Spectral Response of SPHEREx

Abstract The Spectro Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) is conducting the first all-sky near-infrared spectral survey spanning 0.75–5.0 μ m with resolving power R ≈ 35–130. Linear variable filters mounted in front of six H2RG detectors produce a position-dependent spectral response across the focal plane. This paper presents the ground-based spectral calibration of SPHEREx, including the cryogenic apparatus, optical configuration, measurement strategy, analysis pipeline, and resulting calibration products. Monochromatic wavelength scans are used to derive the spectral response function, band center, and resolving power for every pixel. Band centers are measured to better than 1 nm for Bands 1 through 4 (0.75–3.82 μ m) and better than 10 nm for Bands 5 and 6 (3.82–5.0 μ m). Out-of-band leakage is negligible for detectors above 1.64 μ m and is present at the percent level below this wavelength. The resolving power is measured to within 5% and agrees with design expectations to within 10%. An on-sky spectrum of the Cat’s Eye Nebula (NGC 6543) constructed from repeated observations provides in-flight verification and shows agreement between ground-calibrated response and astrophysical emission features. Calibration products, including per-pixel band center and resolving power maps, are released through IPAC to support community use of SPHEREx data. The absolute spectral calibration will continue to improve through in-flight measurements, with further reductions in uncertainty expected for the longest-wavelength bands.

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Publication Details

Journal
The Astrophysical Journal Supplement Series
Published
2026-04-21
DOI
https://doi.org/10.3847/1538-4365/ae522c
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
0.00

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article

Spectral Response of SPHEREx

Yi-Kuan Chiang, Volker Tolls, Tzu‐Ching Chang, C. D. Dowell et al.
The Astrophysical Journal Supplement Series
Astronomy and Astrophysical Research
article

Spectral Response of SPHEREx

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article en

Abstract

Abstract The Spectro Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) is conducting the first all-sky near-infrared spectral survey spanning 0.75–5.0 μ m with resolving power R ≈ 35–130. Linear variable filters mounted in front of six H2RG detectors produce a position-dependent spectral response across the focal plane. This paper presents the ground-based spectral calibration of SPHEREx, including the cryogenic apparatus, optical configuration, measurement strategy, analysis pipeline, and resulting calibration products. Monochromatic wavelength scans are used to derive the spectral response function, band center, and resolving power for every pixel. Band centers are measured to better than 1 nm for Bands 1 through 4 (0.75–3.82 μ m) and better than 10 nm for Bands 5 and 6 (3.82–5.0 μ m). Out-of-band leakage is negligible for detectors above 1.64 μ m and is present at the percent level below this wavelength. The resolving power is measured to within 5% and agrees with design expectations to within 10%. An on-sky spectrum of the Cat’s Eye Nebula (NGC 6543) constructed from repeated observations provides in-flight verification and shows agreement between ground-calibrated response and astrophysical emission features. Calibration products, including per-pixel band center and resolving power maps, are released through IPAC to support community use of SPHEREx data. The absolute spectral calibration will continue to improve through in-flight measurements, with further reductions in uncertainty expected for the longest-wavelength bands.

The Astrophysical Journal Supplement SeriesVol. 284(1)
California Institute of Technology (US), Vietnam National University Ho Chi Minh City (VN), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Jet Propulsion Laboratory (US), Rochester Institute of Technology (US), University of California, Irvine (US), Ho Chi Minh City University of Science (VN), Korea Astronomy and Space Science Institute (KR), Johns Hopkins University Applied Physics Laboratory (US), Center for Astrophysics Harvard & Smithsonian (US), Stanford University (US)
National Aeronautics and Space Administration
Openalex Percentile: Top 16%
Astronomy and Astrophysical Research
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