Curious to know how this recalibration actually works. Any explainer that anyone can point to would be appreciated. Thanks!
So I presume it uses its thrusters to impart a very small spin on one axis, and then on an orthogonal axis.
A mechanism records the signal strength as it sweeps all angles, and once the optimum direction is determined, the thrusters are fired in just the right way to counteract the spin and bring the craft to a halt at the optimum orientation.
Given this was programmed decades ago - the electromechanical system that does all this jugglery and runs reliably for so long would be a great case study for systems design.
Even the programming that ensures that this routine is triggered without fail every few months must also have gone through intense reliability testing.
I skimmed though the Voyager document and it seems to have very good coverage of overall telecommunications system.
For the topic of the periodic calibration the following is all I could spot
>> Four 7-hour and two 0.5-hour attitude control calibration maneuvers are performed per spacecraft every year, each requiring 70-m station downlink coverage to ensure uninterrupted downlink telemetry.
While this is interesting in itself, it merely states the schedule but doesn't satisfy my curiosity about the exact mechanism used to do the recalibration.
Thanks nevertheless. Interesting reads here.
It is billions km away.., is the earth that noisy compare to solar wind and cosmic rays?
The carrier signal from Earth is also powerful on a particular frequency and polarization. While there's definitely noise at the receiver it's looking for a very specific signal so can filter out everything it's not expecting. We do the same thing on the Earth side, filtering out noise to recover the very weak signal received from Voyager.
Doesn't even matter if voyager is heading towards it or not, it's still crazy far away. Voyager is still on our doorstep as far as interstellar distances go.
Here is a photo from Voyager 1 at a distance of 4Bn miles:
Voyager 2 is 160.7 AU.
Light falls off in brightness to the distance squared. So the sun will be 160.7^2 = 25824.5 times fainter for Voyager 2 than it is from Earth. (Since Earth is at 1AU)
The apparent magnitude of the sun from Earth is -26.72. Each step in magnitude is multiplying by 2.512. (2.512^5 = 100, so 5 steps of magnitude is a factor of 100).
log2.512(25824.5) = 11.0295.
11.0295 + -26.72 = -15.6905.
The apparent magnitude of the full moon is only −12.74 (lower is brighter). So for Voyager 2 the sun is still several times brighter than we see the moon. The sun is still many many times brighter than the next brightest star in the sky, Sirius, which has an apparent magnitude of −1.46.
Sources: Voyager 2 distance is https://voyager.jpl.nasa.gov/mission/status/ all else is Wikipedia.