There are answers about Voyager 1 sending messages to Earth, but can Earth still send signals to Voyager 1? I am just wondering if the signal of the Sun will eventually overcome the signal from Earth or if the signal from Earth will become too attenuated for Voyager 1's antenna to pick up.
Yes, the Earth can send Voyager 1 a message as easily as we can receive a message. There are a few differences between the uplink and the downlink paths.
- We cannot upgrade the radio on Voyager 1 to newer equipment (but an upgrade to the Earth station is equally beneficial),
- The gain of the antennas on the spacecraft and on Earth are constant, and the free space path loss is the same for both uplink and downlink. This means that for a given transmit power (either direction) the received power will be the same (But not the intensity of the wave entering the receive antenna. See here for details).
- The performance of the spacecraft's transmitter and receiver may be slightly different from those on earth,
- The noise seen by Earth and Voyager 1 will be slightly different (Voyager is pointed towards the sun, dishes on Earth are pointed into space).
Phew! Now that all of that is stated, YES signals from Earth will become more attenuated as distance increases. BUT, we have the advantage that we can use more and more powerful amplifiers (to a point).
As MSalters pointed out, the limiting factor will likely end up being a lack of electrical power from the RTG to point the spacecraft accurately and/or power the spacecrafts LNA. We can continue improving the ground stations here for quite a while. We even have developed better error correcting codes since the Voyagers were launched (turbo codes vs Reed-Solomon), so any future deep space missions will be able to go even further (all else equal).
EDIT: Updated to clarify several points I had glossed over initially. Thanks SF. EDIT 2: Fixed typo. Thanks JDługosz.
Yes. The onboard sequence on both Voyagers is updated every month and a half or so. What's more, there is a DSN pass every few days, in which there is ranging requiring the receipt and turn-around of a pseudo-noise signal, and there are simple commands in every pass, like resetting the uplink loss timer.
The Voyagers' power will run down well before we can no longer communicate with them. Were it not for power, we could communicate with them for another century, or more (even with no Earth antenna upgrades over that time, which could make it go even longer). The money will likely run out before the power to communicate, once we can no longer operate any science instruments due to insufficient power. This is estimated to be around 2025.
Yes, but it's not sure how long that will last. The problem is that Voyager needs to aim its receiver towards earth, and it's losing its capability to do so.
While we may not have constant signal, we could easily plan when we'd have the best opportunities for a signal and perhaps get better quality during specific times of the year. If deemed valuable enough, we could implement the lifeline method - send another probe as a signal relay, along with the newest version of technology to, and then we can continue such missions, upgrading as we move outward. It could perhaps follow a slightly different trajectory, and travel in a parallel (yet curved) path, and still stay in contact with the Voyager 1, plus have better reception for the rest of its service days.
Given the mathematical geniuses we have in this forum, it would be conceivable to simply upload a short table of dates/times/angles for best signal reception, refreshing it over time, as dates roll off.