Stephen Stough on Sensors at High Altitude

When Bill Bennett, ASC suggested an article on sensors at high altitude, and the perils of shipping digital cameras by air, I immediately got in touch with Stephen Stough (picture at left) — Cinematographer, Producer, and President of Tradecraft Films.

Stephen Stough knows a thing or two about technology, physics (Univ of California at Berkeley) and sensors (he was business unit manager of the company that developed the world’s first 4K digital cinematography camera in 1999). Stephen has lectured at NAB, Hollywood Post Alliance, Naval Air Systems Command, Defense Intelligence Agency, National Reconnaissance Office, Institute for Defense and Government Advancement, ASC, DGA, and SMPTE. He is a member of the Board of Editors of the Motion Imaging Journal, the technical journal of SMPTE. He was the chief technology officer of a $2.4 billion/year business unit of Lockheed Martin, and a principal in the creation of Lockheed Martin spin-offs and independent companies, including Systems Solution Technologies (wafer fabrication automation software), and Terrawave Optical Networks (broadband laser communications).

Stephen writes:

In general, a short exposure of camera equipment at altitude within the atmosphere is not going to cause any measurable damage, even when powered on but much less so if powered off in transit. It is true that heavy particles, such as heavy (fast) protons will leave tracks up to 1 mm long though glass, and eventually glass will turn translucent, metals become embrittled and so forth. But, that takes tens of years in space, and probably hundreds of years at the altitudes at which aircraft fly.

It is always possible that a heavy ionization track will damage the insulator (oxide) at a pixel site to the degree that when the sensor is powered on, the resulting short circuit current would flood that pixel site, and burn it out. The possibility isn’t zero. It would take some time to calculate the possibility in a real situation (where the sensor is buried inside an airframe inside a shipping case and inside a camera).

If it were my camera, I wouldn’t give it a second thought because I think the possibility in a few hundred hours of aircraft flight to be vanishingly small and economically not worth worrying about. That is, the cost of taking extra protective measures would probably never pay off in terms of an actual lost-pixel event being avoided.

If the camera were powered on during flight, there are other effects to worry about. Adding, say, a thicker aluminum case can make things worse, since a heavy particle will generate gamma and secondary electrons that won’t burn out anything, but will upset all the logic in the camera. At 50,000 ft., those operational disruptions could probably be expected about once each hour. The slower the logic speed and the lower the gate impedance, the less likely that there be upsets of this kind. That’s why CMOS or logic levels below 3Volts are so rare in space applications.

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