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Voyager Chronology
tasp
post Jun 19 2008, 08:38 PM
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I recall being very nervous about the Voyager 1 Jupiter flyby as the interesting satellite passes occurred after closest Jovian approach and I was extremely worried about radiation messing up the craft before they happened.

I managed to be in the Huntley Lodge in Montana, as I recall, for the great 1979 solar eclipse. It was a sufficient distraction to make my Voyager anxiety tolerable.

Time magazine managed to cover both events in the same issue.

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Liss
post Jun 21 2008, 06:12 PM
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QUOTE (dmuller @ Apr 18 2008, 12:23 PM) *
I can offer the following, need to do more research to verify timezones and SCET/ERT:

12 Nov 1980 (05:41) Titan: Titan flyby (targetted)
12 Nov 1980 (22:17) Tethys: Tethys flyby (distant)
12 Nov 1980 (23:46) Saturn: Saturn Fly-By
13 Nov 1980 (01:43) Mimas: Mimas flyby
13 Nov 1980 (01:51) Enceladus: Enceladus flyby (distant)
13 Nov 1980 (03:39) Dione: Dione flyby (distant)
13 Nov 1980 (06:22) Rhea: Rhea flyby
13 Nov 1980 (16:45) Hyperion: Hyperion flyby (distant)


Well, I was able to extract the sequence of Voyager 1 Saturn flyby from

Voyager 1 and Voyager 2 Saturn encounter orbit determination
Campbell J.K., Jacobson R.A., Riedel J.E., Synnott S.P., Taylor A.H.
AIAA-1982-419
20th Aerospace Sciences Meeting, Orlando, FL, Jan 11-14, 1982, 17 p.

At http://www.aiaa.org/content.cfm?pageid=406...r&gID=90384
the report is not available without payment but with a carefull googling all the encounter table may be extracted.

Event - Date and time, UTC - Time relative to CA, hours - Distance

Titan CA. 11/12/80 05:40:41 -18.09 6969
Enter Titan Sun-occ. 05:46:22 -17.99
Enter Titan Earth-occ. 05:47:33 -17.97
[Exit] Titan Sun-occ. 05:57:06 -17.81
Descending node 05:58:09 -17.79 1184575
Exit Titan Earth-occ. 05:59:45 -17.77
Tethys CA 22:15:52 -1.50 415855
Saturn CA* 23:45:50 0. 184497
Closest Mimas in light 11/13/80 00:37:41 +0.86 108432
Mimas CA** 01:42:32 +1.95 88996
Enter Saturn Earth-occ. 01:43:16 +1.96
Enceladus CA 01:50:36. +2.08 202796
Enter Saturn Sun-occ. 01:56:54 +2.18
Exit Saturn sun-occ. 02:37:24 +2.86
Exit Saturn Earth-occ. 03:10:35 +3.41
Enter Ring Earth-occ. 03:19:40 +3.56
Closest Dione in light 03:28:13 +3.71 161543
[Exit] Ring Earth-occ. 03:35:09 +3.82
Dione CA*** 03:39:00 +3.89 161285
Ascending node 04:20:06 +4.57 377902
Rhea CA 06:21:13 +6.59 72797
Hyperion CA 16:44:01 +16.97 897277

CA = closest approach
*One-way light time = 01 24 47
**Mimas is in darkness at CA
***Dione is in darkness at CA
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Liss
post Jun 24 2008, 08:37 PM
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QUOTE (dmuller @ Apr 18 2008, 12:23 PM) *
Voyager 2

25 Aug 1981 (09:24) 665,960 km Titan: Titan flyby (distant)
26 Aug 1981 (01:04) 502,250 km Dione: Dione flyby (distant)
26 Aug 1981 (02:34) 309,990 km Mimas: Mimas flyby (distant)
26 Aug 1981 (03:24) 161,081 km Saturn: Saturn
26 Aug 1981 (03:45) 87,140 km Enceladus: Enceladus flyby
26 Aug 1981 (06:12) 93,000 km Tethys: Tethys flyby
26 Aug 1981 (06:29) 645,280 km Rhea: Rhea flyby (distant)


Again I was able to extract Voyager 2 Saturn visit times from the article by Campbell, Jacobson et al.

Date and time, UTC SCET -- Time from Saturn CA -- Event -- Distance, km
1981.08.23 01:26:56.5 -03 01:57:11 Iapetus 909070
1981.08.25 01:25:25.8 -01 01:58:42 Hyperion 470840
1981.08.25 09:37:46.3 -00 17:46:21 Titan 665960
1981.08.25 22:57:33.2 -00 04:26:35 SXII Helene (1980 S6) 318200
1981.08.26 01:04:31.8 -00 02:19:36 Dione 502250
1981.08.26 02:22:16.8 -00 01:01:51 SXIV Calypso (1980 S25) 153518
1981.08.26 02:34:26.X -00 00:49:41 Mimas 309990
1981.08.26 03:08:29.4 -00 00:15:38 SXVII Prometheus (1980 S28) 287170
1981.08.26 03:19:17.5 -00 00:04:50 SXV Pandora (1980 S26) 107000
1981.08.26 03:24:07.8 00 00:00:00 Saturn
1981.08.26 03:33:02.4 +00 00:08:55 SXVI Atlas (1980 S27) 246590
1981.08.26 03:45:16.1 +00 00:21:08 Enceladus 87140
1981.08.26 03:50:03.6 +00 00:25:56 SX Janus (1980 S1) 222760
1981.08.26 04:00:24.6 +00 00:36:17 Earth occult enter Saturn? 166133
1981.08.26 04:05:55.8 +00 00:41:48 SXI Epimetheus (1980 S3) 147010
1981.08.26 04:08:12.1 +00 00:44:04 Sun (umbra) occult enter Saturn
1981.08.26 05:34:36.9 +00 02:10:29 Earth occult leave Saturn 215762
1981.08.26 05:44:56.s +00 02:20:21 Sun (umbra) occult leave Saturn 223334
1981.08.26 06:02:46.7 +00 02:38:39 SXIII Telesto (1980 S13) 284400
1981.08.26 06:12:30.2 +00 02:48:22 Tethys 93000
1981.08.26 06:28:48.4 +00 03:04:41 Rhea 645280
1981.09.05 01:22:33.5 +09 21:58:26 Phoebe 2073640

Notes:
1. Two or more lines for rings crossing were not discernible.
2. Numbers cross-checked against the Saturn CA time.
3. Current names an designations for small satellite discovered in 1979-1980 are used.
4. Don't know why this distance to Phoebe was there in the table.
5. Current estimate for Saturn CA seems to be 03:24:05.
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jasedm
post Jun 26 2008, 09:34 PM
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I never cease to be amazed at the quality of the initial reconnaisance of the Saturn system by the two Voyagers. The amount of data gathered by the two craft, which between them spent less than two weeks within Iapetus' orbit is nothing short of astonishing.
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Astro0
post Aug 20 2008, 11:12 PM
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Happy Anniversary of Launch Day Voyager 2!
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gwiz
post May 15 2009, 11:36 AM
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A few more Voyager 2 dates, source is a diagram in Spaceflight, Nov 81:

1979-07-23 TCM6
1981-07-31 Start Far Encounter 1
1981-08-11 Start Far Encounter 2
1981-08-25 Start Near Encounter (CA-16 h)
1981-08-27 End Near Encounter (CA+28 h)
1981-09-28 End Post Encounter
1981-09-29 TCM10
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Liss
post Jul 22 2009, 01:21 PM
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--- Unnecessary quoting removed! Mod. ---

Thank you very much, qwiz.
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MarcF
post Aug 22 2012, 10:53 PM
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35 years of flight !! Happy Anniversary Voyager 2 !
http://voyager.jpl.nasa.gov/news/voyager_35.html
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djellison
post Jan 22 2014, 11:45 PM
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Thought I would share the graph I plotted to help try and explain to people why sometimes the distance between Voyager 1 and 2... and Earth... sometimes shrinks.
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nprev
post Jan 23 2014, 12:45 AM
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Yeah, orbital motion & points of reference will mess you up every time. smile.gif


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Doug M.
post Feb 8 2014, 03:39 PM
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That raises a question: has anyone worked out exactly when Voyager will hit the mark of 20 billion kilometers from Earth? (It's currently 19.033 billion.) A quick BOTE calculation gives December 2015, but Earth's orbital motion makes that a very rough estimate.

I know 20 billion is just a number. But, dang, it's a big number.


Doug M.
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jamescanvin
post Feb 10 2014, 09:09 AM
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According to Horizons it will be on 4th November 2015, at 05:22 UTC in the Eastern US, 05:23 in the UK and Western US, three minutes later still in Australia.


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Doug M.
post Feb 12 2014, 09:42 AM
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Well, mark our calendars! Thank you, James.


Doug M.
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Doug M.
post Dec 30 2014, 03:25 PM
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So the official NASA extended mission plan for Voyager 1, last updated in June 2014, tells us that this is the year its gyroscope will be shut down: "Discontinue gyro operations (+14.4 W steady state, +3.6 W turn on transient and maneuver) - 2015; TBD. This power load reduction step is currently sequenced to occur on DOY 350, 2015 but could be changed if the RTG output is better than predicted."

I assume DOY 350 would be ooa December 16, 2015... Okay, so does anyone know anything more? Is the RTG output about as expected? And what consequences will there be from turning off the gyroscope?


Doug M.
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jgoldader
post Dec 31 2014, 10:59 PM
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QUOTE (Doug M. @ Dec 30 2014, 10:25 AM) *
So the official NASA extended mission plan for Voyager 1, last updated in June 2014, tells us that this is the year its gyroscope will be shut down: "Discontinue gyro operations (+14.4 W steady state, +3.6 W turn on transient and maneuver) - 2015; TBD. This power load reduction step is currently sequenced to occur on DOY 350, 2015 but could be changed if the RTG output is better than predicted."

I assume DOY 350 would be ooa December 16, 2015... Okay, so does anyone know anything more? Is the RTG output about as expected? And what consequences will there be from turning off the gyroscope?


Doug M.


AFAIK, the RTG output hasn't really changed from predictions. The exponential decay of the plutonium and degradation of the thermocouples are both well understood. Unless something in the power system fails, the wattage should be accurately predictable for the duration of the mission. But two things come immediately to mind with shutting down the gyros.

First, the periodic antenna repointings will require hydrazine when the gyros are powered down. Voyager 1 had 18 kg of hydrazine left as of September 19, and typical consumption is about 5-6 grams per week. I don't know how much a repointing will cost, or how often it needs to be done (I looked at the weekly 2014 reports, which are current up to September 19, and no repointings were obvious for either V1 or V2 during the year). Science observations on V1 (rolling the spacecraft for particles/fields) take 100-400 grams, it seems, so I'd guesstimate that much for a repointing. But if it's done annually or less frequently, there should be enough hydrazine until the RTGs finally run too low to keep the spacecraft operating.

Second, the gyros make heat. It's amazing that the spacecraft are able to function in the cold. Without heaters and insulation, they'd probably be down to 30-40K by now. It wouldn't be a terrible surprise to me if at some point, an important piece just got too cold to work. (E.g., the hydrazine freezes in the fuel lines, or a piece of electronics fails or something.)

I remember listening to Jay Barbree report the launch of one of the Voyagers in 1977, and was glued to the TV during the flybys. I sure hope to see Voyager 2 break through into interstellar space before either it or I shut down. That both V1 and V2 are still working is virtually miraculous, and a testament to the dedication and talent of the people who designed, built, and operate them.
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