John Tonry: A Wider Field of View

John Tonry inspects the Pan-STARRS gigapixel camera

In the mid-1990s, John Tonry invented a new kind of electronic chip – the Orthogonal Transfer Charged Coupled Device or OTCCD. It allowed astronomers to build large digital cameras in which the effects of atmospheric seeing were reduced over a much larger field of view than could be achieved by adaptive optics devices.

During an exposure with an OTCCD the electrons that are being generated by the light are continuously shunted from pixel to nearby pixel to compensate for the movements caused by atmospheric turbulence.

In collaboration with Lincoln Laboratories, a prototype device was built and successfully tested on the UH 88-inch telescope. But the OTCCD really proved its worth when used on Pan-STARRS, the world’s largest and most advanced system.

The focal plane of the Pan-STARRS telescope consists of an array of 60 separate silicon chips. Each 1-inch square chip contains 64 independent OTCCDs, each of which is an array of 600 x 600 pixels. These add up to a total of 1.4 billion pixels, making it the largest camera in the world. This camera was built at the IFA by a group of talented engineers under the supervision of electronic engineer Peter Onaka.

The array enabled Pan-STARRS to image an extremely wide area of the sky with a field of view equivalent to six times the diameter of the Moon or 3 degrees of arc, and also to map the sky detecting stars that are 10 million times fainter than those observed by the naked eye.

“Moving an image on a CCD chip can be done much more quickly than moving one of the mirrors of a telescope, as in a conventional adaptive optics system. Also, this detector is built in a modular way that allows scaling to much larger arrays at low cost.”  — John Tonry