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 and made its closest approach to Jupiter.
On August 26, 1981 it shot past Saturn.
On August 25, 1989 it shot past Uranus.
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?
How can you "shout" across 120 AU? It takes light about 16 hours to travel that far.
@johncarlosbaez Amazingly, the radio power received on earth from the Voyager spacecraft transmitting in the GHz range at 20 W is about an ***attowatt (1e-18 W)***, since they are on the order of 20 billion kilometers from earth !
See info here (it refers to Voyager 1 but for these estimates I think both Voyager are about the same figures):
https://public.nrao.edu/ask/how-strong-is-the-signal-from-the-voyager-1-spacecraft-when-it-reaches-earth/
@FMarquardtGroup @johncarlosbaez
Do they mean that the total energy absorbed by the Earth is ~1e-18W? If not, I'm confused by the units: I'd expect people to talk about power per unit of surface area.
@robryk @FMarquardtGroup @johncarlosbaez ...and also "per Hz of bandwidth". As given, this number really doesn't tell us a lot...
@robryk @johncarlosbaez No, I believe that number already figured in the size of the receiver antennas (and the directionality of the transmission), so it is the overall power received. But it doesn't say explicitly there.