I wrote a script to measure a genereric sensing matrix, and today we tested it for the pitch degree of freedom in the DRMI configuration.

The script (attached) configuration is at the beginning of the python file. One has to set

• the list of excitation channels to be used, the corresponding line frequencies and amplitudes, the duration of each measurement
• the list of error signals (the one you want to include in the sensing matrix, at the "numerator" of the transfer function)
• the list of monitoring channels that are used to measure the motion of the optics (those will be used as the "denominator" in the transfer functions)

When lauched, the script switches on the excitation one at a time (GPS times are saved to a log file for future reference).

When all line injections are done, the script reads the data and compute the sensing matrix. Basically, it's the value of the transfer function (error signals) / (monitoring channels).

The output is saved to an HTML file that contains three tables:

• the absolute values of the sensing matrix, with the dominant degree of freedom emphasized for each error signal, and not coherent elements grayed out
• the table of coherences
• the sensing matrix with the full complex elements

For reference, the attached script shows the configuration we used to measure the ASC pitch sensing matrix in DRMI. Beware that the excitation amplitudes are no more correct, since we changed some of the loop filters. We were injecting the lines at the error point of the ASC loops, monitor the mirror motions using local sensors (optical levers and OSEMs) and considering all the corner  WFS and QPD.

The result, copied directly from the output of the script, follows:

Sensing matrix (abs)

Coherence matrix

Sensing matrix (complex)