This paper reports the design, testing and early operational performance of SPHEREx, a near‑infrared (NIR) space telescope that began science operations after launch on March 12, 2025 UTC. SPHEREx will produce an all‑sky spectral database — a map of light broken down by wavelength across the whole sky — and is optimized to address three main science questions about the Universe and our Galaxy.

The authors describe a full test campaign that ranged from component‑level screening in the laboratory to in‑orbit tests during the commissioning phase. They lay out the design choices and the testing strategies used to check the instrument, then report the measured performance results. According to the abstract, the instrument is currently operating in full science survey mode and meets the mission’s driving requirements.

At a high level, SPHEREx is a spectroscopic surveyor: instead of only taking pictures, it measures the spectrum of light coming from every part of the sky in the near‑infrared. That spectral information lets scientists do things such as look for small departures from simple random patterns in the distribution of matter left over from the Big Bang (so‑called non‑Gaussianity), measure the combined light from many distant galaxies to trace how galaxies formed over time (a technique called intensity mapping), and survey the plane of the Milky Way to find and map water and other biogenic ices.

Each of those science goals requires specific instrument performance. For example, searching for non‑Gaussianity needs precise control of systematic errors; intensity mapping needs stable sensitivity to faint, diffuse light; and the ice survey needs good spectral resolution in the NIR to identify molecular features. The paper reports that SPHEREx meets its driving requirements in optical performance, point‑source sensitivity (ability to detect compact objects), thermal stability, and minimization of correlated noise — all factors that affect the quality of its spectra.