NASA, using images taken from its Lunar Reconnaissance Orbiter (LRO) has released a 680-gigapixel interactive mosaic of the Moon's north polar region. The resolution of the image is one pixel to 6.5 ft (2 m) with the area imaged being the equivalent of slightly more than the land mass of the states of Alaska and Texas combined.
The herculean task of composing the mosaic, named the LROC Northern Polar Mosaic (LNPM), fell to the Lunar Reconnaissance Orbiter Camera (LROC) team, which is also responsible for 3D anaglyphs of the Moon's surface released in 2012. The 10,581 images used in the mosaic were collected over the course of four years by the LRO, which launched aboard an Atlas V rocket in 2009 and was designed to help shed light on the origin of the Earth, Moon and to an extent, our solar system at large.
Whilst collecting the images, the orbiter alternated between noon-midnight and terminator orbits (as displayed in the image below). This is due to the fact that there are subtle seasons on the Moon which affects the lighting at the pole. The team found that the best time to image the pole is during the northern summer with the LRO in a noon-midnight orbit.
The mosaic consists of a staggering 681 billion pixels, covering an area of 2.54 million sq km (0.98 million sq miles). The mosaic was created by projecting each of the 10,581 images onto a 30 m/pixel Digital Terrain Model using a specialist software package. To limit distortion whilst converting the 3D images of the moon into a 2D map, the team used a polar stereographic projection in conjunction with a camera pointing model and advanced ephemeris provided by other teams working on the LRO mission. The combination of these methods created a highly accurate photo placement system with the positions of geographical features in an image being within 20 m (66 ft) of their actual location.
An example of some of the collar mosaics used to create the finished LNPM (NASA/GSFC/Arizona State University)
On a larger scale, the LNPM was assembled from a number of collar mosaics. Each collar was formed by having the LRO orbit the same latitude once every two hours for a month at a time. The reason for having the LRO orbit at the same latitude for an entire month is to unify the lighting, as at some point during the month-long orbit, all areas of the collar mosaic will be imaged under the same lighting conditions.
The detail of the new image is highlighted when compared to the Wide Angle Camera mosaic (shown in the image below) taken of the same region, which had a scale of one pixel to 100 m (328 ft). Comparatively, the most recent mosaic has 50 times the resolution.
The LROC Wide Angle Camera mosaic of the Moon's north pole released in 2011 (Photo: NASA/GSFC/Arizona State University)
In order to allow viewers to zoom into and pan across the stunningly detailed mosaic, each tile of the LNPM was made multiple times in varying pixel scales. In all, the mosaic is comprised of 17,641,035 small tiles of varying resolutions.
Follow this link to enjoy the interactive lunar mosaic for yourself.