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Analyst
QUOTE (Pando @ Jun 14 2007, 05:17 AM) *
Since I couldn't find any info about it on this forum nor any news anywhere else, I'd like to see if anyone knows a bit more what the heck happened there and whether the magnetometer was successfully recharacterized after the recent roll. Also, did this have any long term impact to the health of the spacecraft?


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

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

HYBIC SWAP TEST RESULTS

REDUNDANT HYBIC TEST & TEMPORARY SWAP

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

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

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

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

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

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

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

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

--The permanent swap has been delayed until this investigation is complete.
dilo
I tried to plot the measured magnetic field components reported on the same link where Pando took the warning (note that I sampled only some interesting time windows):
Click to view attachment
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...
abalone
Fantastic birthday.The Voyagers will outlive them all
biggrin.gif biggrin.gif biggrin.gif biggrin.gif

http://www.space-travel.com/reports/Pionee...Flight_999.html
jasedm
QUOTE (Guido @ Aug 11 2007, 08:28 AM) *


I'm very surprised that V2 has more remaining propellant than V1 after double the planetary encounters (see report for 2007-07-06)
brellis
QUOTE (jasedm @ Nov 22 2007, 01:59 AM) *
I'm very surprised that V2 has more remaining propellant than V1 after double the planetary encounters (see report for 2007-07-06)


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

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

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

Doug
ugordan
Or maybe one of the spacecraft is inherently more "stable" and hence does less RCS thrusting?
brellis
"needed less propellant - for what?"

The extra planetary encounters would also help point the craft to its next destination, thus saving propellant on trajectory changes.
ngunn
V1 had no 'next destination' after Saturn and therefore needed no trajectory changes. It's been in freefall since Saturn.
jasedm
Thinking about it, perhaps the answer is a combination of several factors:

1) Maybe voyager operators were more sparing of the propellant for V2 knowing that Uranus (and beyond) were at least 'on the cards' from the off.
2). Different trajectories and speeds of the two spacecraft
3) V1 I think had to make a huge (many minutes) burn to set up for the Titan close encounter.
ugordan
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 .
jasedm
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
djellison
What I was suggesting is that perhaps V1's trajectory inherantly required significantly more Delta V for..

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

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

Doug
ugordan
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.
Bernard1963
I was wondering if anyone else had noticed / had any info on what appears to be a mystery about the low and varying signal from Voyager 1? For well over a month now the signal from Voyager 1 (as shown on https://eyes.nasa.gov/dsn/dsn.html) has been varying by approx 3db over the course of an hour or so and its at best about 2db lower than it should be, at worst 5db or 6db lower. With DSS63 out for long term maintenance its currently often being tracked on 2 x 34m dishes at Madrid which are unable to obtain data lock for much of the time. Only DSS14 now seems able to hold data lock.

Tweeting one of the Canberra DSN controllers he confirms this is the case, its not a website anomaly. The mystery is that he tells me the Voyager project apparently are not seeing any problem with the spacecraft?
stevesliva
A month ago, Voyager 2 notes this sort of activity:

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
Bernard1963
Thank you stevesliva. Even though I've only just joined the forum I'm a long time fan of the Voyagers and follow all posts available. The problem was, there was no answer that could be derived online. The condition of Voyager 1 has deteriorated with the signal variations increasing. Personally I was expecting the spacecraft to be lost before too long. I gather today the Voyager team have finally admitted a problem with the Earth pointing of the spacecraft. In a way of confirmation for the first time today I noticed the tracking schedule was not followed as per https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_22.sfos.pdf with Voyager 1 taking the slot of Voyager 2 on DSS43 and arrayed with DSS34 & DSS35. I understand the team are investigating a yaw error and hope to make corrections shortly. My only fear now is that Voyager 1 is so far off point it may be difficult to upload commands.
Bernard1963
On the subject of Voyager 2 I notice from https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._07_22.sfos.pdf it looks like Voyager 2 will be swapping attitude control trusters to its TCM thrusters on July 9th, as was done with Voyager 1 in Jan 18.
Xcalibrator
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.
Bernard1963
They've fixed it pretty quickly once they admitted the problem, but it had got very bad. The signal is now stable and the strength is as expected :-) https://eyes.nasa.gov/dsn/dsn.html
stevesliva
Coincidentally posted yesterday:
https://voyager.jpl.nasa.gov/news/details.php?article_id=114

I haven't see anything other than this thread mentioning an anomaly... in any event, amazing what they're still doing with these two.
JRehling
I don't nitpick often (do I?) but while the Voyagers are perhaps the oldest spacecraft still operating, Vanguard 1 (launched March 17, 1958) is the oldest spacecraft still flying, though it's been dead and inert since 1965.
Bernard1963
I've noticed the past couple of days Voyager 1's signal is low again into the DSN, presumably off point again. Tracking times available here https://voyager.jpl.nasa.gov/pdf/sfos2019pd..._09_02.sfos.pdf the levels received here https://eyes.nasa.gov/dsn/dsn.html you should see roughly -155db on a 70m and -157db on a 34m dish.
Bernard1963
I should have noted that around the 7th September there was a sun sensor calibration and ASCAL which does appear to have fixed the pointing issue and the signal into the DSN has been as expected since then. However as this was the 2nd such incident in the past 6 months I wonder if the sun sensor is having trouble keeping a lock on the sun, now at 147AU.
Bernard1963
With info taken from one of the controllers at Canberra on twitter and my observations from https://eyes.nasa.gov/dsn/dsn.html, Voyager 2 was lost for a period of 5-10minutes in the early hours of 26/01/20 while attempting a MAGROL. It looks like an attitude control issue occurred causing the S/C to go off point from the earth. I'm assuming the fault protection kicked in and got the S/C back on point fairly quickly. The S/C was then in engineering mode 40bps rather than the usual 160bps. Even though the Voyager tracking schedule showed no further tracking, later in the day Canberras DSS43 70m dish was tracking and the Canberra website showed a horizon to horizon track was taking place. Its therefore reasonable to assume a spacecraft emergency had been declared with other missions being moved off of DSS43. Checking the most recent track earlier today Voyager 2 remains at 40bps (engineering mode).
stevesliva
My brain is hurting because morning in Canberra is so many hours before here, but it sounds like the most recent tracking was to determine whether the commands sent "later in the day" were received. Round trip time is so slow that this seems fast.
DSN antenna DSS-43 at @CanberraDSN opening a 3-1/2 hour listening window to see if recent emergency XMIT was received
Bernard1963
https://www.jpl.nasa.gov/news/news.php?feature=7587
Roby72
Canberra still tracking VGR2 at 39bits/sec as of February 2nd, 21h30UT as seen in DSN NOW
Now one week gap of science data.
Any thoughts ?
stevesliva
QUOTE (Roby72 @ Feb 2 2020, 04:35 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 ?

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