Data Reduction and Correction of Korea Pathfinder Lunar Orbiter (KPLO) Gamma‐Ray Spectrometer (KGRS)

• Published in: Earth and space science (Hoboken, N.J.) Vol. 12; no. 8
• Main Authors: Hong, Ik‐Seon, Kim, Suyeon, Kim, Kyeong Ja
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley & Sons, Inc 01.08.2025
• Subjects: Altitude; Attitudes; Calibration; correction; Cosmic rays; Data processing; Data reduction; Datasets; Energy; Gamma rays; gamma‐ray spectrometer; Korea pathfinder lunar orbiter; Moon; Resource exploration; Solar energy; Thorium
• ISSN: 2333-5084; 2333-5084
• DOI: 10.1029/2024EA004181

The Korea Pathfinder Lunar Orbiter (KPLO) Gamma‐Ray Spectrometer (KGRS) is Korea's first lunar surface resource exploration payload. GRS data include non‐scientific background information in addition to lunar observation information, so reduction and correction are necessary to analyze the lunar surface scientifically. Data subject to correction include solar events, high‐energy events, satellite attitude, and abnormal data. The next step is to go through corrections for solid angle (SA) and galactic cosmic rays (GCR). Solid angle correction is the process of correcting the changes in the SA of KGRS according to the satellite altitude. The correction method normalizes the SA to KPLO's reference altitude of 100 km. GCR correction uses the oxygen@6.129 MeV as a GCR proxy in the gamma‐ray spectrum observed above 85° north latitude to remove the trend of gamma‐ray count rate. Finally, the background spectrum removal is performed. The background spectrum uses cruise data before KPLO arrives on the Moon. A count rate and abundance map in the thorium@2.614 MeV is created to validate the reduction and correction results. When looking at the changes that appear on the thorium count rate map at each stage, it was confirmed that reduction and correction were applied well. It was also confirmed that the result was similar to thorium abundance maps produced by previous GRS missions. If the quality of KGRS is guaranteed, the long observation time of 2 years will be an advantage. Therefore, KGRS data with reduction and correction applied will be able to produce meaningful results through scientific analysis. Plain Language Summary Korea Pathfinder Lunar Orbiter Gamma‐ray spectrometer (KGRS) is an instrument that observes the lunar composition. Raw data include not only lunar information, but also non‐scientific background information. Therefore, we performed reduction and correction to enable scientific analysis with KGRS data. As a result of verification, the processing was performed appropriately. KGRS data has the longest duration on gamma‐ray spectrometers on lunar orbiters and is ready for scientific analysis. Key Points Gamma‐Ray Spectrometer on Korea Pathfinder Lunar Orbiter (KPLO Gamma‐Ray Spectrometer (KGRS)) data reduction and correction was applied The quality of KGRS data was verified by comparing previous GRS mission data. It is sufficient for conducting scientific analysis KGRS data can be expected to have a high signal‐to‐noise ratio due to its being the longest duration orbital lunar gamma‐ray spectrometer measurements