Voyager 2 Contact

[EEVblog]

[Bud]

Thanks God of the Deep Space that the locked loops were not designed by Rigol.

[EEVblog]

All the tech details on the communications!
https://descanso.jpl.nasa.gov/DPSummary/Descanso4--Voyager_new.pdf

[Domagoj T]

You'll have to make a video on noise temperature.
I tried reading the wiki, but got lost on the second sentence

[Richard Head]

Best video yet. Excellent job. Video work was also pretty good considering it was you just pointing and shooting.
Thanks.

[madires]

A big thumbs up!

[FunkyLoiso]

"This account has been terminated due to multiple or severe violations of YouTube's policy against spam, deceptive practices, and misleading content or other Terms of Service violations."

[PA0PBZ]

"This account has been terminated due to multiple or severe violations of YouTube's policy against spam, deceptive practices, and misleading content or other Terms of Service violations."

Yep, seems you can't just shamelessly copy content from the eevblog channel 

[TheSteve]

"This account has been terminated due to multiple or severe violations of YouTube's policy against spam, deceptive practices, and misleading content or other Terms of Service violations."

Indeed, it seems to be MIA. Perhaps they didn't like seeing the same video uploaded(station tour) that was already on another channel.

[firewalker]

The control room on JPL is fancier.



Alexander.

[ekeppel]

It's a shame that both attempts at getting this channel going have failed thus far. 

Could this be due to some automatic YouTube algorithm getting triggered, or is this sort of thing only caused by multiple users flagging a channel? 

Maybe someone has it out for Dave, and controls an army of YouTube channel flagging bots.   

[mgscheue]

Disappointing. I'm teaching astronomy and pointed my students to it. A few saw it before it got shut down, but most of them hadn't. I hope that whatever YouTube managed to screw up, it gets fixed soon.

[madires]

The channel seems to be restored. I can access it without any problems.

[Brumby]

Yes, it's back.

... and even Dave doesn't know why there was a problem.

[rrinker]

 My guess is even YouTube doesn't know why there was a problem.

[josecamoessilva]

A simple explanation is that many of the people making decisions at YouTube can't tell their glutes from a hole in the ground.

An engineering explanation is that they're doing adaptive control on their content management system but changing the parametrization of the feedback controller with a frequency too close to the dominant frequency of the outside drivers of the controlled system. As we know, this leads to all sorts of chaotic behaviors, instability and strange attractors.

No. I think it's more likely that many of the people at YouTube don't know what they're doing. 

[vbalazs]

Bigger telescope

[Beamin]

How did I miss this video!?

So if the signal is 30 hours behind and by that time the earth has spun around, do they take the dish and aim it where voyage would be in 30 hours or at that distance is the voyager antenna sensitive enough that it doesn't matter? Be a very long, long distance phone call just to say "may I ask who is calling?"


If they don't track it do they lose its position forever?

[SeanB]

They aim where it will be, and from the Voyager side aiming at the brightest thing in the sky, the Sun, is enough with even the most narrow of beams the antenna on the craft can produce.  Transmitting from Earth they wind the power up to the highest they can get, because the receiver there is not as sensitive as the cryocooled HEMT receiver back here, which is not a 40 year old design, based on the absolute lowest noise bipolar transistors they hand selected from a massive batch back then, and soldered in place carefully.

Because the receiver has drift issues they also send on a large selection of frequencies so the recovered control signals are decoded correctly, bit difficult to send out somebody there to replace the failed capacitor in the working receiver.

[EEVblog]

Best video yet. Excellent job. Video work was also pretty good considering it was you just pointing and shooting.

Point and shoot, run and gun. In these kinds of shoots you have to "get what you get" whilst on the move to a deadline.

[EEVblog]

How did I miss this video!?

There are several other videos in the series too.

If they don't track it do they lose its position forever?

No, they have an accurate model of exactly were it is at any given time.

[Beamin]

How did they know it had a bad cap? Or were they reading the youtube comments where every arm chair expert tells you to replace the caps when fixing electronics or "OMG you can't leave those old caps in circuit!", when it's clearly not the caps or the person obviously knows that like checking the fuse. 

[Brumby]

How did they know it had a bad cap?

You need to be more critical in your reading.  Nobody said it had a bad cap.  What was said is that the receiver has drift issues.  Considering the time it's been out there, that's a pretty amazing problem.

Determining that the receiver is suffering from drift will be one of the very many procedures they will have developed over the years in dealing with the challenges of communication at such distances.

For example: A command is sent and no response is received after an appropriate amount of time.  The command is repeated a couple of times with the same lack of a response.  There will be several possible faults that could cause this and they will all be considered and a plan will be made of what evaluation and/or corrective measures can be performed.  These will be prioritised and worked through with consideration as to what risks each option entail.

One of these faults will be receiver drift and the test would be to send commands at different frequencies and see if there is a response.

There is no magic involved here - just a lot of thought by engineers with a lot of experience and knowledge.

[rrinker]

  A LOT of skill, thought, and experience. Voyager has to rank up there with the top engineering achievements of all time - the fact that it functions at all after all this time in the harsh environment of space is testament to the quality of both the design and construction of the spacecraft.

[GregDunn]

https://en.wikipedia.org/wiki/Voyager_2

Since early days, the probe has been operating on its backup receiver; the primary blew its power fuse for uncertain reasons.  JPL does not send multiple frequencies, they actually calculate the shift based on probe temperature and some other parameters they observed during the pre-encounter phase.  Even firing the maneuvering thrusters or switching on/off another instrument causes a known shift in the receiver frequency and a specific settling time.

As for the issue itself, JPL engineers modeled the issue locally and came to the conclusion that the fault is a defective capacitor in the receiver frequency tracking feedback loop.  That matched the observed characteristics of the receiver and has allowed them to hit the receiver's center frequency essentially every time since the first encounters.