20220713

Par-focal test between BIB, guiders, and wavefront sensors

In order to better characterize the contributions to Delivered Image Quality and to quantify possible systematic differences in our IQ measurements, we need to measure the focal points of different probes/cameras and determine how par-focal they are. This information is also used by the wavefront sensor pipeline to keep the telescope in the best possible focus.

This test should be attempted when the following conditions are met:

1. It has been at least a week since the last test
2. Stable conditions, <2" DIQ without large variations
3. Pr4 targets in the queue (presumably bright time)
4. Relatively fresh stack (no need to stack specially for this), with tRSE<150

If it looks like you can do it, plan ahead and run target_setup in advance to run shuffle on the star of your choosing. Note that it will take only a few minutes to run the script once the setup is completed.

Procedure

0. Pick a 12th magnitude star from the "focus12" catalog in htopx, run target_setup on Zeus for this target on the BIB (IFU=555). like this:

   [stevenj@zeus ~]$ target_setup 47128 E -ifu 555 -cat f12 -to
   

1. About 10-15 min before transit, go_next on this target with the usual commands from target_setup.

2. Ask the TO to set up on this target on the BIB, guide on the BIB, handshake to a guider (using g` filters), activate a WFS and allow to stabilize for about 3 minutes while storing images.

Be sure the star is NOT saturating on the BIB camera - it will require a short exposure (perhaps 0.1 seconds?)

3. Run this bash script on Zeus and do not change anything in TCS while it runs:

   /data1/archive/users/stevenj/run_parfocal_test_bib_gc_wfs_11point.sh
   

   which will:

a) write information to a log file called focus_curve_bib_gc_wfs.log

b) offset focus by -0.25mm

c) deactivate wavefront sensing so they do not interfere (leaves guider running, to avoid drift! but it won't guide since we just get single exposures on cycling)

d) cycle the GC1/GC2/WFS1/WFS2/BIB pipelines then offset focus by +0.05mm (repeats 10x until the total focus offset is +0.50mm)

e) offset focus by -0.25mm (should return to original focus when the script started)

f) close the PFIP shutter (leaves the pipelines all stopped)

g) beep to indicate the script is finished

4. Return to science observations. Email SJ the log file: focus_curve_bib_gc_wfs.log