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Voyager Status, What is it?
ngunn
post Nov 22 2007, 12:49 PM
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V1 had no 'next destination' after Saturn and therefore needed no trajectory changes. It's been in freefall since Saturn.
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jasedm
post Nov 22 2007, 01:00 PM
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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.
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ugordan
post Nov 22 2007, 01:07 PM
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QUOTE (jasedm @ Nov 22 2007, 02:00 PM) *
1) Maybe voyager operators were more sparing of the propellant for V2 knowing that Uranus (and beyond) were at least 'on the cards' from the off.

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

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


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jasedm
post Nov 22 2007, 01:41 PM
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QUOTE (ugordan @ Nov 22 2007, 01:07 PM) *
Rule of thumb: fewer targetted encounters = less fuel consumed.


That's just the reason for my surprise in post 56 above:
Voyager 1 - housekeeping attitude control since November 1980 (except for the family portrait shot)
Propellant left: 27.7kg on July 6th 2007
Voyager 2 - observations of an additional two planets/ring systems and at least 10 moons since Saturn encounter
I understand the amount of spacecraft slewing at Uranus was huge due to the number of targets at C/A coupled with the planet's axial tilt
Propellant left: 29.41kg on July 6th 2007 smile.gif
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djellison
post Nov 22 2007, 02:03 PM
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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
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ugordan
post Nov 22 2007, 02:07 PM
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QUOTE (djellison @ Nov 22 2007, 03:03 PM) *
Didn't someone say here a while back that one of the two had an LV underperform a little?

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


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Bernard1963
post Jun 20 2019, 09:06 AM
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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?
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stevesliva
post Jun 20 2019, 12:51 PM
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A month ago, Voyager 2 notes this sort of activity:

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

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

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

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

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


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

I take that back... there might be more to be gleaned here: https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_08.sfos.pdf
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Bernard1963
post Jul 5 2019, 08:51 PM
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Thank you stevesliva. Even though I've only just joined the forum I'm a long time fan of the Voyagers and follow all posts available. The problem was, there was no answer that could be derived online. The condition of Voyager 1 has deteriorated with the signal variations increasing. Personally I was expecting the spacecraft to be lost before too long. I gather today the Voyager team have finally admitted a problem with the Earth pointing of the spacecraft. In a way of confirmation for the first time today I noticed the tracking schedule was not followed as per https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_22.sfos.pdf with Voyager 1 taking the slot of Voyager 2 on DSS43 and arrayed with DSS34 & DSS35. I understand the team are investigating a yaw error and hope to make corrections shortly. My only fear now is that Voyager 1 is so far off point it may be difficult to upload commands.
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Bernard1963
post Jul 5 2019, 08:56 PM
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On the subject of Voyager 2 I notice from https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_22.sfos.pdf it looks like Voyager 2 will be swapping attitude control trusters to its TCM thrusters on July 9th, as was done with Voyager 1 in Jan 18.
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Xcalibrator
post Jul 6 2019, 02:35 PM
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QUOTE (Bernard1963 @ Jun 20 2019, 04:06 AM) *
I was wondering if anyone else had noticed...


Looking back, the V1 particle data started showing noticeable gaps around June 6.
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Bernard1963
post Jul 9 2019, 10:38 AM
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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
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stevesliva
post Jul 9 2019, 01:24 PM
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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.
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JRehling
post Jul 10 2019, 05:08 AM
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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.
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Bernard1963
post Aug 17 2019, 12:24 AM
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I've noticed the past couple of days Voyager 1's signal is low again into the DSN, presumably off point again. Tracking times available here https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._09_02.sfos.pdf the levels received here https://eyes.nasa.gov/dsn/dsn.html you should see roughly -155db on a 70m and -157db on a 34m dish.
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