© ISRO
© ISRO
Terrain Mapping Camera-2 (TMC-2) is a follow-on of the TMC on-board Chandrayaan-1. TMC-2 provides images (0.4μm to 0.85μm) at 5m spatial resolution & stereo triplets (fore, nadir and aft views) from a 100 km orbit for preparing Digital Elevation model (DEM) of the complete lunar surface.
The triplet images from TMC-2 when processed into Digital Elevation Models, enable mapping of surface landform morphologies. These include
- Craters (formed by impactors)
- Lava tubes (potential sites for future habitability)
- Rilles (furrows formed by lava channels or collapsed lava tubes)
- Dorsa or wrinkle ridges (formed mostly in Mare regions depicting cooling of and contraction of basaltic lava)
- Graben structures (depicts the structural dislocations on the lunar surface )
- Lunar Domes/ Cones (denoting localized vents of past volcanism on the Moon).
The derived information facilitates estimation of dimensions of above features and its comparison for reconstructing the morpho-structural framework, crater characterization to derive impact geometries, surface age determination through Crater Size –Frequency Distribution (CSFD) methods, Rheological analysis based on the derived morphometric parameters, Lunar reflectance estimation etc.
© ISRO
Figure 2 is one of the m- δ decomposition images from the first datasets acquired over lunar south polar regions in L-band high-resolution (2mslant-range resolution) hybrid polarimetric mode. It is important to note that the obtained resolution is one-order better than the earlier best by a lunar-radar. This image presents many interesting facts about the secondary craters of different ages and origins in the lunar south polar region. The yellowish tone around crater rims in the image shows ejecta fields. The distribution of ejecta fields, whether uniformly distributed in all directions or oriented towards a particular side of a crater, indicates the nature of the impact. The image shows craters of vertical impact and oblique impact on the top-right and bottom-right, respectively. Similarly, the roughness of the ejecta materials associated with the impact craters indicates the degree of weathering a crater has undergone. Three similar sized craters along a row on the bottom-right of the image show examples of young crater, moderately weathered crater and an old degraded crater. Many of the ejecta fields seen in the image are not visible in high-resolution optical image over the same region, indicating the ejecta fields are buried beneath regolith layers.
© ISRO
Chandrayaan-2 Orbiter’s DF-SAR has been operated in full-polarimetry mode- a gold standard in SAR polarimetry, and is the first-ever by any planetary SAR instrument. Figure 3 shows an L-band fully-polarimetric, 20m slant-range resolution image of Pitiscus-T crater. The image is a colour composite of different transmit-receive polarization responses of the imaged region.
