Re-exploring Apollo Lunar Seismic Data: New Insights for the Chang’e-7 Mission

Global interest in lunar exploration has seen a notable resurgence, as reflected in upcoming missions such as NASA's Farside Seismic Suite, the Lunar Geophysical Network, China's Chang’e-7 and Chang’e-8 missions. These missions are expected to provide key observational data to advance our understanding of the Moon's internal structure. In anticipation of this new era, we have re-explored the Apollo seismic records using advanced analysis techniques and provided valuable insights for interpreting future lunar seismic datasets. We first report the discovery of a new type of long-period lunar seismic signal (LPS), which existed every lunar night from 1969 to 1976 with periods ~470-580 s. Analysis suggests that this signal might not be a natural physical phenomenon but related to a cyclic heater within the instrument. The harsh environmental conditions and instrument/spacecraft operations generate diverse “glitches” that hinder robust seismic data processing and interpretation. We then develop a series of AI-enabled methods for glitch detection, removal, and long-term time-frequency analysis. We have mapped the occurrence patterns of acceleration-related glitches, revealed the optimal windows for lunar seismic observation, and discovered glitches associated with lunar eclipses as well as shadows from nearby instruments. These findings provide practical guidance for instrument deployment and seismic observation strategies in upcoming lunar missions. To further address data quality challenges, we have developed an automated algorithm for the detection and removal of glitch signals in lunar seismic data, which successfully recovered LPS in Apollo records that were previously obscured by contamination, and characterized a kind of short-period signal with varying periods from 6 to 12 seconds. Our results demonstrate strong capability for retrieving weak, low-frequency signals, highlighting the potential for future lunar seismic experiments targeting valuable low-frequency phenomena such as free oscillations and even gravitational waves. This suite of studies and methodological developments is broadly applicable to future lunar and other planetary seismic observations, facilitating efficient analysis and interpretation.