Over the course of a month, the LRO spacecraft is able to image the entire lunar surface with the Wide Angle Camera (WAC). By mosaicking thousands of WAC images together, the LROC team produces large-scale maps such as the LROC WAC Global Mosaic. In the polar regions, grazing sun angles create vast shadows that hinder mapping. However, with careful selection, polar mosaics with minimal shadows can be made. For this polar mosaic, we selected and mosaicked images acquired when the sub-solar point was its highest in the northern hemisphere (around 1.5° N) and when the angle between the Sun vector and the orbital plane of the spacecraft is minimized. Using these criteria, we selected images acquired between 3/18/2011 and 4/19/2011.

To produce the mosaic, we map projected the 643 nm band of each WAC image using the GLD100 (WAC derived 100m/pixel DTM) and a LOLA shape model near the pole (80° to 90° N). Accurate positioning of each WAC image was ensured using ephemeris provided by the LOLA and GRAIL team (Mazarico et al., 2013) and an improved camera geometry model (Speyerer et al., 2014). The final mosaic is available in a polar stereographic projection spanning 45° from the pole and in eight different pixel scales: 100 m/pixel, 256 pixels/degree, and 128 pixels/degree, 64 pixels/degree, 32 pixels/degree, 16 pixels/degree, 8 pixels/degree, and 4 pixels/degree.

References:

E. Mazarico et al. (2013) Improved Orbit Determination of Lunar Orbiters with Lunar Gravity Fields Obtained by the GRAIL Mission, 44th Lunar and Planetary Science Conference, Abstract #2414.

E.J. Speyerer et al. (2014) Pre-flight and On-orbit Geometric Calibration of the Lunar Reconnaissance Orbiter Camera, Space Science Reviews. doi:10.1007/s11214-014-0073-3

WAC North Pole Summer Mosaic

100 meters per pixel (click for more information)


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