TOTD 2018-03-30: The Moon, Up Close and Personal

Since 1994, Fourmilab’s Earth and Moon Viewer has provided custom views of the Earth and Moon from a variety of viewpoints, using imagery databases which have evolved over the years from primitive images to gigabyte-scale mosaics collected by spacecraft.  Views were originally restricted to the Earth, but fifteen years ago, in April 2003, the ability to view the Moon was added, using the global imagery collected by the Clementine orbiter.  These data were wonderful for the time, providing full-globe topography and albedo databases with a resolution of 1440×720 pixels.  This allowed viewing the Moon as a whole or modest zooms into localities, but when you zoomed in close the results were…disappointing.  Here is the crater Copernicus viewed from an altitude of 10 km using the Clementine data.

Moon, Copernicus crater, 10 km altitude, Clementine data

It looks kind of like a crater, but it leaves you wanting more.

That was then, and this is now.  In 2009, the Lunar Reconnaissance Orbiter (LRO) was launched into a near-polar orbit around the Moon.  In its orbit, it is able to photograph the entire lunar surface from an altitude as low as 20 km, with very high resolution.  This has enabled the assembly of a global mosaic image with resolution of 100 metres per pixel (total image size is 109164×54582 pixels), or about 5.6 gigabytes of 256-level grey scale pixels).  This image database is now available in Earth and Moon Viewer.  Here is the same view of Copernicus using the LRO imagery.

Copernicus crater, 10 km altitude, Lunar Reconnaissance Orbiter imagery

Bit of a difference, don’t you think?  But it doesn’t stop there.  Let’s swoop down to 1 km above the surface and  look at the central peaks.

Note the small craters and boulder fields which are completely invisible with even the best Earth-based telescopes.

Thanks to LRO, you can now explore the Moon seeing views that only astronauts who orbited, flew by, or landed there have ever seen with their own eyes.  And the entire Moon is yours to explore, including all of the far side and the poles, where Apollo missions never ventured.

The Clementine and LRO imagery were collected a decade apart.  The technology which has enabled this improvement continues to grow exponentially.  The Roaring Twenties are going to be interesting.


Author: John Walker

Founder of, Autodesk, Inc., and Marinchip Systems. Author of The Hacker's Diet. Creator of

4 thoughts on “TOTD 2018-03-30: The Moon, Up Close and Personal”

  1. 10 Cents:
    How big is that crater? It looked miles across.

    Copernicus is 93 km in diameter and 3.8 km deep.  It is a classic ringed wall large crater with a central peak structure.  Apollo 12 landed south of Copernicus in the Oceanus Procellarum, and one of the landing sites proposed for the cancelled Apollo 18 mission was Copernicus crater.


Leave a Reply