# Voyager 1 passes another milestone: It's now 138AU from home

Voyager 1 has just ticked off another milestone: on Tuesday it reached 138 astronomical units from Earth, or about 20,600,000,000km from the planet on which you're (presumably!) reading this story. It's not an achievement that will be widely noticed or celebrated, because every kilometre it travels sets a new record for the …

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Always blows my mind.

2. #### Well light is rather slow

Even if you have a simple gigabit network cable in which the signals travel at roughly 2/3rds of light speed, you end up with many bits in flight even on the cable between your desktop and your switch.

If you had an analogue TV, you could sometimes get multipath reception. You could literally see signals just having a few kilometres more way to get to you.

1. #### Re: Well light is rather slow

I have one of Admiral Hopper's nanoseconds ... Just under a foot of solid-core bell wire.

2. #### Re: Well light is rather slow

Light speed, too slow?!

Yes, we're gonna have to go right to…ludicrous speed!

3. #### Re: Well light is rather slow

It's not too slow. Well, when mixed with acceleration and time dilation. The interesting thing about how it works out, is if you assume 1g constant acceleration, it takes about 30-60 years to reach ANY destination in the universe.

That is of cause assuming you have infinite fuel. Which is rather difficult. And a big shield to protect you while travelling at 0.9999999(9)% the speed of light. But even without the likes of cryogenics, time dilation takes care of the rest of the problems once your close enough to the speed of light.

Problem being, even if you leave now, you won't make it to that party at the other end of the galaxy in time!

PS, also it's funny calling it "too slow" as it is by *definition* "the fastest speed possible". :P

1. #### Re: Well light is rather slow

It's not too slow, it's not too fast, it just has speed 1.

1. #### Re: Well light is rather slow

"It's not too slow, it's not too fast, it just has speed 1."

So we're stuck in the first gear?!? Dang, no wonder we can't make it anywhere in any reasonable amount of time...

3. #### The good news is that all the instruments can be turned back on...

Once the upgrade to V'ger is complete!

4. Voyager 1 has just ticked off another milestone: on Tuesday it reached 138 astronomical units from Earth, or about 20,600,000,000km from the planet on which you're (presumably!) reading this story.

..and is probably still wondering whether it locked the front door before it left.

Way to go, l'il fella :)

5. #### Wonder When

Kirk bumps into it.....

1. #### Re: Wonder When

in 2273 according to Wikipedia:

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

1. #### Re: Wonder When

"Wonder when Kirk bumps into it....."

"in 2273 according to Wikipedia:

https://en.wikipedia.org/wiki/Timeline_of_Star_Trek"

<cough>

That'll be Voyager 6.

</cough>

6. #### What's that work out to?

We're only 8.0e-21% of the way across the Universe?

That's a mind-bogglingly small percentage of a mind-bogglingly large distance (my lizard-hindbrain-sans-slipstick math might be off a trifle, apologies).

You are here. More.

1. #### Re: What's that work out to?

Total Perspective Vortex anyone? :)

2. #### Re: What's that work out to?

We're only 8.0e-21% of the way across the Universe?

Less than that. About a third of it, in fact.

we think that the Universe is about 27 billion light years across

Except that the universe has been expanding at an increasing rate for 13.8bn years, so it's about 92bn light-years across by now. There's also some evidence that the rate of expansion may vary, slowing down a little, then speeding up before slowing down again, with a wavelength of (currently) about 2bn years. The universe may be ringing like a bell from the impact of the Big Bang.

1. #### Re: What's that work out to?

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams

1. #### Re: What's that work out to?

Vogons. El Reg must have one on the forums. Leave immediately if he starts to submit poetry.

1. #### Re: What's that work out to?

Putty. Putty. Putty.

Green Putty - Grutty Peen.

Grarmpitutty - Morning!

Pridsummer - Grorning Utty!

Discovery..... Oh.

Putty?..... Armpit?

Armpit..... Putty.

Not even a particularly

As I lick my armpit and shall agree,

That this putty is very well green.

2. #### Re: What's that work out to?

Vogons. El Reg must have one on the forums.

Well there's me. I used to work for Vogon International many years ago. I wrote data recovery/forensic software for them. Also did a few data recoveries. Oddly enough I happen to be wearing one of the T-shirts they gave us today.

Lol! Their old website (or parts of it) are still around :)

2. #### Re: What's that work out to?

I'm not sure the "rate of expansion" effects that observation. Because the light is also travelling through the expansion as it moves, thus being red shifted accordingly etc. For example " Light that is emitted today from galaxies beyond the cosmological event horizon, about 5 gigaparsecs or 16 billion light-years, will never reach us, although we can still see the light that these galaxies emitted in the past"

It's hard to define objects we can only see the past of, and not even the present. Are they even "in our universe" anymore? Or have they ceased to exist? Thus leaving the "edge of the universe" still at the 14-16~billion light years?

Ah, found the details, it's about 46 light years across "now". https://phys.org/news/2015-10-big-universe.html

However I'd still argue that due to relativity etc we can say that it is now 14 billion across, and once the other light reaches us we could describe it as 46 light years across... at which point it would have expanded even more! ;)

1. #### Re: What's that work out to?

Ah, found the details, it's about 46 light years across "now". https://phys.org/news/2015-10-big-universe.html

I'm afraid you mis-read that. That article correctly says 46bn ly to the edge, so 92bn ly across, as I first said.

3. #### Re: What's that work out to?

"Just remember that you're standing on a planet that's evolving

And revolving at nine hundred miles an hour"......

Galaxy Song

7. #### Middle Age

Couldn't recall how old these were, so checked:

The Voyager spacecraft launched in August and September of 1977 and spent more than 11 years exploring the likes of Jupiter, Saturn, Uranus and Neptune before officially heading off toward interstellar space in 1989.

Not bad for forty year old hardware.

1. #### Re: Middle Age

High-end PC of the era. Mine still works :-)

2. #### Re: Middle Age

"Not bad for forty year old hardware."

a) ruggedized for space

b) uses LEADED solder [no tin whiskers]

c) NUCLEAR powered

all that helps. just sayin'.

and as you get further from Mr. Sun, all of that cosmic radiation isn't affecting your gear as much any more.

1. #### Re: Middle Age

Yeah, it's getting away from Mr Sun and all his radiation. But it's also getting away from Mr Sun's protective magnetic field, so it's getting hit by interstellar radiation instead. Which, by definition, creates an even more interesting class of mutated superhero.

It's also a bit worrying that I'm older than these spacecraft, even though they've travelled an unimaginably long way, although admittedly not so unimagineably long as to have actually got anywhere yet.

The universe really is quite spacious.

Does anyone fancy a piece of fairy cake...

2. #### Re: Middle Age

a) ruggedized for space

b) uses LEADED solder [no tin whiskers]

c) NUCLEAR powered

d) Doesn't run millions of lines of code

1. #### Re: Middle Age

a) ruggedized for space

b) uses LEADED solder [no tin whiskers]

c) NUCLEAR powered

d) Doesn't run millions of lines of code

e) Written by real programmers

1. #### Re: Middle Age

f) Managed to avoid the Windows 10 update.

8. "27 billion light years across, but we're just 19 light hours into it"

Imagine that.

"Are we there yet" for 27 BILLION YEARS ahead of you, and you're barely 19 HOURS into the journey. No saying that Voyager would ever make it even a fraction of that far, but it provides context.

1. It's the same as getting in to your car, and your wife asking you if you're there yet and you answer "Love, I've only just put the key in the ignition".

1. Is that a euphemism?

1. "Is that a euphemism?"

Alas no, I asked her to go dogging with me once. She didn't much care for it.

1. Did you try (carefully) explaining that it does not, in fact, involve dogs?

2. "Are we there yet" for 27 BILLION YEARS ahead of you, and you're barely 19 HOURS into the journey

...

Yeah, but are we there yet?

...

...

I need the toilet.

Yes it's urgent.

No I can't hold on.

9. #### Not sure what they used...

...but commercially available processors during the development period for V'ger would have included: the Zilog Z80, Intel 8080 and Motorola 6800. The MOS 6502 would have been too late to the game to be included... ahh nostalgia.

1. #### Re: Not sure what they used...

There's likely to be a version of Elite that Voyager could keep itself entertained with.

2. #### Re: Not sure what they used...

From Nasa's Voyager mission FAQ found here:

"Question: What kind of computers are used on the Voyager spacecraft?

Answer: There are three different computer types on the Voyager spacecraft and there are two of each kind. Total number of words among the six computers is about 32K.

Computer Command System (CCS) - 18-bit word, interrupt type processors (2) with 4096 words each of plated wire, non-volatile memory.

Flight Data System (FDS) - 16-bit word machine (2) with modular memories and 8198 words each

Attitude and Articulation Control System (AACS) - 18-bit word machines (2) with 4096 words each.

According to my calulations, that's a total of about 68KB, or small potatoes compared to today's microprocessors. We probably could perform all functions with one of today's boards and still have room for solid state data storage and much more fault detection software. We would still need a second unit for redundancy. Today's microprocessors are also much faster than the chips used on Voyager and a comparative system would use less electrical power. On the other hand, software might be more complicated as opposed to that used in an interrupt type system, but it would be much more capable and more flexible.

Let's look closer at the CCS. The CCS has two main functions: to carry out instructions from the ground to operate the spacecraft, and to be alert for a problem or malfunction and respond to it. Two identical 4096- word memories contain both fixed routines (about 2800 words) and a variable section (about 1290 words) for changing science sequences. The CCS issues commands to the AACS for movement of the scan platform or spacecraft maneuvers; to the FDS for changes in instrument configurations or telemetry rates and to numerous other subsystems within the spacecraft for specific actions. Fault-protection algorithms are also stored in the CCS, occupying roughly 10 percent of the CCS memory.

The main functions of the FDS are to collect data from, and controls the operations of, the scientific instruments; and to format engineering and science data for on-board storage and/or real-time transmission. The FDS also keeps the spacecraft "time" and provides frequency references to the instruments and other spacecraft subsystems.

The Voyager spacecraft computers are interrupt driven computer, similar to processors used in general purpose computers with a few special instructions for increased efficiency. The programming is a form of assembly language.

There is no clock chip, as such, in the spacecraft. The "clock" is really a counter, based on one of several electronically generated frequencies. These frequencies, based on a reference, generated by a very stable oscillator, are converted and fed to different locations in the spacecraft as synchronization signals, timers, counters, etc. The "clock" signal is part of the information telemetered to the ground and it is with ground software that we convert to day of year, time of day Greenwich Mean Time.

Voyager was built in-house at JPL; the computers were manufactured by General Electric to JPL specifications.

Question: How fast are the Voyager computers?

Answer:Not very fast compared to today’s standards. The master clock runs at 4 MHz but the CPU’s clock runs at only 250 KHz. A typical instruction takes 80 microseconds, that is about 8,000 instructions per second. To put this in perspective, a 2013 top-of-the-line smartphone runs at 1.5 GHz with four or more processors yielding over 14 billion instructions per second.

1. #### Re: Not sure what they used...

"We probably could perform all functions with one of today's boards and still have room for solid state data storage and much more fault detection software."

Or maybe not. You'd have to fit it round all the bloat of modern software & firmware.

3. #### Re: Not sure what they used...

I don't believe they used COTS microprocessors at all, instead they had custom-designed 18-bit serial processors, which may have used things like the TI 7400.

1. #### Re: Not sure what they used...

I went back and looked it up:

https://en.wikipedia.org/wiki/74181

I'd guess they used something _like_ this, to build the CPUs, hardened for space of course.

2. #### Re: Not sure what they used...

The standard reference for old NASA space computers is

Computers In Spaceflight: The NASA Experience where you'll find out all sorts of quite detailed stuff about how NASA built and ran those missions, right back to the days when the state of the are was a "cam timer," essentially the device used in old washing machines.

Interesting points.

TTL has a rep for being power hungry, but it wasn't too bad if you kept the clock frequency down. The standard 16 and 18 pin packages used made the packing density quite good (for the time). Today we'd go surface mount and increase it 4x at a stroke.

Quite a few of these processors were bit serial, with "word length" set by width of registers (which might also be serial, being a string of ultrasound pulses in a delay line memory).

The availability of a 4 bit ALU (LS74181 and it's CMOS equivalent) made new processors easier, if you could take the clock speed limits and you can operate in chunks of 4 bits, which was OK for a lot of people.

When you control the hardware if it''s not fast enough not only can you hack the code, you can hack the instruction set as well. :-)

Then you hack the assembler to support the new instructions (no HLL, no YACC or Lex to write one)

From that era it seems only the RCA 1802 was available early enough and rugged enough for space use. It's sort of like the SPARC, a big register set and on chip DMA, DMA is very handy for space probes.

A very different world.

Today you hand BAe Systems \$150K for a rad hard POWERPC board instead.

3. #### Re: Not sure what they used...

"which may have used things like the TI 7400"

4. #### Re: Not sure what they used...

I don't know that any off the shelf commercial CPUs of the time would be sufficiently hardened against radiation damage.

1. #### Re: Not sure what they used...

While "off the shelf commercial CPUs" might not be ok there were (outdoutably vastly more expensive) versions made that were rad-hard .... e.g. New Horizons has a MIPS processsor

As for the comms over that distance ... I did a course on error correcring codes in my maths degeree and teh lecturer talked about the level of error correction they had to use on Voyager and how he was amazed that they could actually communicate with it over that distance ... n.b. this was in 1984 when Voyager was between Saturn and Uranus!

1. #### Re: Not sure what they used...

My mate told me (so it must be true) that they used Hamming codes which could correct for 7 incorrect bits in 8, requiring 256 bits to be sent for each 8 bits of final data.

1. #### Re: Not sure what they used...

Yes, think was some extreme hamming code ... also I seem to remember a few years ago they switched from the ECC they had been usign to something even more extreme more extreme to ensure comms could be performed at the cost of reduced bandwidth

2. #### Re: Not sure what they used...

I think the only rad-hard CPU around at the time was the RCA 1802:

https://en.wikipedia.org/wiki/RCA_1802

A completely static design with no minimum clock frequency and you could use any register for the program counter.

The Z80 wouldn't have been released in time for this mission and certainly wasn't rad-hard.

Edit: I've just read the Wiki page and even the 1802 wasn't around in time for the Voyager. Also read:

http://www.retrotechnology.com/memship/1802_spacecraft.html

1. #### Re: RCA_1802

Shame. My first computer had one of those. An Elf II, with 256 bytes of RAM programmed via a hex pad and no ROM. Assembly code would have been a luxury. Circa 1978.

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