The design and reconstruction of the Viking Lander descent trajectories

The success of the Viking Mission is truly a major milestone in this country's planetary exploration program. This paper deals with the trajectory characteristics of the Viking Lander descent trajectories, beginning with the imposed requirements and constraints, the final preflight design based on the final hardware and operational capability, and ending with the actual performance achieved. A comparison between the predicted and actual trajectory characteristics is made to indicate the achieved accuracy and modeling fidelity. Also, estimates of the Martian environment derived from the entry-trajectory reconstruction process are presented.