Spectral response of SPHEREx
Howard Hui (Department of Physics, California Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology), James J. Bock (Department of Physics, California Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology), Samuel Condon (Department of Physics, Stanford University), C. Darren Dowell (Jet Propulsion Laboratory, California Institute of Technology, Department of Physics, California Institute of Technology), Woong-Seob Jeong (Korea Astronomy and Space Science Institute), Young-soo Jo (Korea Astronomy and Space Science Institute), Phillip M. Korngut (Department of Physics, California Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology), Kenneth Manatt (Jet Propulsion Laboratory, California Institute of Technology), Chi Nguyen (Department of Physics, California Institute of Technology), Hien Nguyen (Jet Propulsion Laboratory, California Institute of Technology, University of Science, Viet Nam National University), Stephen Padin (Department of Physics, California Institute of Technology), Sung-Joon Park (Korea Astronomy and Space Science Institute), Jeonghyun Pyo (Korea Astronomy and Space Science Institute), Yujin Yang (Korea Astronomy and Space Science Institute), Matthew L. N. Ashby (Center for Astrophysics, Harvard-Smithsonian), Yoonsoo P. Bach (Korea Astronomy and Space Science Institute), Yi-Kuan Chiang (Academia Sinica Institute of Astronomy and Astrophysics), Asantha Cooray (Department of Physics and Astronomy, University of California Irvine), Brendan P. Crill (Jet Propulsion Laboratory, California Institute of Technology, Department of Physics, California Institute of Technology), Ari J. Cukierman (Department of Physics, California Institute of Technology), Andreas L. Faisst (IPAC, California Insitute of Technology), Jae Hwan Kang (Department of Physics, California Institute of Technology), Carey M. Lisse (Johns Hopkins University, Johns Hopkins University Applied Physics Laboratory), Daniel C. Masters (IPAC, California Insitute of Technology), Roberta Paladini (IPAC, California Insitute of Technology), Zafar Rustamkulov (IPAC, California Insitute of Technology), Volker Tolls (Center for Astrophysics, Harvard-Smithsonian), Michael W. Werner (Jet Propulsion Laboratory, California Institute of Technology), Michael Zemcov (School of Physics and Astronomy, Rochester Institute of Technology, Jet Propulsion Laboratory, California Institute of Technology)
arXiv:2602.09139v1 Announce Type: new
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 to 5.0um with resolving power R~35 to 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 1nm for Bands 1 through 4 (0.75 to 3.82um) and better than 10nm for Bands 5 and 6 (3.82 to 5.0um). Out-of-band leakage is negligible for detectors above 1.64um 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.arXiv:2602.09139v1 Announce Type: new
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 to 5.0um with resolving power R~35 to 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 1nm for Bands 1 through 4 (0.75 to 3.82um) and better than 10nm for Bands 5 and 6 (3.82 to 5.0um). Out-of-band leakage is negligible for detectors above 1.64um 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.