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

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.