Using inertial measurements for the reconstruction of 6-DOF entry, descent, and landing trajectory and attitude profiles

A method was sought for estimating the "stroke" distance between a Mars Exploration Rover (MER) test lander (protected by airbags) and a surface during impact. The authors at JPL have developed a suite of software known as REDLand (for Reconstruction of Entry, Descent and Landing) to accomplish this. REDLand uses data from accelerometers and gyroscopes on board the lander test body as measurements in an extended Kalman filter, in addition to geometric and dynamical constraints, and other data, where available. This paper is a discussion of the formulation of the REDLand filter algorithms and presents results from actual MER airbag-and-lander impact tests made in 2001.