Documentation for WebbPSF

WebbPSF is a Python package that computes simulated PSFs for the JWST instruments, taking into account detector pixel scales, rotations, filter profiles, and point source spectra. It is not a full optical model of JWST, but rather a tool for transforming optical path difference (OPD) maps, created with some other tool, into the resulting PSFs as observed with JWST’s instruments.

Sample PSFs for JWST’s instrument suite, all on the same angular scale and display stretch.

What this software does:

• Uses OPD map(s) precomputed by a detailed optical simulation of JWST
• Computes from those a PSF image with requested properties for any of JWST’s instruments
• Supports imaging & coronagraphy modes with all of JWST’s instruments. IFUs are a work in progress.
• Provides a suite of tools for quantifying PSF properies such as FWHM, Strehl ratio, etc.

What this software does NOT do:

• Contain in itself any detailed thermal or optical model of JWST
• Model any of the spectrograph optics or spectroscopy modes.
• Model any detector effects such as pixel MTF, intrapixel sensitivity variations, interpixel capacitance, or any noise sources. Add those separately with your favorite detector model code.

There are three main Python modules in this distribution: a lower-level optical propagation library (POPPY), an implementation of the JWST instruments using that library (WebbPSF), and a graphical user interface (WebbPSFgui). This documentation explains the programming interface and provides usage examples for each of those three module.

Further information from an optical modeling perspective may be found in Improved PSF Simulations for JWST: Methods, Algorithms, and Validation , M. D. Perrin 2011, JWST Technical report JWST-STScI-002469. That document describes in more detail the relevant optical physics, explains design decisions and motivation for WebbPSF’s architecture, and presents extensive validation tests demonstrating consistency between WebbPSF and other PSF simulation packages used throughout the JWST project.

The current version of WebbPSF is version 0.2.8, released Nov 7, 2011. If you would like to receive email announcements of future versions, please contact Marshall Perrin.

Contents

• Introduction
  • Why a new JWST PSF Simulator?
  • Algorithm Overview
  • Quick Start
• Requirements & Installation
  • Software Requirements
  • Installing WebbPSF via PYPI
  • Installing WebbPSF manually
  • Installing WebbPSF development versions, and/or contributing to its development
  • Installing the Required Data Files
  • Installing or updating pysynphot
  • Note for STScI Internal Users
• Release Notes
  • Known Issues
  • Plans for Future Releases
  • Version 0.2.8
  • Version 0.2.7
  • Version 0.2.6
  • Version 0.2.5
  • Versions 0.2.1 - 0.2.3
  • Version 0.2
  • Version 0.1
• The WebbPSF module
  • Usage and Examples
  • The JWInstrument generic class
  • Notes on Specific Instruments
  • Utility Functions for Display and Plotting
• Graphical User Interface
  • GUI Controls
• Physical Optics Propagation in PYthon (POPPY)
  • List of Classes
  • Wavefront
  • Optical System
  • Optical Elements
  • Instrument
• Appendix: Available Optical Path Difference (OPD) files
• Appendix: Instrument Property References
  • OTE
  • NIRCam
  • NIRSpec
  • NIRISS
  • MIRI
  • Instrument + Filter Throughputs
• More Examples
  • Typical Usage Cases
  • Advanced Usage Tricks
• Appendix: Sampling Requirements for Numerical Accuracy
  • Key Concepts
  • Some Useful Guidance
  • Per-Instrument Sampling Requirements
• Appendix: Optimizing FFT Performance for PSF Computations
  • Planning in FFTW3
  • A comparison of different FFT methods
  • A test comparing all four planning methods
  • A comparison of ‘estimate’ and ‘measure’ for different sizes
  • Caching of plans means that irunning the same script a second time is much faster
  • The Payoff: Speed improvements in POPPY

Indices and tables

• Index
• Module Index
• Search Page

Documentation last updated on June 27, 2012