 1).

At 16.04 UTC the NI RH has been switched OFF.

We switched off the CH and DAS rings to cool down the CP.

The CH has been switched on at 18.37 UTC, the OPL is shown in fig. 2 showing a misalignment of the CH actuator wrt the centre of the mirror, in particular by around 3.5 cm in the horizontal direction and 2 cm in the vertical one.

By acting iteratively on the steering mirror on the CO2 bench, we aligned the CH on the centre of the mirror (fig.3). 

The ITF is left with the cavities locked on IR.