VAMPIRES:Polarization Calibration
❓ TODO: Should we Gen2 archive these cals?
When a PDI run is done on VAMPIRES an associated set of Mueller matrix calibration data should be taken using the AO188 flat lamp. This ensures accurate correction of the instrumental polarization and crosstalk.
To perform PDI calibrations, VAMPIRES must be behind AO188 and an operator or day-crew member must be at the summit to enable the AO188 calibration source. The total time to take calibration data for all filters is 2.5 - 3 hours.
🤝 FastPDI
These calibrations are valuable for FastPDI, too. Consider coordinating with Kudo-san for FastPDI or attempting yourself, since you can archive FastPDI in the background of VAMPIRES without too much hassle.
Ahead of time decide which HWP angles and image rotator angles you want to test. For now, these must be hand-written inside vControl- talk to Miles or Barnaby for help. Set up the AO188 flat lamp at a higher amplitude, typically 2.6 amps. Test the exposure settings- you'll want to keep the exposure time between 10 and 100 ms.
Take darks for the exposure settings used for each filter, at least one for each EM gain level. This can be done after the cal source is removed. You can take flats with the polarizer removed, or you can create a master flat from a set of flats from different HWP angles.
Insert the linear polarizer using the WPU on garde- use Select Operation > Move In and then Move / Exec
From the same WPU dialog as the polarizer, insert the HWP stage- Select Operation > Move In and then Move / Exec
There is an automated function Run AO188 HWP Cal inside vControl which iterates through image rotator and HWP angle combinations.
You will have to manually execute it for each filter you want to test. You set the data type to "FLAT". You will be prompted to make sure the polarizer is in and you can see the estimated time without overheads to image each rotator and HWP position with the current exposure settings.
⛔️ Abort
If you need to abort, press "abort" and all loops will stop. If you start the cal again, it will start from the beginning of all the image rotator and HWP angle combinations.
To be written!