Mars Entry Atmospheric Data System Trajectory Reconstruction Algorithms and Flight Results

Abstract

The Mars Entry Atmospheric Data System is a part of the Mars Science Laboratory, Entry, Descent, and Landing Instrumentation project. These sensors are a system of seven pressure transducers linked to ports on the entry vehicle forebody to record the pressure distribution during atmospheric entry. These measured surface pressures are used to generate estimates of atmospheric quantities based on modeled surface pressure distributions. Specifically, angle of attack, angle of sideslip, dynamic pressure, Mach number, and freestream atmospheric properties are reconstructed from the measured pressures. Such data allows for the aerodynamics to become decoupled from the assumed atmospheric properties, allowing for enhanced trajectory reconstruction and performance analysis as well as an aerodynamic reconstruction, which has not been possible in past Mars entry reconstructions. This paper provides details of the data processing algorithms that are utilized for this purpose. The data processing algorithms include two approaches that have commonly been utilized in past planetary entry trajectory reconstruction, and a new approach for this application that makes use of the pressure measurements. The paper describes assessments of data quality and preprocessing, and results of the flight data reduction from atmospheric entry, which occurred on August 5th, 2012.

Assessment of the Reconstructed Aerodynamics of the Mars Science Laboratory Entry Vehicle

“…Papers by Karlgaard et al [13,14] describe the preliminary reconstruction process and a preliminary Kalman Filter reconstruction using all available data sets. For this analysis, the DIMU and MEADS data were used together to estimate the best entry trajectory of the MSL entry capsule.…”

A Modified Triples Algorithm for Flush Air Data Systems That Allows a Variety of Pressure Port Configurations

“…Predictions were invalid until the flow was at low supersonic numbers, and results are shown from 280 seconds elapsed time. Other authors have noted the issues with numerical stability using just pressure data at supersonic speeds, 2,12 but what is interesting is the large deltas at supersonic speeds and the nearly perfect correlations at subsonic speeds. A plausible explanation would be that the supersonic database is in poor agreement with actual flight conditions due to geometry changes caused by ablation during re-entry.…”

“…However, using inertial velocity, GPS altitude, a temperature profile, and winds aloft, an estimate of the freestream pressure is computed, and the Mach number is iterated until convergence. 2,12 As in the first approach, a guess is made for the Mach number, but now the dynamic pressure is solved from Eq. (48).…”

Consider unobservable uncertain parameters using radio beacon navigation during Mars entry

“…The Mars Entry Atmospheric Data System (MEADS), which is an implementation of the Flush Air Data System (FADS) on the "Curiosity", measures and records the pressure distribution during atmospheric entry; and then these surface pressures are used to reconstruct and validate the trajectory, atmosphere and aerodynamic coefficient. Moreover, these acquired data are used to enhance the MSL performance analysis, and enable a separation of the atmospheric properties from the aerodynamics without confounding by combining with the on-board Inertial Measurement Unit (IMU) data (Little et al, 2013;Karlgaard et al, 2013;Dutta et al, 2013). The engineering validation of aerodynamic, atmospheric, and thermal protection system models are helpful for the future Mars EDL by reducing these associated uncertainties.…”