WFI Design
Introduction to the section of the Wide Field Instrument (WFI) Imaging Mode User Guide describing the overall design of the WFI, and further reading suggestions for new WFI users.
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 simplified Relative Calibration System (sRCS) (an early design is given in 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 the 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 in Description of the WFI Instrument. The detailed description of the optical elements included in the Element Wheel Assembly is given in the WFI Optical Elements article. Additional information on how the WFI is integrated into the Observatory can be found in the Coordinate Systems article in the Data Handbook.
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 plane 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 Roman's optical assembly is given by Bolcar (2022).
Photographs of the WFI and its Subsystems
Images of the constructed WFI and its subsystems. The images are: (a) the fully-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 simplified Relative Calibration System (sRCS) before installation in the WFI (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 the WFI's construction and integration.
For additional questions not answered in this article, please contact the Roman Help Desk at STScI.
References
- “The WFI relative calibration system for WFIRST,” Wright et al. 2020
- "The Roman Wide Field Instrument Design Evolution," Domber et al. 2022
- "The Roman Space Telescope optical system: overview, test, and verification," Bolcar 2022
- NASA's Nancy Grace Roman Space Telescope Flickr Album. Specific images are linked in their captions.
- "Wide Field Instrument Status", J. Schlieder presentation at the Roman Community Forum Sept 14, 2022.