Interstellar Object 3I/ATLAS Surrounded: Observations from 3 sister instruments

Observations of interstellar object 3I/ATLAS were made from Europa UVS (ultraviolet spectrograph), JUICE UVS, and LRO LAMP from November to December 2025.  These sister instruments are from the SwRI UVS/Alice heritage family of ultraviolet spectrographs, with Europa UVS being the most recent addition.  On 6 November 2025 Europa-UVS performed observations pointed mostly sunward with a solar phase angle of ~143° at a comet/spacecraft distance of 1.09 AU.  A simultaneous observation performed by JUICE UVS was conducted with a solar phase angle of ~12° and a comet/spacecraft distance of 0.44 AU.  Other JUICE UVS observations were performed on 2, 3, 5, 6, 12, 19, and 25 of November 2025 (Figure 1).  The LRO-LAMP observation occurred on the same day as the JUICE-UVS scan observation, 25 of November 2025, with a solar phase angle of ~30° at a comet/spacecraft distance of 1.98 AU.  Initial results show detections of extended hydrogen Lyman alpha 121.6 nm, neutral oxygen 130.4 nm, and carbon 156.1 nm and 165.7 nm emissions.  Additional calibrations are needed to further the analysis and provide upper limits or additional, firmer detections.

Figure 1)  Sum of three JUICE UVS stare observations from 2, 5, and 12 November 2026.  The slit length (running vertically) spans 7.5° on the sky, while the spectral dispersion runs 55-206 nm, left-to-right.    Hydrogen, oxygen, and carbon emissions are easily identifiable in the raw data along with a star spectrum near spatial pixel row 1400.