Abstract
A visible-near infrared spectrometer, Spectral Profiler (SP), was proposed and selected as one of mission instruments onboard Japanese Selenological and Engineering Explorer (SELENE) spacecraft. The eventual goal of SP observation is to collect mineralogical and compositional information on the lunar surface and contribute to studies on the origin and the evolution of the moon and its crust. In this paper, performance and calibration requirements for SP based on these scientific objectives are discussed.
Most critical performance requirements are those for spectral capabilities such as spectral coverage, 0.5-2.6μm, and spectral resolution, better than 10nm. Also, the high signal-to-noise ratio, 2000 or better in the 0.7-1.5μm spectral range, is very important to detect subtle absorption features on spectra of lunar highland soils which is often obscured by space weathering.
Due to contamination, radiation, and other phenomena on optical components and detectors, the radiometric sensitivities of space optical instruments often degrade with time. To remove such degradation effects and retrieve accurate reflectance spectra on the moon, radiometric calibration activities are necessary. For SP, two complementary calibration methodologies are currently proposed:Vicarious calibration using the reflectance reference sites such as Apollo 16 landing site and the onboard calibration system including halogen lamps and a spectral filter.By careful analyses of such calibration data, detailed optical characterization of the instrument will be possible and hence accurate spectral data for the whole moon surface will be obtained.
