Mars Pathfinder atmospheric entry: Trajectory design and dispersion analysis

The Mars Pathfinder spacecraft will enter the Martian atmosphere directly from the interplanetary trajectory, with a velocity of up to 7.35 km/s. The definition of the nominal entry trajectory and the accurate determination of potential trajectory dispersions are necessary for the design of the Pathfinder entry, descent, and landing system. Monte Carlo numerical simulations have been developed to quantify the range of possible entry trajectories and attitude profiles. The entry trajectory requirements and constraints are discussed, and the design approach and uncertainties used in the Monte Carlo analysis are described. Three-degree-of-freedom and six-degree-of-freedom trajectory results are compared. The Monte Carlo analysis shows that the Mars Pathfinder parachute will be deployed within the required ranges of dynamic pressure, Mach number, and altitude, over a 3 sigma range of trajectories. The Pathfinder 3 sigma landing ellipse is shown to he roughly 50 x 300 km.