John Carlos BaezAug 6, 2023

I have so many questions about what just happened with Voyager 2. But let's review:

On August 20, 1977, Voyager 2 was launched from Earth.

In December 1977, it entered the asteroid belt.

In June 1978, its main radio receiver failed. Since then it's been using the backup receiver!

On July 9, 1979, it flew past many of Jupiter's moons, made its closest approach to Jupiter, and took tons of beautiful pictures.

On August 26, 1981 it shot past Saturn and took tons of beautiful pictures.

On August 25, 1989 it shot past Neptune and took tons of beautiful pictures.

On November 5, 2018 it crossed the heliopause and entered interstellar space, 120 times farther from the Sun than we are.

On July 18, 2023, it overtook Pioneer 10 and became the second farthest man-made object from the Sun.

3 days later, some idiot sent a command that pointed its high gain antenna 2 degrees away from Earth. HOW EXACTLY DID THIS HAPPEN?

On August 4, 2023, NASA used its most high-powered transmitter to successfully command Voyager 2 to reorient towards Earth, resuming communications. HOW WAS THAT POSSIBLE?

Voyager 2 is now 133 AU away. How can you "shout" across such a distance and attract the attention of someone who is not looking in your direction? That's very far. It takes light about 18 hours to travel that far.

Show threaddragfyreAug 6, 2023

@johncarlosbaez As far as I heard, Voyager was programmed to "right itself" in case it found that it wasn't pointed in the general direction of the Earth, which it would check by taking pictures of reference stars. Don't quote me on that, though.

EDIT: Corrections given in replies!

Show threadRicardo
@dragfyre @johncarlosbaez That would have happened, eventually, but that's not what actually happened. AFAIK, the antena does not have a single high sensitivity direction (think of diffraction patterns), so even if it's pointing in the wrong direction it's possible to target one of the lower "secondary sensitivity peaks" if you beam loud enough. But bear in mind that IANAVI (I'm not a Voyager engineer)
Aug 6, 2023 at 9:55amWeb
Show threadJonathan WilliamsAug 6, 2023

@RGBes
@dragfyre @johncarlosbaez

That's correct. As with all antennas, Voyager's high gain antenna has an antenna pattern with a main high gain lobe, but also has sidelobes. In other words, it will pick up signals from other directions, but they have to be stronger.

The farther off axis, generally speaking, the lower the gain and the stronger the signal has to be, but it's not an even decline.

In this case, fortunately, NASA was able to send a signal of sufficient strength that Voyager picked it up anyway.

Show threadDavid J. AtkinsonAug 6, 2023
@johncarlosbaez @RGBes @Jwilliams @dragfyre About that error in commands: there is an investigation in progress and we will learn what happened. I spent most of my career at JPL. I pushed for automation of the operations consoles in the Deep Space Network. In addition to controlling the antennas and ground data systems, these consoles are used to send routine commands to spacecraft. (continued)
Show threadDavid J. AtkinsonAug 6, 2023
@johncarlosbaez @RGBes @Jwilliams @dragfyre I did not succeed in persuading NASA to upgrade the ops consoles. Why? International prestige and labor politics. DSN stations are located worldwide, with the largest 60 meter antenna dishes in the US, Spain, and Australia. Other than in the US, the operator console jobs are considered very high tech and important to national prestige. (continued)
Show threadDavid J. AtkinsonAug 6, 2023
@johncarlosbaez @RGBes @Jwilliams @dragfyre The jobs are also staffed by union members under contract. Any proposed change to the consoles that would even appear to automate them is rejected immediately. My hypothesis about the mid command: operator error. Why? In my day, consoles used a command line. Everything was typed manually. Typos are not frequent, but they occur. 🤷‍♂️