Thank you for answering my question in language I can understand. 😊
That variation just goes back and forth every 6 months. Earth swings around in its orbit sometimes going towards V and then it starts receding. Seems to happen like clockwork😉
What does happen though is doppler shift. Doppler shift is heard by people hearing a train approach and recede, it sound different coming and going. Same thing happens to radio waves, if you go towards the source, the frequency goes up and if you go away from the source the frequency goes down. That is the basis for cops highway radar. It has to be accounted for when you have tight frequency bands to deal with. At the rate of transmission from 4 billion miles away the data rate is only about a thousand bits per second and they are lucky to get that with the transmitter only being a few watts but helped out by huge radio telescopes tracking it.
There was one probe that was out near Jupiter and the ability to track frequency changes needed to compensate for doppler shift was lost so the brains at NASA had to come up with an exact number to change the TRANSMIT signal to make sure they still could communicate with that probe.
My little bit was Apollo tracking and timing. I also worked on early weather sats. One of my best times was in class using a student dish, maybe 12 feet in diameter at Goddard, the assignment was to find and lock signal with an orbiting Mars probe. So first I had to figure out exactly where Mars was ATT, get the proper co-ordinates to the antenna motors and then phase lock on the signal.
It all went perfectly, locked on to that sucker in record time😉 I was thinking at the time, Mars was about 100 million miles from Earth ATT and I was locked on to that signal being sent by a FIVE WATT transmitter, the power of a frigging CB set! It was awe inspiring. Another awesome moment was working at Goddard and got to talking to my next door neighbor and he said he worked at Goddard also. His job was geological technician, he cut the moon rocks into slices for the scientists to analyse. So he invited me into his lab and that turned out to be a fort Knox size vault the size of a whole room, and he took me in there and there were dozens of moon rocks waiting to be sliced and diced by him. He hands me a moon rock and I was like religious mode😉 Then I asked him, why can you put this rock right in my hand without me wearing gloves or something. He answered, just when the rocks come back from the moon, and we open the case they were brought in, they are already contaminated, but on the outside only. That is why he sliced of bits of the rocks for analysis, you do that in a pristine environment and you get uncontaminated insides of the rocks. It was like epiphany for me to see the results of all those astronauts coming back from the moon, a dozen men all told walked on the moon.
It must have been awesome for your dad you have worked on Voyager. One thing I though neat about the sat I worked on, they had lots of switching relays but the ones I deal with need power to hold them on in one state or the other, off or on.
But the sat relays were designed with little magnets on the moving reeds so that the only power needed was a 100 millisecond pulse to overcome the magnetic field of the magnets on the reeds so that when it switched, it stuck together without power. I thought that was genius. But then, I am a lifelong nerd😉