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Confirm the source of faint post‑C/A background illumination in LICIACube images

Determine whether the faint background illumination observed behind Didymos between approximately 172 and 183 seconds after impact in LICIACube LUKE images is produced by the high‑speed vapor plume by quantifying temporal variations of the sky brightness and isolating the plume contribution from instrument sensitivity limits, calibration uncertainties, and contamination from the ejecta cone.

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Background

The authors propose that the faint background illumination seen behind Didymos soon after close approach is most likely due to the vapor plume viewed from a changing geometry. They attempted to verify this by tracking sky brightness changes corresponding to expected in/out‑of‑field transitions of the plume.

Instrument sensitivity and contamination from ejecta prevented a conclusive test, leaving the origin of the measured background signal unconfirmed by photometric time series.

References

We attempted to support this proposed scenario by measuring the sky brightness over time, looking for changes when the plume was expected to be in or out of the field of view, but were not successful. The sensitivity of the camera, imperfect calibration and reduction procedures, and contamination from the ejecta cone preclude any solid conclusions about variations in the sky brightness.

— High-Speed Boulders and the Debris Field in DART Ejecta (2506.16694 - Farnham et al., 20 Jun 2025) in Section 3.4 (Post-Close Approach Sky Background / Plume)