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Comment by mrb | Hacker News Reader

Well, let me do a comparison:

I can watch much higher quality videos streamed over the Internet, from servers thousands of miles away, around the world, through many routers, fiber optics, and complex technological stacks (DOCSIS, TCP/IP, fiber optics signal modulation, video codecs, etc).

Yet the ISS has a clear line of sight to ground receiving stations 230-1000 miles away (or to satellites which are perfectly able to transmit digital data), yet the video signal quality is that bad?

Don't get me wrong. As a space enthusiast I love being able to watch live spacewalks. But as an engineer I sigh at certain technical aspects...

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Both you and the servers you're pulling the content from are stationary on the ground, and any satellites used are in geosynchronous orbit. ISS is travelling 17000 mph. So while it may have clear line of sight to a ground station in New Mexico one minute, the next minute that same line of sight is in Texas.

Also, for a spacewalk the video source is from a space suit, so the video signal is sent wirelessly from the spacesuit to ISS, then sent to a TDRS satellite, then to the ground. The spacesuit camera is admittedly not as good as I'd like it to be, but considering all the architecture supporting it started being put in orbit over 10 years ago, and was designed before that, it's pretty good.

That's cool did you directly work on any of the systems? I have been poking around the NSTS 07700 Volume X Book 1 Flight and Ground Specification. The EVA, and Video subsystems are highlighted there.

Crazy stuff.

As an engineer, you should know that engineering involves designing systems that will get the job done with the minimal amount of resources possible.

What would be the point of a higher quality video in this context? Is it necessary, or simply a nice-to-have?

One of the most popular axioms of engineering is "if it ain't broke, don't fix it." It could be revised for this scenario: "if it gets the job done, don't improve it."

As an engineer he should know that the ISS has to be rad-resistant. They'll upgrade soon enough.

Being rad-resistant does not prevent the ISS from having many other communication links which are digital and not analog.

Sure, if you want to spend the money to add (more) redundant links. You want to front a few thousand dollars?

Unless you mean that digital links aren't more vulnerable to radiation, in which case I recommend you read up on large-scale analog circuitry and get back to me.

Wait for SpaceX or somebody else to bring the per-kg cost down and we'll have all the digital video anyone could ever want.

You seem to be arguing rad-resistance is the factor that made them decide on analog instead of digital video.

I doubt it.

Like someone said, initially they chose analog because back in the day nobody did digital video streaming. It has worked okay since then. And there just hasn't been enough reasons to justify a change to digital.

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