Currently `ts_phosim` when running `imgCloseLoop` without specifying the skyfile simulates stars at the OPD locations. It works fine for comCam and lsstFam, where OPD locations coincide with many sensors (for comCam its the center of each CCD and for lsstFam GQ field locations that span multiple sensors).  However , for corner sensors (with `–inst lsst` ) the OPD locations are in between the two half-sensors. When running the loop with default setting:

python /project/scichris/aos/ts_phosim/bin.src/imgCloseLoop.py --inst lsst --output /project/scichris/aos/expnum_DM-35389/wfs 

I get the `skyfile` with only 4 sources 

0 1.176 1.176 15.0

 1 358.824 1.176 15.0

 2 358.824 -1.176 15.0

 3 1.176 -1.176 15.0

all for SW0 sensors, so that the pipeline fails at 

 lsst.ctrl.mpexec.singleQuantumExecutor ERROR: Execution of task 'estimateZernikesCwfsTask' on quantum {instrument: 'LSSTCam', ex

 posure: 4021123106000, ...} failed. Exception ValueError: Unequal number of intra and extra focal detectors.

 Process task-{instrument: 'LSSTCam', exposure: 4021123106000, ...}:

(full trace wfs_trace_DM-35507.txt).

This  ticket is to fix that problem by specifying any other default field locations for corner sensors (when skyfile is not provided), as long as they make at least one star per half-chip.