The LROC team assembled 10,581 NAC images, collected over 4 years, into a spectacular northern polar mosaic. The LROC Northern Polar Mosaic (LNPM) is likely one of the world’s largest image mosaics in existence, or at least publicly available on the web, with over 680 gigapixels of valid image data covering a region of the Moon (2.54 million km², 0.98 million miles²) slightly larger than the combined area of Alaska (1.72 million km²) and Texas (0.70 million km²) -- at a resolution of 2 meters per pixel! To create the mosaic, each LROC NAC image was map projected on a 30 m/pixel Lunar Orbiter Laser Altimeter (LOLA) derived Digital Terrain Model (DTM) using a software package called Integrated Software for Imagers and Spectrometers (ISIS). A polar stereographic projection was used in order to limit mapping distortions when creating the 2-D map. In addition, the LROC team used improved ephemeris provide by the LOLA and GRAIL teams and an improved camera pointing model to enable accurate projection of each image in the mosaic to within 20 meters.
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LNPM by the numbers:
- Square image; 931,070 pixels across and down
- Total pixels: 866,891,344,900 (867 billion)
- Pixels with image data: 680,808,991,627 (681 billion)
- NAC images: 10,581
- Size of compressed mosaic: 950 Gigabytes