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Three years ago, Zach Meredith, then an intern at GLAS Education, was part of the team that started the plug plate project funded by a grant from the Wisconsin Space Grant Consortium. The plug plate project is pretty straightforward. Find a way to use sonification to give the blind and visually impaired an idea of the distances from earth to 20 other astronomical objects: stars, galaxies, and pulsars. The concept is simple. The user pulls a tab corresponding to a cosmic object and the more distant the object the longer the wire and the lower the tone, but making it work is another matter.

This year, Zach returned to GLAS as a temporary staff member with the goal of finishing the plug plate and getting it ready for the Wisconsin Space Grant Consortium Conference at Carroll University, Waukesha, on August 12. He is being assisted by former intern Simon Mork and GLAS consultant Olivia Smithmier.

In an August 3rd presentation, Zach laid out the difficulties and trial and error process used to find solutions to the plug plate’s technical problems. Originally, a fishing line was used to connect the pull tabs to the sound device but the line kept fraying. Zach said he replaced the line with a necklace chain, which is fine enough to fit in the pull tab holes and tough enough to withstand repeated pulling. Then there is the sound. Zach wanted a central processing unit to control the tones that represented the cosmic distances between earth and the extrasolar objects. Zach tried the Arduino microcomputer. While compact and simple to use, the Arduino could not process multiple sounds. If more than two tabs were pulled on the plug plates, the Arduino stopped working. Zach is still convinced that a single processor is the way to go, but until the bugs are worked out, each of the 20 pull tabs will be connected to a separate printed circuit board (each just 1 by 1.5 inches) which will control the tones.

Getting the pull tab chains to retract after each pull was also a challenge. The chains are retracted to a spool behind the plug plate by a spring. Zach said he had to try three different kinds of springs, a clock spring, a constant force spring, and a constant torque spring. In the end, he selected the constant torque spring as the way to go. Designing the back of the plug plate was just as important as designing the front. The plug plate’s works needed to be properly protected from damage. The plate is intended to be a mobile exhibit, which means the works will have to resist the expected bumps and bangs from travel and set up. Zach has designed protective housings for the plug plate works and is 3D printing them.

The plug plate was originally designed for the Sloan Digital Sky Survey for a telescope during a single session could gather light from dozens of astronomical objects, stars, galaxies, and pulsars, at once. Each hole in the plug plate corresponds to the locations of specific objects in the sky. Fiber optic cables were plugged into the holes. The plate is affixed to a telescope and aligned with the objects. The fiber optic cables picked up the light from each object and directed it to a bank of spectrographs. The Spectrographs refract the light, splitting it into various colors, called absorption lines. Astronomers can use the absorption lines to determine an astronomical object’s chemical composition, along with its distance and speed relative to the earth.

GLAS Education acquired the plug plate through the University of Chicago Yerkes Observatory. Kate Meredith, former director of the Yerkes education outreach and now director of GLAS, said she helped develop dozens of plug plates (a total of nearly 6,000 were made) for education purposes. When the University of Chicago shut down public access to the observatory and ended the Yerkes education program, she took the plate along with her while creating the new nonprofit GLAS Education.

With a commitment to providing access to astronomy to the blind and visually impaired, GLAS began adapting a sonification system to the plate to give blind individuals an idea of the vastness of the universe.

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