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Preliminary Debris Risk Analysis for Mega-Constellation Architectures After Orbit-Raising Fragmentation Event
No full textThis paper presents a theoretical examination of the potential debris conjunction dangers faced by mega-constellations in both low Earth orbit (LEO) and medium Earth orbit (MEO). The analysis focuses on the risks posed by debris fields created by breakups occurring during an orbit-raising maneuver for vehicle replacement and/or capability reconstitution, using current telecommunications mega-constellations, such as Starlink and OneWeb, as examples. The mega-constellation designs consist of 750 and 150 satellites arranged using the Walker-Delta design for the LEO and MEO cases, respectively. The research employs physics-based orbital propagation and Monte Carlo simulations to evaluate the potential consequences of a single satellite breakup during orbit raising. The results of the simulations are used to calculate the probability of catastrophic collision and compare the debris risk between the LEO and MEO mega-constellations, with a bimodality analysis conducted for the MEO constellation. Monte Carlo analysis indicates that the LEO mega-constellation features the highest percentage of potential catastrophic collisions between debris fragments and the mega-constellation. Specifically, satellite breakup events starting within an altitude range of 100–199 km below the LEO mega-constellation, or approximately at the midpoint of a Hohmann transfer from a 300-km parking orbit, pose the greatest risk to the constellation
Aerospace Vehicle Comprising Module for Method of Terrain, Terrain Activity and Material Classification
No full textA method of classifying terrain, terrain activity and materials through panchromatic imagery a module programmed to provide such classification and aerospace vehicles comprising such module is provided. Panchromatic images of known materials terrains and terrain activities are taken and processed to form a multiband texture cube, that due it amount of data, is stored as a computer data base. New panchromatic images of unclassified materials, terrains and/or terrain activities are processed and compared via computer with such database that allows for inexpensive, quick and efficient classification of such new images
Stereo Vision Relative Navigation of Airborne Vehicles
No full textAn automated aerial formation (AAF) system includes an imaging device mounted on an imaging first aircraft that receives reflected energy from an imaged second aircraft. A controller is communicatively coupled to the imaging device and a flight control system of one of the first and the second aircraft. The controller generates a three-dimensional (3D) point cloud based on the reflected energy and identifies a target 3D model in the 3D point cloud. The controller rotates and scales one of a pre-defined 3D model and the target 3D model to find a 3D point registration between the target 3D model and the pre-defined 3D model. The controller steers the flight control system of the one of first and the second aircraft into formation based on the distance and the relative pose determined from the rotating and scaling
Closed-loop Adaptive Optics in the Presence of Speckle and Weak Scintillation
Get PDFIn this paper, we show that speckle averaging helps to improve adaptive-optics (AO) performance in closed loop as a result of reduced measurement error associated with a Shack–Hartmann wavefront sensor (SHWFS); however, this reduction is rendered ineffective with increasing beacon anisoplanatism. We do so operating in a weak-scintillation regime, where the SHWFS offers robust performance, and using in-plane translation of the illuminated rough surface to accomplish frame-to-frame speckle diversity. Understanding these trade-space limitations is critical when performing AO with non-cooperative, extended-source beacons
A Framework for Using Priors in a Continuum of Testing
No full textA strength of the Bayesian paradigm is that it can leverage all available information, to include subject matter expert (SME) opinion and previous (possibly dissimilar) data, through prior probabilities (priors). This article develops a framework for thinking about how differently characterized priors can be appropriately used throughout the continuum of testing. In addition to the application of various priors, the application of the evolution of the priors also contributes greatly to analytical understanding and will be addressed, considering cases such as when a system\u27s state significantly changes (e.g., is modified) during phases of testing. The evolution of priors can start with priors attempting to provide no information and evolve toward priors that capture the (newly) available information. This article further discusses priors based on institutional knowledge, as well as those based on previous testing data; the focus will be on previous, in some ways dissimilar, data, relative to a current test event. A discussion on which priors might be more common in various phases of testing, types of information that can be used in priors, and how priors evolve as information accumulates is also included. Finally, a real-world example using the Stryker family of vehicles demonstrates how priors can be employed in a continuum-of-testing construct
Image correction and wavefront sensing with a digital holographic sensor using implicit neural representations
No full textSun-Earth debris study, part 1: Preliminary investigation of debris propagation dynamics near the Sun-Earth collinear Lagrange points
No full textExcerpt: The Sun-Earth L1 and L2 Lagrange points offer a unique and advantageous location for missions related to heliophysics, astronomy, and the overall study of the Solar System. As interest in these points grows and becomes more populated, however, the chance for artificial space debris to inflict hazard on the region increases. The Circular Restricted Three-Body Problem (CR3BP) may be used to propagate the motion of debris in the region, and this paper investigates the debris propagation dynamics associated with a catastrophic spacecraft breakup occurring in currently used orbits about the Sun-Earth L1 and L2 points
Aerosol Extinction from Combined Micro- & Nano-Particle Counts
No full textAnalysis suggests combining nanoparticle (i.e. MAGIC) and air pollution (i.e. Purple Air) micro-particle number concentrations can yield fairly accurate quantifications of aerosol scatter and absorption coefficients without having to employ larger footprint aerosol instrumentation
Practical implementation of pseudo-arclength continuation to ensure consistent path direction
No full textPseudo-arclength continuation is a scheme used to generate a set of solutions for nonlinear equations and has been applied in numerous fields. In continuation schemes, solutions are obtained by tracking a parameter associated with the system as it varies, thereby creating a solution path. Pseudo-arclength continuation employs the nullspace vector, which is tangent to the path, as an approximation of the arclength in order to determine the direction of variation at each point on the path. However, the nullspace vector has both positive and negative solutions that are equally valid, leading to uncertainty in the direction of travel along the path at each location. Selecting the wrong nullspace vector can result in returning to a previously located solution instead of continuing the mapping of the solution path. Techniques to ensure consistent path direction have been developed; however, their efficacy does not extend to all scenarios. This paper addresses this gap by introducing a “flipping condition” to track previously determined path directions and ensure continuous following of the same path direction. A clear description of the process used to incorporate the flipping condition into the pseudo-arclength continuation scheme, practical implementation of the scheme, and examples demonstrating its application to the nonlinear circular restricted three-body problem (CR3BP), is provided. The inclusion of the flipping condition ensures a consistent direction of travel along the solution path and allows for families of solutions to be developed
Landing Field Performance of Low L/D Gliding Airframes
No full textPractical High-Mach airframes need to safely land under all circumstances, including situations with engines inoperative. We review and expand upon work which originated during the 1940s, 1950s and 1960s regarding “dead-stick” landing of low peak L/D research airframes (such as the X-1, X-2, X-3, X-15 and the famous “lifting body” series M2 F1, M2-F2, M2-F3,X-24 and HL-10). Such airframes will fly neither a standard stabilized approach nor execute a standard flare as would conventional aircraft. Instead, they perform a complex dynamical maneuver initiated far from the runway threshold to arrest their sink rate. We document the necessary speeds and maneuvering procedures to safely land such aircraft