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I remember a recent article on HN about being able to receive signals from Tianwen-1 with a homemade satellite dish - is it possible to receive these pictures o

I remember a recent article on HN about being able to receive signals from Tianwen-1 with a homemade satellite dish - is it possible to receive these pictures over radio with the right equipment, or do they come down encrypted?

soheil 6y ago
I would think encryption would slow down the transmission rate. So most likely are sent in the clear
- hackeraccount 6y ago
  I'm not saying they are encrypted but I thought that encryption is a close cousin to compression - that it generally doesn't add overhead.
ddevault 6y ago
If I recall correctly, the Tianwen-1 amateur signal reception was (1) shortly after launch, and (2) using a 20 meter dish. Receiving the downlink from a deep space object requires much more sophisticated technology than most amateurs have access to, both to track the object, and to listen hard enough. That being said, I doubt that the transmissions are encrypted. Hell, I bet some amateurs with a very powerful transmitter might be able to transmit a software update and take control of the rover. https://xkcd.com/1337/ https://xkcd.com/1337/
azernik 6y ago
Data comes from Perseverance through two channels: * A low-bandwidth direct link to Earth (160bps-800bps depending on receiver dish- no, that's not a typo) * A high-bandwidth link to orbiting satellites, which then forward traffic to Earth (~2Mbps for the rover->orbit hop, anywhere from 0.5-4Mbps for the orbit->Earth) . I strongly suspect that the low-bandwidth telemetry signals - equivalent to the homemade reception from satellites I've heard of - are sent in the clear. Bandwidth is just too precious to waste. I would not be surprised either way for the image data - on the one hand, computing power is relatively scarce, while on the other hand it already has to go through a compression pipeline. https://mars.nasa.gov/msl/spacecraft/rover/communication/ https://mars.nasa.gov/msl/spacecraft/rover/communication/

soheil 6y ago

I would think encryption would slow down the transmission rate. So most likely are sent in the clear

hackeraccount 6y ago
I'm not saying they are encrypted but I thought that encryption is a close cousin to compression - that it generally doesn't add overhead.

ddevault 6y ago

If I recall correctly, the Tianwen-1 amateur signal reception was (1) shortly after launch, and (2) using a 20 meter dish. Receiving the downlink from a deep space object requires much more sophisticated technology than most amateurs have access to, both to track the object, and to listen hard enough. That being said, I doubt that the transmissions are encrypted. Hell, I bet some amateurs with a very powerful transmitter might be able to transmit a software update and take control of the rover. https://xkcd.com/1337/ https://xkcd.com/1337/

azernik 6y ago

Data comes from Perseverance through two channels: * A low-bandwidth direct link to Earth (160bps-800bps depending on receiver dish- no, that's not a typo) * A high-bandwidth link to orbiting satellites, which then forward traffic to Earth (~2Mbps for the rover->orbit hop, anywhere from 0.5-4Mbps for the orbit->Earth) . I strongly suspect that the low-bandwidth telemetry signals - equivalent to the homemade reception from satellites I've heard of - are sent in the clear. Bandwidth is just too precious to waste. I would not be surprised either way for the image data - on the one hand, computing power is relatively scarce, while on the other hand it already has to go through a compression pipeline. https://mars.nasa.gov/msl/spacecraft/rover/communication/ https://mars.nasa.gov/msl/spacecraft/rover/communication/