WFI Design

Introduction to the section of the Wide Field Instrument (WFI) Imaging Mode User Guide describing the overall design of WFI and suggestions for users new to WFI to learn.



Overview of Content

The WFI is composed of several key subsystems. The subsystems most relevant to users are: the Focal Plane System (FPS) that contains the Focal Plane Array (FPA) and the Element Wheel Assembly (EWA), and the Relative Calibration System (RCS) (Wright et al. 2020). Several of these systems are identified in the engineering diagrams and photographs of the WFI construction in the figures below. High-Level information on the instrument is provided in the Introduction to WFI articles, including the WFI Quick Reference. Detailed information regarding the detectors used in the Focal Plane Assembly is given in the WFI Detectors section of the Wide Field Imaging Mode User Guide.

This section of the user guide provides technical details that are intended for users to understand the components of the WFI and how to consider them when either planning Roman programs or using Roman data. The detailed overview of the instrument is given on Description of WFI Instrument. The detailed description of the optical elements included in the Element Wheel Assembly is given in WFI Optical Elements. Additional information on how the WFI is integrated into the Observatory, e.g. its location in the focal plane, will be added to the RDox in the future. 


Diagram of Major Subsystems in WFI

Engineering diagrams of the Wide Field Instrument (WFI) design from Domber et al. (2022). The full WFI is shown on the far left and the components of the instrument are expanded out moving toward the right. This view shows the cryoradiator on the external part of the WFI, the focal plan electronics that connect to the Focal Plane Array (FPA), the optical bench and Element Wheel Assembly (EWA), and the aperture cover. A presentation of how the WFI fits into the NGRST optical assembly is given by Bolcar (2022). 



Images of the constructed WFI and its subsystems. The images are: (a) the assembled WFI enters the Titan test chamber at Ball Aerospace for Thermal Vacuum testing in September 2023 (Image Credit: Ball Aerospace; Link to Original); (b) the WFI after hardware integration in September 2023 (Image Credit: Ball Aerospace; Link to Original); (c) the Roman Focal Plane System (FPS) – with the electronics box in the upper right, assembled in May 2023 (Image Credit: NASA/Chris Gunn; Link to Original); (d) the Relative Calibration System (RCS) before installation (Image Credit: Hawaii Aerospace; Link to Original); (e) the Element Wheel Assembly (EWA) in December 2022 (Image Credit: Ball Aerospace; Link to Original). The NASA's Nancy Grace Roman Space Telescope Flickr album contains additional photos of WFI construction and integration. 




For additional questions not answered in this article, please contact the Roman Help Desk at STScI.


References

  1. “The WFI relative calibration system for WFIRST,” Wright et al. 2020
  2. "The Roman Wide Field Instrument Design Evolution," Domber et al. 2022 
  3. "The Roman Space Telescope optical system: overview, test, and verification," Bolcar 2022
  4. NASA's Nancy Grace Roman Space Telescope Flickr Album. Specific images are linked in their captions. 
  5. "Wide Field Instrument Status", J. Schlieder presentation at the Roman Community Forum Sept 14, 2022.



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Initial publication of the article.