MARS PATHFINDER ATMOSPHERIC ENTRY - TRAJECTORY DESIGN AND DISPERSION ANALYSIS

The Mars Pathfinder spacecraft will enter the Martian atmosphere direc tly 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 th e design of the Pathfinder entry, descent, and landing system. Monte C arlo numerical simulations have been developed to quantify the range o f possible entry trajectories and attitude profiles. The entry traject ory requirements and constraints are discussed, and the design approac h and uncertainties used in the Monte Carlo analysis are described. Th ree-degree-of-freedom and six-degree-of-freedom trajectory results are compared. The Monte Carlo analysis shows that the Mars Pathfinder par achute 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 .