Journal of Astronomy and Space Sciences

The Korean Space Science Society (한국우주과학회)
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Preliminary Characterization of Secondary Illumination at Shackleton Crater Permanently Shadowed Region from ShadowCam Observations and Modeling

  • Received : 2023.10.25
  • Accepted : 2023.11.19
  • Published : 2023.12.15
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Abstract

Lunar permanently shadowed regions (PSRs) never see direct sunlight and are illuminated only by secondary illumination - light reflected from nearby topography. The ShadowCam imaging experiment onboard the Korea Pathfinder Lunar Orbiter is acquiring images of these PSRs. We characterize and discuss the nature of secondary illumination for the Shackleton PSR from ShadowCam radiance-calibrated images. We also use modeling to understand the magnitude and direction of the secondary illumination. Results from our analysis highlight the non-homogeneous, dynamic, and complex nature of PSR secondary lighting. Knowledge of the direction of the secondary illumination is crucial for reli-able interpretation of contrasts observed in ShadowCam images. This preliminary analysis of the floor of Shackleton crater from images acquired over multiple secondary illumination conditions does not reveal indications of exposed surface ice, even though temperatures are constantly below 110K.

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Acknowledgement

This work was supported by the National Aeronautics and Space Administration ShadowCam Project. The authors would like to thank the work of ShadowCam and KPLO operations personnel who made it possible to acquire high-resolution images. The authors would also like to thank the LRO LROC, LOLA and Diviner personnel for the context WAC image, the topographic data and the surface temperature maps. The contribution of J.-P. Williams was funded by the NASA KPLO Participating Scientist Program under award number 80NSSC21K0711.

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