I saw a movie in the early 80's that could be from the late 70's and I remember that the crew had at least five or six members. So it's not Strange New World (just three members) as one answer suggested, nor any of the other like Planet Earth or Genesis II. They were all men, or maybe there was also a woman. I saw it on TV just one time and never saw it again. It was a simple plot, but really well done and with a very unexpected finale.
The crew return to earth and like the other question says, they don't receive any kind of signal. They don't know what happened and everything looks deserted and depopulated. In finding some ruins, they seem to understand that there's been a nuclear war. The movie is about their struggle to find out what happened and determine whether there's any civilization left. They have almost no food and water. They begin to lose hope, and even fight with each other. Some become ill and die. And maybe, in fighting, someone gets killed. It was all very dramatic.
I don't remember the dialogue, the characters, or the scenes, but I remember the end quite well. At the end, just one of them is walking in the desert and falls down exhausted and ready to die. After all that's happened, you think it's really the end, but then he kind of wakes up and seems to hear something and, after walking a few steps more, behind the next dune he starts seeing the blurry sketch of a city not so far away — blurry because of the heat of the desert. And the movie ends showing the man walking through a street of the city where people are walking and children are playing, not paying attention to him, and leaving you to wonder why they aren't helping him even while you are happy that he survived.