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> Beginning in 1928, a small statue of the popular cartoon character Felix the Cat was featured in television test broadcast transmissions So, cats have been d

by devsda 3y ago

> Beginning in 1928, a small statue of the popular cartoon character Felix the Cat was featured in television test broadcast transmissions So, cats have been dominating the airwaves from the beginning of broadcast video. The article says the video was sent to earth at 267 Mbps. As much as we are interested in watching interstellar feline adventures, I'd imagine future astronauts will be equally or more interested in watching videos of their favorite cats(or humans occasionally). So, I'm curious to know the max speed at which we can transmit from earth to a spacecraft at similar distances.

daltont 3y ago
"cats have been dominating the airwaves from the beginning of broadcast video." Maybe the Kzinti will think we are long lost relatives after receiving them. (https://en.wikipedia.org/wiki/Kzin https://en.wikipedia.org/wiki/Kzin)
Sanzig 3y ago
All else being equal, you could conceivably push a higher data rate on the forward link. The apertures are the same size, just the transmit and receive apertures are reversed, so geometric losses would be exactly the same. However, you can get a much more powerful laser on the ground since you don't have to worry about the power and thermal constraints you have with the transmitter on the spacecraft. This advantage will be pared down somewhat as the spacecraft won't have as sensitive a detector as the ground station (since it's harder to actively cool it for low dark count, for example). But on balance I expect you will come out ahead. That said, on real world deep space missions, forward links are generally much slower than return links. This is because the slower you go, the better margin you have to close a link in adverse conditions (eg: mis-pointed spacecraft antenna for an RF link). Since you are completely screwed if you can't command the spacecraft, TT&C engineers will always go for a slower rate on the forward link for added Murphy insurance unless there's a pressing need to do otherwise.

by devsda 3y ago

daltont 3y ago

"cats have been dominating the airwaves from the beginning of broadcast video." Maybe the Kzinti will think we are long lost relatives after receiving them. (https://en.wikipedia.org/wiki/Kzin https://en.wikipedia.org/wiki/Kzin)

Sanzig 3y ago

All else being equal, you could conceivably push a higher data rate on the forward link. The apertures are the same size, just the transmit and receive apertures are reversed, so geometric losses would be exactly the same. However, you can get a much more powerful laser on the ground since you don't have to worry about the power and thermal constraints you have with the transmitter on the spacecraft. This advantage will be pared down somewhat as the spacecraft won't have as sensitive a detector as the ground station (since it's harder to actively cool it for low dark count, for example). But on balance I expect you will come out ahead. That said, on real world deep space missions, forward links are generally much slower than return links. This is because the slower you go, the better margin you have to close a link in adverse conditions (eg: mis-pointed spacecraft antenna for an RF link). Since you are completely screwed if you can't command the spacecraft, TT&C engineers will always go for a slower rate on the forward link for added Murphy insurance unless there's a pressing need to do otherwise.