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Unmanned Spaceflight.com _ Voyager and Pioneer _ Voyager Status
Posted by: tuvas Dec 6 2006, 05:48 AM
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...)
Posted by: dilo Dec 6 2006, 06:31 AM
Curious, http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm was published in August, exactly when V1 hit 100au milestone... 
Anyway, the two spacecrafts still alive, as confirmed by http://voycrs.gsfc.nasa.gov/heliopause/heliopause/recenthist.html updated to one week ago and V2 ftp://space.mit.edu/pub/plasma/vgr/v2/ha/key/ updated yesterday... 
Posted by: Analyst Dec 6 2006, 08:45 AM
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
Posted by: Myran Dec 6 2006, 10:37 PM
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.
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Posted by: Littlebit Dec 7 2006, 06:15 PM
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.
Posted by: tasp Dec 8 2006, 12:26 AM
. . . 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
Posted by: edstrick Dec 8 2006, 06:49 AM
Space is Big.
Space is Dark.
It's hard to find
a place to park.
. burma shave.
Posted by: lyford Dec 8 2006, 07:21 AM
http://en.wikipedia.org/wiki/Marco_Polo_%28game%29
.......
......
......
Posted by: AndyG Dec 8 2006, 11:47 AM
Shame it's too late to get http://en.wikipedia.org/wiki/Hawkwind's 1973 recording of http://www.youtube.com/watch?v=ugTLEkPi1Jc 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
Posted by: mchan Dec 9 2006, 03:55 AM
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.
Posted by: tuvas Dec 9 2006, 07:54 AM
I never knew there was a song about Benson, such a little town in Arizona, but it has it's own song... Sigh.
Posted by: dvandorn Dec 9 2006, 09:06 AM
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
Posted by: alan Dec 9 2006, 06:26 PM
.......
......
......
.......
.......
.......
".......Polo"
Posted by: edstrick Dec 10 2006, 10:08 AM
"Why do I always have to feed the alien?"
"Cause you brought the stupid thing on board in the first place!"
Posted by: tasp Dec 10 2006, 03:10 PM
How could it be alive it was just a bag of gas?
Posted by: Myran Dec 10 2006, 07:04 PM
"......and dont dare play that record one more time!"
Posted by: mchan Dec 11 2006, 09:12 AM
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.
Posted by: nprev Dec 11 2006, 05:43 PM
We have to be careful not to teach the Voyagers phenomenology...
Posted by: edstrick Dec 12 2006, 10:17 AM
"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.
Posted by: monitorlizard Jan 1 2007, 07:19 PM
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).
Posted by: Analyst Jan 5 2007, 07:54 AM
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
Posted by: edstrick Jan 5 2007, 10:06 AM
"...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.
Posted by: ljk4-1 Jan 5 2007, 02:57 PM
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?
Posted by: tuvas Jan 5 2007, 03:45 PM
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!
Posted by: Analyst Jan 5 2007, 05:11 PM
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
Posted by: Analyst Jan 7 2007, 05:06 PM
http://www.nasm.si.edu/research/dsh/artifacts/GC-Voyager.htm is another spare HYBIC, flight-qualified, but not quite on location.
Analyst
Posted by: Paolo Feb 11 2007, 08:48 PM
Any update on this?
Posted by: monitorlizard Feb 12 2007, 01:37 PM
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.
Posted by: PhilCo126 Feb 12 2007, 06:44 PM
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!
Posted by: Steffen Feb 14 2007, 07:53 PM
That's 3 AU per year. Will these overtake the Pioneers?
Posted by: PhilCo126 Feb 14 2007, 08:31 PM
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 )
Posted by: remcook Feb 14 2007, 09:08 PM
ehm...I thought they already did??
Posted by: Analyst Feb 15 2007, 01:16 PM
Voyager 1 already did in 1998, Voyager 2 will in about 2022.
http://www.heavens-above.com/solar-escape.asp?lat=0&lng=0&alt=0&loc=&TZ=CET
Analyst
Posted by: Analyst Mar 5 2007, 08:12 PM
The tracking schedules on the Voyager http://voyager.jpl.nasa.gov/mission/soe-sfos/sfos_2007.html 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
Posted by: PhilHorzempa Mar 9 2007, 07:51 PM
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
Posted by: djellison Mar 9 2007, 08:09 PM
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
Posted by: Analyst Mar 9 2007, 08:30 PM
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
Posted by: edstrick Mar 10 2007, 09:50 AM
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?
Posted by: Gsnorgathon Mar 11 2007, 12:40 AM
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 http://www.cfa.harvard.edu/iau/lists/OuterPlot.html 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. 
Posted by: Analyst Mar 11 2007, 08:58 AM
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
Posted by: John Flushing Mar 22 2007, 09:48 PM
http://www.tucsoncitizen.com/daily/local/43056.php
I noticed some false information in this article.
Posted by: brellis Apr 30 2007, 06:17 AM
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!
Posted by: Paolo Apr 30 2007, 08:41 AM
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.
Posted by: Dominik Apr 30 2007, 11:42 PM
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.
Posted by: brellis May 1 2007, 12:50 AM
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.
Posted by: tasp May 1 2007, 04:42 AM
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?)
Posted by: Paolo May 1 2007, 06:58 AM
Having been at sub-freezing temperatures for years since their heaters were turned off I think the cameras are now damaged and unusable
Posted by: AndyG May 1 2007, 10:09 AM
Surely that's: "are no longer focussed."
Andy
Posted by: Pando Jun 14 2007, 05:17 AM
During my recent explorations into the bowels of Nasa's web servers, I came across this recent mishap of Voyager 2:
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?
Posted by: dilo Jun 14 2007, 06:21 AM
Thanks for the info, Pando. Let's hope magnetometer will fully recover!
PS: In the meanwhile, http://voycrs.gsfc.nasa.gov/heliopause/heliopause/recenthist.html confirm that a still increasing regime of low-energy particles and turbulence, compared to 1 year ago...
Posted by: Analyst Jun 14 2007, 06:25 PM
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
Posted by: monitorlizard Jun 14 2007, 06:53 PM
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.
Posted by: dilo Jun 14 2007, 07:58 PM
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...
Posted by: Guido Aug 11 2007, 08:28 AM
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-reports/2007-03-16.html
to
http://voyager.jpl.nasa.gov/mission/weekly-reports/2007-07-06.html
Posted by: abalone Aug 21 2007, 12:47 PM
Fantastic birthday.The Voyagers will outlive them all
http://www.space-travel.com/reports/Pioneering_NASA_Spacecraft_Mark_Thirty_Years_Of_Flight_999.html
Posted by: jasedm Nov 22 2007, 08:59 AM
http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm
http://voyager.jpl.nasa.gov/mission/weekly-reports/2007-03-16.html
to
http://voyager.jpl.nasa.gov/mission/weekly-reports/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)
Posted by: brellis Nov 22 2007, 11:13 AM
If I understand correctly, the planetary encounters added velocity, so V2's extra encounters mean it would have needed less propellant.
Posted by: djellison Nov 22 2007, 11:52 AM
"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
Posted by: ugordan Nov 22 2007, 12:24 PM
Or maybe one of the spacecraft is inherently more "stable" and hence does less RCS thrusting?
Posted by: brellis Nov 22 2007, 12:32 PM
"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.
Posted by: ngunn Nov 22 2007, 12:49 PM
V1 had no 'next destination' after Saturn and therefore needed no trajectory changes. It's been in freefall since Saturn.
Posted by: jasedm Nov 22 2007, 01:00 PM
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.
Posted by: ugordan Nov 22 2007, 01:07 PM
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 .
Posted by: jasedm Nov 22 2007, 01:41 PM
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
Posted by: djellison Nov 22 2007, 02:03 PM
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
Posted by: ugordan Nov 22 2007, 02:07 PM
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.
Posted by: Bernard1963 Jun 20 2019, 09:06 AM
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?
Posted by: stevesliva Jun 20 2019, 12:51 PM
A month ago, Voyager 2 notes this sort of activity:
@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/sfos2019pdf/19_06_13-19_07_08.sfos.pdf
Posted by: Bernard1963 Jul 5 2019, 08:51 PM
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/sfos2019pdf/19_06_27-19_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.
Posted by: Bernard1963 Jul 5 2019, 08:56 PM
On the subject of Voyager 2 I notice from https://voyager.jpl.nasa.gov/pdf/sfos2019pdf/19_06_27-19_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.
Posted by: Xcalibrator Jul 6 2019, 02:35 PM
Looking back, the https://voyager.gsfc.nasa.gov/_recent/v1la1.html started showing noticeable gaps around June 6.
Posted by: Bernard1963 Jul 9 2019, 10:38 AM
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
Posted by: stevesliva Jul 9 2019, 01:24 PM
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.
Posted by: JRehling Jul 10 2019, 05:08 AM
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.
Posted by: Bernard1963 Aug 17 2019, 12:24 AM
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/sfos2019pdf/19_08_15-19_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.
Posted by: Bernard1963 Sep 24 2019, 11:25 AM
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.
Posted by: Bernard1963 Jan 28 2020, 12:39 PM
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).
Posted by: stevesliva Jan 28 2020, 03:17 PM
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.
https://twitter.com/NSFVoyager2/status/1222070573536350213?s=20
Posted by: Bernard1963 Jan 29 2020, 06:48 AM
https://www.jpl.nasa.gov/news/news.php?feature=7587
Posted by: Roby72 Feb 2 2020, 09:35 PM
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 ?
Posted by: stevesliva Feb 3 2020, 04:11 AM
Now one week gap of science data.
Any thoughts ?
https://twitter.com/NSFVoyager2/status/1224145488993247233?s=20
Posted by: stevesliva Aug 23 2020, 02:52 AM
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/voyager-2-nasa-deep-space-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.
Posted by: Explorer1 Nov 3 2020, 12:58 AM
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-contacts-voyager-2-using-upgraded-deep-space-network-dish
Posted by: Liss Aug 17 2021, 01:32 PM
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/
Posted by: stevesliva Aug 17 2021, 04:26 PM
Tweet from @NSFVoyager2 on Feb22 confirms it, too:
https://twitter.com/NSFVoyager2/status/1364410980927741952
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.)
Posted by: stevesliva May 19 2022, 02:33 AM
Voyager 1 sending odd telemetry, acting normally:
https://www.jpl.nasa.gov/news/engineers-investigating-nasas-voyager-1-telemetry-data
Never too late to learn a new language, they say.
Posted by: stevesliva Jun 26 2023, 03:25 PM
https://www.jpl.nasa.gov/news/nasas-voyager-will-do-more-science-with-new-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.
Posted by: stevesliva Jul 31 2023, 02:32 AM
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-update-voyager-2-communications-pause
Posted by: climber Aug 1 2023, 06:38 AM
It looks like DSN has picked up a carrier signal
Posted by: climber Aug 4 2023, 08:35 PM
Voyager II, the best of the best is back on line : https://www.jpl.nasa.gov/news/nasa-mission-update-voyager-2-communications-pause
Posted by: Bernard1963 Oct 13 2023, 10:53 AM
Thought I should draw attention to the latest SFOS 12th October https://voyager.jpl.nasa.gov/pdf/sfos2023pdf/23_10_12-23_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 :-(
Posted by: stevesliva Oct 13 2023, 04:52 PM
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.
Posted by: Explorer1 Oct 21 2023, 04:44 PM
Press release regarding various strategies of the team to deal with recent issues:
https://www.jpl.nasa.gov/news/nasas-voyager-team-focuses-on-software-patch-thrusters
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.
Posted by: climber Dec 12 2023, 05:21 PM
https://blogs.nasa.gov/sunspot/
Voyager 1 issue
Posted by: Bernard1963 Dec 13 2023, 10:21 AM
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.
Posted by: stevesliva Dec 13 2023, 05:50 PM
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.
Posted by: stevesliva Dec 14 2023, 11:07 PM
Speaking of SEU. Found in IEEE Spectrum June 1987...
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.
Posted by: stevesliva Jan 24 2024, 04:20 AM
No news that I've heard this year. Anyone else?
Posted by: Bernard1963 Feb 6 2024, 11:31 PM
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.
Posted by: stevesliva Feb 8 2024, 01:08 AM
Ars Technica did the good ol' fashioned thing and... called the project manager:
https://arstechnica.com/space/2024/02/humanitys-most-distant-space-probe-jeopardized-by-computer-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.
Posted by: mcaplinger Feb 8 2024, 02:04 AM
The article says this:
I find it incredible that they don't have any kind of simulator. I wouldn't even try to support a mission without at least a software simulator.
There's a little FDS information in Chapter 6 of https://ntrs.nasa.gov/api/citations/19880069935/downloads/19880069935.pdf but all of the specifics are in JPL internal reports.
Posted by: Brian Swift Feb 8 2024, 07:00 AM
I have no trouble envisioning systems running a simulator (or other GSE) becoming unmaintainable, and operations budget becoming too small to pay for port and validation of old software to a new platform.
Interesting doc. Thanks for sharing.
Posted by: mcaplinger Feb 8 2024, 03:10 PM
Sure, but if they had tools that ran on some 60s-70s platform, they might be operable with a simulator. A slightly newer example -- all of the tools for the MOC on MGS ran on a Microvax. By the end of the mission, I was running them on a simh software simulator since the Microvax hardware was long dead.
The biggest problem could be media -- it's progressively harder to read 9-track tapes -- but I'm sure there's a solution somewhere.
Posted by: stevesliva Feb 8 2024, 07:37 PM
That FDS history is better than anything else I found a few weeks back. And James Wooddell might be unhappy to hear them say that so many people of import have passed. It appears that he might be turning 91 before the month is out. The text cites a graduate paper from USC in 1974 as having a lot of documentation on the architecture.
That text does make it clear that the bigger issue is... what's the software on there, and if a bit's become stuck, what do you do about it. There, Edgar Blizzard is (maybe) 89. Richard Rice is a more generic name, but I can't see that he's necessarily passed, either.
I did sort of glean that the "registers" might simply be specific words in the memory, and "bad register" might be what means the other FDS was abandoned. Which might make a bad bit in a register harder to work around vs. like it was in a specific word of instruction memory like in the hard error in 1985. Yes, there are other registers, but rewriting that much of the code...
Oh, and it says a full FDS software load took 4hrs in 1984, which was then considered real slow because of lower bandwidth.
Posted by: mcaplinger Feb 8 2024, 08:06 PM
I'm not sure why you take issue with the simple claim that a lot of people who worked on the project are dead. And even if they're not, they may not be able to help for other reasons.
I note that the document talks about a software simulator that ran on an Interdata system. The 8/32 has SIMH emulator support (likely due to its use in the early development of Unix) so maybe there's some hope there. https://en.wikipedia.org/wiki/Interdata_7/32_and_8/32
FWIW, I reached out to the Voyager team and mentioned all of these possibilities.
Posted by: stevesliva Feb 8 2024, 10:31 PM
Oh, I'm not taking any truck with it, just wondering about particular players. And actually surprised that I came up 0/3 on, well, obituaries for those three, and I was looking for that mainly to get a sense of when they'd have stopped being involved in things. All retired in the 90s, maybe. But I dunno.
It sort of describes the shape of the problem to me. Because it sure looks like a fix will mean changing to FDS firmware, and how lost to history that process might be. So here's hoping it doesn't.
Oh, and maybe I can square my prior "internal redundancy" comment with the Ars report that 1 of 2 FDS on V1 is dead-- your text does say the processor could address memory in either unit. So the system is semantically two intertwined units, one of which is dead on V1. So some higher level block diagrams might call that intertwined unit "the FDS" which internally has lost some redundancy.
Posted by: Floyd Feb 9 2024, 01:01 AM
The Voygers were launched in 1977 and their computers date to the pre Intel microprocessor era. The 8080 came out in 1974 and had 7 8 bit registers. The 8085 came out in 1976 and also had only 7 key registers. The 8086 came out in 1978 and had about 14 registers. What the registers do in each of these computer is explained in Wikipedia. Registers are specific memory locations often with very specific functions such as stack pointer, program counter, status register flags and a limited number of Main register. Most every instruction in 8080 and 8085 code referenced registers A thru E. If one of these registers died, you don't just rewrite your program using the 4 remaining registers. A register was the accumulator, so used in math operations. You lose any of the registers and you are dead. Someone who know how many registers were in the Voyager computer can speak up, but I assume it was no more powerful than the early Intel chips and had similar limitations. My first 8080 computer had 16 K of 8-bit memory. Programs usually occupied 4-8 K leaving 8 to 12 K of memory (minus 2K for screen memory).
I'm 77 and did machine programing for these chips in the late 1970's and early 1980's. Anyone with better memory of early computers please correct my misstatements.
Posted by: mcaplinger Feb 9 2024, 02:45 AM
The Voyager FDS was designed several years before the first microprocessors. It has some unusual architectural features, including 128 general-purpose registers (mapped from the main RAM and not as separate logic entities) and a six-clock basic instruction cycle operating on 4-bit values per clock.
I'm not sure how the Voyager team is proceeding. If I were faced with this problem, I would try to build the smallest possible software load that would send useful telemetry to the transmitter. And to support that, I would build a software simulator of the system and make sure the behavior of existing loads was understood. The FDS memory (8K, I think) is loaded through the CCS, so it should be possible to experiment a bit with new FDS loads without the possibility of bricking everything, assuming of course that the CCS keeps working.
Posted by: stevesliva Feb 9 2024, 06:39 AM
What I gathered from Ars was simply that they're going to try to command it into "encounter mode" or some such other modes. Which make sense, try that before software reload, see what happens.
Floyd -- the very long PDF linked by mcaplinger above has lots of details, including that tidbit about the massive amount of registers. The images basically look like the "8K" memory is probably something like 256 discrete CMOS ICs -- making each 32 bits, so if each register is 4bits, maybe there are 16 chips for the "registers" and 240 for the rest of the memory. All that to say -- the reason the registers are mapped from "main" memory is because the MPU itself is a collection of discrete ICs on a huge board with probably hundreds of SRAM ICs... the memory bottlenecks aren't analogous to CPUs.
In any event, if there really were 128 x 4 = 512 bits of registers over 16 separate chips, simple programs probably don't need to use all 128. So I was thinking a bad register would be hypothetically easy to work around, esp since there's not image processing happening. There is some text on page 187 of the PDF about how DMA instructions take the same time that all other instructions take... or I don't quite follow. Probably the biggest distinction between the regs and the other memory words was that the regs were addressable with 7 bits of a 16-bit instruction, while the memory addresses were 4k/16=8bits? So separate instructions were needed to access the "lower 4k" instruction memory vs. upper 4k scratch vs. upper 4k scratch in other unit? Also not clear to me how a 16-bit memory word would load into 4-bit registers, but this is a special ISA, so perhaps 4 registers load at a time. The other thing indicated is that arithmetic would be slow... a several cycle operation because it was doing 4-bits a cycle. Perhaps a more common operation was to simply forward along specific ranges of data, or MSBs, etc.
All that to say, a bit flip in one of the registers shouldn't be more fatal than a bit flip in instruction memory... just even harder to work around at this stage, because you have to change and reload the firmware. And sure, if a 16-bit word has to load into 4 registers, maybe there are effectively 32 and not 128 registers, when it comes to programs loading from memory. But 32 --> 31 should still be manageable.
Posted by: mcaplinger Feb 9 2024, 04:09 PM
I don't think the registers are 4 bits, I think the ALU does arithmetic 4 bits at a time on presumably 16-bit registers. This is called bit-slicing and was a fairly common design technique at the time: https://en.wikipedia.org/wiki/Bit_slicing
Posted by: Doug M. Feb 18 2024, 10:51 AM
So, does anyone have a prognosis here? How likely does it seem that we'll get Voyager back?
Posted by: MahFL Feb 18 2024, 06:55 PM
My gut feeling, is sadly no.
Posted by: mcaplinger Feb 18 2024, 07:20 PM
I wouldn't count the team out, but not being able to get any useful debugging telemetry back makes it much harder to diagnose than the last problem. And it's not clear they have the resources it would take to either recreate the problem on the ground or start over with a new FDS software image.
Posted by: Doug M. Feb 21 2024, 06:48 PM
I wrote a post on the situation here: https://crookedtimber.org/2024/02/19/death-lonely-death/
Written by a non-technical person for a non-technical audience, so please be kind to any errors.
Doug M.
Posted by: mcaplinger Feb 21 2024, 08:55 PM
Nice post, but I feel compelled to nit-pick a little, sorry.
They had all of that for Voyager, they just don't have it today, probably because the hardware died and couldn't be repaired. Missions I've worked on (MGS for example) have been severely challenged late in the mission to keep those resources going. The situation has been improving, but I wouldn't call it "solved". And it is rarely if ever a "perfect duplicate" -- on MGS our MOC ground hardware was a bare circuit board mounted to a big sheet of plywood. The spacecraft simulator is usually what's called a "flatsat" -- a collection of boards on tables or in racks, hardly a complete spacecraft.
And good luck finding any of that Pathfinder hardware even today, much less in the near future of "The Martian". All of that stuff was likely scrapped shortly after the mission ended.
Posted by: Tom Tamlyn Feb 21 2024, 11:31 PM
What about the Pathfinder models that JPL occasionally trots out for "group portrait" photo ops to show the evolution of Mars rovers from, e.g., Pathfinder to Perseverance? Are those dummies without the electronic innards?
Posted by: mcaplinger Feb 21 2024, 11:55 PM
Pathfinder wasn't a rover, do you mean Sojourner?
It's possible that they still have a working flight-like Sojourner, maybe. But the last time I saw it in person actually driving was nearly 20 years ago now.
Posted by: Tom Tamlyn Feb 22 2024, 12:37 AM
<groan>
Naturally I meant to refer to the Sojourner component of the Pathfinder mission.
A few ... well, quite a few years ago, Doug Ellison put up some interesting posts on twitter showing how he had borrowed a Sojourner-shaped object from JPL and taken it into his home shop, to spruce it up for a JPL open house.
I guess it's unlikely to have been a drivable model. 
Posted by: djellison Feb 22 2024, 02:48 AM
The only flight-like rover testbeds in the wild are Marie Curie (Sojourner testbed rover, at one point destined to fly on the cancelled 2001 lander) and 'Dusty' ( MER testbed ) which are both now at the Air and Space museum. There were others 'driveable' MER and Sojourner testbeds that were significantly lower fidelity - more like the 'Scarecrow' rover used for Perseverance and Curiosity. The Perseverance and Curiosity Vehicle System Test Beds are both in the garage at the Mars Yard at JPL. Perseverance and Curiosity also share an avionics testbed (MSTB) which is more analogous to what testbeds are usually like for missions that are not rovers/landers - the 'flat-sat' Mike mentions above.
This is Marie Curie, Dusty, and Maggie - the Sojourner, MER and MSL testbeds...
https://mars.nasa.gov/resources/3792/three-generations-of-rovers-in-mars-yard/
I don't know if Voyager has an equivalent to the MSTB functioning right now. I would be surprised if it does. I will say, keeping our testbeds up and running is VERY non-trivial. Having spares to fix them when things break gets harder and harder with age - and can reach a point where it's simply not possible to get the parts to do it. Older missions get parts poached from their testbeds in support of newer missions etc etc. If there IS a Voyager testbed, I suspect in terms of technicians certified to maintain it or operate it, the engineer trained by the engineer trained by the engineer trained by the engineer who built it probably got laid off 2 weeks ago.
Posted by: Doug M. Feb 22 2024, 02:06 PM
I would have expected nothing less!
Really! TIL.
And as for Voyager... they just tossed it? I mean, Voyager's not that big, and storage is cheap... But on the other hand, 46 years is a very long time, I guess.
Posted by: mcaplinger Feb 22 2024, 02:43 PM
Storage is not as plentiful as you might think on the JPL campus. It could easily be in some off-site storage where no one can find it (think the last scene of RAIDERS OF THE LOST ARK) and probably non-functional if it could be found.
From https://ntrs.nasa.gov/api/citations/19880069935/downloads/19880069935_Optimized.pdf
M. Blizzard joined Richard Rice to develop the flight version of the code. Others have been involved in testing and management, but these two JPL engineers have been the key programmers for the entire mission to date. They sit in the same area as the "Laboratory Test Set," an
Interdata computer and peripherals that contain the software simulator of the data computer and the assembler and flight load generator. Across from them is the CDL, the loose conglomeration of hardware that represents the real spacecraft.
You want to bet on the chances of an Interdata computer from 1975 still being in working order? I did find emulator support for the Interdata and data files for the Interdata operating system, but finding and reading the unique Voyager software on old tapes if they still exist might be a challenge. Even if anyone knows how those tools work any more.
It is a little surprising that they didn't plan ahead for this a bit better, but it's understandable.
Posted by: Floyd Feb 22 2024, 06:17 PM
mcaplinger the PDF you linked is amazing reading. Thank you for posting.
Posted by: HSchirmer Feb 22 2024, 07:23 PM
... finding and reading the unique Voyager software on old tapes if they still exist might be a challenge. Even if anyone knows how those tools work any more.
<GRIN>Yikes, that brings back memories of my father bringing home giant spools from an IBM 360 to work on over the weekend, and me as a little kid looking up references for him in a 4-inch thick IBM binder.
"Mom, is COBOL a curse word?" "Sometimes dear, sometimes when your father uses it..."
Posted by: stevesliva Feb 22 2024, 10:18 PM
Yes. But the "open in case of emergency" kit that I'm envisioning prob still wouldn't have a working emulator. Might be something more like several "phone home" FDS OS versions that each used subsets of the FDS registers/SRAM, that could be loaded relatively quickly, and tried.
(I am actually somewhat surprised that the "died in 1981" side of the FDS wasn't better diagnosed in that sort of way. I guess in 1981 they presumed they would still have the expertise to so something like develop a modified OS if they needed to cross that bridge, and never did. Or maybe it was diagnosed, and plans to workaround whiteboarded, and forgotten.)
Also, I second what Floyd wrote above. The book from the NTRS site is great reading. So thanks again.
Posted by: mcaplinger Feb 27 2024, 03:38 AM
It might still be garbage (probably is), but DSS-63 Madrid is receiving at 40 bps from Voyager 1 right now.
Posted by: stevesliva Mar 7 2024, 04:28 PM
NPR had some more color on this, yesterday:
https://www.npr.org/2024/03/06/1236033493/nasas-voyager-1-spacecraft-is-talking-nonsense-its-friends-on-earth-are-worried
No news except perhaps reconfirmation that they're trying mild commanding well before anything drastic, so perhaps expect this to take a long long while.
Posted by: climber Mar 11 2024, 11:17 AM
It looks like we have encouraging progress (sorry for the very long link) : https://www.pasadenastarnews.com/2024/03/09/jpls-voyager-team-extremely-hopeful-after-ailing-faraway-craft-shows-signs-of-former-self/?sfnsn=mo&mibextid=VhDh1V&fbclid=IwAR1HLD97SajQYV-Th6UM8EPGaQ3C6Qsg-VQAZ-UGkib39o_t4ctexhFHAQM
Posted by: Tom Tamlyn Mar 13 2024, 09:16 PM
From the article: "Today, the Voyager team consists of only 12 full-time employees."
Interesting. Somehow I had gotten the notion that Voyager was no longer a full-time job for anyone, except, of course, when there's a problem. I guess that's incorrect?
Posted by: mcaplinger Mar 13 2024, 09:57 PM
Either the article is wrong or your notion was, yes.
I don't find it hard to believe that they have 12 FTEs just at JPL for routine ops for the two spacecraft. They have to manage DSN scheduling, build uplink, process downlink, generate PDS archives, etc. And I presume that there are other people at the instrument institutions involved also, though maybe not full-time.
Posted by: deedan06 Mar 13 2024, 10:02 PM
Well they still need a permanent team to deal with the dwindling power supply, even if it takes years, the measurements to extend their lifespans are probably extremely well calculated. And you need at least some guys to maintain base knowledge of the probe.
Posted by: mcaplinger Mar 13 2024, 10:21 PM
Voyager costs $5-7M per year according to the 2024 NASA budget request https://www.nasa.gov/nasa-fiscal-year-2024-budget-request/
I expect most of that is for labor, not sure how DSN time is accounted for.
Posted by: djellison Mar 13 2024, 10:45 PM
Also it's worth noting - the phrase " 12 full time employees " may not mean 12 people who are full time on Voyager. FTE is a unit of currency for work like this. 12 'full time employees' might be......4 people working 100% on Voyager, 8 people working 50% on Voyager, and 16 people working 25% on Voyager.
As an example - I know the power lead for both MSL and M20 also works on Voyager.
Posted by: Tom Tamlyn Mar 14 2024, 12:00 AM
That makes sense (and I realize that it's an example, not the actual roster of the Voyager team).
I knew that there are people "permanently" assigned to Voyager, but I assumed that all of them -- or all but a few -- also had regular responsibilities for other missions or projects.
Posted by: Bernard1963 Mar 14 2024, 12:36 AM
Well, this is looking more hopeful than I was expecting. V1 has provided a full memory read out of the FDS, presumably missing framing / sync so it took a bit of work to pull it out of the data stream. https://blogs.nasa.gov/sunspot/?fbclid=IwAR1sVNuIWv7dnvwPKVnh6-Y135n1zw3bK-MbPJJdpQTW3K_Q5h4e4iY3tyc
Posted by: Explorer1 Mar 14 2024, 02:36 AM
There's a 2022 documentary https://www.imdb.com/title/tt17658964/ Not sure if anyone else here has watched it, but good for insight into the current goings-on.
Posted by: Bernard1963 Mar 14 2024, 09:22 AM
I gather a bare bones version of the FDS software was loaded and thats how comms has been restored. I assume its now a case of running tests to find the faulty area of memory.
Posted by: mcaplinger Mar 14 2024, 04:32 PM
Excellent and available on Prime Video. I seem to have something in my eye...
It's hard to tell since the blog has been so dumbed down.
Doesn't sound like new software to me, but it might be a patch of some kind.
Posted by: Floyd Mar 14 2024, 06:03 PM
In some old computer languages, the peek command was used to read a location in memory and a poke command to write to memory. No idea if they poked some addresses in memory to program the peek into memory that was returned????
Posted by: Tom Tamlyn Mar 14 2024, 06:46 PM
Thanks Explorer1 for suggesting It's Quieter in the Twilight. It's available for streaming from PBS, and it's an interesting documentary, quite moving, as mcaplinger noted upthread.
And I now recall reading a good New York Times piece (gift link below) about the same team.
As the Voyager mission is winding down, so, too, are the careers
of the aging explorers who expanded our sense of home in the galaxy.
New York Times (Aug. 3, 2017).
https://www.nytimes.com/2017/08/03/magazine/the-loyal-engineers-steering-nasas-voyager-probes-across-the-universe.html?unlocked_article_code=1.ck0.5GRy.0PPGdzBHiXYK&smid=url-share
The article contains a passage which I had obviously forgotten when I posted yesterday:
I wonder to what extent the team has been able to rely on additional resources outside of their team during the current crisis.
Posted by: stevesliva Mar 14 2024, 08:04 PM
My speculation is that the "dump memory" routine was in instruction memory that they decided to command the FDS to try. I would not guess they changed the instruction memory, because then it'd be running the program they expected, not "eureka! it's a core dump." (Commanding might simply be "start program at this instruction address" but it's not really worth clarifying that because it'll come out in time.)
https://arstechnica.com/space/2024/02/humanitys-most-distant-space-probe-jeopardized-by-computer-glitch/
This is a lot more complicated than it might seem on the surface. For one thing, the data modes engineers might command Voyager 1 into haven't been used for 40 years or more. Nobody has thought about doing this with Voyager's flight data computer for decades.
... so what I'm speculating is that one of those "modes" had a "dump memory" routine and they didn't expect it.
Posted by: Bernard1963 Mar 16 2024, 12:45 AM
It's hard to tell since the blog has been so dumbed down.
Doesn't sound like new software to me, but it might be a patch of some kind.
My comment about a new FDS software isnt from the blog article.
Posted by: mcaplinger Mar 16 2024, 03:20 AM
Then where is it from?
Posted by: Bernard1963 Mar 20 2024, 11:50 PM
A NASA source, and it would be unfair of me to say who.
Posted by: stevesliva Mar 21 2024, 12:22 AM
Media reports of a DSN engineer having a eureka moment are a poor game of telephone in that case. But, we've seen that before. Time will tell.
Posted by: Bernard1963 Mar 31 2024, 12:41 PM
Going by the latest SFOS this looks very hopeful. FDS memory update was sent Friday. Upon the response V1 is getting close to 24hrs coverage! I'll be checking the DSN website to see if we get a data rate of 160bps (cruise mode) :-) https://voyager.jpl.nasa.gov/pdf/sfos2024pdf/24_03_28-24_04_15.sfos.pdf
Posted by: Bernard1963 Apr 3 2024, 09:52 AM
Thought I'd post an update as clearly Voyager 1 did not return to science / cruise mode following the update. I gather the update however fully restored telemetry, hence the 24hr track afterwards. This article seems to confirm it is a memory failure and they are having to rewrite / move code to avoid the failed area. https://spacenews.com/nasa-optimistic-about-resolving-voyager-1-computer-problem/
Posted by: stevesliva Apr 3 2024, 01:37 PM
This makes me wonder if the "died in 1981" side of the FDS has more working memory words in the lower region they use as instruction memory. In an earlier post, I wondered how well documented what the bad bits or words were from that 1981 failure.
That failure meant that when the FDS glitched this time, they could not just switch to the other side. (And the sides are intertwined, but there's a lower region of memory that's dedicated to the processor logic on either side, while either side can retrieve data from the upper memory of the other side)
Because if the 1981 failure was also bad memory, they're now contemplating what they didn't do then... which is to rewrite the programs to avoid the bad addresses. And that makes me wonder which side is more functional now that they're both bad.
Posted by: stevesliva Apr 5 2024, 05:32 PM
https://blogs.nasa.gov/voyager/2024/04/04/engineers-pinpoint-cause-of-voyager-1-issue-are-working-on-solution/
NASA suspecting entire SRAM chip is bad. Saying 3% of memory, which I suspect is 256/8192=0.03125. That might make one chip 256bytes: 2048bits, 16bit word, 128 addresses. 128x16 is what we'd call it.
If it's instruction memory, that's 6% of instruction memory, but the FDS isn't processing many images these decades.
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