Enabling Dynamic Vehicle Analyses With Improved Atmospheric Attenuation Models in Glenn Research Center Communication Analysis Suite

To aid in meeting the NASA objective of returning humans to the Moon, the Glenn Research Centers Communication Analysis Suite was augmented with two distinct capabilities. The first capability added was the vehicle propagator. This allows the addition of dynamic aircraft and ground vehicles around any celestial body within the solar system during an analysis. This functionality interpolates the position and velocity of the vehicle relative to a celestial body at the time steps analyzed using the type of path and either a series of waypoints or a direction and duration of travel. The implications of this new capability include lunar rovers and/or drones, such as Dragonfly, where the vehicle propagator will analyze the communications architecture. The newly created vehicle propagator is now in use in communications studies for the 2024 lunar missions, simulating the movement of lunar rovers across the Moons southern pole. The second capability added was the augmentation of the atmospheric attenuation model. The previous model did not have a uniform low-elevation attenuation model due to the trigonometric approximation for path length and the exponential nature of low-elevation scintillation. User-defined weather parameters were also added to the updated atmospheric attenuation model. The previous model solely used tabular data based upon the season and location of the transmitting antenna. Multiple simulations of the same configuration now return different results based on the differing weather parameters. Cognitive communications analysis efforts can use this second capability to generate neural network training data based on differing weather conditions at utilized ground stations, a critical step in allowing neural networks to learn how weather parameters impact communications performance

The Harold C. Ernst Collection of Portable Sundials

A catalog of sundials from the Harold C. Ernst Collection of Portable Sundials, and a handy reference book on the subject of portable sundials. The sundial is the most ancient scientific instrument to come down to us unchanged. As such it is deserving of a better position in life than that of an ornament. It has played a vital part in the life of man for many thousands of years, and even today it serves us well where the mechanical watch fails. The authors particularly draw attention to the system of classifying, labeling, and cataloging sundials, described in Chapter II. This is the first attempt to bring order out of confusion in sundials

Path discrepancies between great circle and rhumb line

A mathematical model for a comparative analysis of great circle vs. rhumb line navigation in the continental United States has been developed at the Avionics Engineering Center, Ohio University. A FORTRAN simulation of the model has been implemented on the IBM 370 computer. The simulation predicts pertinent navigation information for the two flight paths. The basis for the project, which is a part of an M.S. thesis, is to provide a data base for computing discrepancies between the two flight paths. This document briefly describes the model and discusses the implications of the results obtained

Pictorial communication: Pictures and the synthetic universe

Principles for the design of dynamic spatial instruments for communicating quantitative information to viewers are considered through a brief review of the history of pictorial communication. Pictorial communication is seen to have two directions: (1) from the picture to the viewer; and (2) from the viewer to the picture. Optimization of the design of interactive instruments using pictorial formats requires an understanding of the manipulative, perceptual, and cognitive limitations of human viewers

Quantization of the conformal arclength functional on space curves

By a conformal string in Euclidean space is meant a closed critical curve with non-constant conformal curvatures of the conformal arclength functional. We prove that (1) the set of conformal classes of conformal strings is in 1-1 correspondence with the rational points of the complex domain $\{q\in \mathbb{C} \,:\, 1/2 0,\,\, |q| < 1/\sqrt{2}\}$ and (2) any conformal class has a model conformal string, called symmetrical configuration, which is determined by three phenomenological invariants: the order of its symmetry group and its linking numbers with the two conformal circles representing the rotational axes of the symmetry group. This amounts to the quantization of closed trajectories of the contact dynamical system associated to the conformal arclength functional via Griffiths' formalism of the calculus of variations.Comment: 24 pages, 6 figures. v2: final version; minor changes in the exposition; references update

Long and short-range air navigation on spherical Earth

Global range air navigation implies non-stop flight between any two airports on Earth. Such effort would require airplanes with the operational air range of at least 12,500 NM which is about 40-60% longer than anything existing in commercial air transport today. Air transportation economy requires flying shortest distance, which in the case of spherical Earth are Orthodrome arcs. Rhumb-line navigation has little practical use in long-range flights, but has been presented for historical reasons and for comparison. Database of about 50 major international airports from every corner of the world has been designed and used in testing and route validation. Great Circle routes between many major international airports have been generated and waypoints designed for both GC and rhumb-line routes. Some global-range flights including to polar crossings and/or long flights over open water with not many alternate landing sites available may be ETOPS limited. Additionally, we summarized short-lines navigation theory with particular emphasis on Polar Regions and very short distances elsewhere on the Earth. Working equations and algorithms have been coded into several high-level programming languages, such as, Fortran 90/95/2003/2008, Matlab, and True Basic. Considerable testing of programs have been conducted and compared with the publicly-available geodesic computations over the surface of the terrestrial reference ellipsoid. Distance computations usually were no more than 0.3% in error, while the angles and courses discrepancies were mostly within few angular minutes. Further development will include computations of gliding distances from any altitude under arbitrary winds depending on the type of aircraft and the calculations of PET and PNR for every segment of the route and arbitrary wind conditions

Development of a novel method for autonomous navigation and landing of unmanned aerial vehicles

In this work, control techniques for the autonomous navigation and landing of an Unmanned Aerial Vehicle (UAV) are developed and compared. Controllers were developed and implemented on two different aircraft models: the Lockheed-Martin F-16 and AAI Corporation/Israel Aircraft Industries RQ-2 Pioneer. Due to the expense of modifying the pre-existing F-16 flight control system, the controller is implemented outside of the closed loop. Proportional-integral-derivative and proportional-integral controllers are developed for holding the aircraft at a desired velocity and altitude. The aircraft are approximated as Dubins vehicles constrained to travel on a two-dimensional surface for decreased simulation time. Using the simplified model two control techniques are developed and then compared. The first uses a proportional feedback controller based on the Rhumb-line that the aircraft is traveling along. The second control technique uses a trajectory determined from an algorithm using the Dubins path determination for the shortest travel distance between two points. A sliding mode controller is developed to guide the simplified model along the Dubins path trajectory. The advantage of the Dubins path trajectory is that it allows for a closed-form time estimate to reach the desired way-point. Comparison between the two navigation techniques using the simplified system shows a significant decrease in time to way-point for the Dubins curve trajectory controller. The Rhumb-line controller and a hybrid Rhumb-line/Dubins path controller are implemented on nonlinear models of both aircraft. Simulation of both controllers on the nonlinear model shows acceptable performance in guiding the aircraft between way-points. Also, the time to way-point for the nonlinear aircraft model guided by the hybrid controller is within 5% of the closed-form Dubins trajectory estimate. Autonomous landing is accomplished utilizing the path guidance and altitude controllers. The nonlinear simulated aircraft successfully followed the glideslope from way-point to runway

A NOTE ON MID RULES OPTIMIZATION OF DISTANCE ON THE SPHERE

In this article Mid-latitude and mid-longitude rules are used to find the free turning point along the Great Circle ensuing optimized distance. Namely, to reach Great Circle vertex with two rhumb line legs ensuing optimized distance, an initial rhumb line course equal to the orthodromic course at Mid-latitude may be used. The initial course is thereupon optimized by the incremental value steps. Alternatively, mid-longitude point at the same Great Circle can be beneficial in optimizing process. Optimized distance is achieved if the rhumb line course is altered towards the vertex at the orthodrome-loxodrome intersection point

Acoustic/Gravity Wave Phenomena in Wide-Field Imaging: From Data Analysis to a Modeling Framework for Observability in the Mlt Region and Beyond

Acoustic waves, gravity waves, and larger-scale tidal and planetary waves are significant drivers of the atmosphere’s dynamics and of the local and global circulation that have direct and indirect impacts on our weather and climate. Their measurements and characterization are fundamental challenges in Aeronomy that require a wide range of instrumentation with distinct operational principles. Most measurements share the common features of integrating optical emissions or effects on radio waves through deep layers of the atmosphere. The geometry of these integrations create line-of-sight effects that must be understood, described, and accounted for to properly present the measured data in traditional georeferenced frames or in thin-layer representations. These effects include intensity enhancements/cancellations, filtering of scales, and apparent phase shifts relative to the underlying wave dynamics. We have designed a simulation framework that uses 2D and 3D input model data to perform these line-of-sight integrations based on ray tracing and geodesic transformations. The primary objective is to characterize these effects, to define quantifiable impacts on measurable parameters, and to create a basis for synthetic data for processes to be revealed in current and future measurements