J. Kissel

Having been bitten by "clipping" in PCALY beforehand, I've gotten into the habit of trending the PCAL's reported test mass displacement before / during calibration measurements. Further, I've been worried that the residual temperature fluctuations after end-station's HVAC upgrade will impact the accuracy of the PCALY's RX PD's reported reported displacement.

Sure enough, the attached trend shows that the residual 0.2 [deg C] diurnal temperature swing is causing a 1.0 to 1.5% deviation in reported displacement. I'm not sure whether to request that the PCAL system be less sensitive to temperature, or if the HVAC system to control the temperature better, but we can't use the RXPD as a fundamental reference, with claimed accuaracy / precision of 0.75% if its impacted by temperature at twice that level.

For record, we're in no way sure that this isn't caused by test mass pitch (also from temperature fluctuations) steering the beam into a spot that has more clipping, if the PCAL periscope's position is oscillating with temperature, it's something inside the receiver box, or something we otherwise haven't considered. That the TXPD's reported displacement remains rock-solid implies that the fluctuations are not on the input side.

For now, I'll record the TXPD as reference during transfer functions.