Rana, Hang

After adding the res G's at 0.47 Hz our ASC loops appeared to be quite and stable at 25 W for more than 20 mins. However, as we tried to power up to 28 W, our dithering loops, especially the yaw ones started to drift away. This then triggered the ~ 0.5 Hz oscillation in CHARD YAW and then in other ASC loops. In the second attempt we tried to increase the dithering loops gain as we power up. However this did not kept the dithering loops stable. While the error signal still crosses zero, the oscillation seemed to be growing. The further the soft dithering loops' error signal deviated from 0, the more sever the 0.5 Hz oscillation in CHARD YAW. Or it might be the other way around, as the CHARD YAW RMS increases, the spot motion naturally made the dithering loops oscillates more.

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In addition to power up, we also tried to go to LOWNOISE at 20 W.

In the lownoise asc state, we reduced the CHARD YAW dc gain to 0.7, giving it roughly 3 Hz UGF. Then we could re-engage the ELP10 (FM2) filter to reduce its noise.

However, we kept losing lock at LOWNOISE_ESD_ETMX, specifically when we tried to transition ETMX to ITMX+ETMY. The ITMX part seemed fine. The ETMY ESDOUTF_DC_OUTPUT was zero before the transition, which seemed weird. In the guardian there also seemed to be no explicit commands setting up ETMY ESD in that state.