SPHEREx observations of Comet 3I/ATLAS

SPHEREx observed the interstellar comet 3I/ATLAS in August and December 2025. The calibrated spectral images are available through IRSA, alongside all other SPHEREx mission data. This page provides resources that help you find, view, and work with SPHEREx observations of Comet 3I/ATLAS.

Identify and visualize SPHEREx observations of 3I/ATLAS

A table listing all SPHEREx observations of 3I/ATLAS is available to aid browsing and visualization. For each spectral image, the table provides a URL for access, the predicted sky position of 3I/ATLAS for the exposure (comet_ra, comet_dec), and other metadata.

You can upload this table into the IRSA Viewer web application, which will interactively display each observation. You can also read the table into your programming language of choice to create cutouts or custom visualizations.

Note: SPHEREx observations of 3I/ATLAS have low signal-to-noise at many wavelengths. See the SPHEREx publications below for details on data quality and interpretation.

Download the observation table (VO Table format).

Download scripts

Scripts are available to download all calibrated SPHEREx image files that include 3I/ATLAS. One uses wget and another uses curl, so you can choose the version that works best for your system. These scripts retrieve the full set of calibrated image products for offline analysis. Download the scripts:

Photometry guidance

At the resolution of SPHEREx, 3I/ATLAS is spatially extended at many wavelengths (see the publications below). Because of this, we do not recommend using the SPHEREx Spectrophotometry Tool, which is designed for point-like or nearly point-like sources.

Related SPHEREx publications

  1. SPHEREx Team Research Note on August 2025 data
    SPHEREx Discovery of Strong Water Ice Absorption and an Extended Carbon Dioxide Coma in 3I/ATLAS
    Lisse et al. 2026, RNAAS, Volume 9, Issue 9, id.242

  2. SPHEREx Team publication on August 2025 data
    SPHEREx Pre-Perihelion Mapping of H2O, CO2, and CO in Interstellar Object 3I/ATLAS
    Lisse et al. 2025, submitted to ApJL

  3. SPHEREx Team Research Note on December 2025 data
    SPHEREx Re-Observation of Interstellar Object 3I/ATLAS in December 2025: Detection of Increased Post-Perihelion Activity, Refractory Coma Dust, and New Coma Gas Species
    Lisse et al. 2026, submitted to RNAAS