Cheung and Lee plotted the orbits of navigation satellites from the United States’s Global Positioning System and two of its counterparts, Europe’s Galileo and Russia’s GLONASS system—81 satellites in all. Most of them have directional antennas transmitting toward Earth’s surface, but their signals also radiate into space. Those signals, say the researchers, are strong enough to be read by spacecraft with fairly compact receivers near the moon. Cheung, Lee and their team calculated that a spacecraft in lunar orbit would be able to “see” between five and 13 satellites’ signals at any given time—enough to accurately determine its position in space to within 200 to 300 meters. In computer simulations, they were able to implement various methods for improving the accuracy substantially from there.
A mini-network of relays—a couple of satellites in lunar orbit, say—could improve accuracy further. [Geography Realm]
A new unified geologic map of the Moon, based on digital renovations that updated 1970s-era geologic maps to match more recent topographic and image data gathered by lunar orbiters, was released by the USGS last month. The map is “a seamless, globally consistent, 1:5,000,000-scale geologic map”; the paper version (25 MB JPEG) provides azimuthal projections beyond the 55th parallels and an equirectangular projection between the 57th parallels. [Geography Realm]
Mapping the Moon in Black and White, an exhibition curated by the Harvard Map Collection at Harvard’s Pusey Library, “guides you through the mutually reinforcing efforts to map the Moon using orbital imagery and the race to walk on the Moon. At ‘Mapping the Moon in Black and White,’ you will also learn how these mapping efforts sat within larger critiques of the Space Race, especially from Civil Rights organizations like the Southern Christian Leadership Conference and the Black Panther Party.” Runs until 31 October 2019; a reception and curatorial talk will take place on 18 September.
With the 50th anniversary of Apollo 11 almost upon us, there’s been an uptick in moon-related content, which includes moon-related map content. For example:
New Exhibition. Opening today at The Map House in London, The Mapping of the Moon: 1669-1969, an exhibition of three centuries of lunar cartography. “The exhibition includes rare early 17th and 18th Century observations of the moon from astronomers such as Athanasius Kircher and Jean-Dominique Cassini, important maps produced by NASA for lunar exploration, globes and signed material by astronauts Neil Armstrong, Buzz Aldrin, Alan Bean and Jim Lovell.” Runs until 21 July. [ARTFIXDaily]
New Map. The July 2019 issue of National Geographic has a new map of the Moon that updates the 1969 painted version (see above) with a mosaic based on Lunar Reconnaissance Orbiter imagery. I don’t know whether that means a physical version of the map will be included with the issue as an insert, but I hope it does.
New Way to Navigate. NASA has a post on using GPS on the Moon. Now, I’d thought that using GPS on another world would require the deployment of a GPS satellite constellation around said world. No, this is about using Earth-orbiting GPS signals for lunar navigation, which simulations suggest is possible. The mind boggles.
Writing for Crosscut, Tom Reese memorializes his father, who worked as a cartographer and engineer for NASA’s Aeronautical Chart and Information Center during the Apollo program. Harlan Reese left behind a collection of maps, photos and charts in his garage which, Tom says, still contains “mesmerizing detail and mystery”:
One box has odds and ends of early lunar photography, some of the prints overlain with Dad’s hand-drawn compass points, landing site X’s and handwritten notations. The images were made through large telescopes on Earth, by the Surveyors and Rangers and Lunar Orbiters and early Apollos flying around and over the most promising landing sites. You can also see those smudged fingerprints that likely belong to Dad, mixed with those of many others who used magnifiers and X-Acto knives to carefully slice apart select sections of crater fields. Some small globs of cracked glue remain where they dripped during the process of pasting together the cut pieces to form mosaics of the unexplored landscape.
Some small indentations probably show how the prints were positioned in viewing devices like the extremely precise optical comparator, which helped human eyes interpret the length of shadows inside craters for the first time. These results were coordinated with data about altitude and lunar daylight to provide the most precise terrain measurements possible. Careful airbrushing would smooth over and fill in terra incognita with educated guessing. Finally, this data would be transformed into the precisely printed maps and charts that would help lunar lander pilots to, among other things, second-guess in real time the navigation decisions made by computers of the late 1960s and early 1970s.
The Digital Museum of Planetary Mapping is an online collection of maps of the planets and moons of our solar system. There are more than two thousand maps in the catalogue, some dating as far back as the 17th century, but the bulk of them, understandably, are much more recent; also understandably, Mars and the Moon are the subject of most of the maps (40 and 46 percent, respectively).
The site is more like a blog than a library catalogue: it’s powered by WordPress and the individual listings are blog posts, but that’s perfectly legitimate, albeit less elegant. (But then who am I to judge?)
The project was presented at the European Planetary Science Congress in Berlin last month: for news coverage, see Phys.org and Space.com; the press release is here. [WMS/WMS]
In 2016 I told you about Michael Plichta’s first globe, a delightfully retro hand-crafted globe of Mars based on Percival Lowell’s maps that showed the world covered in canals. Plichta’s second globe project is also cool and unusual, but in a completely different way: it’s a relief globe of the Moon. No globe gores were used to make this 30-cm globe: the textured surface is cast in artificial plaster and then painted by hand, a compulsively exacting process laid out in this short video:
Hand-crafted globes are never inexpensive, and though Michael never mentions prices, this one cannot be either. (I’ve seen his Mars globe listed for $1,850.) That said, this is a definite lust object. I desperately want one.
The Moon and Mars were relatively early additions to Google Earth; that application may have been migrated to the web, but the planets and moons keep coming. Yesterday Google announced the addition of a dozen other worlds in our solar system; the space layer of Google Maps now includes planets Mercury, Venus and Mars; dwarf planets Ceres and Pluto;1 Jupiter’s moons Io, Europa and Ganymede; and Saturn’s moons Dione, Enceladus, Iapetus, Mimas, Rhea and Titan. Large moons Callisto and Triton aren’t included, and Iapetus is projected onto a sphere rather than appearing as the bizarre space walnut it is.
Maps of planets, moons and other objects in our solar system always get me excited, though truth be told they were among the less popular posts on my old Map Room blog. Here are a couple of rather colourful recent examples:
NASA has released a free-airgravity map of the Moon: “If the Moon were a perfectly smooth sphere of uniform density, the gravity map would be a single, featureless color, indicating that the force of gravity at a given elevation was the same everywhere. But like other rocky bodies in the solar system, including Earth, the Moon has both a bumpy surface and a lumpy interior. … The free-air gravity map shows deviations from the mean, the gravity that a cueball Moon would have.” Gravity data comes from the GRAIL mission, with the digital elevation model provided by the Lunar Reconnaissance Orbiter laser altimeter. Image credit: NASA’s Goddard Goddard Space Flight Center Scientific Visualization Studio.