There were many independent parties that tracked the Apollo missions.
The most important of these is the Soviet Union. They were at war with the USA (the Cold War). The Soviet Union had their own Moon program, which, although very promising early-on, failed to land a person on the Moon before NASA did.
The Soviet Union tracked the Apollo Moon missions, from Earth to the Moon, and from the Moon back to Earth. They confirmed the landings, and this is why they eventually shut-down their Moon program. They lost the race.
Here’s a thought: Given the stakes, don’t you think that the Soviet Union would have been the first to jump at the idea, if NASA had really “faked it”? They didn’t have a sliver of doubt about the Apollo landings – because they actually watched them happen, using their own equipment. Make sense?
Other countries, organizations, universities, and schools also tracked the Moon missions, using radar, visible-light telescopes and other equipment.
Aside from all that, this is what I find most fascinating:
There were many amateur astronomers and space enthusiasts who took the trouble to set-up their individual telescopes and observe the missions by themselves. Some even listened in on radio transmission data from the Moon to Earth. Because they were receiving radio signals from the Moon, the recordings are one-sided – you only hear the transmission from the Moon to Earth, without Mission Control’s responses. How wonderful is that?
To find out more about this, you can check-out the link below: