J. Kissel, J. Oberling
Work Permit 8109
FRS Ticket 12394

Jason installed new components for SR3 optical lever this morning, which had died mid-February 2019 (LHO:47066). To check it's functionality, I've 
- Checked that the SUM is nice and high (good!)
- Checked its centering (good!), and
- Compared its amplitude spectral density in Pitch, Yaw, and SUM against PR3's optical lever -- a similar optical lever watching a similar suspension on a similar isolation system. (not yet good)

The noise above ~50 Hz is dominated by some white noise at the equivalent of ~1.5e-11 rad/rtHz, which I suspect is ADC noise. 
The straightforward solution is to just apply some analog whitening as has been done with all other levers. 
PR3's lever doesn't hit white noise until ~500 Hz, at the equivalent of 2e-12 in YAW; PIT is not limited by ADC noise, so we should be able to achieve this level of performance.

Once the whitening has been tuned, this test will need to be repeated, so I've stored the template for this measurement in 
    /ligo/home/jeffrey.kissel/Templates/DTT/
        H1_XR3_OpLev_Comparison.xml
for that future use.