Explained: Why doesn't NASA's Webb space telescope have cameras?

According to NASA, the spacecraft is equipped with a comprehensive set of sensors - mechanical, thermal, and electrical sensors - that provide a wide array of critical information regarding the status and performance of the telescope while it is in space.

The James Webb Space Telescope, the world's largest and most powerful space science telescope, is in the process of unfolding into its final configuration in space. While the observatory is making big progress for its launch, you will be surprised to know that there are no engineering cameras onboard to watch its complicated deployments.

"A system of surveillance cameras to watch deployments was considered for inclusion in Webb's toolkit of diagnostics and was studied in-depth during Webb's design phase, but ultimately this was rejected," NASA says.

Here's why Webb has no surveillance cameras onboard:

Complexity

Webb is big and undergoes many configuration changes during deployment. Monitoring its deployments with cameras would require either multiple narrow-field cameras, adding significant complexity, or a few wide-field cameras that would yield little in the way of helpful detailed information.

Lighting and temperature

The sun-facing side of the observatory is so shiny that cameras there would have glare and contrast issues. Meanwhile, cameras on the cold and shaded side would need added lighting and would have to work at very cold cryogenic temperatures. This would either require ‘ordinary’ cameras to be encapsulated or insulated or the development of special-purpose cryogenic-compatible cameras.

Power

NASA says it would have to run cables and power out to cameras on Webb, and the power balance on the cold side of the observatory is especially delicate. More cables add more of a threat of heat and vibration transfer through the wires, which could impact image quality.

So how do the ground teams monitor the health and status of Webb?

According to NASA, the spacecraft is equipped with a comprehensive set of sensors - mechanical, thermal, and electrical sensors - that provide a wide array of critical information regarding the status and performance of the telescope while it is in space.

"Webb's built-in sense of ‘touch’ (for example, switches and various mechanical, electrical, and temperature sensors) provides much more useful information than mere surveillance cameras can," says Paul Geithner, deputy project manager – technical for the Webb telescope at NASA's Goddard Space Flight Center.