Bending mode data for Rubin Observatory Simonyi Survey Telescope

Bending mode data for Rubin Observatory Simonyi Survey Telescope

Bending modes sags are represented as sums of Zernike polynomials and a bicubic spline for each mirror.

Source of bending mode data is: https://github.com/bxin/ZEMAX_FEMAP/tree/main

To resolve an extrapolation error in previous legacy bending modes, new modes were created by:

1. Reading original unit load cases
2. Weighting unit load case forces to match previously determined bending mode forces
3. Applying above weights to unit load surface deviations
4. Decomposing into Zernikes + bicubic splines

The corresponding actuator forces for these bending modes can be found in:

• https://github.com/bxin/ZEMAX_FEMAP/tree/main/0M1M3Bending/2bendingModes
• https://github.com/bxin/ZEMAX_FEMAP/tree/main/1M2Bending/2bendingModes

Representative files:

• M1M3_bend_zk.fits.gz: Zernike coefficients (in meters) for M1M3 sag perturbations.  20 modes x 29 coefficients

• M1M3_bend_forces.fits.gz: Forces on each actuator for each bending mode.  20 modes x 156 actuators

• M1M3_actuator_table.fits.gz: IDs and locations of actuators.

• M1_bend_coords.fits.gz: Grid coordinates for bicubic spline nodes on M1. 2 dimensions x 204 points

• M1_bend_grid.fits.gz: Bicubic spline coefficients on M1.  First dimension is split into z, dz/dx, dz/dy, dz^2/dxdy.  Second dimension is 20 bending modes.  Third and fourth dimensions are x and y grid locations.

• bend.yaml: YAML file indicating which grid coordinates, grid, and Zernikes to use for each mirror. Also indicates inner and outer radii of annuli for Zernike components, and the ordering of modes to use inside of the batoid_rubin package.

Additional files for M2 or M1 and M3 separately follow the same pattern described above.