Viking 1

Viking 1 was successfully launched on 20 August 1975 by a Titan III E rocket from complex 41 at Cape Canaveral. After an incident-free 10 month journey, the orbiter took its first photographs of the planet Mars 5 days after the crucial stage of orbital insertion. The probe was put into orbit around Mars on 19 June 1976. The initial orbit was quickly modified to the orbit for landing site certification. This orbit, reached on 21 June, has a periapsis of 1513 km and an apoapsis of 33,000 km. The period of revolution is 24.66 hours, synchronised with the rotation of the planet. The orbiter can therefore fly over the same region on each periapsis, which is very useful in certifying landing sites.

Viking 1 landed on Martian soil to the west of Chryse Planitia on 20 July 1976.

Source: www.nirgal.net/explora_1976.html