Payloads : 7. Moon mineral mapper (M3)

The Hyper-spectral Imager (HySI) and the SIR-2, described above, cover a spectral range from 400 nm to 2400 nm and provide lunar reflectance spectra which can be used for mineral mapping of the Moon. However, there is critical information beyond 2400 nm which may be useful in identifying hitherto unidentified minerals or potential polar resources, such as volatiles and organic compounds, if they are deposited on the lunar poles, and therefore a moon mineral mapper (M3), proposed by the American group of Carle Pieters, has been included in the Chandrayaan payloads. M3 operates between 700 and 3000 nm with 10 nm resolution. It has a swath of 20 km with a spatial resolution of 30m. The reflected solar light enters the M3 instrument, having 12◦ field of view, through an f/2.7 three mirror telescope. The focused light from the telescope passes through a slit into the high efficiency offner spectrometer. The spectrometer also uses an electron beam written convex dual blaze grating to achieve uniformity of design.  At the focus of the spectrometer is located a 640 spatial by 231 spectral HgCdTe detector array sensitive from 700 to 3000 nm. A cryocooler is used for cooling the detector array. The long wavelength part (2600–3000 nm) is specially designed to investigate potential polar resources. It will have some overlap with HySI as well as SIR-2 and thus the three instruments together will make a comprehensive set of payloads for mineral mapping of the lunar surface.