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Voyager Status, What is it?
Guest_Myran_*
post Dec 10 2006, 07:04 PM
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"......and dont dare play that record one more time!"
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mchan
post Dec 11 2006, 09:12 AM
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QUOTE (dvandorn @ Dec 9 2006, 01:06 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...

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. smile.gif
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nprev
post Dec 11 2006, 05:43 PM
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We have to be careful not to teach the Voyagers phenomenology... blink.gif


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A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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edstrick
post Dec 12 2006, 10:17 AM
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"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.
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monitorlizard
post Jan 1 2007, 07:19 PM
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QUOTE (tuvas @ Dec 5 2006, 11:48 PM) *
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).
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Guest_Analyst_*
post Jan 5 2007, 07:54 AM
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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.

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edstrick
post Jan 5 2007, 10:06 AM
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"...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.
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ljk4-1
post Jan 5 2007, 02:57 PM
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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?


--------------------
"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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tuvas
post Jan 5 2007, 03:45 PM
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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!
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Guest_Analyst_*
post Jan 5 2007, 05:11 PM
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QUOTE (ljk4-1 @ Jan 5 2007, 03:57 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?


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.).

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Guest_Analyst_*
post Jan 7 2007, 05:06 PM
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There is another spare HYBIC, flight-qualified, but not quite on location. smile.gif

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Paolo
post Feb 11 2007, 08:48 PM
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QUOTE (monitorlizard @ Jan 1 2007, 08:19 PM) *
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?
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monitorlizard
post Feb 12 2007, 01:37 PM
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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.
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Guest_PhilCo126_*
post Feb 12 2007, 06:44 PM
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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!
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Steffen
post Feb 14 2007, 07:53 PM
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That's 3 AU per year. Will these overtake the Pioneers?
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