Spacecraft Will Test Satnav Reception from Lunar Orbit

More on the astonishing idea that Earth-orbiting GNSS satellites can be used for navigation at the Moon. The European Space Agency reports that among the instruments carried by the upcoming Lunar Pathfinder commercial mission will be a 1.4 kg satnav receiver that will test its ability to receive GPS and Galileo signals from lunar orbit. “Satnav position fixes from the receiver will be compared with conventional radio ranging carried out using Lunar Pathfinder’s X-band transmitter as well as laser ranging performed using a retroreflector contributed by NASA and developed by the KBR company.” Lunar Pathfinder is currently scheduled to launch in 2024.

Previously: Many Moon MapsCan GPS Be Used on the Moon?

Looking for Lightning, Finding Meteors

Map of bolides detected from space by the Geostationary Lightning Mapper
NASA Earth Observatory/Joshua Stevens

It turns out that the Geostationary Lightning Mapper (GLM) aboard the GOES-16 and GOES-17 earth observing satellites can do more than just detect lightning—it can also detect bolides, or very bright meteors, thanks to a new automatic detection algorithm. NASA Earth Observatory: “The map above shows the distribution of more than 3,000 bolides detected by the GLMs aboard GOES-16 and GOES-17 between July 2017 and January 2022. Blue points are bolides detected by GOES-16; pink points were detected by GOES-17. The lone pink point over the Atlantic Ocean was detected by GOES-17 during its commissioning phase before it was moved into its operational orbit over the West Coast.” (Bolides in the middle of the map are detected by both, and as you can see there’s a bit of parallax.)

VERITAS Mission to Map Venus Later This Decade

Artist's concept of the VERITAS mission to Venus (NASA/JPL-Caltech)
Artist’s concept of the VERITAS mission (NASA/JPL-Caltech).

VERITAS is one of two missions to Venus announced by NASA last week. Expected to launch between 2028 and 2030, VERITAS will produce an improved map of the Venusian surface with its two instruments: synthetic aperture radar to generate a high-resolution 3D topographic map, and a spectral emissions mapper to map rock types. News coverage: CNN, Global News, Slate, The Verge. Background from NASA; analysis from the Planetary Society.

A Mars Map Roundup

Nathaniel Green's map of MarsNational Geographic looks at the rivalry between two early cartographers of Mars who based their maps on observations made during Mars’s “Great Opposition” in 1877: Nathaniel Green, whose Mars “was a delicately shaded world with landforms that gradually rose from vast plains and features that blended into one another” (pictured here) and Giovanni Schiaparelli, whose Mars had more detail—including those famous canals—but was less accurate.

A new study maps the possible locations of subsurface water-ice reservoirs, vital for any crewed missions. [Sky & Telescope]

Kenneth Field’s virtual globe of Mars follows in the footsteps of his 2016 map.

Interactive maps showing the locations and paths of the Curiosity and Perseverance rovers. [Maps Mania]

The Closest Stars

The Closest Stars is the latest astronomical map produced as part of Kevin Jardine’s long-running Galaxy Map project: it shows stars within 10 parsecs (32.6 light years) of our solar system. (Earlier maps covered much more territory: this map goes out to 6,000 pc.)

It’s fascinating, and has a lot of interesting information, but there’s a problem. Like all maps, it reduces three dimensions to a flat plane; as such it distorts the distance of stars that are substantially above or below the galactic plane but not very far away on the x or y axis. Take Beta Comae Berenices: it’s 9.18 pc away and as such should be at the edge of the map, but because it’s 9.18 pc away on the z axis, at nearly a right angle to the plane, it appears on the map as one of the closest stars. The distance above or below the plane is marked in parentheses, but that’s not enough: a label can’t compensate for a misleading position on the map. On the smaller-scale maps this isn’t as much of an issue, because the galaxy is more or less a disk or a lens, but within a 10-pc radius? This isn’t the right projection for the job.

Fifteen Ways to Depict Elevation on Mars

How do you depict elevation on a map of Mars? Earlier this year, Daniel Huffman posted a roundup of hypsometric tints for Mars.

I have a peculiar hobby of collecting Martian hypsometric tinting schemes: those sets of colors that cartographers use to depict elevations on the Red Planet. It’s a fascinating cartographic frontier. While the classic (and somewhat flawed) way of showing Earth’s elevations is to use a color scheme that starts with green lowlands, and then proceeds through some combination of brown/yellow/orange/red until it reaches white in the highest areas, there’s no standard yet for Mars. Maybe centuries from now, one of the schemes below will become that standard.

Huffman looks at fifteen schemes in total in the post, and in this video on YouTube:

Two Geologic Maps of Venus

Excerpted from López, I. and Hansen, V.L. (2020), Geologic Map of the Niobe Planitia Region (I‐2467), Venus. Earth and Space Science 7: e2020EA001171. doi:10.1029/2020EA001171; and Hansen, V. L., López, I. (2020). Geologic map of Aphrodite Map Area (AMA; I‐2476), Venus. Earth and Space Science 7: e2019EA001066. doi:10.1029/2019EA001066

Two geological maps of Venus have been published in Earth and Space Science. Produced by Vicki L. Hansen and Iván López, they each cover a 60-million-square-kilometre section of Earth’s twin: the Niobe Planitia Map Area geologic map (above, top) ranges from the equator to 57° north, and from 60° to 180° east longitude; the geologic map of the Aphrodite Map Area (above, bottom) is the Niobe Map Area’s southern hemisphere equivalent, covering the area from 60° to 180° east longitude, but from the equator to 57° south.

Star Maps: History, Artistry, and Cartography

The March 2020 issue (PDF) of Calafia, the journal of the California Map Society, has as its theme the mapping of space. It also has something from me in it: my review of the third edition of Nick Kanas’s Star Maps: History, Artistry, and Cartography. An excerpt:

It’s important to remember a book’s target audience—its imagined ideal reader. In the case of Star Maps this is Kanas’s younger self, who came to map collecting via his lifelong interest in amateur astronomy. “I was frustrated that there was not a single book on celestial cartography that could inform me about the various aspects of my collecting,” he writes in the preface to the first edition. “What I needed was a book that not only was a primer for the collector but also had sufficient reference detail to allow me to identify and understand my maps. Nothing like this appeared, so I decided to write such a book some day” (p. xxi). In other words, for a compendium this is a surprisingly personal book, one that reflects his own journey into the subject and, presumably, his interests as a collector.

I’ll post the full review on The Map Room once I’ve checked my draft against the published copy. In the meantime, check out the issue of Calafia (PDF) in which it appears. (Update, 24 Jun 2020: Here it is.)


Star Maps: History, Artistry, and Cartography
3rd edition
by Nick Kanas
Springer Praxis, Sept 2019
Amazon (Canada, UK) | Apple Books | Bookshop

Can GPS Be Used on the Moon?

More on the question of whether GPS can be used for navigation on the lunar surface—that is to say the existing constellations of Earth-orbiting GNSS satellites, not a new constellation of satellites around the moon. A new study suggests that the answer is yes: GPS and other navigation systems could be used.

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]

Previously: Many Moon Maps.

Unified Geologic Map of the Moon

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]

Previously: Lunar Geology and the Apollo Program.

Update, 22 April 2020: Version 2 of this map was released in March to address a number of errors in the first version.

First Geologic Map of Titan

Geologic map of Titan
NASA/JPL-Caltech/ASU

The first global geologic map of Titan, based on radar and infrared data from the Cassini probe, has been released.

The map legend colors represent the broad types of geologic units found on Titan: plains (broad, relatively flat regions), labyrinth (tectonically disrupted regions often containing fluvial channels), hummocky (hilly, with some mountains), dunes (mostly linear dunes, produced by winds in Titan’s atmosphere), craters (formed by impacts) and lakes (regions now or previously filled with liquid methane or ethane). Titan is the only planetary body in our solar system other than Earth known to have stable liquid on its surface—methane and ethane.

The map is the result of research published today in Nature Astronomy.

Previously: Titan in Infrared; Mapping Titan with VIMS; A Topographic Map of Titan.

Mapping the Local Void

R. Brent Tully

A team of researchers led by University of Hawaii astronomer Brent Tully has mapped the structure of the universe at a vast scale. In particular, they have mapped the shape of the Local Void, an empty expanse of intergalactic space hundreds of millions of light years across; the Milky Way is found at the edge of the Void. From the University of Hawaii’s Institute for Astronomy press release:

Now, Tully and his team have measured the motions of 18,000 galaxies in the Cosmicflows-3 compendium of galaxy distances, constructing a cosmographic map that highlights the boundary between the collection of matter and the absence of matter that defines the edge of the Local Void. They used the same technique in 2014 to identify the full extent of our home supercluster of over one hundred thousand galaxies, giving it the name Laniakea, meaning “immense heaven” in Hawaiian.

A video map and interactive 3D model are available. The study behind this model was published in The Astrophysical Journal (paywall). [NBC News]

Mapping the Moon in Black and White

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.

Previously: Lunar Cartography During the Age of Apollo; Many Moon Maps; Lunar Geology and the Apollo Program.

Lunar Geology and the Apollo Program

Geologic Map of the Copernicus Quadrangle of the Moon
H. H. Schmitt, N. J. Trask and E. M. Shoemaker, “Geologic Map of the Copernicus Quadrangle of the Moon,” 1967. USGS.

Planetary geologist David Rothery writes about the early attempts to map the Moon’s geology, both before and after the Apollo program. There was a symbiotic relationship between the map and the mission: maps suggested where landings might be most profitable from a geological perspective; and field work by the astronauts informed later moon maps.

National Geographic’s Atlas of Moons

The Atlas of Moons (screenshot)

The Atlas of Moons is National Geographic’s interactive guide to every single moon in the solar system (except for a few moons of dwarf planets and asteroids that we know next to nothing about). The big ones get interactive globes and additional description (as do Mars’s moons Phobos and Deimos, because we have imagery for them). Note that this is an extremely resource-intensive page that will use gigabytes of RAM if you let it.