World Mappers

Lunar Melt: The Data

One of the LROC NAC cameras in the lab on the optics bench. Credit: NASA/Arizona State University/Intuitive Machines

Images shown in the Lunar Melt project come from the Narrow Angle Camera (NAC) which is part of the Lunar Reconnaissance Orbiter (LRO) Camera (which is actually three cameras, 2 Narrow Angle Cameras and 1 Wide Angle Camera). We can’t explain why the LRO Camera (LROC) is actually three cameras, but we can explain just how amazing the NAC data happens to be.

LRO has been orbiting the Moon since 2009. Its current orbit keeps it between 20km (12mi) and 165 km (103mi) above the Lunar surface. The mission’s low altitude and high-resolution cameras work together to allow images so detailed that a basketball player lying on the surface of the Moon with their arms spread out would appear as a tiny blob. Put into numbers, each pixel in the best NAC images is about 0.5 m (or about 1.5 feet) across. (When the LRO is higher up, the pixels are more like 2m across, which would make that basketball player just over 1 pixel in size.)

The LRO is a PI-led mission, led by Mark Robinson from Arizona State University and also the company Intuitive Machines. Spacecraft development took place at NASA Goddard Space Flight Center. Today, you can access all the mission’s data and learn about its current activities on the project website. They even have a data exploration tool, QuickMap, that will let you look at different images taken over time. LRO’s data are regularly used to monitor the Moon for impacts, study potential mission landing sites, and check out the health and well-being of spacecraft that have landed (or impacted) on the Moon.

The region of the Moon explored during Apollo 15 as imaged by LRO.
Per the LRO Team, this image, “Highlights of the Apollo 15 landing site, as seen in LROC NAC image M175252641R. This image has a resolution of 27 cm/px, and shows an area of 262 m by 186 m. The Lunar Module is clearly visible, as are many tracks from the Lunar Roving Vehicle (whose final resting place is just east of the edge of this image). The Apollo 15 astronauts left a number of science instruments at the site, including the Passive Seismometer Experiment (PSE), Lunar Ranging Retroreflector (LRRR), and others; these instruments were collectively part of the Apollo Lunar Surface Experiments Package (ALSEP). These landmarks and more are annotated in LROC’s new Apollo 15 spatiotemporal map.”

In this project, you’ll mostly see images with the sunlight coming in at an angle that creates dramatic shadows. When the Sun is straight overhead on the Moon, it is easy to see how different regions are made of different colored images (left image below), but some craters will completely disappear. When the sun sinks toward the horizon, shadows cause otherwise invisible craters to pop into view. Over time, LRO has captured regions of the entire moon that show its surface illuminated in many different ways.

The exact same 660m wide region of the Moon is shown at two different times of the Lunar day. On the left (M108108187L), the Sun is near “noon”, and variations in surface color are easy to see. On the right (M103388681R), the Sun is off to the left, and the shadows make all the craters in the image visible. Note: These images have very different contrasts. Credit: NASA/GSFC/Arizona State University. Learn more