Ice Detection and Avoidance

Geographic Response Strategies (GRSs) proliferating in the Prince William Sound and Kodiak Island, Alaska area are relying increasingly on the Graphical Resource Database (GRD) sensitive resources maps. GRD allows response planners to select GRS sites from thousands of miles of remote, highly sensitive shoreline. GRD consists of a stand-alone Geographic Information System (GIS) containing maps, photos, and thousands of records contributed by 15 state and federal agencies and two citizens' regional councils. GRD addresses the Southcentral Alaska coastline centered on Prince William Sound and stretching 800 kilometers from the Copper River to Kodiak Island. Alyeska Pipeline Service Company in Valdez maintains the database as a GIS. Alyeska distributes annual updates on 500-megabyte CD-ROMs to more than 40 public and industry response-planning groups.

TECHNOLOGY AND CULTURE Book Reviews 437 The Trans-Alaska Pipeline Controversy: Technology, Conservation, and the Frontier. By Peter A. Coates. Bethlehem, Pa.: Lehigh University Press; Cranbury, N.J.: Associated University Presses, 1991. Pp. 447; illustra­ tions, notes, bibliography, index. $57.50. There are pipes and then there are pipes. The Trans-Alaska Pipeline (TAP) must rank as one of the most monumental pipes in the history of the world. From Prudhoe Bay to Valdez, the TAP measures 800 miles in length. About half the pipe is elevated, and half buried in the ground as it wends its way south, forging over the Brooks Range before descending across the Yukon River past Fairbanks and then climbing over the Alaska Range before disgorging itself at Valdez, the now infamous port on Prince William Sound. At one point there were more than 28,000 workers out there in the wilderness, making the 100,000 welds it took to connect the joints of this tubular monster that now cuts the nation’s largest state in half like a Mississippi River of steel. That pipe was built by the Alyeska Pipeline Service Company, a consortium made up of this world’s largest and most powerful oil companies, including ARCO, Humble, and BP. It was finished in the summer of 1977, and since then we have heard little about it, that is, not until 1989, when a drunken ship captain grounded his tanker, the Exxon Valdez, on a reef, turning the Alaska coast black with oil. What is there to say about a pipe? A good deal indeed, judging from this thick volume written by Peter Coates. To be fair, Coates’s book is about more than just the TAP. In an effort to put the pipeline in historical perspective, Coates takes us back to the 19th century, to the time when the United States first acquired Alaska. Then the narrative moves forward in time to look at the role of technology and conserva­ tion in the history of the state. He covers the history of the Rampart Dam, which was never actually built, and of Project Chariot, a plan by the Atomic Energy Commission (AEC) to use nuclear explosives to blow a hole at the mouth of Ogotoruk Creek (over 100 miles north of the Arctic Circle) in order to turn the area into a harbor. Edward Teller— that tireless promoter of the control of nature—told an audience in 1959 that, if the AEC wanted to, it could “dig a harbor in the shape of a polar bear” (p. 121). Although the harbor was never built, when it comes to Alaska, Americans have tended to think big and arrogantly. And it was precisely this philosophy—that we can indeed do what we want with the natural world—that seems to have informed the TAP project from the start. Coates aims to use the pipeline controversy to uncover the meaning of the frontier forAlaska and forAmerican history more generally. What he finds is that supporters and defenders of the pipeline project (and the other technological projects that were planned for the state) invoked the rhetoric of the frontier to advance their respective causes. So Spiro Agnew, in defending the pipeline, recalled how we had 438 Book Reviews TECHNOLOGY AND CULTURE conquered the American West and its frontier back in the 19th century. Alaska was simply the logical extension of that frontier, and it too needed to be conquered. That promoters of the pipeline and others used such frontier rhetoric is not by itself all that surprising. Frontier ideology has long occupied a place at the center of American culture. Thus the book left me feeling rather disappointed. One is hard-pressed to say exactly what Coates is trying to tell us. This is because the book lacks a coherent focus. Coates’s foray into Alaska conservation history leading up to the TAP is not sufficiently well connected with the story of the TAP controversy itself. What is the real meaning and historical lesson of the pipeline project? It is difficult to say what Coates’s answer would be, but his emphasis on the frontier is not entirely misguided. He just does not go far enough...

The Ship Escort Response Vessel System (SERVS) of Alyeska Pipeline Service Company (Alyeska) in Valdez Alaska is responsible for overseeing the prevention, preparedness, and response activities for the safe transportation of oil through Prince William Sound. Since the inception of SERVS in 1989, escort vessels have accompanied laden tankers through Prince William Sound from the Valdez Marine Terminal to the Gulf of Alaska, a distance of approximately 70 miles. The tankers pass through the pristine Prince William Sound, which encompasses over 2,500 square miles, with fjord-like topography and a subarctic climate. The evolution of the tanker escort system began with the emergency order issued by the state of Alaska in 1989 immediately after the grounding of the Exxon Valdez. A fleet of 12 vessels, each singular in purpose, was quickly developed: three dedicated pairs of escorts (comprised of an escort response vessel and tug), response barge standby vessels, and four dedicated docking tugs. The emphasis was more on oil spill response than prevention, and there was little interchangeability between vessels and their missions. In subsequent years, a variety of factors has caused changes to the escort system and vessel mix. These included the Disabled Tanker Towing Study, Prince William Sound Risk Assessment Promulgation of Federal Escort Requirements, oil spill response responsibility in the Gulf of Alaska, tanker vapor recovery, reduction in pipeline throughput, and weather restrictions. Additionally, industry instituted voluntary measures such as ice scouts and sentinel standby escorts for inbound tankers in ballast have affected the escort system, in addition to the experience gained in the operation the system. As the escort system matured, there was a marked emphasis and focus on oil spill prevention, fleet modernization, and multipurpose vessels to increase capabilities while maximizing efficiencies. Alyeska/SERVS embarked on a dedicated strategy to upgrade the specialized vessel fleet of 12 vessels to a fleet composed of fewer multipurpose vessels. This strategy encompassed a technological and operational enhancement of the fleet, significantly improving the prevention posture while maintaining the necessary response capabilities. Today, the Alyeska/SERVS escort fleet consists of nine multipurpose vessels. The cornerstones of the escort fleet are the two 10,192 horsepower Voith Schneider enhanced tractor tugs and the three 10,192 horsepower ? drive Prevention and Response Tugs, all specifically designed, constructed, and outfitted for tanker escorting. The combination of these vessels for tanker escorting utilizes complimentary best available technology to ensure the safe transit of tankers through Prince William Sound.

<div class="section abstract"><div class="htmlview paragraph">The EU Horizon 2020 project SENS4ICE addresses reliable detection and discrimination of supercooled large droplets (SLD) icing conditions. These conditions are considered as particularly safety-relevant and have been included in airplane certification specifications. The SENS4ICE project comprises technology development, icing wind tunnel upgrading/testing and flight testing. A novel hybrid approach for icing detection combines direct sensing (atmospheric conditions / ice accretion) with an indirect technique based on changing aircraft characteristics. The first part of the project was devoted to the development and maturation of icing detection technologies, with a focus on Appendix O (of 14 CFR Part 25 and CS-25) icing conditions. Furthermore, several icing wind tunnel facilities have improved capabilities to represent Appendix O conditions. Icing wind tunnel testing (including Appendix O) of several icing detection sensors developed in the SENS4ICE project concluded the first part of the project. Examples of initial results are presented. The second part of the project is dedicated to flight testing of icing technologies in natural icing conditions including Appendix O. Two flight test campaigns in early 2023 served to test and demonstrate eight of the direct ice detection technologies under development as well as the hybrid ice detection system, including the indirect ice detection system. Extensive meteorological and climatological analysis was done in order to have the best chances to encounter icing conditions including Appendix O conditions.</div></div>

Sedimentological and geochemical investigation of sediment cores collected in the deep (>400 m) central basin of Prince William Sound, along with geochemical fingerprinting of sediment source areas, are used to identify earthquake-generated sediment gravity flows. Prince William Sound receives sediment from two distinct sources: from offshore (primarily Copper River) through Hinchinbrook Inlet, and from sources within the Sound (primarily Columbia Glacier). These sources are found to have diagnostic elemental ratios indicative of provenance; Copper River Basin sediments were significantly higher in Sr/Pb and Cu/Pb, whereas Prince William Sound sediments were significantly higher in K/Ca and Rb/Sr. Within the past century, sediment gravity flows deposited within the deep central channel of Prince William Sound have robust geochemical (provenance) signatures that can be correlated with known moderate to large earthquakes in the region. Given the thick Holocene sequence in the Sound (~200 m) and correspondingly high sedimentation rates (>1 cm year−1), this relationship suggests that sediments within the central basin of Prince William Sound may contain an extraordinary high-resolution record of paleoseismicity in the region.

Using system simulation to model the impact of human error in a maritime system

UAV Icing: A Survey of Recent Developments in Ice Detection Methods

Ice accretion poses a threat to fixed-wing aerial vehicles as it alters the wings' shape and thus degrades the aerodynamic performance. In manned aircraft, the icing detection system assists the pilot and utilises dedicated sensors. However, in unmanned aerial vehicles (UAVs), onboard icing detection can generally only be achieved using standard sensors in conjunction with dynamical models, because dedicated sensors are rarely available. In this paper, we propose two approaches based on the particle filter for both icing detection and accurate state and aerodynamic parameter estimation in the presence of icing, with different levels of severity. The first approach uses the observation likelihood for icing hypothesis testing with a complement of the Gaussian kernel to compute icing probability. The second approach uses a discrete jump approach based on a Bernoulli process and a subset of particles to test the icing hypothesis for faster icing detection by estimating changes in icing-related aerodynamic parameters. Using both approaches, the simulation results demonstrate improved estimation accuracy compared to an extended Kalman filter (EKF), under both moderate and severe icing conditions. With adequate tuning, the proposed approaches show potential for indirect icing detection in UAVs. They also enable the computation of icing severity and provide a more accurate and reliable estimate of the icing probability compared to the EKF.

Flight in all weather conditions has necessitated correctly detecting icing and taking reasonable measures against it. This work aims at the detection and identification of airframe icing based on statistical properties of aircraft dynamics and reconfigurable control protecting aircraft from hazardous icing conditions. A Kalman filter is used for the data collection for the detection of icing, which aerodynamically deteriorates flight performance. A neural network process is applied for the identification of icing model of the aircraft, which is represented by five parameters based on past experiments for iced wing airfoils. Icing is detected by a Kalman filtering innovation sequence approach. A neural network structure is embodied such that its inputs are the aircraft estimated measurements and its outputs are the parameters affected by ice, which corresponds to the aircraft inverse dynamic model. The necessary training and validation set for the neural network model of the iced aircraft are obtained from the simulations of nominal model, which are performed for various icing conditions. In order to decrease noise effects on the states and to increase training performance of the neural network, the estimated states by the Kalman filter are used. A suitable neural network model of aircraft inverse dynamics is obtained by using system identification methods and learning algorithms. This trained model is used as an application for the control of the aircraft that has lost its controllability due to icing. The method is applied to F16 military and A340 commercial aircraft models and the results seem to be good enough.

Possible hydrocarbon production on the Grand Banks of Newfoundland, associated with the Hibernia discovery, has intensified interest in sea ice and iceberg conditions in this region. It is the seasonal presence of sea ice and icebergs which distinguishes the Grand Banks from other harsh environment hydrocarbon production regions. In this paper, the seasonal patterns of sea ice and icebergs around eastern Newfoundland and on the Grand Banks are described. Sea ice is discussed in terms, of areal, age, floe size and thickness distributions, and of deformation processes. Icebergs are described in the context of seasonal distributions, size and deterioration. Features of the sea ice and iceberg regimes which affect hydrocarbon production and transportation are identified. The application of ice forecasting, ice detection and ice management techniques to hydrocarbon related operations on the Grand Banks is then outlined.

Spill responders, state and federal agencies, and responsible parties have all acknowledged the fact that the permits, forms, and applications required to mount an effective oil spill response can often slow down the response progress or lead to unnecessary confusion. In Alaska, there are forms in use that are copies of copies of forms that have not been updated in years. In other cases, standard agency forms that are available as Word documents have been slightly modified by various users over time. Some forms appear unnecessary in the response effort and may well be carryovers from other venues. This problem has been exacerbated as many Alaska state agencies have reorganized and in some cases, permitting authorities have been transferred. The Spill Response Permits Project was initiated by the Cook Inlet Regional Citizens Advisory Council (CIRCAC) in response to a common concern, voiced by response organizations, responsible parties, and state and federal agencies, that the paperwork burden associated with an Alaska oil spill response is excessive. CIRCAC provided initial funding to form a work group of industry, agency, and response organization representatives that would be charged with taking a fresh look at Alaska's spill permitting requirements. The work group, co-chaired by the Alaska Department of Environmental Conservation, the US Coast Guard, and the Tesoro Alaska Company, began by identifying all oil spill response activities that might generate the need to fill out a permit or authorization form. Next, they inventoried and collected the most up-to-date versions of all permits. Work group participants, including oil spill response cooperatives as well as state and federal agencies with permitting authority, then reviewed all forms and deleted outdated or duplicated requirements. Once the list of permits had been updated, the work group then developed a computer-based organizational tool that could be used to sort, fill out, submit, and file applicable permit forms during an oil spill response or exercise. The computer interface allows the user to enter incident-specific information into a central data set, so that the data may then be exported to the required permit forms with a simple mouse click. The computer tool can be run on any computer platform, with files available for download from the Internet or stored on a CD-Rom. The tool uses the Adobe Acrobat® software application and fills out and stores permit forms in Adobe portable document format (PDF). Additional information about this ongoing project is available at http://www.akgrs.net/Circac/home.htm.

<div class="section abstract"><div class="htmlview paragraph"> For nearly a century, ice build-up on aircraft surfaces has presented a safety concern for the aviation industry. Pilot observations of visible moisture and temperature has been used a primary means to detect conditions conducive to ice accretion on aircraft critical surfaces. To help relieve flight crew workload and improve aircraft safety, various ice detection systems have been developed. Some ice detection systems have been successfully certified as the primary means of detecting ice, negating the need for the flight crew to actively monitor for icing conditions. To achieve certification as a Primary ice detection system requires detailed substantiation of ice detector performance over the full range of icing conditions and aircraft flight conditions. Some notable events in the aviation industry have highlighted certain areas of the icing envelope that require special attention. </div><div class="htmlview paragraph"> Following the CRJ accident in Fredericton, New Brunswick, Canada, in December 1997, industry interest and scrutiny in the performance of ice detection systems at warmer temperatures has increased. [ <span class="xref"> 1 </span> ] In particular, the concern lies in potential differences between ice accretion on the ice detector sensing surfaces and the critical aircraft surfaces (e.g. wing, nacelle). This has led both the FAA and EASA to update advisory material to ensure that ice detector performance at low freezing fractions is addressed. </div><div class="htmlview paragraph"> To minimize this concern and alleviate the risk, Collins Aerospace (Rosemount Aerospace, Inc.) has developed an enhanced ice detection algorithm for its magnetostrictive ice detector (MID). Traditionally the MID has only been used to detect ice accretion resulting from supercooled liquid water. This new algorithm enables the MID to sense the presence of non-freezing liquid water on its sensing surface and couple that with ambient temperature information to provide a signal when conditions may be conducive for ice accretion on critical aircraft surfaces. </div><div class="htmlview paragraph"> The discussion in this paper describes the development of this new algorithm for the MID and performance verification of the algorithm through icing wind tunnel testing and icing flight tests. </div></div>

This study presents a time division multiplexing (TDM) multiple-input–multiple-output (MIMO) digital beamforming (DBF) radar concept based on a single transceiver (one transmitter and one receiver). Compared with a conventional MIMO DBF radar system with M-element transmitting array and N-element receiving array, the proposed concept can reduce the number of transmitter/receivers from M + N to 2 for a drastic cost reduction. In addition to theoretical analysis and numerical simulation, an experimental TDM MIMO DBF radar demonstrator is realised and tested for verification using real data. Numerical analysis and experimental results show that the proposed concept can achieve considerable higher angular resolution at lower cost compared to conventional DBF radar concepts using the same antenna array with one-way or two-way beamforming.

The rapid proliferation of unmanned aerial vehicles has created new challenges in surveillance, defence, and air-traffic safety. Conventional radar or vision-based systems fall short under poor lighting, occlusion, or low radar cross-section, hence motivating the need for acoustic detection. Drone rotors generate unique harmonic and broadband signatures that can be captured through microphones, but these signals are easily masked by ambient environmental noise. We propose MR-CA-AST, a Multi-Resolution Channel-Attention Audio Spectrogram Transformer that effectively combines local convolutional denoising and global Transformer-based temporal modelling. The model employs two convolutional branches running on high and low-resolution Melspectrograms, further empowered by a channel-attention mechanism suppressing irrelevant frequency bands. The combined embeddings are then tokenised using patch embedding and processed by a Transformer encoder to learn from long-range temporal correlations. Experimental results on the Drone Audio Detection Samples dataset (DADS) with 180,320 samples show that the proposed architecture attained a test accuracy of 99.57%, F1-score of 0.995, and ROC-AUC of 0.998, outperforming existing CNN, CRNN, and AST baselines. This method exhibits strong robustness under conditions with heterogeneous noise and forms a promising basis for further integration with distributed acoustic sensing systems in covert drone tracking.

Autonomous ships require a sense-and-collision-avoidance functionality based on surveillance of the ocean surface in order to detect unmapped and potentially non-cooperative obstacles and hazards, and to engage into evasive manoeuvres to avoid impending collisions. In this paper, we study the concept of using an autonomous ship being assisted by an unmanned aerial surveillance system (UASS) that provides information to the ship in order to implement collision avoidance in compliance with the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS). The motivation is that a UASS provides complementary sensing capabilities that can be combined with a conventional maritime radar and Automatic Identification System (AIS) to detect smaller obstacles that may be hidden in clutter, behind other objects, or submerged close to the surface. We propose a system architecture and implement a simulation environment to illustrate the concept and study the feasibility of the key control algorithms based on receding-horizon optimization.