K. Venkateswara
Sensor correction on X and Z at ETMX was left on last night. I turned it off this morning at 8 am as Filiberto and I were planning to work in the EX VEA. I modified the temperature sensors to take in +/-12V from the PEM power supply (thanks to Filiberto) and added a differential amplifier (with gain~50) to it.
In the afternoon, wind speeds were routinely hitting 50 mph. I've attached a pdf showing the ASD of the ground motion, BRS output and Stage 1 motion and some interesting coherences. Sensor correction was off in X and Z during this period.
Sensor correction has now been turned on and I will add plots of the result later.
J. Warner, K. Venkateswara
The X sensor correction we tried on ETMX was producing too much longitudinal motion in the X-arm at low frequencies. Sheila had to turn it off at 1:30 AM local time, this morning.
I've attached an ASD plot showing the GND_T240, GND_Super-sensor and Stage 1_T240 all along X. While SC improves Stage 1 motion above ~50 mHz, it injects a huge amount of low frequency motion. I think there are two main reasons for this:
1. While the super-sensor is likely measuring real displacement above 50-60 mHz, it is mostly measuring noise below ~30 mHz (see Brian's detailed SEI alog 602) . I'm still investigating the reason for this but it may not be an easy fix.
2. The SC filter is too aggressive (for the noise we have). Shifting it up to a higher corner frequency/faster roll-off may reduce low-frequency motion while hopefully keeping some of the benefit at 0.1-0.5 Hz.
Attempts are being made at better modelling. I apologize for rushing things without clearer understanding but hopefully, modelling and understanding will converge soon :)
