Niko, Ethan

Today (12/17/19), a standard PCal endstation calibration measurement was undertaken. The results of the calculation are consistent with previous calibration measurements of the endstation. Some attached documents are the procedure document (with the measurement times), the trends documents with the final datapoint in each plot corresponding to today's measurement, WS/GS responsivity trends document, and the pictures of the alignment of the beams on the RX PD. The alignment seems similar to the last time it was checked (alog 53373). 

Some things to note:

1. Jeff K was inadvertently changing the gain on the optical follower servo at EY during the calibration. The times for this are

• OFS gain offset changes introduced: 2019-12-17 17:05:40 UTC => GPS time 1260637558.874
• OFS gain offset changes reverted: 2019-12-17 17:09:20 UTC => GPS time 1260637778.187

These times align with one of the sets of measurements at the endstation, labelled measurement 2, when the WS is in the outer beam of the TX module. This is seen in the data during the measurement, see the middle two panels of attached WS_at_TX.png. However, this has no effect on the calibration, as these two timeseries are taken as a ratio. It does, however, affect the measurement of the power imbalance (not used in the calibration), see power_imbalance.pdf. 

2. The portable temperature probe was moved from the TX module to the RX module. This is seen in the attached photos labelled temperature_probe_*.png. The reason for moving the probe is to coordinate reducing uncertainty in the RX PD responsivity due to temperature, as this is the photodetector used for IFO calibration.