Safely on its way
Night time in Cape Canaveral, and the countdown for the launch of the NASA space shuttle has begun: 10, 9, 8, 7… The ground shakes on all sides, a blinding light fills the sky and the shuttle takes off. Some distance away, evaluation cameras are busy recording the launch for subsequent analysis. Their ranks include a high-speed camera made by the company PCO AG from Kelheim, Germany, equipped with a ZEISS lens.
In 2009, the American National Aeronautics and Space Administration (NASA) asked several digital high-speed camera makers to film the launch of a space shuttle. Among them was the company PCO, one of the leading manufacturers of digital cameras for use in research and development applications. With the launch repeatedly delayed by bad weather, the cameras and lenses ended up operating non-stop for over a week—access to them was prohibited once they had been set up, so they were left outside day and night.
Analog or digital?
The United States has launched more than 100 space shuttles into space over recent years, and NASA has filmed every single launch in order to learn how to make future flights safer and more reliable. The cameras and lenses used for this purpose are subject to rigorous requirements: NASA has primarily stuck to traditional film cameras because, until very recently, digital technology was still not up to the challenge for a number of different reasons.
For a long time, one of the major problems was that digital high-speed cameras were simply not fast enough to photograph shuttle launches. When a camera is taking several hundred—or even several thousand—pictures a second, the exposure time for each image is tiny, which means that the ability of the camera and lens to gather enough light for each shot becomes a major issue. The whole thing was complicated further by the fact that many shuttles are launched at night. “High-speed cameras used to be essentially ‘blind’,” says Horst, “but over the last few years the image sensors have become much more sensitive to light thanks to their additional micro lenses.” But that is not the only requirement: The application also calls for extremely fast lenses to ensure enough light hits the camera’s sensor. In addition, the cameras and lenses have to be capable of dealing with tremendous variations in light intensity: At the start of the launch, everything is virtually pitch black, but the flames from the rocket boosters soon throw the whole scene into dazzling light, producing intense reflections that can be difficult for the camera to cope with.
The second sticking point when it came to introducing digital technology was image quality. Up until about three years ago, digital high-speed cameras offered a maximum resolution of 1000 x 1000 pixels—in other words one megapixel—which was simply not enough to replace film. For a shuttle launch, some cameras are positioned some 300 meters from the launch ramp, yet it is the close-up details of the launch that are crucial. Did the shuttle separate correctly from the launch platform? Did all the engines ignite? Did the heat shield remain intact? NASA depends on this information to perform its subsequent launch analysis, a process that could enable it to determine why a part became detached from the shuttle during launch or even prevent a potential catastrophe in space. Picking out that level of detail from such a large distance requires cameras with a very high resolution, and today’s digital high-speed cameras offer resolutions of up to 2000 x 2000 pixels. Holst adds: “Obviously it doesn’t just come down to the camera. You also need a lens with a very high resolution—at least as high as that of the camera.” Otherwise information gets lost before it even reaches the camera’s sensor.
Cameras and lenses built to withstand wind and weather
So could digital high-speed cameras end up replacing traditional film cameras? They certainly have a strong case, because—quite apart from the issue of image quality—digital technology offers a number of very real benefits: For example, NASA can process the images digitally and load them directly into image processing software without going through the laborious task of scanning them in first. But the nagging question has still been whether the images would really be of sufficient quality, which is why NASA decided to put the camera systems through their paces last year. And the results were impressive.
The tests revealed a further quality advantage in terms of the workmanship of the cameras and lenses. “The shuttle launch produces huge vibrations,” explains PCO’s head of research, “plus you are having to deal with high humidity and significant temperature variations, because it gets a lot colder in Florida at night.” Once the cameras have been set up and focused, they are simply left outside—protected from the weather by nothing more than a mini roof—because access is subsequently prohibited for safety and security reasons. The fact that NASA had to repeatedly postpone the launch meant that the equipment was exposed to adverse weather conditions for more than a week—an indication of just how robust the systems need to be. So PCO chose the Makro-Planar T* 2/100 ZF from ZEISS, a very fast lens that offers an equally impressive resolution. “As well as superb image quality, the lens also had to be manually operated and compatible with the F-mount system, which is the standard format in the scientific arena.” He certainly has no regrets that the choice of suitable lenses was so limited: “When we were photographing the shuttle launch we had the comfort of knowing that we could rely 100 percent on the quality of the lens.”
Quality that pays off
NASA have so far kept their conclusions from the tests under wraps and the question of whether they might soon switch to digital photography remains tantalizingly unclear. No American shuttles are scheduled for launch after 2011 now that NASA has announced its intention to retire the space transportation system, but the results of the test could also be of great interest for the shuttle’s planned successor, the Orion spacecraft, as well as for other applications in the aerospace arena. There is certainly no denying any longer that high-speed cameras and industrial camera lenses are finally up to the challenge.