Maciej Stachura

Cooperative Target Localization with a Communication-Aware Unmanned Aircraft System

This paper presents an approach to generating information-gathering trajectories for a cooperative unmanned aircraft system that takes into account the reliability of multihop networked communication. The algorithms presented here implicitly consider the communication limitations of the aircraft within a path-planning algorithm in which there is a position dependency on both the sensing and communication capabilities of the network. A communication-aware performance metric is derived by combining the extended information filter with a packet- erasure channel model and stochastic model of packet routing. Informative trajectories that maximize this metric are generated by a distributed, hierarchical planning algorithm. Flight results are used to characterize the communication channel model for use in a multivehicle simulation. Finally, simulation studies are used to evaluate the path-planning approach through the specific application of stationary WiFi source localization. These studies show that the approach leads to improved estimation performance relative to path-planning that does not consider communication reliability. Further, the approach leads to the emergence of natural roles whereby some of the aircraft contribute largely to the sensing portion of the objective, while others improve communication reliability by serving mainly as communication relays.

The tempest unmanned aircraft system for in situ observations of tornadic supercells: Design and VORTEX2 flight results

This paper reports results from field deployments of the Tempest Unmanned Aircraft System, the first of its kind of unmanned aircraft system designed to perform in situ sampling of supercell thunderstorms, including those that produce tornadoes. A description of the critical system components, consisting of the unmanned aircraft, ground support vehicles, communications network, and custom software, is given. The unique concept of operations and regulatory issues for this type of highly nomadic and dynamic system are summarized, including airspace regulatory decisions from the Federal Aviation Administration to accommodate unmanned aircraft system operations for the study of supercell thunderstorms. A review of the system performance and concept of operations effectiveness during flights conducted for the spring 2010 campaign of the VORTEX2 project is provided. These flights resulted in the first-ever sampling of the rear flank gust front and airmass associated with the rear flank downdraft of a supercell thunderstorm by an unmanned aircraft system. A summary of the lessons learned, future work, and next steps is provided.

Overview of Small Fixed-Wing Unmanned Aircraft for Meteorological Sampling

AbstractSampling the atmospheric boundary layer with small unmanned aircraft is a difficult task requiring informed selection of sensors and algorithms that are suited to the particular platform and mission. Many factors must be considered during the design process to ensure the desired measurement accuracy and resolution is achieved, as is demonstrated through an examination of previous and current efforts. A taxonomy is developed from these approaches and is used to guide a review of the systems that have been employed to make in situ wind and thermodynamic measurements, along with the campaigns that have employed them. Details about the airframe parameters, estimation algorithms, sensors, and calibration methods are given.

Active Sensing by Unmanned Aircraft Systems in Realistic Communication Environments

Abstract This paper describes an information-theoretic framework for active sensing by unmanned aircraft systems in realistic communication environments. The position dependency of wireless networked communication is modeled using the standard empirical radio model in combination with Shannon capacity or a packet erasure channel. The covariance of the extended information filter is used to model sensed information content. The two information-theoretic concepts are then combined into a single optimization metric. Decentralized control laws are developed for simplified network scenarios. Stochastic approximation and extremum seeking control techniques are used to estimate the gradient of the sampled objective function. Experimental flight results demonstrate the capabilities of the active sensing framework.

Adaptive Planning Horizon Based on Information Velocity for Vision-Based Navigation

This paper presents a receding horizon planning algorithm for vision-based navigation using bearings-only SLAM that adapts the planning horizon to the velocity of the information gained about the environment. Bearings-only SLAM has an inherent dynamic observability property such that specific motion is needed in order to determine the relative positions between the camera and obstacles. Thus, the estimates of new obstacles are always highly uncertain and information about the obstacles is dependent on the relative motion between the camera and objects. Receding horizon planners are typically used in conjunction with SLAM algorithms because they continually adjust to new information about the world. We present a receding horizon planner that incorporates information metrics explicitly into the receding optimization cost function. Furthermore, an adaptive horizon is used based on the intuition that when the information about the world is rapidly changing, planning does not need to be too long. Control and planning horizons are computed based on the sensor range and the eective speed of the UAV, which is computed as a weighted sum of estimated vehicle speed and time rate of change of the uncertainty of the obstacle position estimates. Simulation results demonstrate the integrated receding horizon system for vision-based SLAM; illustrate the value of integrating information-theoretic costs into the objective function and the adaptive approach; and extension of the planning approach to other applications such as exploration, target intercept, and cooperative active sensing.

Communication-Aware Information-Gathering Experiments with an Unmanned Aircraft System

This paper presents single and multiaircraft flight experiments to assess an information-theoretic path planning algorithm that incorporates sensing and communication to guide an unmanned aircraft. The communication is modeled with packet erasure channels for each link in a multihop mesh network. The planning objective is to maximize the mutual information between the target state and measurements received at a single base station from all aircraft. A novel unmanned aircraft system was developed to facilitate experiments with multiple unmanned aircraft utilizing multihop mesh networking. The value of communication-aware planning was assessed through flight experiments with a single aircraft localizing a radio emitter. Additional experiments with two aircraft demonstrated and assessed the performance of the approach, showing that the improvement in sensing can be appreciable when utilizing multihop communication.

Bering Glacier surge 2011: analysis of laser altimeter data

Abstract The Bering Glacier–Bagley Icefield system in Alaska is currently surging (2011). Large-scale elevation changes and small-scale elevation-change characteristics are investigated to understand surge progression, especially mass transport from the pre-surge reservoir area to the receiving area and propagation of the kinematic surge wave as manifested in heavy crevassing characteristic of rapid, brittle deformation. This analysis is based on airborne laser altimeter data collected over Bering Glacier in September 2011. Results include the following: (1) Maximal crevasse depth is 60 m, reached in a rift that separates two deformation domains, indicative of two different flow regimes. Otherwise surge crevasse depth reaches 20–30 m. (2) Characteristic parameters of structural provinces are derived by application of geostatistical classification. Parameters include significance and spacing of crevasses, surface roughness and crevasse-edge curvature (indicative of crevasse age). A classification based on these parameters serves to objectively discriminate structural provinces, indicative of surge progression down-glacier and up-glacier. (3) Elevation changes from 2011 and 2010 altimetry show 40–70 m surface lowering in the reservoir area in lower central Bering Glacier and 20–40m thickening near the front in Tashalich arm. Combining elevation changes with results of crevasse profilometry and pattern analysis, the rapid progression of the surge can be mathematically–physically reconstructed.

Unmanned aircraft systems for communication and atmospheric sensing missions

This paper describes the Research and Engineering Center for Unmanned Vehicles Heterogeneous Unmanned Aircraft System. The unmanned aircraft system is comprised of a fleet of small and miniature unmanned aircraft connected through a multi-tiered, net-centric command and control architecture. Components of the unmanned aircraft system are described, including different airframes, autopilots, ground control stations, payload sensors, and networking middleware. Emphasis is placed on the design of the system for in situ atmospheric sampling and communication applications.

Applications of Geostatistics in Optimal Design of Satellite Altimetry Orbits and Measurement Configurations

The Geoscience Laser Altimeter System (GLAS) aboard NASA’s Ice, Cloud and land Elevation Satellite (ICESat) is a pulse-limited laser that records measurements in a geophysical track-line ground pattern of single discrete points along a sub-satellite track. Spacing between tracks depends on latitude and repeat cycle. Derivation of digital elevation models (DEMs) of the ice surface from GLAS data requires interpolation, which due to the spatial data distribution is mathematically an extrapolation problem, best solved using a form of geostatistical estimation. In this article, we investigate the relationships between observing ice surface elevations with single-beam and multi-beam altimetry, regional coverage and spatial resolution, orbit ground track design and repeat-track spacing, analysis with ordinary and advanced universal Kriging algorithms and resultant DEM accuracy. The study is a contribution to the ICESat-2 ad-hoc Science Definition Team tasks and analyzes GLAS data and several potential multi-beam configurations proposed for the ICESat-2 instrumentation. Measurement of elevation change at the accuracy required by the U.S. National Research Council (2007) “Decadal Survey” recommendations requires understanding the effects of spatial variability of the elevation measurement, in particular for complex, rough or steep natural surfaces. This problem, which is important to correctly assess the cryosphere’s contribution to sea-level rise, is treated using scale-dependent simulation. Results indicate that multi-beam laser measurements are needed and provide a solution to the trade-off problem between repeat-mission and geodetical coverage. More generally, the article demonstrates links between space mission planning, orbit design, spatial distribution of measurements from future instrumentation and improved mathematical data processing algorithms.

The Tempest UAS: The VORTEX2 Supercell Thunderstorm Penetrator

The Tempest UAS was developed to demonstrate the feasibility of in-situ sampling of supercell thunderstorms with small unmanned aircraft, operating under the constraints of FAA certificates of authorization. The UAS and the mission concept of operations were validated with the interceptions and sampling of six supercell thunderstorms during the spring 2010 VORTEX2 field deployment. A description of the science drivers for the engineering requirements is presented. The mission concept of operations that determined the performance requirements for the airframe, and command, control, and communications systems are then discussed, and results of the supercell flights are shown.