Abstract
Abstract The Moon is the nearest celestial body to the Earth. Understanding the Moon is the most important issue confronting geosciences and planetary sciences. Japan will launch the lunar polar orbiter SELENE (Kaguya) (Kato et al., 2007) in 2007 as the first mission of the Japanese long-term lunar exploration program and acquire data for scientific knowledge and possible utilization of the Moon. An optical sensing instrument called the Lunar Imager/Spectrometer (LISM) is loaded on SELENE. The LISM requirements for the SELENE project are intended to provide high-resolution digital imagery and spectroscopic data for the entire lunar surface, acquiring these data for scientific knowledge and possible utilization of the Moon. Actually, LISM was designed to include three specialized sub-instruments: a terrain camera (TC), a multi-band imager (MI), and a spectral profiler (SP). The TC is a high-resolution stereo camera with 10-m spatial resolution from a SELENE nominal altitude of 100 km and a stereo angle of 30° to provide stereo pairs from which digital terrain models (DTMs) with a height resolution of 20 m or better will be produced. The MI is a multi-spectral imager with four and five color bands with 20 m and 60 m spatial resolution in visible and near-infrared ranges, which will provide data to be used to distinguish the geological units in detail. The SP is a line spectral profiler with a 400-m-wide footprint and 300 spectral bands with 6–8 nm spectral resolution in the visible to near-infrared ranges. The SP data will be sufficiently powerful to identify the lunar surface’s mineral composition. Moreover, LISM will provide data with a spatial resolution, signal-to-noise ratio, and covered spectral range superior to that of past Earth-based and spacecraft-based observations. In addition to the hardware instrumentation, we have studied operation plans for global data acquisition within the limited total data volume allotment per day. Results show that the TC and MI can achieve global observations within the restrictions by sharing the TC and MI observation periods, adopting appropriate data compression, and executing necessary SELENE orbital plane change operations to ensure global coverage by MI. Pre-launch operation planning has resulted in possible global TC high-contrast imagery, TC stereoscopic imagery, and MI 9-band imagery in one nominal mission period. The SP will also acquire spectral line profiling data for nearly the entire lunar surface. The east-west interval of the SP strip data will be 3–4 km at the equator by the end of the mission and shorter at higher latitudes. We have proposed execution of SELENE roll cant operations three times during the nominal mission period to execute calibration site observations, and have reached agreement on this matter with the SELENE project. We present LISM global surface mapping experiments for instrumentation and operation plans. The ground processing systems and the data release plan for LISM data are discussed briefly.
Highlights
The Moon is the nearest celestial body to the Earth
An optical instrument, the Lunar Imager/Spectrometer (LISM), will be installed on the Japanese 2-ton class SELENE lunar orbiter, which will be launched in the summer of 2007
LISM consists of three sub-systems: a terrain camera (TC), which is a stereo-camera with 10 m resolution and a stereo angle of 30◦, a multi-band imager (MI), which is a multicolor imager with four and five color bands with 20 m/60 m spatial resolution in the visible and near-infrared regions, and a spectral profiler (SP), which is a line spectral profiler with a 400-mwide footprint and 300 spectral bands with 6–8 nm spectral resolution in the visible to near-infrared range
Summary
The Moon is the nearest celestial body to the Earth. these two bodies exhibit totally different features: the Earth has an atmosphere, oceans, and living plants and animals, whereas the Moon appears to have ceased all internal activity and is covered by nothing but fine dust (regolith) with small to massive craters. Correlating crater data of a region with radiometric ages from returned samples on the Moon, the crater counting chronology was developed to infer the ages of even unsampled geological units and provide the lunar stratigraphy (Hiesinger and Head, 2006; Neukum et al, 2001). The 10 m scale global coverage with appropriate solar elevation angle conditions of less than 30–40◦ is definitely required for imagery exploration of the Moon from the perspective of crater-counting chronology Another approach to investigate the relative age is specific examination of the degradation state of smaller craters of less than 1 km diameter. Lunar explorations of the 1960s and 1970s acquired numerous imagery data, in which the difference of albedo, the
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