Improved Reference Sampling and Subtraction: A Technique for Reducing the Read Noise of Near-infrared Detector Systems

Thumbnail Image

Files

Rauscher_2017_PASP_129_105003.pdf (3.13 MB)

Links to Files

https://iopscience.iop.org/article/10.1088/1538-3873/aa83fd

Permanent Link

https://doi.org/10.1088/1538-3873/aa83fd
 http://hdl.handle.net/11603/24849

Collections

UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
UMBC Faculty Collection

Author/Creator

Author/Creator ORCID

https://orcid.org/0000-0001-8403-8548

Date

2017-09-06

Type of Work

journal articles
Text

Department

Program

Citation of Original Publication

Rauscher, Bernard J. Improved Reference Sampling and Subtraction: A Technique for Reducing the Read Noise of Near-infrared Detector Systems. Publications of the Astronomical Society of the Pacific 129 (Sept. 6, 2017), no. 980. https://doi.org/10.1088/1538-3873/aa83fd

Rights

This is a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain Mark 1.0

Subjects

Abstract

Near-infrared array detectors, like the James Webb Space Telescope (JWST) NIRSpec's Teledyne's H2RGs, often provide reference pixels and a reference output. These are used to remove correlated noise. Improved reference sampling and subtraction (IRS2) is a statistical technique for using this reference information optimally in a least-squares sense. Compared with the traditional H2RG readout, IRS2 uses a different clocking pattern to interleave many more reference pixels into the data than is otherwise possible. Compared with standard reference correction techniques, IRS2 subtracts the reference pixels and reference output using a statistically optimized set of frequency-dependent weights. The benefits include somewhat lower noise variance and much less obvious correlated noise. NIRSpec's IRS2 images are cosmetically clean, with less $1/f$ banding than in traditional data from the same system. This article describes the IRS2 clocking pattern and presents the equations needed to use IRS2 in systems other than NIRSpec. For NIRSpec, applying these equations is already an option in the calibration pipeline. As an aid to instrument builders, we provide our prototype IRS2 calibration software and sample JWST NIRSpec data. The same techniques are applicable to other detector systems, including those based on Teledyne's H4RG arrays. The H4RG's interleaved reference pixel readout mode is effectively one IRS2 pattern.