The latest episode of the Off-Nominal podcast[1] had a great interview with Shannon Stirone[2] all about DSN. They go into just how critical the infrastructure is, how little support it gets, and just the insane level of planning required for any planetary mission. Definitely worth a listen. See also Stirone's longread[3] about the DSN.
The thing I find really impressive is how weak the signals are.
From that page, the downlink from New Horizons is currently 1.89kbps at -143.72 dBm (4.25 x 10-21 kW). That's 0.00000000000000000425 W. Not a lot of signal to work with there, but the DSN is still able to extract a usable carrier. Amazing.
Apparently the signals from Voyager have a "received power 20 billion times weaker than that of a digital wristwatch."[0]
The DSN website is a really good read. Along with supercooling the amplifiers they also use "special techniques to encode signals so the receiving system can distinguish the signal from the unwanted noise."
The capability to dig such a weak signal out of the noise is, indeed, a remarkable feat. I also think the ability to orient the spacecraft to point the antenna at where the earth is from a distance of a couple billion miles is pretty amazing. Obviously, a signal is going to spread a great deal over those distances but its still important to be close. I'd be curious to know how far off the pointing is from Voyager distance from boresight.
Actually, thinking about this, I made a mistake. Voyager isn't pointing its antenna at earth at that instant. It's actually pointing it to where the earth WILL be in 16 to 20 hours. Technically, that is probably no more difficult but my statement is more accurate.
From the distance of Voyager, I doubt it makes any difference where Earth is for pointing the antenna. As in, it is pointing to the same spot no matter the day or season. They probably dial in an inertial coordinate and that is it.
The difficulty of communicating from deep space spurred the development of error correcting codes. In particular, Concatenated codes [1] were developed for the Voyager program in 1977.
Cooling the LNAs on the earth station? Yes. I doubt the LNA on Voyager is actively cooled.
I wonder if any feed components (prior to LNA) on the earth station are cooled? [1] does not indicate.
Read a paper recently on converting an old NASA earth station with beam waveguide over to a wideband feed. They had to put a rigid waveguide horn on place of the waveguide and actively cool it.
I'm about 15 mins into the first video, and I want to buy the camera guy a new taller tripod. I feel like I am a small child having to look up at the speaker.
Getting past that, it's a cool interview. Thanks for these links.
Recently I read a wonderful review paper about some of the problems engineers faced with early space communication.
It's really amazing how fast things moved back then. From 1954 to 1962 they went from using the moon as a relay satellite to having Telstar in orbit, which was capable of live trans-atlantic TV broadcasts.
What is the reason that "Wind Speed" is tracked and provided on this website. What does wind speed interact with communication between these antennas and the spacecraft?
It's hard to point a big dish accurately if the wind is too strong. They have wind limits above which they stow the dishes (by pointing them straight up to reduce the wind profile).
1: http://offnominal.space/10
2: https://twitter.com/shannonmstirone
3: https://longreads.com/2018/03/15/welcome-to-the-center-of-th...