6 ms·

> it is programmed to recalibrate its position a few times a year. October 15 is the next scheduled reset. Curious to know how this recalibration actually work

> it is programmed to recalibrate its position a few times a year. October 15 is the next scheduled reset. Curious to know how this recalibration actually works. Any explainer that anyone can point to would be appreciated. Thanks!

ZiiS 3y ago
Not a rocket scientist; but I have tuned in a TV. I imagine it is simply programed to turn a few degrees then turn back to wherever it saw the strongest signal from earth.
- albert_e 3y ago
  Makes sense. 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.
  - ilyt 3y ago
    doesn't even need thrusters if it has reaction wheels that are still operational
- j16sdiz 3y ago
  But....How does it know it's the earth? It is billions km away.., is the earth that noisy compare to solar wind and cosmic rays?
  - giantrobot 3y ago
    Voyager has a star sensor that is meant to align with the Sun and Canopus (IIRC). If both are properly aligned it means it's pointed in the right direction. At its current distance the beam width is wide enough to cover all of Earth's orbit. So really it just needs to point at the Sun anymore. 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.
JdeBP 3y ago
Start at the Voyager book at https://descanso.jpl.nasa.gov/DPSummary/summary.html https://descanso.jpl.nasa.gov/DPSummary/summary.html .
- albert_e 3y ago
  Excellent link - thanks 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.
  - JdeBP 3y ago
    The Voyager Neptune Travel Guide mentions things like the Canopus Star Tracker and the Sun Sensor. https://ntrs.nasa.gov/citations/19900004096 https://ntrs.nasa.gov/citations/19900004096
    - albert_e 3y ago
      Thanks!
sqrt_1 3y ago
Good video on the topic - there is a sun sensor on the dish - looks for the brightest object and orients to face it. https://www.youtube.com/watch?v=NbsHgE89qO4&t=340s https://www.youtube.com/watch?v=NbsHgE89qO4&t=340s
- albert_e 3y ago
  Superb! Thanks for the link.
- superb_dev 3y ago
  For all the distance Voyager has covered, our Sun is still the brightest object in its view? That’s incredible
  - BenjiWiebe 3y ago
    Approx one light-day out. The nearest star is 4.2 light-years out. 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.
  - Rebelgecko 3y ago
    The space between stars is truly immense. The sun is still 2,000 times closer to Voyager 2 than the next star
- qingcharles 3y ago
  How bright does the Sun appear compared to other stars at a distance of 32Bn km? Here is a photo from Voyager 1 at a distance of 4Bn miles: https://photojournal.jpl.nasa.gov/catalog/PIA00450 https://photojournal.jpl.nasa.gov/catalog/PIA00450
  - Laremere 3y ago
    Trying to see if I can work this out. 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/ https://voyager.jpl.nasa.gov/mission/status/ all else is Wikipedia.

ZiiS 3y ago

Not a rocket scientist; but I have tuned in a TV. I imagine it is simply programed to turn a few degrees then turn back to wherever it saw the strongest signal from earth.

albert_e 3y ago
Makes sense. 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.
- ilyt 3y ago
  doesn't even need thrusters if it has reaction wheels that are still operational
j16sdiz 3y ago
But....How does it know it's the earth? It is billions km away.., is the earth that noisy compare to solar wind and cosmic rays?
- giantrobot 3y ago
  Voyager has a star sensor that is meant to align with the Sun and Canopus (IIRC). If both are properly aligned it means it's pointed in the right direction. At its current distance the beam width is wide enough to cover all of Earth's orbit. So really it just needs to point at the Sun anymore. 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.

JdeBP 3y ago

Start at the Voyager book at https://descanso.jpl.nasa.gov/DPSummary/summary.html https://descanso.jpl.nasa.gov/DPSummary/summary.html .

albert_e 3y ago
Excellent link - thanks 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.
- JdeBP 3y ago
  The Voyager Neptune Travel Guide mentions things like the Canopus Star Tracker and the Sun Sensor. https://ntrs.nasa.gov/citations/19900004096 https://ntrs.nasa.gov/citations/19900004096
  - albert_e 3y ago
    Thanks!

sqrt_1 3y ago

Good video on the topic - there is a sun sensor on the dish - looks for the brightest object and orients to face it. https://www.youtube.com/watch?v=NbsHgE89qO4&t=340s https://www.youtube.com/watch?v=NbsHgE89qO4&t=340s

albert_e 3y ago
Superb! Thanks for the link.
superb_dev 3y ago
For all the distance Voyager has covered, our Sun is still the brightest object in its view? That’s incredible
- BenjiWiebe 3y ago
  Approx one light-day out. The nearest star is 4.2 light-years out. 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.
- Rebelgecko 3y ago
  The space between stars is truly immense. The sun is still 2,000 times closer to Voyager 2 than the next star
qingcharles 3y ago
How bright does the Sun appear compared to other stars at a distance of 32Bn km? Here is a photo from Voyager 1 at a distance of 4Bn miles: https://photojournal.jpl.nasa.gov/catalog/PIA00450 https://photojournal.jpl.nasa.gov/catalog/PIA00450
- Laremere 3y ago
  Trying to see if I can work this out. 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/ https://voyager.jpl.nasa.gov/mission/status/ all else is Wikipedia.