By Bob Snyder
It’s an image so large it would take 378 4K ultra-high-definition TV screens to display. The resolution is so high you could see the dimples’ texture on a golf ball even if it was 24 kilometers away.
This month, a lab at Stanford University, operating on behalf of the U.S. Department of Energy’s Office of Science, snapped the largest photo ever taken in a single shot, the first 3200-megapixel image. The SLAC National Accelerator Laboratory built an out-of-this-world array of imaging sensors as their contribution of a camera for the new Vera C. Rubin Observatory in Chile.
From the successful test of their sensors, SLAC will go on to soon build the world’s most massive digital camera for the new observatory. The observatory in Chile is an international effort under the management of the Association of Universities for Research in Astronomy (AURA). Its main task (called the Legacy Survey of Space and Time or LSST) will be to make a Facebook of galaxies, a photo survey of the 20 billion or so visible galaxies. It will also map the motions of various astrophysical objects. (So, who knows, maybe we’ll be seeing ʻOumuamua again?)
Using the LSST Camera, the observatory will create the largest astronomical movie of all time as it explores the biggest mysteries of the universe, including dark matter and dark energy. The first images taken with the sensors were a test for the LSST camera’s focal plane. The focal plane is more than half a meter wide (compared to the usual 3.1-centimeter-wide imaging sensor in your digital camera). It contains in “rafts” 189 individual sensors (CCDs), each bringing 16 megapixels to the 3200-megapixel photos.
The gaps between sensors on neighboring groups (rafts) are less than five human hairs wide — a tight tolerance since imaging sensors easily crack if they touch each other. It took first a year of practice and then six months of work to create the sensor array.
This is the short story of their longer novel procedures.
For example, the focal plane also needs to be placed inside a cryostat where the sensors can be cooled to negative 101 degrees Celsius, their required operating temperature.
Not only does it contain 3.2 billion pixels, but its pixels are also very small — only about 10 microns wide — and the focal plane itself is extremely flat, varying by no more than a tenth of the width of a human hair. This allows the camera to produce sharp images in very high resolution.
The imaging sensors can spot objects 100 million times dimmer than those visible to the naked eye. If your eyes had that super-human power, you could spot a lit candle from thousands of miles away. By mid-2021, the camera (the size of an SUV) will be ready for final testing before it goes to work in Chile.
Space exploration is a gift that just keeps giving to the tech industries: Some of the developments from the space program include memory foam, freeze-dried food, firefighting equipment, emergency “space blankets,” DustBusters, cochlear implants, LZR Racer swimsuits — and those CMOS image sensors that create our very desirable high-definition video.
You can click on the links below to explore images taken with the focal plane of the LSST Camera in full resolution. Without a fully assembled camera, the SLAC team had to use a 150-micron pinhole to project images onto the focal plane.
With history clearly in the making and all the expectations of subsequent publicity, one wonders how the scientists picked the subjects for their history-making test photos. These are meticulous people who would practice placing sensors for a year before having a real go. Hence, no doubt there was some serious discussion as we ended up with photos of a head of Romanesco broccoli and a Flammarion engraving.
If you spend your time looking for black holes and dark matter, broccoli can be fascinating.