NASA Explains Why Webb Doesn’t Have Any External Cameras

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NASA launched the James Webb Space Telescope on Christmas Day a few weeks ago. So far, the observatory is hitting every one of its deployment milestones as it heads out into interplanetary space. However, Christmas was probably the last time anyone would ever see Webb. There are no external cameras on the spacecraft, and now NASA has detailed the numerous reasons it opted to go this route. 

While Webb is in many ways the successor to Hubble, it’s not just a bigger, better telescope. It’s also operating in a completely different environment than the aging observatory. Webb is on its way to the Earth-Sun L2 Lagrange point, a region of gravitational stability outside the moon’s orbit. Here, Webb will be able to use its sunshield to keep its instruments ultra-cool, allowing for the best-ever infrared observations. This plan guided the spacecraft’s design, and that left little room for extra cameras with no scientific value. 

For Webb’s instruments to operate correctly, they have to be cooled to below 50 Kelvin (−223 C; −370 F). You can’t just slap an off-the-shelf camera on the craft and expect it to work. NASA would have had to engineer specialized hardware that wouldn’t degrade in a cryogenic environment. Even if they had done that, what sort of camera do you make? A narrow-field camera would be very complex to integrate, and a wide-field camera doesn’t provide much useful data. Even if there were cameras, you wouldn’t see much. Hubble is in low-Earth orbit where it’s fairly bright, but Webb’s gold-coated mirrors will be pitch black thanks to the sunshield. Meanwhile, the sunward side would be so bright as to reduce contrast to zero. Luckily, NASA doesn’t need cameras to know how Webb is doing. There are mechanical, thermal, and electric sensors integrated throughout the design that tell the team back on Earth everything they need to know. 

Adding more cameras could also endanger the true mission. Because Webb was launched in a 5.4-meter-wide rocket, it had to be folded up. It has just completed unfurling the sunshield, which caused delays on the ground as engineers worked out how to unfold it without causing damage. Adding external cameras just to peek at the spacecraft would have meant running more cables and mounting hardware. That would have added further design complications, of which NASA already had plenty, and might have introduced heat leakage and vibration that could spoil important observations. 

The James Webb Space Telescope will be too far away for service missions, which is why it may never be seen again. However, NASA believes it will last for at least five years and maybe even ten or more. It recently said its perfect launch saved some fuel, which could push operations beyond a decade. We hope to see the first images from Webb around the middle of the year.

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