Geometric Calibration of the Orion Optical Navigation Camera using Star Field Images
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Geometric Calibration of the Orion Optical Navigation Camera using Star Field Images John A. Christian1 · Lylia Benhacine1 · Jacob Hikes1 · Christopher D’Souza2
© American Astronautical Society 2016
Abstract The Orion Multi Purpose Crew Vehicle will be capable of autonomously navigating in cislunar space using images of the Earth and Moon. Optical navigation systems, such as the one proposed for Orion, require the ability to precisely relate the observed location of an object in a 2D digital image with the true corresponding line-of-sight direction in the camera’s sensor frame. This relationship is governed by the camera’s geometric calibration parameters — typically described by a set of five intrinsic parameters and five lens distortion parameters. While pre-flight estimations of these parameters will exist, environmental conditions often necessitate on-orbit recalibration. This calibration will be performed for Orion using an ensemble of star field images. This manuscript provides a detailed treatment of the theory and mathematics that will form the foundation of Orion’s on-orbit camera calibration. Numerical results and examples are also presented. Keywords Camera calibration · Optical navigation · Orion
This work was made possible by NASA under award NNX13AJ25A. An earlier version of this paper appeared as AAS 16-116 at the 39th Annual AAS Guidance, Navigation, and Control Conference in Breckenridge, CO. John A. Christian
[email protected] 1
Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia, 26506, USA
2
GNC Autonomous Flight Systems Branch, NASA Johnson Space Center, Houston, Texas, 77058, USA
J of Astronaut Sci
Introduction The Orion Multi Purpose Crew Vehicle (MPCV) is NASA’s next generation crewed vehicle and will take astronauts to exploration destinations beyond low Earth orbit. As a result, crew safety concerns require that the Orion be capable of returning to Earth independent of ground-based tracking and communication. The navigation aspect of this requirement is being met via optical navigation (OPNAV). Orion will use images of the Earth and Moon to enable the autonomous estimation of the vehicle’s translational states while in cislunar space [5]. A critical ingredient for precision OPNAV is high-quality geometric calibration of the camera system used to collect the OPNAV images. By geometric calibration, we mean estimation of the calibration parameters that govern where a physical object in the 3D world will appear in a 2D digital image. The radiometric calibration of the OPNAV camera (which would calibrate things such as the spectral responsivity of each pixel) is not considered in this paper. The parameters estimated in a geometric camera calibration routine can generally be divided into three categories: (1) camera intrinsic parameters, (2) lens distortion parameters, and (3) camera misalignment. The camera intrinsic parameters describe image formation under perfect perspective projection and capture the effect of things
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