Selenography

Selenography is a continuous, real-time sonification of the lunar surface, read crater by crater.

A scanning gantry crosses the Earth-facing hemisphere of the Moon at a deliberate pace. Wherever the gantry pauses, the catalogued craters that fall inside its window are struck. The piece is designed to play without repetition for many hours. Nothing is sequenced in advance. What is heard at any moment is a direct function of which craters the gantry is presently reading.

The work was conceived for the gallery: low-frequency information carried by large speakers, long reverberant tails, and a slow cadence of attacks that rewards extended attention. It is also intended to function at home, on headphones, as a stable accompaniment to other work.

The visual surface follows the same reading. The lunar disc occupies the centre of the canvas; the gantry passes over it as a soft horizontal band. Each strike emits a brief outward pulse from the crater's coordinate. The image of the Moon does not move. The gantry, the strikes, and the slow drift of regional emphasis are the only things in motion.

The catalog seed is the named-feature gazetteer maintained by the IAU Working Group for Planetary System Nomenclature — Tycho, Copernicus, Plato, Clavius, Theophilus, Petavius, Grimaldi, and roughly a hundred and twenty other named craters across the visible hemisphere. The synthesized population that fills out the field obeys the empirical lunar size–frequency distribution, suppressed inside the mare basins where the basalt is younger.

Each crater carries four values: its latitude and longitude on the lunar surface, its diameter in kilometres, and a degradation index — a measure of how much subsequent impact gardening, slumping, and isostatic relaxation have softened its rim. The freshest Copernican-age craters score near zero; the oldest pre-Nectarian relics score near one.

The base image is the LROC Wide-Angle Camera global mosaic produced by NASA's Lunar Reconnaissance Orbiter, projected orthographically onto the disc so that the sub-Earth point sits at its centre and the libration limbs at its edge.

Each strike is bound to its crater's four values. The mapping is fixed and deterministic: the same crater always produces the same pitch class, the same timbre, the same panning position, and the same decay length. Repeated listening teaches the ear to recognise particular features by sound alone.

• Diameterregister — large to low, small to high
• Degradationtimbre — fresh to bell, eroded to felt
• Latitudestereo position
• Depth-to-diameterdecay length
• Highland / mareattack character

The pitch material is fixed to the Dorian mode whose root sits at G2, ninety-eight hertz. Drone voices are arranged at the root, fifth, octave, and twelfth. Plucks are quantized to the same scale; their register rises and falls with crater diameter. A slow pad walks through the bright degrees of the mode — i, IV, ♭VII, v — as the gantry's emphasis migrates across the disc.

A composite reading — the average diameter, the average degradation, and the highland-to-mare ratio of craters currently within the window — biases the underlying drone bed and the colour temperature of the canvas. The southern highlands sound denser and darker; the northern maria sound sparser and warmer.

Selenography runs on two audio paths from the same mapping. The first is a web engine that synthesizes sound entirely in the browser. Its voices are four detuned drones, a felted mallet pluck with a long decay, a slow chord pad, four high shimmer tones that pulse on the smaller, fresher strikes, and a distant filtered wash. Everything is summed into a procedural convolution reverb with a long tail. The second is a control-voltage path that drives an analog modular synthesizer assembled for the installation. Eight channels carry pitch, a pluck gate, four slow control voltages tied to the live state of the gantry's window, a divided clock, and an occasional random gate.

The web path is the default. The modular path is reserved for the gallery installation.

Joshua Borsman is an artist working in sound, kinetic sculpture, and generative systems. Recent work includes Lightcurve (2024–), a real-time sonification of deep-field photographs from the James Webb Space Telescope; Sounding (2026), a sonification of ocean weather and tide patterns along the Pacific Northwest coast; and Ephemeris (2025), a sonification of the orbital traffic above the listener. His practice spans gallery, public, and digital environments.

joshuaborsman.com

Set in Cormorant Garamond and IBM Plex Mono. Synthesis via the Web Audio API. Control voltages routed to an external modular synthesizer. Lunar imagery from NASA's Lunar Reconnaissance Orbiter; nomenclature from the IAU Working Group for Planetary System Nomenclature; size–frequency statistics after Robbins (2018).

The code, audio synthesis, visual artwork, and accompanying text are © 2026 Joshua Borsman, all rights reserved. Fair-use viewing and sharing of the work as presented here is permitted; commercial or exhibition use requires the artist's written consent. NASA imagery and IAU nomenclature referenced by the work are in the public domain as works of the U.S. federal government and an international scientific body, respectively.