LROC Wide Angle Camera (WAC) view of the Moon seen from 90° east longitude. Half the nearside is visible to the left, and half the farside to the right [NASA/GSFC/Arizona State University].
The LROC WAC is a real workhouse and gets little attention, at least so far. Since the WAC is a wide angle camera, it maps nearly the whole Moon over a course of about 4 weeks and the lighting and viewing geometries are complicated. In the first case, the Sun angle at the equator changes about 28°. This change in lighting over a mosaic cycle results in a very different surface brightness where the end of the mosaic meets the beginning. The viewing angle of the WAC changes from straight down at the center to 45° at the edge since the camera's field-of-view is 90°. The extreme angle at the edges results in geometric distortion and an apparent change in brightness of the surface. Both effects need to be removed to make mosaics and the LROC team has been working on corrections since this Spring. The global mosaic from which this view was produced contains over 3700 WAC images, which translates into a lot of processing! Note that the black "holes" (gores) are the result of LRO slewing off nadir to acquire NAC stereo images. Over the course of the mission these gores will be imaged and the mosaic completed.
Annotated version of the WAC eastern hemisphere orthographic mosaic: Se=Mare Serenitatis,T=Mare Tranquillitatis, F=Mare Fecunditatis, C=Mare Crisium, M=Mare Marginis, S=Mare Smythii, A=Mare Australe, Ts=Mare Tsiolkovskiy, Mv=Mare Moscoviense. Lat/lon grid in increments of 30° with the center coordinate at 0°N and 90°E [NASA/GSFC/Arizona State University].
Great progress has been made and the preliminary products are now starting to flow. Keep checking back as more WAC products are released in the coming weeks.
Explore the 400 m/pixel WAC view of the eastern hemisphere of the Moon!