The 3.7 m dish antenna of Voyager - Page 1
Forum section: electronics / rf-microwave

author: prabhatkarpe4
author_rank: Contributor
timestamp: September 08, 2024, 12:40:28 pm
content: I need to know how Voyager-I was able to communicate with the base station on earth using the 3.7m dish antenna? Usually any dish antenna needs to be pointed towards the receiver and Voyager must be in random direction.

author: Andy Chee
author_rank: Super Contributor
timestamp: September 08, 2024, 01:11:38 pm
content: As of today, Voyager still has just enough electricity for dish pointing, so not random direction.But power is definitely low, and is expected to run out after 2025.

author: BrokenYugo
author_rank: Super Contributor
timestamp: September 08, 2024, 02:24:29 pm
content: IIRC they use two big dishes, one right on target, one slightly off, because both receive about the same noise the data can be picked out by looking at the difference between the two signals. Bitrate is also kept very low, google seems to indicate they run no more than 160bps.

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 08, 2024, 03:41:03 pm
content: https://eyes.nasa.gov/dsn/dsn.htmlAt the moment 40 bits/second, signal strength -160 dBmThis may interest you too:

author: joeqsmith
author_rank: Super Contributor
timestamp: September 13, 2024, 05:00:20 pm
content: This could be total BS. As we age, these memories become faint.I thought maybe in the 80s that Texas Instruments collaborated with Toshiba (or some other Japanese company) to develop new receivers based on quantum well technology to get the sensitivity they needed to push the spacecraft out further.Again, could be a total memory failure on my part. It seems that I had read about it in EDN or some other trade magazine.

author: KE5FX
author_rank: Super Contributor
timestamp: September 13, 2024, 06:54:58 pm
content: Thinking of ruby masers, maybe?

author: joeqsmith
author_rank: Super Contributor
timestamp: September 13, 2024, 07:50:12 pm
content: I don't think so. At the time it seems there was a lot being published about how the quantum well transistor was going to change the world. Giving us better CCD imaging, higher density storage, LASER density that we could tune the frequency, and super sensitive transistors that we could buy from Radio Shack within 10 years.... Seems they talked about the entire library of congress fitting into a walnut sized storage device. They wanted to push the probes out and seemed they were at the limit of what the current technology could offer. I think this was the first paper I had read where the technology had been developed for actual use.Again, based on total memory and the shriveled up brain doesn't function like it used to.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 13, 2024, 11:15:22 pm
content: Searching the internet, I came up with nothing.Before the internet and Google, I would save interesting articles. This binder is about 2" thick of nothing but clippings, newest to oldest. Top article is dated 1991 dating back to the early 80s.I found several articles on quantum well transistors. Including the one talking about storing the entire library of congress. The last image 6 talks about GE making the quantum sensors for the NASA Voyager. So not TI, not the receivers, no involvement with Toshiba. But hey, one sentence from an article I read several decades ago, a few cylinders are still firing.

author: KE5FX
author_rank: Super Contributor
timestamp: September 14, 2024, 12:27:58 am
content: That is fascinating. Tunnel diodes had a real cult following for a while, composed of true believers who swore they would dominate the market one day. The 'quantum well transistor' sounds like something the tunnel-diode cult might have pivoted to fixate upon before dying out altogether (or moving on to memristors, I guess.)

author: Andy Chee
author_rank: Super Contributor
timestamp: September 14, 2024, 03:52:10 am
content: Quote from: joeqsmith on September 13, 2024, 05:00:20 pmVoyager was launched in '77, so are you talking about the ground station receivers?

author: joeqsmith
author_rank: Super Contributor
timestamp: September 14, 2024, 09:41:52 pm
content: Quote from: Andy Chee on September 14, 2024, 03:52:10 am

author: coppercone2
author_rank: Super Contributor
timestamp: September 15, 2024, 02:20:23 am
content: I thought they used high Q maser preselectors essentially so they can get more gainIt says most ruby masers have a narrow bandwidth,usually under 50MHz when they operate in the multi GHz band. One maser ( RWM) says it has a bandwidth of 300MHz, but it does operate in the Ku band. They appear to give around 20-50 dB gain

author: coppercone2
author_rank: Super Contributor
timestamp: September 15, 2024, 02:35:00 am
content: It looks like basically anything needed to replace that maser has a priority of being low noise, with a second priority of being a preselector and to have low IMD. I am guessing that 'in band' the voyager itself is still the most powerful signal by miles. I wonder how low a noise temperature you would need before the problem becomes discriminating the signal from in-band interference.. it seems like its down to luck of what is infront of voyager.If I am understanding it, the DSN relay has a 80 meter antenna reflector (diameter) that it uses to communicate with voyager at a low microwave frequency.you could probobly send out more relays to boost the signal behind voyager if you don't wait too long............The Voyager mission plans were for the two spacecraft to encounter Saturnin November 1980 and in August 1981, and for Voyager 2 to encounter Uranusin January 1986 and Neptune in August 1989. The distances from Earth wouldbe 10 A.U. at Saturn, 19 A.U. at Uranus, and 30 A.U. at Neptune. The115,200 bps data rate at a 5 A.U. from Jupiter translates into data rates of about28,800 bps from Saturn, 8000 bps from Uranus, and 3200 bps from Neptunedue to the square-of-the-distance penalty. Many enhancements were needed andimplemented to enable the data rates of 44,800 bps from Saturn, 29,900 bpsfrom Uranus, and 21,600 bps from Neptune that were achieved. One of theenhancements was a reduction in the system operating noise temperature of theDSN 64-m, and later 70-m, antennas. The Block II X-band masers weredeveloped between 1976 and 1980 to contribute to this noise reduction.In 1980 D. L. Trowbridge reported, “Four X-band traveling-wave maser(TWM) systems with effective input noise temperatures of 3.5 K andbandwidths varying from 65 to 108 MHz have been supplied to the Deep SpaceNetwork . These TWMs are used on the 64-m antennas at Deep SpaceStations 14, 43, and 63 at 8420 MHz to meet the requirements of the VoyagerSaturn encounter. The TWMs use shortened and cooled signal input waveguideto reduce noise and are equipped with superconducting magnets and solid statepump sources to provide the required stability performance.”https://descanso.jpl.nasa.gov/monograph/series10/03_Reid_chapt3.pdfI think that the next step would be to build a orbital deep space antenna satellite, send it out near jupiter, and then you can track voyager for way longer at higher bitrate. I don't know if we actually have deep space relays yet, the deep space network is terrestrial despite its namehttps://descanso.jpl.nasa.gov/monograph/series4/Mono4_Ch10.pdfhttps://en.wikipedia.org/wiki/Square_Kilometre_ArraySo I guess if you think about it, voyager with its proximity to us, is still pretty damn strong, compared to distant stars (light years), as weak as its little transmitter is, on a cosmic scale it has not gotten out of bed yet

author: Andy Chee
author_rank: Super Contributor
timestamp: September 15, 2024, 03:16:20 am
content: Quote from: coppercone2 on September 15, 2024, 02:35:00 amIt's already too late. Voyager is due to run out of power in the next few years. It would take that long just for a relay station to arrive in position, let alone design a relay station and organise a suitable launch window.That said, several Mars orbiters have the capability of acting as a relay for the surface rovers. And the surface rovers also have the capability to communicate directly with earth.

author: coppercone2
author_rank: Super Contributor
timestamp: September 15, 2024, 03:24:47 am
content: Quote from: Andy Chee on September 15, 2024, 03:16:20 amthats just faith in life time models :p

author: Andy Chee
author_rank: Super Contributor
timestamp: September 15, 2024, 04:16:39 am
content: Quote from: coppercone2 on September 15, 2024, 03:24:47 amWhat would make better sense is to launch a probe to Uranus, where it can do scientific study of the Uranian system, AND act as a potential relay for deep space probes.

author: coppercone2
author_rank: Super Contributor
timestamp: September 15, 2024, 04:21:21 am
content: its annoying that you need to piggy back things to con politicians rather then missions specific projects. every space project is like a over loaded pack horsei wonder if you could have sold a VCR with a bottle opener on it in the 80's" im gonna change the tape "they should have put a bottle of wine on voyager there would already be a recovery mission planned for 2035

author: Andy Chee
author_rank: Super Contributor
timestamp: September 15, 2024, 06:34:06 am
content: Quote from: coppercone2 on September 15, 2024, 04:21:21 amwell they did include a phonograph stylus for aliens to playback the golden record, does that count?

author: JimboJack
author_rank: Regular Contributor
timestamp: September 15, 2024, 10:20:02 pm
content: electrical power is split between the anything left of instruments of and keep the pointy directional fuel warm from freezeing up and that is using more and moreA documentary on the Voyager team, is like the movie office space, they keep moving further and further away, from HQ, there operational place, was next to a fast food chain, down town some were looked like a motel, the lead in charge is the grad that started on the project, everyone else has since long gone.

author: coppercone2
author_rank: Super Contributor
timestamp: September 18, 2024, 02:10:01 am
content: i wonder if they took away some handy old HP power supply with red knobs too because its not regulation

author: tatel
author_rank: Frequent Contributor
timestamp: September 18, 2024, 05:49:54 am
content: Don't know if what is said on this YT video is accurate but here's the link. It speaks about -among other things- communications. It seems that antenna is still oriented towards the Earth

author: radiolistener
author_rank: Super Contributor
timestamp: September 18, 2024, 08:00:35 am
content: It is possible because Earth antenna is very large and has high gain due to high directivity.Some years ago I done some calc about it and if I remember correctly, the free space signal attenuation is about 220 dB.