NASA - Voyager 1 and 2 updates

[catdlr]

calex

calex,
It hasn't been mentioned before, but welcome to the forum, and thanks for the excellent contribution. Feel free to introduce yourself in this thread:

https://forum.nasaspaceflight.com/index.php?topic=606.0


Tony

[Targeteer]

A poster on X is speculating something is wrong with Voyager 1 because recent coverage by DSN has shown no receipt of signals.  3 terminals at Canberra, including the 70m are currently tasked to Voyager 1 but there is no signal being received...

[Targeteer]

Still no signal being received...  https://twitter.com/vlex26/status/1849618522823065655

[Lee Jay]

DSS 14 from Goldstone is on Voyager 1, no signals coming in.  I'm concerned too.

[Targeteer]

I found the poster I mentioned above.  https://twitter.com/Bernard1963/status/1849515784617299972

[MickQ]

Currently no one is looking at Voyager 1.  Canberra is rx’ing Voyager 2.

[sanfordshazam]

Canberra big dish is seen doing Voyager 1 upward transmit (S band) currently. No data seen coming down.

[cwr]

Canberra big dish is seen doing Voyager 1 upward transmit (S band) currently. No data seen coming down.

2 way light time is 1.91 days.
That means that a command is sent and its almost 2 days later that a response is heard.

Did anyone observe when the DSN transmitted anything to Voyager 1?

thanks

Carl

[Targeteer]

The 70m dish at Canberra is transmitting 99kw on S band right now https://eyes.nasa.gov/apps/dsn-now/dsn.html

[cwr]

The 70m dish at Canberra is transmitting 99kw on S band right now https://eyes.nasa.gov/apps/dsn-now/dsn.html

I only look at "DSN Now" a few times a year, but I've been doing that since it became available.
So I'm not a DSN Now expert, but I thought that for an antenna to be transmitting, then it
would show the upward moving wave. If it was receiving then the icon would show the downward
moving wave and if communication was two way then both waves would be shown.

Hence the way I interpret the state of DSN 43 is that it sent a signal some time in the past but is no longer transmitting.
I thought that meant irt was waiting for a return signal.
But as I say I am not a DSN Now expert and could be way off base.
But these are what I've observed in other Voyager communication periods.

Can someone more knowledgeable clarify the meaning of all the nuances in DSN Now?

Thanks

Carl

[Targeteer]

The 70m dish at Canberra is transmitting 99kw on S band right now https://eyes.nasa.gov/apps/dsn-now/dsn.html

As I already reported.  https://twitter.com/Bernard1963/status/1850141695075123231

[Hobbes-22]

Can someone more knowledgeable clarify the meaning of all the nuances in DSN Now?

Instead of interpreting squiggles, you can select the antenna, and see info in the bottom right pane. Click 'More detail' to see what they're transmitting and receiving.
When the antenna is grayed out and cannot be selected, it's offline.

[ccdengr]

Instead of interpreting squiggles, you can select the antenna, and see info in the bottom right pane. Click 'More detail' to see what they're transmitting and receiving.

Also, the downlink data rate is very informative.  If it's extremely low (a few bits/sec) that usually indicates safe mode entry.  IIRC, Voyager can't communicate at all on the low-gain antenna any more, so if it loses Earth pointing, it has to be restored before any signal can be received.

If the signal is present but not in lock, I think the current DSN Now doesn't display any downlink at all -- it used to have more information but my recollection is this got stripped out a few years ago.

[Steven Pietrobon]

After nearly six months of effort I have finally obtained a copy of the paper "Design of a CMOS Processor for use in the Flight Data Subsystem of a Deep Space Probe" by Jack Woodell! Unfortunately, the agreement I signed with Wichita State University (WSU) means I can not share the paper with anyone else. If you want a copy you will need to contact [email protected] and [email protected] to get permission. They will provide a copy free of charge if its for personnel research only. I have asked WSU if they can place the paper on their website. They said they can do this, but they first need permission from JPL.

Now back to the paper. Unfortunately, there is little information on how the memory was implemented or which chips were used. The initial feasibility design was implemented using low power TTL and 4Kx18 plated wire memory. This of course was latter changed to an all CMOS design with 8Kx16 of CMOS memory. The paper gives a block diagram and instruction set (with mnemonics, number of cycles and general description) of both the initial and final designs. No opcodes are given. I guess you could make up your own opcodes if you wanted, trying to guess what the operands of the opcodes are supposed to be!

There are a total of 36 instructions. I'm guessing that the upper four bits was used to select the main opcode with the lower 12 bits being the operand. For example, the ABS (Load Value) instruction loads a 12 bit value given in the operand. The WAT (Wait) instruction has a length from 2 to 4097 cycles. The lower 4Kx16 of memory has 128 special registers. There are 16 general registers, 31 memory pointers, 7 indexing registers and 74 counters.

[Targeteer]

https://twitter.com/Bernard1963/status/1851244635152080936/photo/1 3 terminals are tracking Voyager 1, 2 are receiving.

[Targeteer]

https://blogs.nasa.gov/voyager/2024/10/28/after-pause-nasas-voyager-1-communicating-with-mission-team/


After Pause, NASA’s Voyager 1 Communicating With Mission Team

On Oct. 24, NASA reconnected with the Voyager 1 spacecraft after a brief pause in communications. The spacecraft recently turned off one of its two radio transmitters, and the team is now working to determine what caused the issue.

The transmitter shut-off seems to have been prompted by the spacecraft’s fault protection system, which autonomously responds to onboard issues. For example, if the spacecraft overdraws its power supply, fault protection will conserve power by turning off systems that aren’t essential for keeping the spacecraft flying. But it may take days to weeks before the team can identify the underlying issue that triggered the fault protection system.

When the flight team, which is based at NASA’s Jet Propulsion Laboratory in Southern California, beams instructions to the spacecraft via the agency’s Deep Space Network, Voyager 1 sends back engineering data that the team assesses to determine how the spacecraft responded to the command. This process normally takes a couple of days — almost 23 hours for the command to travel more than 15 billion miles (24 billion kilometers) from Earth to the spacecraft, and another 23 hours for the data to travel back.

On Oct. 16, the flight team sent a command to turn on one of the spacecraft’s heaters. While Voyager 1 should have had ample power to operate the heater, the command triggered the fault protection system. The team learned of the issue when the Deep Space Network couldn’t detect Voyager 1’s signal on Oct. 18.

The spacecraft typically communicates with Earth using what’s called an X-band radio transmitter, named for the specific frequency it uses. The flight team correctly hypothesized that the fault protection system had lowered the rate at which the transmitter was sending back data. This mode requires less power from the spacecraft, but it also changes the X-band signal that the Deep Space Network needs to listen for. Engineers found the signal later that day, and Voyager 1 otherwise seemed to be in a stable state as the team began to investigate what had happened.

Then, on Oct. 19, communication appeared to stop entirely. The flight team suspected that Voyager 1’s fault protection system was triggered twice more and that it turned off the X-band transmitter and switched to a second radio transmitter called the S-band. While the S-band uses less power, Voyager 1 had not used it to communicate with Earth since 1981. It uses a different frequency than the X-band transmitters signal is significantly fainter. The flight team was not certain the S-band could be detected at Earth due to the spacecraft’s distance, but engineers with the Deep Space Network were able to find it.

Rather than risk turning the X-band back on before determining what triggered the fault protection system, the team sent a command on Oct. 22 to confirm the S-band transmitter is working. The team is now working to gather information that will help them figure out what happened and return Voyager 1 to normal operations.

Voyagers 1 and 2 have been flying for more than 47 years and are the only two spacecraft to operate in interstellar space. Their advanced age has meant an increase in the frequency and complexity of technical issues and new challenges for the mission engineering team.

For more information about the Voyager mission, visit:

https://science.nasa.gov/mission/voyager

[LouScheffer]

[...]
Then, on Oct. 19, communication appeared to stop entirely. The flight team suspected that Voyager 1’s fault protection system was triggered twice more and that it turned off the X-band transmitter and switched to a second radio transmitter called the S-band. While the S-band uses less power, Voyager 1 had not used it to communicate with Earth since 1981. It uses a different frequency than the X-band transmitters signal is significantly fainter. The flight team was not certain the S-band could be detected at Earth due to the spacecraft’s distance, but engineers with the Deep Space Network were able to find it.

Debugging with the S-band transmitter will be REALLY slow.  According to Voyager Telecommunications, Voyager 1 in 2024 could barely maintain 160 bits/sec with X band to a 34 meter antenna.  The spacecraft antenna has 12db less gain (16x) at S-band, so with a 34 meter antenna it could work at 10 bits/sec, if the transmitter power was the same.  But it appears the S-band is also lower power, so not even that.  So they will need a 70 meter antenna and at most get 10-20 bits/sec.  That's one or two bytes per second.  You can type a lot faster than that.

[ccdengr]

So they will need a 70 meter antenna and at most get 10-20 bits/sec.

39.52 bps at S band right now through Madrid.

[Lee Jay]

So they will need a 70 meter antenna and at most get 10-20 bits/sec.

39.52 bps at S band right now through Madrid.

For calibration, I can type faster than that!

(But not from as far away).

Glad it's at least communicating.

[LouScheffer]

So they will need a 70 meter antenna and at most get 10-20 bits/sec.

39.52 bps at S band right now through Madrid.

Good catch.  They are using an array of one 70 meter and 3x 34 meter.  I was assuming the 70 meter alone, which could get 40 bps discounting the lower S band power.  Looks like the arraying makes up for that.  It's also possible that S band has lower noise, but that depends on details such as which diplexer is in use.