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Optimization Strategies for the NIRSpec MSA Planning Tool

Optimization Strategies for the NIRSpec MSA Planning Tool

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Optimization Strategies for the NIRSpec MSA Planning Tool

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  1. Optimization Strategies for the NIRSpec MSA Planning Tool James Muzerolle

  2. Special thanks to NIRSpec teamlet members and APT developers: Diane Karakla Tracy Beck Jason Tumlinson Jeff Valenti Tom Donaldson Rob Douglas Karla Peterson

  3. Quick NIRSpec overview • 3 spectroscopic modes: MOS, fixed slit, IFU • 3 resolutions: R ~ 100 (prism), 1000 and 2700 (gratings) • effective wavelength range 0.6 – 5 microns • FOV ~ 3.6’ x 3.4’

  4. Microshutter Array (MSA) 4 x 365 x 171 shutters, individually addressable shutter pitch = 0.26” x 0.51”, (actual FOV = 0.2” x 0.45”) activated with magnet sweep

  5. prism spectral layout R=2700 spectral layout

  6. MSA planning tool prototype (APT v17.0.3)

  7. Preliminary optimization study • IDL code to simulate planning tool analysis of target placement within MSA shutters • heuristic iterative scheme to optimize the number of targets per MSA configuration from an input “candidate” target sample • grid of MSA center pointings and position angles • optimized solution = grid point with largest number of targets • loop for multiple configurations • test cases to evaluate various parameters: • input sample size/spatial distribution • number of “sky” shutters • including known failed shutters • dithers • target priorities

  8. Optimization results

  9. Default test case: • UDF-derived input candidate target catalog (1009 objects) • 3x3 center pointing grid, 20.1” x 36.2” offsets • 3-shutter slitlet • ideal MSA • 1 configuration per target set (no cross-slitlet dithers)

  10. Optimization results

  11. Default test case with failed shutters

  12. Optimization results

  13. Default test case with failed shutters, 2-shutter slitlet

  14. Optimization results

  15. Default test case with failed shutters, 1-shutter dither (0.26”) in dispersion direction

  16. Optimization results

  17. Default test case with failed shutters, detector gap dither (18”)

  18. prism spectral layout R=2700 spectral layout

  19. Optimization results

  20. Optimization results

  21. Recommendations • Tool should incorporate iterative scheme for optimizing the number of targets in a configuration using a grid of center pointings and/or position angles. • Account for “acceptance zone” where flux losses are minimized. • Failed shutters must be tracked and updated. No targets in failed closed. Generate warnings for targets in rows with failed opens. • Include an option for dithers requiring separate configurations (e.g., detector gap coverage), for an arbitrary number of dithers. • Target priorities, with an arbitrary number of layers, should be a key part of the optimization scheme. • Include a diagnostic plot summarizing characteristics of all targets in a given configuration, such as relative shutter position, priority, dither status, user-defined properties (magnitude, redshift, etc).

  22. To do • optical distortion across the FOV must be included, with the ability to update the distortion solution as needed • better treatment of prism spectra (can fit more than one in the same shutter row without overlap) • target acquisition: visualization and selection of reference stars, avoiding failed closed shutters • explore more observing scenarios