The sound of space stars on a virtual stage

Artists can find themselves working in many different worlds. Over the past 12 months, my world has been that of space. More specifically, I have been Leverhulme artist in residence at the Space Research Centre (SRC) at Leicester University, UK. This has in no way been an uneasy mix; more of a fantastical and heady collaboration between cutting edge science and art. I have thus been working at the interface between the realms of factual data and conceptual interpretation.

As a multi-media composer and artist stepping into the world of the staff and researchers of Space Research Centre, I enjoyed having a free role in identifying what research areas interested me most from the breadth of work being undertaken in this space research laboratory. Such freedom sounds ideal. But the first challenge was to determine one single starting point from so much possibility.

Space: a new political and economic frontier

I was fortunate to meet Nigel Bannister, a senior lecturer in astrophysics and astronomy, at an early stage of my artist residency in Leicester. Our contact provided both the inspiration and resources for what became the Trajectory (Earth Chorus) installation.At the time of our first meeting, Nigel was working to create a real time model for the launch, mission trajectory and orbits of a research project called JUICE—which stands for Jupiter Icy Moons Explore. It is a European Space Agency (ESA) spacecraft designed to visit the Jovian system.

This mission is specifically focused on studying three of Jupiter’s moons—namely Ganymede, Callisto, and Europa—using a technology called Systems Tool Kit (STK). This is a software designed for calculating and planning trajectory paths of objects for both terrestrial and space application.Use of STK to track the orbits of satellites produced a complex, beautiful and mesmerising visualisation in real time.

This other-worldly vista was impressive in its redefinition of the territory now occupied by humanity: a representation of a new political and economic frontier. There appeared to be no end to the possibilities of creative conceptualisation and visual interpretation of this data.

200 sources of space sound

While working with a multi-media approach, my primary interest is in sound and audio composition. I prefer to describe myself as a ‘multi media composer’ arranging work within a demarcated timeline, as opposed to an ‘artist’, which implies emphasis on the visual and non-linear structures. To this end, I amassed in excess of 200 sources of sound in space, such as whistlers, bow shock waves, solar flares and plasma pulses, each with a distinct audio spectrum.

The earth chorus stood apart, even from other chorus data, such as that from Jupiter. The earth chorus consists of brief, rising-frequency tones emulating the chorus of birdsong at sunrise, hence referred to as ‘chorus’ or ‘dawn chorus’. It is generated by electrons in earth’s so-called Van Allen radiation belts, which is made of energetic charged particles held in place around the earth by the planet’s magnetic field. Once generated, the chorus waves affect the motions of the electrons through a process called a wave-particle interaction. These interactions disturb the trajectories of the radiation belt electrons causing the electrons to hit the upper atmosphere…

Visualising the sound of space

There are many recordings and long wave radio data of the earth chorus. I only used a two minutes data file from the ESA Cluster II satellite, recorded on 9 July 2001. This provided the link between aural and visual landscapes.Using the available stored satellite data I could programme STK to track the orbit of Cluster II, which is a high-altitude spacecraft, using a polar orbit, on the day it recorded the audio data. I was thus able to create visualisations of its orbit and the resulting data path on the Earth’s atmosphere. To provide a varied visual landscape I also collected data from 250 other satellites capable of observing the Earth on the 9th of July 2001, using STK.

I used these orbits records to create 3D visual material for several video screens. In addition to 3D mapping of the satellite trajectories it is possible to include visual information relating to the area of the Earth that the orbit is tracking or receiving data. These trajectories are represented within my visualisations as triangles, squares or dotted circles across the surface of the Earth. The satellites themselves are shown as dots, sometimes labelled with their names, and their orbits are visualised as continuous white lines. The world appears in different forms. As a wire frame with continents showing, as a ball of cloud or sometimes hidden by the mass of circling satellites..


Seen together they present a continually evolving visual picture comprising complex elliptical patterns, not unlike a Spiro graph. The data streams in numeric and symbol form and it features distinct points of reference between the sound, the data and the visual world. The occasional use of wire frame human heads superimposed over the satellite orbits create additional metaphorical images relating to a new political and economic territory for humanity.

And suddenly there was sound!

These signals stemming from terrestrial plasma waves and radio emissions in the 2 Hz to 80 kHz range were first analysed in numeric form. But they can also be played as sound – just like any radio signal. However, because the upper frequencies are outside of the range of human hearing (20Hz – 20KHz) they need to be transposed to fall into this range so that we could perceive then as audio. This is another and very interesting way to access the same data – using sound.

The audio for the earth chorus installation was composed by shaping, filtering—removing some frequencies to reveal the detail and texture of others—and spatially placing each sound within a multi-speaker diffusion system to recreate the spatial qualities of the earth chorus within a gallery space.Although it has been composed and therefore treated within a musical structure, Chorus 1 remains a true record of the original data. This is important for me, as throughout this process I have been interested in creating work that helps people to access, understand and visualise data without destroying or corrupting its value.

I hope that the next 12 months will provide the opportunity to develop Trajectory as a project, involving other artists, researchers and new data, to realise its potential as a full touring multimedia installation. 

Andrew Williams

Composer, multimedia artist, director and facilitator working in time based art and live performance since 1987.

Featured image credit: Andrew Williams

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