Comments by "H. de Jong" (@h.dejong2531) on "" video.

  1. Parkes was used back then (and is still used these days occasionally) to provide more coverage for important events. When Buzz Aldrin switched on the TV camera on the Lunar Module, three antennas received the signals simultaneously: the 64-metre Goldstone antenna in California, the 26-metre antenna at DSN Canberra, and the 64-metre dish at Parkes. Since they started the spacewalk early, the Moon was only just above the horizon and below the visibility of the main Parkes receiver. Although they were able to pick up a quality signal from the off axis receiver, the international broadcast alternated between signals from Goldstone and Honeysuckle Creek, the latter of which ultimately broadcast Neil Armstrong's first steps on the Moon worldwide.
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  2. A dish antenna concentrates all of the signal into a single receiver. An ESA has lots of receivers that each get a small portion of the signal. That means the signal-to-noise ratio of an ESA is a lot lower. With the weak signals the DSN works with (down to -170 dBm) you need all the S/N you can get. There's also a practical problem: DSN receivers are cooled to 4K. It's a lot easier to do that with one large receiver than with hundreds spread over the antenna surface.
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  3. That depends on the spacecraft. Normal operations use a 20 kW transmitter, with 20 kW rarely being necessary. But Canberra also has a 400 kW transmitter, which is used to transmit to Voyager 2 at 75 kW to compensate for Voyager 2's receiver, which isn't working correctly.
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  4. JPL estimates they can keep in contact with Voyager 2 until 2050, which would put it at 250 AU. That's for 40 bps, and a single 34-m HEF antenna. Arraying more antennas would increase the range a lot (they're doing 1400 bit/s with an array of 3x34 m and 1x 70 m now, when a single 34 m antenna gets 160 bit/s), and they could even use the VLA to increase it further.
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  5. 8:40 'Hundreds' of AU? The Voyagers are at 120 and 150 AU, I dunno if that can be called 'hundreds'. 13:40 I think DSS 14 at Goldstone is the only DSN antenna with a radar transmitter.
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  6. Missing word, maybe? first and only commercial DS antenna?
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  7. As far as I know, Arecibo has never been used to communicate with spacecraft - because Arecibo wasn't steerable, a spacecraft would quickly move out of view.
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  8. No. 150 AU is 1 light day, or 1/1200 the distance to the nearest star.
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  9. It's mostly sufficient because most missions are near enough the ecliptic that these 3 stations can see them. There are a few exceptions: Voyager 2 is so far south of the ecliptic that Canberra is the only station that can see it, so we have only 8 h/day coverage for Voyager 2. Most missions can store data onboard so they don't need continuous coverage anyway: most missions have one downlink session per day. Voyager 2 can't store data on board any more, so we're losing data from it. But the region it's in only changes slowly, so we can get away with that.
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  10. it's called DSN Now.
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  11. That solves one problem (spacecraft being masked by the Sun on occasion), but it makes the antennas a lot more expensive for little gain. The DSN will probably switch to laser comms for new missions, that does require receivers in space, but they'll probably be placed in Earth orbit.
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  12. Setting up a comms relay on the moon is pretty pointless. It makes the process much harder and more expensive for little benefit. The first commercial deep space communications stations are already operational: Goonhilly in the UK is one. I expect most commercial operators will use laser comms, for which a satellite in Earth orbit may be beneficial.
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  13. A new 34-meter antenna on the ground costs about $100M. A satellite with an antenna that large would be a lot more expensive, for little gain. (Literally: the extra gain you get from moving the antenna from the ground to Earth orbit is a tiny amount). A dish antenna concentrates all of the signal into a single receiver. A phased array has lots of receivers that each get a small portion of the signal. That means the signal-to-noise ratio of a phased array is a lot lower. With the weak signals the DSN works with (down to -170 dBm) you need all the S/N you can get. DSN receivers are cooled to 4K, that's not achievable with passive cooling in Earth orbit.
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  14.  @Seantmalone42  JPL has written a series of reports called 'DESCANSO' that gives a lot of detail on this.
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  15.  @Seantmalone42  A signal from Alpha Centauri will be 1 million times weaker than one from Voyager. So you need 1 million times the collection area of a 34 m dish...
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  16. A new 34-meter antenna on the ground costs about $100M. A satellite with an antenna that large would be a lot more expensive, for little gain. (Literally: the extra gain you get from moving the antenna from the ground to Earth orbit is a tiny amount).
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  17.  @DrDeuteron  Power, mainly. Most antennas on the DSN have 20 kW transmitter. DSS 14 has a 500 kW transmitter.
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  18. It's not necessary for the Voyagers (if they didn't run out of power, we'd still be able to reach them in 2050). For new missions at much larger distances, a relay might be useful, but it'd be expensive: you'd need to launch a giant antenna with a large power source. The DSN uses 70 m antennas and up to 20 kW of transmitter power (that's 50 x more power than the Voyagers had at launch). The relay would have to be in deep space itself, so you're launching a multi-ton spacecraft on a Voyager-like trajectory (compared to the Voyagers which weighed ~800 kg at launch). You'd also need a relay for each mission because a relay halfway between us and Voyager 1 would be useless for Voyager 2. It's easier and cheaper to just build better antennas on Earth: a 34 m antenna costs $100M, a deep-space antenna would cost billions.
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  19. As far as I know, Arecibo has never been used to communicate with spacecraft - because Arecibo wasn't steerable, a spacecraft would quickly move out of view.
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  20. You can do the same with WiFi. I've got a USB Wifi module with external antennas, you can get those in various sizes with the larger ones having more gain. I use these when camping - where my computer's built-in Wifi doesn't find a signal, I can connect easily using the external antenna. - I've made connections at more than 100 meters from the nearest access point.
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  21. For more detail on what goes on at a DSN station, this 3-part series is very informative: https://www.youtube.com/watch?v=FzRP1qdwPKw https://www.youtube.com/watch?v=1rCrfQUcXDI https://www.youtube.com/watch?v=sP_hleOXTaU
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  22. It's called DSN Now.
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