Voyager 1 is still on its way to outer space and currently (Jan. 2024) 24.4 billion km away from earth.

Due to dimishing radioactiv power a lot of instruments had to shut down, but the probe is still able to send data. Even though that takes 22.5h one way and currently only transmits glitched data this counts for the purpose of this market.

This market will resolve to the year in which the last successful communication with the probe will be made.

https://en.wikipedia.org/wiki/Voyager_1