From the galaxy to the gallery: Making the GRB-Locator-Array

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The GRB-Locator Array was one of four projects commissioned by Science Gallery at Trinity College Dublin and Science Foundation Ireland for IN CASE OF EMERGENCY. It was created by artist Fiona McDonald, working in collaboration researchers from CONNECT, the Science Foundation Ireland Research Centre for Future Networks and Communications, and with help from AMBER, the Advanced Materials and BioEngineering Research centre. The project builds on work initiated while Fiona was artist-in-residence in Parity Studios, at the UCD School of Physics.

In this post, Fiona explains the origins of the exhibit, which responds to real-time satellite data from the Gamma-ray Coordinates Network (GCN). As a result of her collaboration with CONNECT, she was able to use Pervasive Nation's Low Power Wide Area networking technology to send real-time gamma ray burst data directly to the first floor of Science Gallery Dublin.

Gamma-ray bursts (GRBs) are extremely energetic explosions that have been observed in distant galaxies. In a few seconds, they can release three times as much energy as the Sun will in its entire lifetime. A GRB aimed at the Earth could deplete the ozone layer, cause acid rain and initiate a round of global cooling from as far as 6,500 light years away. Such a disaster may have been responsible for the mass die-off of 70% of marine creatures that thrived during the Ordovician period, 488 to 433 million years ago.

The collaborative project GRB-Locator-Array explores real-time data that records the distribution of GRB locations detected by the spacecraft Integral, Fermi and Swift. It also sends real-time GRB light curve data from Swift, containing information on the brightness and the energy generated by the burst.

Data is tracked in real time, but as GRBs have travelled billions of light years from distant galaxies before they are detected by the spacecraft, in some ways, the exhibit lets us look into the past.

With collaborator David Murphy, a researcher at the Space Science Group at UCD, we developed the initial python code to receive GCN data in real time. This gave us the positions of GRBs in celestial coordinates, known as right-ascension and declination, derived from the idea that we are marking a position on a sphere around the Earth.

The GRB celestial coordinate is then transformed into local, or topocentric, coordinates known as azimuth (degrees from north) and altitude (degrees above the horizon). The transformation is dependent on the sculpture’s location and the time. The coordinate position data is then used to rotate the GRB-Locator-Array azimuth and altitude axes, and to position its mirrors to point in the direction of the most recently observed GRB.

The intense radiation of most observed GRBs ('long' bursts) is believed to be released during a supernova or hypernova, as a rapidly rotating high-mass star collapses to form a neutron star, quark star, or black hole. A subclass of GRBs (the 'short' bursts) appear to originate from a different process: the merger of binary neutron stars.

One such 'short'  burst detection was made by Fermi and Integral was made on 17th August this year — an event simultaneously observed by LIGO, the gravitational wave observatory. You can read more about that burst here.  

The light curve data set collected by the spacecraft and used by GRB-Locator-Array contains detailed information not only on how bright the GRB was, but also on how much energy and power it generated. The LED display axis of the exhibit represents the level of gamma ray radiation of the burst, versus time; if only the first two columns of the display light up, it represents a short burst, while all six columns illuminate only when a long burst is detected.  

GRB-Locator-Array (LoRaWan Prototype (ii)) // Photo by John McDonald

CONNECT researcher Neil Smyth also collaborated on the project to sonify the light-curve data in real time, using FM synthesis. At ten-minute intervals, we hear sonified data which maps one of the last five detected GRB light curves.

Working with Brian Murphy, a researcher from Pervasive Nation at CONNECT, Ireland’s Internet of Things testbed, we attempted to represent the light curve’s large, complex data set using low data and low-power devices. Pervasive Nation specialise in the use of wireless communication over wide area and long distances.

A custom-made python script written by Antonio Martin-Carrillo of the UCD Space Science group processes the GRB light curve data automatically via an email alert from the Swift spacecraft. Once retrieved by an intermediary web server, the data is processed and prepared into the appropriate Hex format for sending to the LED structure.

This process, in the form of a data downlink, is sent via the Pervasive Nation network server to broadcast to all gateways across the city. The appropriate device, in this case the LED structure, recognises the message via the LoRa transceiver and then incorporates the new data into its display.

LoRa devices are best used for sending and receiving lesser amounts of data wirelessly over long distances, or to hard-to-reach places, with the minimum power usage many times a day, building up rich data sets over time. This allows devices to operate in the field, sending and receiving data over long periods, typically greater than six months.

This research will allow me to explore incorporating technology into outdoor spaces using LoRaWan technology. I am also intrigued by the different ways of encoding and decoding information, the nerd in me enjoyed the the complexities of sending and receiving data over the LoRa network, converting complex data to bytes of data in HEX format and finally extracting this data into its appropriate binary (01010101) value to control the LED matrix.

This could be used with other low-power devices. I look forward to exploring future mobile/weatherproof prototype designs, which will allow us to explore temporary or permanent interventions at locations around the city and further afield. Another strand of the research will also explore incorporating low-powered sensors as used in citizen science into future objects.

The GRB-Locator-Array is part of IN CASE OF EMERGENCY, a free exhibition exploring global disaster, open at Science Gallery Dublin until 11th February 2018.