Concerning the measurement performed during the lock acquisition, I re-run the analysis by using different wavefronts as reference.

Here the lists of all steps in detail:

1. the lock acquisition started at 17.10.30 UTC

2. first wavefront after starting the lock acquisition: WF 11 (17.12.08 UTC)

3. CH OFF at  17.11.57 UTC, WF 14 acquired at 17.12.08 UTC

4. WF 15 acquired at 17.12.44 UTC

5. CARM NULL 3F acquired at  17.12.48 UTC 

6. WF 16 acquired at  17.13.14 UTC

7. ITF unlock at 17.22.56 (WF 33)

The data have been re-processed considering the wavefronts in the range between 11 and 17 but, only the differential wavefronts computed wrt the images #17 look reliable.

An example is shown in fig.1 where both YAG and point absorbers OPLs are shown.

The WF17 has been acquired when the ITF lock index was 104.

Note that by re-analyzing the data considering the previous wavefront , WF16, acquired at ITF lock index 100, you can not see anything.

Madda told me that 100 corresponds to CARM NULL 3F and 104 to CARM null 1F

Thus, to perform HWS measurements during the lock acquisition, it is needed to take the reference at CARM null 1f (ITF LOCK INDEX 104).