Mars reappeared from behind the Sun, as viewed from Earth in mid-December 1976. This signaled the start of the so-called extended mission. Communication with all four spacecraft was reestablished. This phase of the mission was planned to continue through May of 1978, perhaps even longer.
Examples abound in the annals of exploration, particularly mountaineering.
So it is with the extended mission. Complicated sequences of trenching and sample acquisition are carried out without fanfare. Many more pictures have been taken than during the primary mission. Before the Viking mission is completed we will have monitored the environment for almost a complete martian year, or one revolution about the Sun, a total of 687 Earth days. The scientific return is just now being cataloged.