Voyager Status, What is it? Options

[tuvas]

Anyone know the latest Voyager status? I've hear rumors, but I'm wondering if anyone has anything more concrete (I won't share the rumors, as I really don't know much about it, so...)

[dilo]

Curious, last report was published in August, exactly when V1 hit 100au milestone...
Anyway, the two spacecrafts still alive, as confirmed by Cosmic Ray Subsystem data updated to one week ago and V2 Plasma Science data updated yesterday...

[Guest_Analyst_*]

The Voyager status reports are always late: very small team in an extended, extended, extended mission. But the DSN tracking schedules are up to date, and they show normal activity. There has been the standard once per year memory readout recently. So there is no hint of a spacecraft issue I can see right now.

But Voyager 2 should cross the termination shock about now, Voyager 1 did this a couple of years ago. I have no insight and understanding of the science data. They should show this. And Voyager 1 should cross the next "shock" (I can never remember these solar system bondaries) in the not so far future.

Analyst

[Guest_Myran_*]

You might be thinking of the Heliopause Analyst. Voyager 1 should be in the Heliosheath where the solar wind begins to mix with the Interstellar medium. The bow shock could be a bit further away than this image shows. It might be some time before Voyager 1 reach the bowshock, but it would be wonderful if it did. There wont be any TAU mission in the forseeable future so the two Voyagers will be the best shot we have of studying this region.

Attached thumbnail(s)

 

[Littlebit]

You might be thinking of the Heliopause Analyst. Voyager 1 should be in the Heliosheath where the solar wind begins to mix with the Interstellar medium. The bow shock could be a bit further away than this image shows. It might be some time before Voyager 1 reach the bowshock, but it would be wonderful if it did. There wont be any TAU mission in the forseeable future so the two Voyagers will be the best shot we have of studying this region.

The 'Soft' cosmic ray rate has been increasing since September and is up to ~30ips. It last peaked about Nov 2005. I have to wonder if this is correlated - with an appropriate time lag, with the increase in solar activity. It is a roller coaster out there.

[tasp]

. . . BEEP . . .

cold and dark


. . . BEEP . . .


still cold and dark


. . . BEEP . . .

yep, it's really cold, and really dark


. . . BEEP . . .

yawn



. . . BEEP . . .

really, really cold, and still dark

[edstrick]

Space is Big.
Space is Dark.
It's hard to find
a place to park.
. burma shave.

[lyford]

"Marco.............."

.......


......


......

[AndyG]

Shame it's too late to get Hawkwind's 1973 recording of Space is Deep added to the Voyagers' records...twelve string guitar, psychaedelic synths and memorably cheesy lyrics... Yep, that'd do me as I drifted off into the endless AUs...

The path goes onward through the night
Beyond the realms of ancient light



Andy

[mchan]

On that note, my bit of wistfulness for the Voyager music as it travels thru interstellar space would be the song from John Carpenter's early film Dark Star...

Benson, Arizona,
Warm wind thru your hair,
My body roams the galaxy,
My heart longs to be there.

Benson, Arizona,
Same stars in the sky,
But they look so much better,
When we watch them, you and I.

Coincidentally, Benson is less than an hour down the road from LPL.

[tuvas]

Coincidentally, Benson is less than an hour down the road from LPL.

I never knew there was a song about Benson, such a little town in Arizona, but it has it's own song... Sigh.

[dvandorn]

It's not merely a song about Benson, AZ. It's the somewhat improbable theme song of the John Carpenter student film-cum-cult-classic, Dark Star. It's a country-and-western song in format, but the lyric is about a lonely guy, flying through interstellar space at relativistic speeds, and thinking of everything -- and one special person -- he left behind.

If I can recall the words...

A million suns shine down,
But I see only one.
When I think I'm over you,
I find I've just begun.
The years move faster than the days,
There's no warmth in the light.
How I miss those desert skies,
Your cool touch in the night.

CHORUS:
Benson, Arizona, blew warm wind through your hair.
My body flies the galaxy, my heart longs to be there.
Benson, Arizona, the same stars in the sky,
But they seemed so much kinder when we watched them, you and I.

Now the years pull us apart,
I'm young and now you're old.
But you're still in my heart,
And the memory won't grow cold.
I dream of times and spaces
I left far behind,
Where we spent our last few days,
Benson's on my mind.

(CHORUS)



-the other Doug

[alan]

"Marco.............."

.......
......
......

.......


.......



.......



".......Polo"

[edstrick]

"Why do I always have to feed the alien?"

"Cause you brought the stupid thing on board in the first place!"

[tasp]

How could it be alive it was just a bag of gas?

[Guest_Myran_*]

"......and dont dare play that record one more time!"

[mchan]

It's not merely a song about Benson, AZ. It's the somewhat improbable theme song of the John Carpenter student film-cum-cult-classic, Dark Star. It's a country-and-western song in format, but the lyric is about a lonely guy, flying through interstellar space at relativistic speeds, and thinking of everything -- and one special person -- he left behind.

If I can recall the words...

Thanks for posting the lyrics. Your memory is much better than mine. I could only recall the chorus and even missed some of the words there, but remembered the feeling of flying thru space alone and leaving someone behind. Over-anthromorphising Voyager here. Crikey, maybe that's where ST:TMP came from.

[nprev]

We have to be careful not to teach the Voyagers phenomenology...

[edstrick]

"How could it be alive it was just a bag of gas?"

Yeah.. but I'm still convinced it was smarter than the entire crew put together.

[monitorlizard]

Anyone know the latest Voyager status? I've hear rumors, but I'm wondering if anyone has anything more concrete (I won't share the rumors, as I really don't know much about it, so...)

Tuvas, this is probably what you're referring to, and it's not a rumor. There hasn't any press on this to my knowledge, but the JPL JURAP site describes a problem with Voyager 2 in its November meeting minutes. There is a problem with a part of the AACS (attitude and articulation control system) called HYBIC, which has something to do with an analog-to-digital converter not working properly some of the time. This apparently has affected the sun sensor and star tracker on the spacecraft. The part that grabbed my attention was where it said "Impact: Possible loss of spacecraft".

This is not a trivial problem, but the minutes described a swap procedure to a backup HYBIC. The process runs from November, 2006, through February, 2007, but it should result in a healthy spacecraft again. I'm sure the Voyager folks didn't want to make this too public until they know more of how well the swap is succeeding (although JURAP is a publicly-accessible website).

The whole Voyager presentation runs 13 pages, and I'm sure many of you will understand the technical details better than I. It's a complicated web address, so I'll break it down a bit:

(1) go to: rapweb.jpl.nasa.gov

(2) in the right-hand column, click on "Joint Users Allocation and Planning Committee (JURAP) Minutes

(3) click on "Voyager 2 November 2006" (probably in Acrobat format)

This reminds us that the Voyager spacecraft are slowly degrading and unfortunately won't last forever (though it sometimes seemed that they would).

[Guest_Analyst_*]

This is the same switch they did on Voyager 1 in early 2002. Switching HYBIC means you have to use the redundant star tracker (roll) and sun sensor (pitch and yaw) as well, even if the current used ones are just fine. On the other hand, the scan platform pointing information (azimuth and elevation) is no longer needed. So there is some risk because you use other sensors with different and not completely known biases. And there is the possibility HYBIC 1 is not working and you have to switch back to the dedraded HYBIC 2. The AACS computer in charge remains the same, there is no switch planned.

Interesting note: One branch of attitude control trusters for pitch and yaw failed in 1999. But they are not critical on that because they can use the (larger) TCM trusters if the second branch fails.

Analyst

[edstrick]

"...because they can use the (larger) TCM trusters if the second branch fails."

Might mean a much higher rate of use of attitude control propellant, leading to eventual end-of-mission before other expected problems <like low voltage or inadequate suntracker sensitivity> ends mission.

[ljk4-1]

Since the main receiver failed on Voyager 2 shortly after launch back in 1977,
and they had to rely on the backup receiver which is apparently tone deaf, for
lack of a better technical phrase, how is that rather critical piece of equipment
holding up? And how are they keeping it so finely in tune after all this time?

[tuvas]

Thanks for the info. The only thing I knew was that we lost one of our 70m passes due to some kind of emergancy with one of the Voyagers. This seems to fit quite well with the details included here, so... Thanks for your help!

[Guest_Analyst_*]

Since the main receiver failed on Voyager 2 shortly after launch back in 1977,
and they had to rely on the backup receiver which is apparently tone deaf, for
lack of a better technical phrase, how is that rather critical piece of equipment
holding up? And how are they keeping it so finely in tune after all this time?

The only working receiver (there are two) is unable to change its receiving frequency, so it can only listen in a very, very narrow frequency spectrum. It can't stay in lock if the incomming frequency shifts.

There are at least two problems resulting:

- The receiving frequency can't be changed by the spacecraft to stay in lock, but it can change because of temperture variations. A one degree temperature change means a frequency shift of x Hz. So you have to look very carefully at the receiver temperature when the signal arrives (Ten hours or so after being sent). If there is an attitude change (MAGROL etc.) of the spacecraft, the temperature and therefore the frequency can't be predicted good enough. Then they declare a command moratorium and no commands are sent for some days.

- But even if you know the receiving frequency you have to take into acount the doppler effect: Voyager is moving away from the sun, but the earth moves arround the sun and so the distance between earth and spacecraft sometimes rises, sometimes falls. Earth itself rotates, this complicates things too. And the atmosphere changes the signal too.

So you must predict the receiver frequency and then sent a command at a frequency, that adjusted for the doppler effect and atmospheric changes matches this predicted frequency within a few Hz. Because of the uncertainty commands are sent more than once at different frequencies nearby (brackated) so that at least some get through. They do since 1978!

If this last receiver fails, the Voyager 2 command loss routine will configure the spacecraft for longterm science return even without further commanding from earth. Of course you lose the capability to react to science events and failures of other subsystem components, but you get (limited) science as long as nothing happens the spacecraft can't handle by itself (by switching to redundant subsystems etc.).

Analyst

[Guest_Analyst_*]

There is another spare HYBIC, flight-qualified, but not quite on location.

Analyst

[Paolo]

This is not a trivial problem, but the minutes described a swap procedure to a backup HYBIC. The process runs from November, 2006, through February, 2007, but it should result in a healthy spacecraft again. I'm sure the Voyager folks didn't want to make this too public until they know more of how well the swap is succeeding (although JURAP is a publicly-accessible website).

Any update on this?

[monitorlizard]

The January JURAP meeting did discuss the status of the HYBIC swap, but the report of that meeting hasn't been released yet. JURAP minutes are released on a somewhat irregular basis, so it's hard to say when we ordinary people will get to see them.

[Guest_PhilCo126_*]

Last things I've read on the Grand Tour spacecraft:
Voyager 1 crossed the termination shock at 94 AU in December 2004, 100 AU in December 2006 and estimates show it will pass the Heliopause by 2015.
Voyager 2 is now at ~82 AU and is likely to cross the shock sometime this year.
Fingers crossed both will still have some electrical power to keep operating.
By The Way: this year is the 30th anniversary of the summer 1977 launches!

[Steffen]

That's 3 AU per year. Will these overtake the Pioneers?

[Guest_PhilCo126_*]

Indeed, both voyagers will overtake the Pioneer 10 and 11 as the Voayager 1 & 2 have a significant speed advantage. I didn’t calculate when they will out-distance the Pioneers but here are the formulas for the distances traveled by both Voyagers:

Voyager 1: 76.34 + 3.50 ( future year – 2000 ) = distance in AU
Voyager 2: 59.75 + 3.13 ( future year – 2000 ) = distance in AU

( 1 AU = Astronomical Unit is the average distance between Sun & Earth : approx 150 million kilometers )

[remcook]

ehm...I thought they already did??

[Guest_Analyst_*]

Voyager 1 already did in 1998, Voyager 2 will in about 2022.

Link

Analyst

[Guest_Analyst_*]

The tracking schedules on the Voyager homepage from February/March 2007 don’t show the permanent HYBIC switch as planned in November last year. Maybe some unexpected results from the short test swap in early December.

Analyst

[PhilHorzempa]

Has anyone tried to determine if Voyager 1 or 2 will fly
anywhere near a Kuiper Blet Object?
Is there enough fuel on the Voyagers to conduct
a Mid-Course Maneuver to enable a close flyby of a KBO?
Assuming all of that, what is the status of each camera
on the Voyagers? When were they last used?

I bring this up because the Voyagers are now in the Kuiper
Belt, whose components were discovered after the launches
of the Voyagers, and because "new" KBO's are being detected
all the time. Perhaps one of those ice balls will be in the right
place at the right time.


Another Phil

[djellison]

The scan platforms have been switched off for many years, and there would not be the power to operate enough systems to make this a feasable exercise.

Doug

[Guest_Analyst_*]

Aren't the majority of the Kuiper belt objects more or less (+/- 10 or so degrees) in the plane of the ecliptic? The Voyagers are going north and south by 25 or 30 degrees and are therefore in a region with not so many Kuiper belt objects, if I am correct with my assumption. The last time a Voyager camera was used was in February 1990. The heaters on the scan platforms are turned off and even if there is power to spare it is doubtful the cameras would work again.

Analyst

[edstrick]

Not only have the scan platform instruments been switched off.. the scan platform HEATERS have been switched off. Hardware on the platforms is probably at pretty seriously cryogenic temperatures.

And while the majority of KB objects are near the ecliptic, that is increasingly seeming to be an artifact of where we're searching. a *LOT* of them have higher inclinations and spend much of their time outside the near-ecliptic search zones and have been found by accident as they crossed the zone.

Isn't Eris, the biggest KB Planet/Dward-whatever in a 45 deg orbit?

[Gsnorgathon]

Eris's orbit is indeed inclined nearly 45 degrees, though that doesn't necessarily mean it was 45 degrees away from the ecliptic when it was discovered. Your point about the artifact of where astronomers look for objects is a very good one. The Minor Planet Center's outer solar system plot is a great illustration of this. There's a big hole! And - surprise! - it's in the direction of the center of galaxy, where finding really dim objects is not so easy. (I suppose the fact that New Horizons is flying right into that big hole is great reason for optimism that some nice juicy targets will be found for post-Pluto encounters.)

I'd guess we should expect large numbers of TNOs at high inclinations, based on what I've read about planetary migration driving up TNO inclinations.

As always, this kind of discussion reminds me of the joke about the drunk who's looking for his car keys under the streetlight, not because that's where he thought he lost them, but because it's easier to look for them there.

[Guest_Analyst_*]

Voyager Mission Operations Status Report # 2006-12-01, Week Ending December 01, 2006

Voyager 2 performance was nominal during this report period. Activity consisted of the Attitude Control System Hybrid Buffer Interface Circuit swap test on 11/30 (DOY 335). The test executed as planned; however, extraneous commands were issued to turn on the out-board Magnetometer flipper and the IRIS instrument. Spacecraft operations have been returned to normal and the investigation into the anomaly continues.

There we have the reason why the permanent HYBIC switch has not occured yet. The MAG flipper (A mechanical device to reorientate the MAG sensor, it did put some torque on the spacecraft.) and the IRIS instrument (Unsued for years, on the scan platform.) turned on during the swap test. So the permanent HYBIC switch won't come before this is understood. Meanwhile, normal operation goes on.

Analyst

[Guest_John Flushing_*]

http://www.tucsoncitizen.com/daily/local/43056.php

I noticed some false information in this article.

Voyager 2 was turned off in 1998 and is presumably coasting through space without a power source. Before the spacecraft was abandoned, it became the only spacecraft to have flown by the sun's most distant planet, Neptune, and its moons, Holberg said. (Pluto once was thought to be the planet farthest from the sun, but most scientists no longer consider it a planet.)

[brellis]

Regarding KBO's, which were undiscovered prior to Voyagers' launch: do the spacecraft have any way to scan ahead to see if they might run into or near anything, as unlikely as it would be? Even if they couldn't image anything, it would be a great feather in the cap of the Voyager team to detect a new object more than 30 years into the mission!

[Paolo]

Regarding KBO's, which were undiscovered prior to Voyagers' launch: do the spacecraft have any way to scan ahead to see if they might run into or near anything, as unlikely as it would be? Even if they couldn't image anything, it would be a great feather in the cap of the Voyager team to detect a new object more than 30 years into the mission!

The cameras have long since been powered off. They were last used in 1990. Their software has been erased, and the imaging team has dispersed.

[Dominik]

May be, it's a little bit off topic but would it be possible to power on the voyager camera again with the remaining power? Unnecessarily to say that they couldn't see much, because it's distance to the sun.

[brellis]

My earlier question pertained to whether any of Voyagers' operating instruments might pick up an indication of a distant KBO or even some wandering interstellar object of significant proportions. Pioneer may have already captured the prize, having possibly been deflected by an undiscovered KBO at around 8Bn km. It was affected by the object in 1992, and it took 7 years to figure out what might have happened.

I realize my original question is just a speculative exercise in a fantastic "what if", but here's what I've found in a quick search:

I read through the VIM proposal for the 2005 NASA funding review. As mentioned above and in other Voyager threads, the only devices left on are for measuring helioshperic and extraheliospheric features.

"The entire Voyager 2 scan platform, including all
of the platform instruments, was powered down in
1998. All platform instruments on Voyager 1, except
UVS, have been powered down. The Voyager 1 scan
platform was scheduled to go off-line in late 2000, but
has been left on at the request of the UVS investigator
(with the concurrence of the Science Steering Group)
to investigate excess in UV from the upwind direction.
The PLS experiment on Voyager 1 which had been
turned off in 2000 to provide power to extend UVS
lifetime, was turned on again in 2004 when there was
evidence that the spacecraft was in the vicinity of the
26
termination shock. UVS data are still captured, but
scans are no longer possible."

While it seems unlikely for the Voyagers at 100 AU to closely encounter any KBO's, they'll be in the KBO neighborhood for a long time -- Sedna's 10,000 year orbit takes it out to 900AU!

As to whether either Voyager craft could maneuver towards a newly-discovered object:

"The thrusters currently in use are expected to
last the rest of any mission projection. Nearly 1/3 of the
original propellant remains available."

While they're only using thrusters to keep the craft in optimal contact with earth, it is kind of amazing how much fuel is left. They sure saved a lot of juice using the "Grand Alignment" of the outer planets for gravity-assists to sling-shot the Voyagers out of the solar system!

Real world note: One of the many compelling reasons to keep the program alive is that the Voyager craft are making the first beyond-the-shock measurements of Radio Wave events generated during the declining phases of solar cycles. I have the mental image of the Voyager craft being the first to measure waves lapping at the shore of the "lake" that is the solar system.

[tasp]

I am aware of the futility of examining 'do overs' but just for old times sake, here's one:

IIRC, the 'window' for possible Uranus flyby dates was roughly a week long, and the nav team selected one that gave a nice close up of Miranda, good resolution on Ariel and Titania, and so-so for Umbriel and Oberon.

It seems a good satellite configuration existed just before the opening of the Uranus window (although I have no information on the specific satellite config at that time).

Would the surplus manuvering fuel on Voyager II have allowed this encounter, and would it have been sufficient to put Voyager II back on the the exquisite Neptune 'polar crown' trajectory 3 years later ??


(I realize the mission team had specific requirements for fuel margins and the line needed to be drawn somewhere, but I can dream, can't I?)

[Paolo]

May be, it's a little bit off topic but would it be possible to power on the voyager camera again with the remaining power? Unnecessarily to say that they couldn't see much, because it's distance to the sun.

Having been at sub-freezing temperatures for years since their heaters were turned off I think the cameras are now damaged and unusable

[AndyG]

The cameras have long since been powered off. They were last used in 1990. Their software has been erased, and the imaging team has dispersed.

Surely that's: "are no longer focussed."

Andy

[Pando]

During my recent explorations into the bowels of Nasa's web servers, I came across this recent mishap of Voyager 2:

Notes on Voyager 2 Quick Look Data: Data after Nov 29, 2006

On November 30, 2006, a spacecraft systems command was incorrectly decoded by the spacecraft as a command to turn on the heaters associated with the mechanical flipper mechanism for the outboard magnetometer on Voyager 2. The heaters on remained until Dec 4, 2006, resulting in extremely high temperatures (> 130C). The sensors rotated away from the orientation in which they were designed to operate, and the characteristics of the instrument were changed in ways that are not yet fully understood. The result is seen in the quick look data as extremely high magnetic fields. It has not been possible to fully diagnose and correct for the damage to the Voyager 2 magnetometer, although efforts to do so are ongoing. Data from the spacecraft roll scheduled for March 15, 2007 and special coil orientations before and after, will provide crucial information needed to design a process to recover scientific data from the modified instrument.

ftp://vgrmag.gsfc.nasa.gov/pub/voyager/quicklook/v2-warning

Since I couldn't find any info about it on this forum nor any news anywhere else, I'd like to see if anyone knows a bit more what the heck happened there and whether the magnetometer was successfully recharacterized after the recent roll. Also, did this have any long term impact to the health of the spacecraft?

[dilo]

Thanks for the info, Pando. Let's hope magnetometer will fully recover!

PS: In the meanwhile, last data from cosmic ray detector confirm that a still increasing regime of low-energy particles and turbulence, compared to 1 year ago...

[Guest_Analyst_*]

Since I couldn't find any info about it on this forum nor any news anywhere else, I'd like to see if anyone knows a bit more what the heck happened there and whether the magnetometer was successfully recharacterized after the recent roll. Also, did this have any long term impact to the health of the spacecraft?

The reason for this is the HYBIC swap test. The test itself has been successful, but it changed the status of the MAG and turned on IRIS (turned off since then). The permanent HYBIC swap is on hold because of this. I have no information about the MAG status. I also do not know if all four MAG instruments are involved or not.

Analyst

[monitorlizard]

This is old news from the January 18, 2007, JURAP meeting, but it expands on the news Pando gave:

HYBIC SWAP TEST RESULTS

REDUNDANT HYBIC TEST & TEMPORARY SWAP

-PURPOSE OF THE TEST
. Validate operability of HYBIC 1 and health of celestial sensors
. Refine sun sensor bias offsets between HYBIC 2 and 1
. Gather information in preparation for a permanent swap and calibration or futher study

--The HYBIC test was performed on 11/30/2006, DOY 335/02:32:37 UTC (6:32 PM PST). All events executed as planned. HYBIC 1 functioned properly and the pointing offset data were obtained.

--At the time of the swap, the available power dropped to an unexpected level.

--The MAG instrument status indicated that the Out-Board flipper status had changed and that the flipper is now ON. The instrument temperature increased significantly.

--Our investigation revealed that one of the commands issued to reinstate HYBIC 1 also caused the Out-Board Flipper ON command to be issued. This caused an additional 10.2 watt of power consumption. This similar anomaly happened once before in 1998. The cause was thought to be contamination of the 2N222A transistors in the Power System (power command decoder).

--It's believed that the excessive heat caused the wax pellet actuators that move the flipper back and forth from the "forward" to "reverse" position to melt. Data indicate that the flipper position is "reverse", near O degrees.

--Early indications are that the Out-Board MAG is still functioning. We are awaiting more feedback from the PI's.

--We have formed a team of consultants to investigate the cause of this anomaly.

--The permanent swap has been delayed until this investigation is complete.

[dilo]

I tried to plot the measured magnetic field components reported on the same link where Pando took the warning (note that I sampled only some interesting time windows):

The anomaly associated to HYBIC test is clearly visible at the center, while on the right side the values recorded at the beginning of January appear 2/3 times the levels at beginning of November (left)... I do not know if this can be normal or is an indication of damaged magnetometer, however...

[Guido]

Voyager reports for weeks 03-16-2007 to 07-06-2007 Available

http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm

http://voyager.jpl.nasa.gov/mission/weekly...2007-03-16.html
to
http://voyager.jpl.nasa.gov/mission/weekly...2007-07-06.html

[abalone]

Fantastic birthday.The Voyagers will outlive them all


http://www.space-travel.com/reports/Pionee...Flight_999.html

[jasedm]

Voyager reports for weeks 03-16-2007 to 07-06-2007 Available

http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm

http://voyager.jpl.nasa.gov/mission/weekly...2007-03-16.html
to
http://voyager.jpl.nasa.gov/mission/weekly...2007-07-06.html

I'm very surprised that V2 has more remaining propellant than V1 after double the planetary encounters (see report for 2007-07-06)

[brellis]

I'm very surprised that V2 has more remaining propellant than V1 after double the planetary encounters (see report for 2007-07-06)

If I understand correctly, the planetary encounters added velocity, so V2's extra encounters mean it would have needed less propellant.

[djellison]

"needed less propellant"

For what? V1 hasn't been consuming prop in an attempt to catch up. One could imagine that with 4 required targetting points, V2 would have required more prop for TCM's etc.

However - perhaps V1's trajectory was slightly less optimal than V2's and thus it required more Delta-V for targetting.

Doug

[ugordan]

Or maybe one of the spacecraft is inherently more "stable" and hence does less RCS thrusting?

[brellis]

"needed less propellant - for what?"

The extra planetary encounters would also help point the craft to its next destination, thus saving propellant on trajectory changes.

[ngunn]

V1 had no 'next destination' after Saturn and therefore needed no trajectory changes. It's been in freefall since Saturn.

[jasedm]

Thinking about it, perhaps the answer is a combination of several factors:

1) Maybe voyager operators were more sparing of the propellant for V2 knowing that Uranus (and beyond) were at least 'on the cards' from the off.
2). Different trajectories and speeds of the two spacecraft
3) V1 I think had to make a huge (many minutes) burn to set up for the Titan close encounter.

[ugordan]

1) Maybe voyager operators were more sparing of the propellant for V2 knowing that Uranus (and beyond) were at least 'on the cards' from the off.

You can't spare propellant, saving it for Uranus because if you didn't do the necessary burn now there would not be any Uranus encounter, but a huge miss instead.
Rule of thumb: fewer targetted encounters = less fuel consumed.

I seem to remember it was V2 that performed a big burn to set up a trajectory to the Uranus aimpoint and cleanup all the perturbations after passage through the Saturnian system .

[jasedm]

Rule of thumb: fewer targetted encounters = less fuel consumed.

That's just the reason for my surprise in post 56 above:
Voyager 1 - housekeeping attitude control since November 1980 (except for the family portrait shot)
Propellant left: 27.7kg on July 6th 2007
Voyager 2 - observations of an additional two planets/ring systems and at least 10 moons since Saturn encounter
I understand the amount of spacecraft slewing at Uranus was huge due to the number of targets at C/A coupled with the planet's axial tilt
Propellant left: 29.41kg on July 6th 2007

[djellison]

What I was suggesting is that perhaps V1's trajectory inherantly required significantly more Delta V for..

Post launch TCM
Targetting at Jupiter
Clean up after Jupiter
Targetting for Saturn.

Didn't someone say here a while back that one of the two had an LV underperform a little?

Doug

[ugordan]

Didn't someone say here a while back that one of the two had an LV underperform a little?

Yep, something like the Titan IV booster undeperformed and the Centaur was barely able to compensate (IIRC with only 3 seconds of burn time left). The difference is most likely due to the TCMs in the end.

[Bernard1963]

I was wondering if anyone else had noticed / had any info on what appears to be a mystery about the low and varying signal from Voyager 1? For well over a month now the signal from Voyager 1 (as shown on https://eyes.nasa.gov/dsn/dsn.html) has been varying by approx 3db over the course of an hour or so and its at best about 2db lower than it should be, at worst 5db or 6db lower. With DSS63 out for long term maintenance its currently often being tracked on 2 x 34m dishes at Madrid which are unable to obtain data lock for much of the time. Only DSS14 now seems able to hold data lock.

Tweeting one of the Canberra DSN controllers he confirms this is the case, its not a website anomaly. The mystery is that he tells me the Voyager project apparently are not seeing any problem with the spacecraft?

[stevesliva]

A month ago, Voyager 2 notes this sort of activity:

@NSFVoyager2 May 14 Changing my data transmission rate back from Engineering Low to Science Cruise (40 to 160 bps) FDS:MRO XB CR-5T (2019:135:002845:2ECa)

@NSFVoyager2 May 14 Starting Command & Control Subsystem timing test, measuring difference btw CCS timing chain & FDS frame start CCSTIM(COARSE) (2019:135:001813:2T)

@NSFVoyager2 May 14 Starting Command & Control Subsystem timing test, measuring difference btw CCS timing chain & FDS frame start CCSTIM(FINE) (2019:135:000013:2T)

@NSFVoyager2 May 14 Flight Data System clock reset! FDS CLOCK RESET BML (2019:134:214300:2EC)

‏ @NSFVoyager2 May 14 Changed my data transmission rate from Science Cruise to Engineering Low (160 to 40 bps) FDS:MRO XB EL-40 (2019:133:205741:2ECa)

... There is no equivalent data source for V1. I note it more as a form of "what's it (maybe) been up to" than an explanation.

I take that back... there might be more to be gleaned here: https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_08.sfos.pdf

[Bernard1963]

Thank you stevesliva. Even though I've only just joined the forum I'm a long time fan of the Voyagers and follow all posts available. The problem was, there was no answer that could be derived online. The condition of Voyager 1 has deteriorated with the signal variations increasing. Personally I was expecting the spacecraft to be lost before too long. I gather today the Voyager team have finally admitted a problem with the Earth pointing of the spacecraft. In a way of confirmation for the first time today I noticed the tracking schedule was not followed as per https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_22.sfos.pdf with Voyager 1 taking the slot of Voyager 2 on DSS43 and arrayed with DSS34 & DSS35. I understand the team are investigating a yaw error and hope to make corrections shortly. My only fear now is that Voyager 1 is so far off point it may be difficult to upload commands.

[Bernard1963]

On the subject of Voyager 2 I notice from https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_22.sfos.pdf it looks like Voyager 2 will be swapping attitude control trusters to its TCM thrusters on July 9th, as was done with Voyager 1 in Jan 18.

[Xcalibrator]

I was wondering if anyone else had noticed...

Looking back, the V1 particle data started showing noticeable gaps around June 6.

[Bernard1963]

They've fixed it pretty quickly once they admitted the problem, but it had got very bad. The signal is now stable and the strength is as expected :-) https://eyes.nasa.gov/dsn/dsn.html

[stevesliva]

Coincidentally posted yesterday:
https://voyager.jpl.nasa.gov/news/details.php?article_id=114

I haven't see anything other than this thread mentioning an anomaly... in any event, amazing what they're still doing with these two.

[JRehling]

I don't nitpick often (do I?) but while the Voyagers are perhaps the oldest spacecraft still operating, Vanguard 1 (launched March 17, 1958) is the oldest spacecraft still flying, though it's been dead and inert since 1965.

[Bernard1963]

I've noticed the past couple of days Voyager 1's signal is low again into the DSN, presumably off point again. Tracking times available here https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._09_02.sfos.pdf the levels received here https://eyes.nasa.gov/dsn/dsn.html you should see roughly -155db on a 70m and -157db on a 34m dish.

[Bernard1963]

I should have noted that around the 7th September there was a sun sensor calibration and ASCAL which does appear to have fixed the pointing issue and the signal into the DSN has been as expected since then. However as this was the 2nd such incident in the past 6 months I wonder if the sun sensor is having trouble keeping a lock on the sun, now at 147AU.

[Bernard1963]

With info taken from one of the controllers at Canberra on twitter and my observations from https://eyes.nasa.gov/dsn/dsn.html, Voyager 2 was lost for a period of 5-10minutes in the early hours of 26/01/20 while attempting a MAGROL. It looks like an attitude control issue occurred causing the S/C to go off point from the earth. I'm assuming the fault protection kicked in and got the S/C back on point fairly quickly. The S/C was then in engineering mode 40bps rather than the usual 160bps. Even though the Voyager tracking schedule showed no further tracking, later in the day Canberras DSS43 70m dish was tracking and the Canberra website showed a horizon to horizon track was taking place. Its therefore reasonable to assume a spacecraft emergency had been declared with other missions being moved off of DSS43. Checking the most recent track earlier today Voyager 2 remains at 40bps (engineering mode).

[stevesliva]

My brain is hurting because morning in Canberra is so many hours before here, but it sounds like the most recent tracking was to determine whether the commands sent "later in the day" were received. Round trip time is so slow that this seems fast.
DSN antenna DSS-43 at @CanberraDSN opening a 3-1/2 hour listening window to see if recent emergency XMIT was received

[Bernard1963]

https://www.jpl.nasa.gov/news/news.php?feature=7587

[Roby72]

Canberra still tracking VGR2 at 39bits/sec as of February 2nd, 21h30UT as seen in DSN NOW
Now one week gap of science data.
Any thoughts ?

[stevesliva]

Canberra still tracking VGR2 at 39bits/sec as of February 2nd, 21h30UT as seen in DSN NOW
Now one week gap of science data.
Any thoughts ?

Data rate should be back all the way up to 160 now.

[stevesliva]

There was a post from climber in a another thread about the Canberra DSN 70m 11mo shutdown, but this one continues discussion about the V2 anomaly... so, here is an informative now 5-months-old article from the paywalled NY Times:
https://www.nytimes.com/2020/03/04/science/...ce-network.html

It is spurred by the DSN maintenance, but has some interesting commentary about the anomaly. Nice to see reporters finding who to ring up, and talking to them.

[Explorer1]

Voyager 2 is doing well! DSN maintenance has progressed to the point that they have commanded (and heard back) from it after the hiatus.
https://www.nasa.gov/feature/jpl/nasa-conta...ce-network-dish

[Liss]

According to SFOS schedules, first steps in Voyager energy plan has been executed.
LECP MAIN SUPPLEMENTAL HEATER OFF commands were sent and implemented:
* to Voyager 2 -- on 22/23 Feb 2021;
* to Voyager 1 -- on 16 May 2021.

Confirmed at https://voyager-mac.umd.edu/docs/

[stevesliva]

Tweet from @NSFVoyager2 on Feb22 confirms it, too:
https://twitter.com/NSFVoyager2/status/1364410980927741952

Shutting off the main supplemental heater for the Low Energy Charged Particle instrument to save power. PWR LECP MAIN SUPP HTR OFF

I did get stuck on the tangent about why they're dealing with a "damaged tracking loop capacitor." Apparently they've been dealing with it since 1978. (Primary failed, and backup is a bit wonky.)

[stevesliva]

Voyager 1 sending odd telemetry, acting normally:
https://www.jpl.nasa.gov/news/engineers-inv...-telemetry-data

Never too late to learn a new language, they say.

[stevesliva]

https://www.jpl.nasa.gov/news/nasas-voyager...-power-strategy

This original report from April, but I've seen it re-reported a few places including another today.

They have bypassed a voltage regulator on V2, and the need to not have headroom for the regulator means that a planned instrument shutoff in 2023 can be postponed until 2026.

[stevesliva]

Some sort of commanding error means V2 isn't pointing antenna at earth. Should reset pointing October 15th:
https://www.jpl.nasa.gov/news/nasa-mission-...nications-pause

[climber]

It looks like DSN has picked up a carrier signal

[climber]

Voyager II, the best of the best is back on line : https://www.jpl.nasa.gov/news/nasa-mission-...nications-pause

[Bernard1963]

Thought I should draw attention to the latest SFOS 12th October https://voyager.jpl.nasa.gov/pdf/sfos2023pd..._10_30.sfos.pdf Note this is the second time the deadband has been widened in about a month. IE the free drift between thruster firings. It was originally 0.1deg, widened to 0.3deg a few weeks ago, now 0.5deg. The only reason I can see for this is to reduce the thruster firings. So either they've found theres less fuel than expected or the final thrusters (the TCM's) are failing. I hope theres another reason but I cant think of it :-(

[stevesliva]

Optimistically they are exploring strategies to lessen fuel usage with Voyager 2 (presumably s/c 32 vs. 31), the nearer/slower, before also sending to V1. Same as they are trialing the voltage regulator turnoff first on V2.

Googling says that hydrazine was estimated to runout in ~10 years from now for V2, and the vreg* article (me, above) talks to that date now overlapping the years that science instruments will be active. So it may well just be trying to ensure proactively that hydrazine is not the limit that Pu238 will be.

*vreg --> voltage reguator. Not a scrambling of vger.

[Explorer1]

Press release regarding various strategies of the team to deal with recent issues:
https://www.jpl.nasa.gov/news/nasas-voyager...patch-thrusters

Propellant flows to the thrusters via fuel lines and then passes through smaller lines inside the thrusters called propellant inlet tubes that are 25 times narrower than the external fuel lines. Each thruster firing adds tiny amounts of propellant residue, leading to gradual buildup of material over decades. In some of the propellant inlet tubes, the buildup is becoming significant. To slow that buildup, the mission has begun letting the two spacecraft rotate slightly farther in each direction before firing the thrusters. This will reduce the frequency of thruster firings.

The adjustments to the thruster rotation range were made by commands sent in September and October, and they allow the spacecraft to move almost 1 degree farther in each direction than in the past. The mission is also performing fewer, longer firings, which will further reduce the total number of firings done on each spacecraft.

[climber]

https://blogs.nasa.gov/sunspot/
Voyager 1 issue

[Bernard1963]

I would just add. Info from Canberra DSN is that no data is being recovered. Including the engineering channel but they have proved V1 is still responding to commands.

[stevesliva]

A close parsing of the nasa update says that, too. "No science or engineering data is being sent back."

It is then colored by a lot of what they've deduced. And yes, after reading it yesterday, I did have to remind myself... but they're getting nothing.

It does say they're scrutinizing old documents, and there sure is not a lot out there that I've just discovered in a quick search. The FDS is one unit, no A/B units, though it's redudant internally, I think. It also might be one of the first uses of volatile (presumably SRAM) memory. And that means, this could be an SEU. Whether there have been prior SEU that have done this to either V1 or V2 FDS, I can't discover.

[stevesliva]

Speaking of SEU. Found in IEEE Spectrum June 1987...

A faraway bit fix
Just six days before Voyager 2's closest approach to Uranus, in 1985, compressed photographic images transmitted from the spacecraft's cameras began to include large blocks of black-and-white lines.
Engineers at the Jet Propulsion Laboratory, Pasadena, Calif., ran an old data stream received from the craft through the programs used to decompress the images back on earth. The engineers concluded that the problem lay not in the ground computers, but in the craft's flight-data subsystem (FDS), which controls on-board instruments and formats data for transmission back to earth. To test the theory, they directed the FDS to transmit the contents of its 8-kilobyte CMOS memories. By comparing that copy of the image-compression program with the original on earth, engineers Dick Rice and Ed Blizzard determined that a single bit of one 16-bit instruction word had changed from a 0 to a 1. Rice and Blizzard prepared a patch that would circumvent the faulty location in the memory. The patch overwrote the instruction before the failed memory cell with a jump command to unused memory. It then executed a copy of the overwritten instruction and the instruction from the defective location, and jumped back to the address following the failed cell.
The patch was transmitted to Voyager, along with a command to reset the incorrect bit. The patch corrected the failure, and in the least possible time, since transmitting a message to Voyager and receiving a response took 41 hours. The reset command failed, and Rice and Blizzard therefore concluded that the bit failure was permanent. With the patch installed, the program sent error-free images. But engineers acknowledged that the actual cause of the failure would likely never be known. The craft will not return to earth "within our lifetime," said a Voyager team member.

So, precedented. Of 32kbit on both, there's been at least one bit failure.

[stevesliva]

No news that I've heard this year. Anyone else?

[Bernard1963]

From Twitter...... A Voyager update: Engineers are still working to resolve a data issue on Voyager 1. We can talk to the spacecraft, and it can hear us, but it's a slow process given the spacecraft's incredible distance from Earth.

We’ll keep you informed on its status.

[stevesliva]

Ars Technica did the good ol' fashioned thing and... called the project manager:
https://arstechnica.com/space/2024/02/human...omputer-glitch/

Interesting that it's mentioned there are two FDS on V1 and the other "failed in 1981" -- so whatever got me thinking there wasn't originally a spare was wrong.