The SPHEREx Sky Simulator: Pre-launch Science Data Modeling

We describe the SPHEREx Sky Simulator, software to create simulated science data for NASA’s SPHEREx mission. SPHEREx is a two-year mission to carry out an all-sky spectrophotometric survey at ∼6.2" spatial resolution in 102 spectral channels spanning 0.75 to 5 μm. The Simulator software implements novel techniques to generate realistic infrared astrophysical sky scenes as observed by SPHEREx during its planned survey. The resulting simulated science data includes noise and systematic effects introduced to the data by the instrument, based on characterization from the pre-launch integration and test campaign. The software is a critical tool for the SPHEREx science analyses, which rely on statistical characterization of noise and sky realizations, in addition to forward modeling of systematic effects to characterize their effects on final data products. The Simulator enables a pre-launch prediction for the 5σ point source sensitivity of SPHEREx, ABMag 18.5–19 from 0.75 to 3.8 μm and 24 ABMag 16.6–18 from 3.8 to 5 μm, limited by the zodiacal light background.