The Imaging Infrared Spectrometer (IIRS) payload onboard Chandrayaan-2 has sent the first illuminated image of the Moon, announced the Indian Space Research Organisation (ISRO) on Thursday.
The image covers part of the lunar farside in the northern hemisphere and a few prominent craters--Sommerfield, Stebbins and Kirkwood--are also seen in the image.
See the first illuminated image of the lunar surface acquired by #Chandrayaan2’s IIRS payload. IIRS is designed to measure reflected sunlight from the lunar surface in narrow and contiguous spectral channels.
— ISRO (@isro) October 17, 2019
The major objective of IIRS is to understand the origin and evolution of the Moon in a geologic context by mapping the lunar surface mineral and volatile composition using signatures in the reflected solar spectrum.
The IIRS is designed to measure reflected sunlight and emitted part of the Moon light from the lunar surface in narrow and contiguous spectral channels. With this, the Chandrayaan-2 began its spectroscopic studies of the lunar surface. The study refers to the interaction between matter and electromagnetic radiation.
The channels (bands) range from 800 – 5000 nanometer (0.8-5.0 micrometer (µm)). It uses a grating to split and disperse the reflected sunlight (and emitted component) into different spectral bands.
The preliminary analysis suggests that IIRS could successfully measure the variations in the reflected solar radiation that bounces off the lunar surface from different kinds of surface types, namely, crater central peaks (e.g., Stebbins), crater floors (e.g., Stebbins and Sommerfield), very fresh reworked ejecta associated with small craterlets within the crater floor of a large crater (e.g., Sommerfield) and also the sun-illuminated inner rims of craters (e.g., Kirkwood).
The variations in the spectral radiance are primarily due to the mineralogical or compositional variations that exist in the lunar surface and also due to the effect of space weathering. A more detailed analysis that follows, is expected to yield important results on the heterogeneity of lunar surface composition.