An Efficient Ray-Tracing Method for Determining Terrain Intercepts in EDL SimulationsThe calculation of a ray's intercept from an arbitrary point in space to a prescribed surface is a common task in computer simulations. The arbitrary point often represents an object that is moving according to the simulation, while the prescribed surface is fixed in a defined frame. For detailed simulations, this surface becomes complex, taking the form of real-world objects such as mountains, craters or valleys which require more advanced methods to accurately calculate a ray's intercept location. Incorporation of these complex surfaces has commonly been implemented in graphics systems that utilize highly optimized graphics processing units to analyze such features. This paper proposes a simplified method that does not require computationally intensive graphics solutions, but rather an optimized ray-tracing method for an assumed terrain dataset. This approach was developed for the Mars Science Laboratory mission which landed on the complex terrain of Gale Crater. First, this paper begins with a discussion of the simulation used to implement the model and the applicability of finding surface intercepts with respect to atmosphere modeling, altitude determination, radar modeling, and contact forces influencing vehicle dynamics. Next, the derivation and assumptions of the intercept finding method are presented. Key assumptions are noted making the routines specific to only certain types of surface data sets that are equidistantly spaced in longitude and latitude. The derivation of the method relies on ray-tracing, requiring discussion on the formulation of the ray with respect to the terrain datasets. Further discussion includes techniques for ray initialization in order to optimize the intercept search. Then, the model implementation for various new applications in the simulation are demonstrated. Finally, a validation of the accuracy is presented along with the corresponding data sets used in the validation. A performance summary of the method will be shown using the analysis from the Mars Science Laboratory's terminal descent sensing model. Alternate uses will also be shown for determining horizon maps and orbiter set times.
Document ID
20160007698
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Shidner, Jeremy D. (Analytical Mechanics Associates, Inc. Hampton, VA, United States)
Date Acquired
June 20, 2016
Publication Date
March 5, 2016
Subject Category
Mathematical And Computer Sciences (General)
Report/Patent Number
NF1676L-22770
Meeting Information
Meeting: 2016 IEEE Aerospace Conference
Location: Big Sky, MT
Country: United States
Start Date: March 5, 2016
End Date: March 12, 2016
Sponsors: Institute of Electrical and Electronics Engineers