(Georgia Institute of Technology, 2012-01)
Dutta, Soumyo; Braun, Robert D.; Russell, Ryan P.; Clark, Ian G.; Striepe, Scott A.
Flight data from an entry, descent, and landing (EDL) sequence can be used to
reconstruct the vehicle's trajectory, aerodynamic coefficients and the atmospheric profile
experienced by the vehicle. Past Mars missions have contained instruments that do not
provide direct measurement of the freestream atmospheric conditions. Thus, the
uncertainties in the atmospheric reconstruction and the aerodynamic database knowledge
could not be separated. The upcoming Mars Science Laboratory (MSL) will take
measurements of the pressure distribution on the aeroshell forebody during entry and will
allow freestream atmospheric conditions to be partially observable. This data provides a
mean to separate atmospheric and aerodynamic uncertainties and is part of the MSL EDL
Instrumentation (MEDLI) project. Methods to estimate the flight performance statistically
using on-board measurements are demonstrated here through the use of simulated Mars
data. Different statistical estimators are used to demonstrate which estimator best quantifies
the uncertainties in the flight parameters. The techniques demonstrated herein are planned
for application to the MSL flight dataset after the spacecraft lands on Mars in August 2012.
(Georgia Institute of Technology, 2011-06)
Dutta, Soumyo; Clark, Ian G.; Russell, Ryan P.; Braun, Robert D.
The Phoenix Lander successfully landed on the surface of Mars on May 25, 2008. During the entry, descent and landing (EDL), the vehicle had instruments on-board that took sensed acceleration, angular rates and altimeter measurements. In this study, methodology used to reconstruct the trajectory and other EDL performance information using a statistical filter to process the observations from the sensors is demonstrated. A statistical filter estimates parameters simultaneously with the uncertainty in the estimates. The results presented here will include Phoenix’s event timeline, trajectory information, time-of-flight atmosphere and aerodynamic coefficients of an EDL subsystem as well as the uncertainty in the estimated states.