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Comment by wargames | Hacker News Reader

I'm curious for anyone who may know the answer... with no mention of encryption, are these streams free for anyone with the equipment to receive? Conversely, what kind of security is in place on JWST for command updates to ensure that some rogue group couldn't cause mischief and send it commands?

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There is a decent amateur community for receiving satellite transmissions. I'm not super knowledgable on it, but 2 resources that may interest you:

Scott Tilley, who gained a lot of recognition in the past year in analyzing radio signals to see how Russia was using satellites in Ukraine: https://twitter.com/coastal8049

An amateur group revived 2-way communications on an abandoned satellite: https://sservi.nasa.gov/articles/isee-3-reboot-project/#:~:t....

NOAA satellite downlink is unencrypted, at least: https://news.ycombinator.com/item?id=9949278 https://news.ycombinator.com/item?id=24129162

I think in scientific satellites, the downlink is unencrypted and only the command channel is usually encrypted for obvious reasons.

Is 25 Ghz something an amateur could practically expect to capture from earth without ridiculous (or improbable) electronics? My understanding of higher frequencies was that something this high is likely to have been almost completely absorbed by the atmosphere

You'll probably need a pretty big dish...

I remember talking to someone who works on the Deep Space Network. The commands they send to their devices are definitely encrypted and have checksums so nobody can inject bogus commands. It was super important that the device receives the correct command at the right time. Not sure if their downstream is secured.

This is an exceptionally old document, referencing the 2013 launch expectation, but it contains a bunch of interesting information on the platform database and the communications segment. [1]

Apparently, they have to have accurate ranging to receive from JWST. The interesting portion:

"Ranging is required for JWST, using alternate ground stations in the southern and northern hemisphere. For LEO and L2 missions the accuracy of the ranging is dependent on the tracking of the spacecraft across the sky. For the JWSTs L2 orbit, 21 days of tracking equals about 15 minutes of tracking for a LEO spacecraft."

https://ntrs.nasa.gov/api/citations/20080030196/downloads/20...

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