Mars Pathfinder atmospheric entry navigation operations

On July 4, 1997, the Pathfinder spacecraft ushered in a new era of planetar y exploration by successfully landing on the surface of Mars. The atmospher ic entry and approach navigation activities required in support of this mis sion are discussed. In particular, the flight software parameter update and landing site prediction analyses performed by the Pathfinder operations na vigation team are described. A suite of atmospheric entry simulation tools, developed during Pathfinder's design cycle and utilized during flight oper ations, is also presented. Data regarding the accuracy of the primary parac hute deployment algorithm are extracted from the Pathfinder flight data, de monstrating that this algorithm performed as predicted. The increased proba bility of mission success through the software parameter update process is discussed. The importance of modeling atmospheric flight uncertainties in t he estimation of an accurate landing site is also demonstrated. With these atmospheric effects included, the center of the final pre-entry landed elli pse prediction differs from the postflight determined landing site by less than 0.5 km in downrange and 5.0 km in crossrange.