How Cosmic Rays Damage Camera Sensors in Space

By Norman Chan

Those speckles you see in Chris Hadfield's videos are dead pixels on the camera's sensors from space radiation.

Here's a little behind-the-scenes detail for you. For this week's videos with Chris Hadfield (you've seen them by now, right?), Chris actually played cameraman himself for all the footage shot on the ISS. This was likely the case for his now-famous Space Oddity music video, which makes the feat that much more impressive. The video clips the Canadian Space Agency relayed to us were 720p video shot from on a Nikon DSLR, and while we were reviewing the footage, we noticed speckles of static white pixels throughout the video. It looked like dead pixels on our monitors, but they were actually damaged pixels on the ISS cameras!

The prosumer-grade cameras used on the International Space Station aren't heavily modified for use in space (they are certified through a rigorous testing process), so they actually aren't shielded from the cosmic radiation that exists both outside and inside the station. So when video is being recorded and the DSLR's mirror is flipped up, high-energy particles slam into the digital sensor and damage it permanently. According to astronaut Rex Walheim of STS-135, cameras that are taken on space walks may suffer severe radiation damage on sensor pixels. NASA evaluates the damage and decides whether or not to retire that camera for use.

Cosmic radiation (primarily gamma rays) are a well-known phenomenon for NASA and its astronauts. Some astronauts, including Neil Armstrong and Buzz Aldrin, have even reported seeing streaks of light that were determined to be cosmic rays zipping past their eyes. The most prolific astronaut photographer, Don Pettit, described the rays' effects on ISS equipment on his blog:

"Free from the protection offered by the atmosphere, cosmic rays bombard us within Space Station, penetrating the hull almost as if it was not there. They zap everything inside, causing such mischief as locking up our laptop computers and knocking pixels out of whack in our cameras. The computers recover with a reboot; the cameras suffer permanent damage. After about a year, the images they produce look like they are covered with electronic snow. Cosmic rays contribute most of the radiation dose received by Space Station crews. We have defined lifetime limits, after which you fly a desk for the rest of your career. No one has reached that dose level yet."

So rewatch our videos with Chris Hadfield and see if you can catch those speckles of damaged pixels--it's just another consideration that astronauts have to be mindful about when living on orbit!