The eighteen H4RG-10 detectors used in the Roman WFI focal plane represent the most advanced IR detector technology at this time. This section of the Instrument Handbook describes the detectors, the programs aimed at characterizing them, and our current understanding of their performance for Roman science. 

The eighteen H4RG-10 detectors used in the Roman WFI focal plane represent the most advanced IR detector technology at this time. The science requirements for Roman demand that these detectors be calibrated to unprecedented levels, which requires that the detectors go through a rigorous characterization program on the ground and in orbit. This section of the Instrument Handbook describes the detectors, the programs aimed at characterizing their performance, and the best understanding of their performance at the current time.

This article presents an overview of the H4RG-10 technology and its impact on scientific performance, with particular attention to detector characterization. A detailed summary of the WFI ground testing campaigns is included, along with available data, results (see WFI Ground Testing Campaigns), and a brief outline of the current on-orbit calibration plan (see On-Orbit Calibration Plan). Ongoing evaluation of detector performance will continue though commissioning and into regular operations (see Detector Performance).

Overview

The Wide Field Instrument (WFI) focal plane is populated with 18 H4RG-10 detectors. The H4RG-10 detectors are HgCdTe 4096 pixel by 4096 pixel photodiode arrays with a 10 micron pixel pitch. Prototype detectors were extensively characterized at the Detector Characterization Laboratory (DCL) at Goddard Space Flight Center. More specifically, their performance was demonstrated in a relevant space-like environment (thermal vacuum, vibration, acoustic, and radiation testing). Detailed results were presented by Mosby et al. (2020).

Roman detector development was a decade long program with key early investments, dozens of detectors fabricated and screened, then characterized and tested at GSFC through the Detector Technology Advancement Program (DTAP). The testing undertaken by the Roman proejct advanced the H4RG-10’s technology readiness level (TRL) to TRL-6 (Mosby et al. 2020). The Table of Teledyne Infrared Detectors provides context on the evolution of these detectors into the Roman era (adapted from Schlieder 2022, presentation). 

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

References

Journal Papers or Reports:

• "Properties and characteristics of the WFIRST H4RG-10 detectors", Mosby et al. 2020

Instrument Update Presentations:

• "Wide Field Instrument Status" presentation at the Roman Community Forum on September 12, 2022 by J. Schlieder