Details
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Type:
Improvement
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Status: Done
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Resolution: Done
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Fix Version/s: None
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Component/s: ts_aos
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Labels:
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Story Points:3
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Epic Link:
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Team:Telescope and Site
Description
The finding of DM-34065, which confirms https://confluence.lsstcorp.org/display/LTS/Closed-Loop+Simulation+with+Non-Zero+Camera+Rotation+Angle was that rotTelPos does not change the angle between the camera and the M1M3 assembly. As https://sitcomtn-003.lsst.io/#camera-rotator explains, there are various ways to address nonzero camera rotator angle, and one is implemented in ts_ofc (https://github.com/lsst-ts/ts_ofc/blob/develop/python/lsst/ts/ofc/camrot.py used in https://github.com/lsst-ts/ts_ofc/blob/f33ffaf1f84dcdd7e7d526118c647cffcc7bf4ef/python/lsst/ts/ofc/ofc.py#L232 ).
The goal of this ticket is to rotate the calculated grid surface for M1, such as `randSurfInM` in https://github.com/lsst-ts/ts_phosim/blob/2d3ab7a18d5ba89c719a232a4beba19f8443724e/python/lsst/ts/phosim/telescope/M1M3Sim.py#L631 . It would be physically correct to rotate M1, M2, and M3 to "fake" the camera rotation. However, the main perturbation terms come from M1, and dominates those of M2,M3. So to test the principle, we try first only rotate M1. Then inspect the generated donut images and OPDs, and compare to the un-rotated images. Check whether retrieved Zernikes are rotated or not.
Attachments
Issue Links
- is child task of
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DM-33116 Validate AOS for a rotated camera
- Done
Activity
In summary, we simulate rotation of the M1M3 surface map, exploring angles 0, 30, 90 (attached image shows a 90 degree CCW rotation). The surface is random, but repeatable, thanks to identical simulation seed passed to `np.random.seed(int(seedNum))`
The expectation was that since M1M3 contributes to the majority of perturbations, the orthogonal pairs of Zernikes would be rotated (eg. between 0 and 90, zk5 <–>zk6, etc. ). To confirm that M2 has negligible contribution to wavefront error, we simulated both case where M1M3 and M2 is simulated (M2_M1M3 below), or only M1M3 (with the M2 subsystem turned off). The figure below shows the recovered Zernike coefficients for various rotations of M1M3 surface map, with or without M2. The top panel shows indeed very small difference whether M2 is included or not for the same rotation of M1M3 surface. For this reason the bottom panel displays the residuals between M2_M1M3 and M1M3 only simulations for a given rotation of M1M3 surface. They are on the order of few tens of nm, i.e. contribution of M2 is <1% for most Zk numbers.
Fine to close this; nothing to merge.
The notebook with this test is at https://github.com/suberlak/AOS/blob/main/AOS_DM-34424_rotate_M1_surfaceGrid.ipynb