On June 19, 1976, after a 10-month trip from the Earth to Mars, the first Viking spacecraft, a combined orbiter and lander, fired its engines for thirty-eight minutes and entered orbit around Mars. That Mars Orbit Insertion (MOI) maneuver officially started what was known on Viking as the Landing Site Certification Period. According to the detailed timelines and procedures that had been painstakingly developed during months of planning and testing, over the next ten days the preselected landing site at 19.5 degrees north latitude, 34 degrees west longitude, a site that had been chosen after literally years of scientific deliberation, would be confirmed as safe. The post-MOI plan originally called for the Viking lander to separate from the orbiter and land on Mars on July 4, 1976, as part of the nations bicentennial celebration.

As the geologists and other scientists analyzed the photographs in detail, a consensus quickly emerged that the pre-selected site would not be a safe place to land. A few days later, Viking project manager Jim Martin announced to the world that the project would actively search for another, safer landing site, and that a landing on July 4 was no longer possible. The next three weeks were extraordinary. Driven by the knowledge that the second Viking spacecraft was approaching Mars, and would require the full attention of the key flight team members beginning July 28, the Viking team conducted an exhausting site certification process that culminated with the historic first successful landing on another planet on July 20, 1976.

Viking was an ambitious mission. Altogether there were four spacecraft, two orbiters and two landers. Each orbiter and lander flew as a coupled pair from Earth to Mars, and separated in Mars orbit when the lander was ready to descend to the Martian surface. The twin Viking orbiters had cameras, an infrared thermal mapper, and a Mars atmospheric water detector. In addition to instrumentation to measure the composition and structure of the Martian atmosphere during descent, the Viking landers carried a full suite of sophisticated science experiments, including cameras, a meteorology boom, three biological instruments, separate organic and inorganic chemistry experiments, and a seismometer. Although the primary purpose of the landed mission was the search for life, the characterization of the Martian surface was also of great scientific importance.

The Langley Research Center managed Viking for NASA. JPL built the two Viking orbiters and provided both the Deep Space Network for tracking and the Mission Operations Center in California. Martin-Marietta was the prime contractor for the twin landers. Jim Martin from NASA-Langley was the project manager from conception to completion. He managed all the diverse elements of the project and was, without question, the single person most responsible for Vikings ultimate success.