Chandrayaan 2's IIRS took the first illuminated image of Moon's surface which covered part of the lunar farside in its northern hemisphere.
ISRO’s Chandrayaan 2 has started capturing the lunar surface and has sent stunning pictures of illuminated surface of the Moon. Chandrayaan-2 has lunar surface Imaging Infrared Spectrometer (IIRS) on-board its orbiter which is used for spectroscopic studies of the lunar surface as it is designed to measure the sunlight reflected and emitted as Moon light from the lunar surface. IIRS captures it in a in a extremely narrow and contiguous spectral channels (bands) which ranges from ~800 to 5000 nanometer (0.8-5.0 micrometer).
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.
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— ISRO (@isro) October 17, 2019
IIRS uses grating technique for splitting and dispersing the reflected sunlight (and its emitted component) into different spectral bands. IIRS’ major objective is to understand the origin and evolution of the Earth’s only natural satellite Moon in a geologic context. It is doing so by mapping Moon’s surface mineral and its volatile composition by using signatures in the reflected solar spectrum.
What did the first illuminated image reveal!
Chandrayaan 2’s IIRS took the first illuminated image of Moon’s surface which covered part of the lunar farside in its northern hemisphere. The image shows some prominent craters on Moon’s northern hemisphere viz., Sommerfield, Stebbins and Kirkwood.
ISRO’s preliminary analysis of the illuminated image suggested that IIRS can successfully map the variations seen in the reflected solar radiation that come from Moon’s different kinds of surfaces like crater central peaks (e.g., Stebbins), crater floors (e.g., Stebbins and Sommerfield), very fresh reworked ejecta associated from small craterlets inside a big crater’s floor (e.g., Sommerfield). IIRs can also map the inner rims illuminated by the Sun in a crater (e.g., Kirkwood). A spectral radiance’s variations are mainly because of the mineralogical/composition nature that exist in the lunar surface. Also, space weathering has some impact too. ISRO is conducting a detailed analysis which is expected to shed light on on the heterogeneity of Moon’s surface composition.
Earlier, Chandrayaan Orbiter’s High-Resolution Camera (OHRC) also took an image of the lunar surface from approximately 100 km altitude. ISRO said that the images were the highest resolution pictures ever taken of the Moon. ISRO’s soft landing attempt on Lunar south polar region did not go as per plan on 7 September when Vikram lander lost contact with mission center. ISRO and NASA are still trying to locate Vikram lander.