The devil’s in the details when you head inside a cleanroom. Everything you plan on bringing inside, from your phone to your camera tripod, needs to be wiped down with lint-free wipes. You need to put on a special bunny suit. If you put the gloves on wrong, you need to throw them away and get a new pair. You absolutely cannot touch your bare skin with those gloves — they could pick up oils, dead skin cells, and who knows what else. It felt like I spent as much time getting ready to enter the room as I did inside the room itself — but that’s probably because I had to change my gloves so many times.
But that’s a small price to pay to visit a 3.2 gigapixel digital camera, the largest one ever built. It’s the size of a small car, with a table-sized focal plane. This digital camera will live inside the Large Synoptic Survey Telescope, currently under construction, that will sit high in the dry air of the Andean foothills in Chile. The camera will allow the telescope to perform a task as monumental as its size: photographing the stars every night in order to create two full views of the entire southern hemisphere’s sky per week. The scientists behind the project seek to understand the nature of dark matter, dark energy, and other astronomical mysteries.
The LSST will be the most advanced survey of the night sky yet. Unlike the Hubble Space Telescope, which peers at individual objects or small patches of the sky, the LSST will create a movie of the entire night sky. Light that suddenly appears out of darkness could signal a supernova, and other changes could indicate the presence of the universe’s mysterious gravitational scaffolding, called dark matter, or the force driving it apart, called dark energy.
You might wonder what makes this behemoth a “digital camera.” It helps to break a digital camera into its component parts: a lens directs light onto a sensor, turning the light into an electrical signal and then into data stored on a computer. Your iPhone’s camera sensor is somewhere around 7 or 12 mega, or million, pixels, while a DSLR can have somewhere from 18 to 50 megapixels. The LSST will have 189 16-megapixel chips, all aligned on a perfectly flat plane.
Consumer cameras typically employ “CMOS” sensors, while the LSST’s are charge-coupling devices, or CCDs. They’re slightly different: CMOS detectors essentially have wires to send out the electrons at every pixel, while CCDs move the charge to be read elsewhere on the chip. CCDs are traditionally more expensive and power hungry than CMOS sensors, but they also experience less noise—fewer erroneous blips.
The sensors go into a cryostat which holds them in a vacuum at -100 degrees Celsius (-150 Fahrenheit). This further prevents noise and keeps dust off of the sensors—that’s why we had to put on the bunny suits. Then, there are mirrors to gather the light, which the lenses focus. The LSST’s largest lens measures a baffling 1.55 metres, or about five feet wide.
And they will produce a crapload of data, perhaps 15 terabytes per night. Computers process that data on the spot, and high-speed fibre optics send it down the mountain and on to the United States. The final data will be immediately available to anyone, even non-scientists.
But the LSST won’t do everything. When it detects something interesting, other telescopes, like those that collect infrared or ultraviolet light, can then follow up on the spot to learn more. It’s just one tool, after all.
Featured image: Todd Mason, Mason Productions Inc. / LSST Corporation