James Webb Space Telescope runs an extended version of JavaScript [pdf]

The whole thing really felt like a post facto justification rather than a design flowing from requirements/constraints.

I get that it is valuable to be able to have the spacecraft take certain actions without reliable communications, but that isn’t unique to this spacecraft in any way, nor does it require using a scripting language. It seems like they just wanted an easier development environment, which is fine as long as it doesn’t compromise mission reliability.

I’m also concerned they suggest ascii encoding of the code instead of binary means the uploaded code doesn’t require verification. All data can be corrupted in transit, and I would be very surprised if they don’t still use error correction.