Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search is conducted over. These include mountain rescue; ground search and rescue, including the use of search and rescue dogs; urban search and rescue in cities; combat search and rescue on the battlefield and air-sea rescue over water.
Search and Rescue (SAR) is receiving a lot of attention recently due to several high-profile incidents on land, in the air and at sea. Flight MH370 left Kuala Lumpur was bound for Beijing in March 2014 when it disappeared, with 239 people on board. Even after the largest and most expensive search in aviation history, to date, neither any confirmed debris from the aircraft nor any survivors have been found. Every year, hundreds of people die at sea because of vessel and airplane accidents.
The ocean is a messy and turbulent space, where winds and weather kick up waves in all directions. When an object or person goes missing at sea, the complex, constantly changing conditions of the ocean can confound and delay critical search-and-rescue operations. In 2016, the United Nation Migration Agency recorded over 5000 deaths among people trying to reach Europe by crossing the Mediterranean Sea. But in the Southern Hemisphere this can be a daunting prospect considering 80% of the area is covered by water. Both the Air France AF-447 & Malaysian Airlines MH-370 crashes occurred in this region. The current there is the worst in the world, the weather there is the worst in the world and the sea floor there is less well-known than the surface of the Moon. Ships have been surveying tens of thousands of square kilometers of the bottom of the southern Indian Ocean, The mapping is necessary because the area of ocean, far off the Western Australian coast, is so remote that its depth and seafloor terrain were largely unknown.
Maritime search and rescue is carried out at sea to save sailors and passengers in distress, or the survivors of downed aircraft. The type of agency which carries out maritime search and rescue varies by country; it may variously be the coast guard, navy or voluntary organizations. When a distressed or missing vessel is located, these organizations deploy helicopters, rescue vessels or any other appropriate vessel to return them to land. In some cases, the agencies may carry out an air-sea rescue (ASR). This refers to the combined use of aircraft (such as flying boats, floatplanes, amphibious helicopters and non-amphibious helicopters equipped with hoists) and surface vessels.
In short-to-medium range SAR missions, UAVs are a SAR multiplier and enabler by replacing the SAR helicopter pilot and crew who, according to the US Coastguard, spend 99% of their mission in search mode and 1% in Rescue and/or Recovery mode. Long range SAR is currently performed using fixed wing maritime patrol aircraft and satellites. With UAV flying times increasing exponentially and fuel efficiency also improving – particularly with hydrogen-powered systems – the UAV becomes even more attractive as a SAR asset.
This calls for an enhancement of the efficiency of SAR at sea, which requires improved modeling of drifting objects, as well as optimized search assets allocation. Flow models used in SAR operations combine sea dynamics, weather prediction, and in situ observations, such as self-locating datum marker buoys deployed from air, which enhance model precision near the last seen location. Even with the advent of high-resolution ocean models and improved weather prediction, however, SAR planning is still based on conventional practices that do not use more recent advances in understanding transport in unsteady flows. A key challenge in reducing the number of these fatalities is to make Search and Rescue (SAR) algorithms more efficient.
Search and Rescue technologies
MEOSAR – The Next-Generation Satellite-Aided Search and Rescue System
Global Search and Rescue (SAR) operations quickly locate and help people in distress. Cospas-Sarsat Participants implement, maintain, co-ordinate and operate a satellite system capable of detecting distress alert transmission from radio beacons and of determining their position anywhere on the globe. The system is available to maritime and aviation users and to individual persons in distress situations on a non-discriminatory basis. It is free of charge for the end-user.
Since 1982, the Cospas-Sarsat international satellite SAR system has been instrumental in helping to save nearly 40,000 lives by pinpointing the location of emergency distress beacon signals. In 2014 alone there were nearly 700 SAR incidents assisted by Cospas-Sarsat resulting in over 2,300 people rescued. The next-generation version of Cospas-Sarsat, known as MEOSAR (or Medium Earth Orbit Search and Rescue), is expected to revolutionize the entire SAR process..
MEOSAR includes global satellite coverage and near-instantaneous distress beacon detection (72 MEOSAR satellites vs. 12 today), more accurate beacon location calculations (by using 6 MEOSAR ground station antennas) and a unique Return Link Service feature that confirms receipt of the distress signal. With MEOSAR, a distress beacon can be located within 100 meters (328 feet), 95% of the time, and within 5 minutes instead of taking up to several hours today. Several countries are already using or implementing MEOSAR systems including two of the world’s most active SAR regions – the U.S. and, as announced recently, the southern Asia Pacific region of Australia/New Zealand.
An amphibious aircraft or amphibian is an aircraft that can take off and land on both land and water. Amphibious aircraft are heavier and slower, more complex and more expensive to purchase and operate than comparable landplanes but are also more versatile. The U.S. military designed AAV in order to deploy troops rapidly from an amphibious assault ship onto land.
Amphibious aircraft can be much faster and have longer range than comparable helicopters, and can achieve nearly the range of land based aircraft, as an airplane’s wing is more efficient than a helicopter’s lifting rotor. This makes an amphibious aircraft, such as the Grumman Albatross and the Shin Meiwa US-2, useful for long-range air-sea rescue tasks. In addition, amphibious aircraft are particularly useful as “Bushplanes” engaging in light transport in remote areas, where they are required to operate not only from airstrips, but also from lakes and rivers.
Drones – The Emerging Life Savers
Unmanned Aerial Vehicles (UAVs) and drones are taking a more prominent role in SAR operations. Drones are being used as the “first response” to analyze accident scenes, determine emergency routes and locate potential survivors. Drones can fly to an emergency location in the ocean and then dropping life preserver rings directly to people in distress. In another concept unmanned rescue raft maneuvering to a location, “scooping up” people from the ocean then transporting them to medical assistance.
Scanning capability over water is also allowing easier and more accurate target identification against the ocean’s ever-changing surface. Fitted with high-resolution cameras, IR & Thermal Imaging, datalinks and other sensors UAVs can cover vast tracts of ocean and, should they come upon mariners in distress, mark the location and relay real-time video information to coastguard vessels or command-and-control aircraft in the area. Coast Guard ships and helicopters capable of carrying rescue swimmers or delivering life-saving equipment can be vectored to the disaster scene more efficiently.
Northrop Grumman’s long-range Global Hawk drones can stay aloft for 30 hours and fly 11,000 miles (17,700 kilometers) with their 116-foot (35-meter) wingspans. It can reach and remain on station over a disaster area performing valuable surveillance even when the weather is a shocker. Deployed in numbers UAVs can scan vast tracts of sea for missing aircraft or vessels. When UAVs are swarmed – where multiple UAV systems are programmed and deployed in different search patterns and staggered formations – they can also potentially save precious search time, costly manned aircraft fuel, and a potential loss of crew should rescue efforts prove disastrous due to poor weather conditions or aircraft malfunction.
Automatic Identification System (AIS)
The Automatic Identification System (AIS) is an automatic tracking system used on ships and by vessel traffic services (VTS) for identifying and locating vessels in real time. AIS technology identifies every vessel individually, along with its specific position and movements, enabling a virtual picture to be created in real time. Aerial AIS receivers are a powerful tool for: Search and Rescue (SAR); Surveillance and Reconnaissance; Threat Identification; Law Enforcement and Other time-sensitive vessel location and tracking applications. Automatic Identification System (AIS) technology is used worldwide for the identification and monitoring of maritime traffic.
Several industry initiatives including GMDSS (Global Maritime Distress and Safety Systems) and GADSS (Global Aviation Distress and Safety Systems) are proposing to send position data of a plane or a ship every few minutes, not necessarily continuously. If a critical situation is detected on board, however, then location and vessel data is automatically triggered to be sent more frequently, for example, every minute or every few seconds. This data could then be reviewed in real-time by air traffic control, fleet operators or other personnel who could provide real-time guidance to the pilot, captain or crew.
Airplane accidents may be detected by the IMS infrasound system if that explosion occurred near the station at a range less than 100 Km. Under favorable sea conditions, the pingers can be heard 2 nautical miles away, but high seas, background noise, wreckage or silt can all make pingers harder to detect.
Advanced Data Recording Devices – Finding Data More Easily
Flight Data Recorder (FDR) – device used to record specific aircraft performance parameters. The purpose of an FDR is to collect and record data from a variety of aircraft sensors onto a medium designed to survive an accident. An FDR has historically been one of two types of “flight recorder” carried on aircraft, the other being a cockpit voice recorder (CVR). Where both types of recorder are fitted, they are now sometimes combined into a single unit. The recorder is installed in the most crash survivable part of the aircraft, usually the tail section.
Most recent recorders utilise solid state technology. Solid state uses stacked arrays of memory chips, so they don’t have moving parts. With no moving parts, there are fewer maintenance issues and a decreased chance of something breaking during a crash. Data from both the cockpit voice recorder (CVR) and FDR is stored on stacked memory boards inside the crash-survivable memory unit (CSMU).
The most modern FDR systems incorporate an Emergency Locator Transmitter (ELT) and some up-to-date recorders are also equipped with an Underwater Locator Beacon (ULB) to assist in locating in the event of an overwater accident. A device called a “pinger” is automatically activate when the recorder is immersed in water. It transmits an acoustic signal on a frequency of 37.5 KHz that can be detected with a suitable receiver. In the case of the latest recorders, these transmissions are detectable at all but the most extreme oceanic depths but since they are battery-powered, their transmissions only continue for a limited period.
Data recording devices such as Flight Data Recorders (FDRs) or Cockpit Voice Recorders (CVRs) in aviation and Voyage Data Recorders (VDRs) in maritime will play a much larger role in the storage, communications and analysis of key vessel information. Several ideas are being considered by aviation organizations and manufacturers which entail making FDRs and CVRs deployable or ejectable before a crash while integrating distress beacon technology to make them more easily located outside of the accident zone or floating on water. Similar concepts are being considered for VDRs so that they can be found more rapidly in maritime incidents.
Safety Wearables and Gear – Beacon-Embedded Devices and Clothing
Beacons are small, embedded devices that advertise or beacon out small pieces of information used for proximity identification. Common Beacons use the radio frequency (RF) protocol Bluetooth Low Energy (BLE), also known as Bluetooth Smart. A distress beacon is an electronic device that, when activated in a life threatening situation, assists rescue authorities in their search to locate those in distress. Beacon registration is mandatory in some cases and can be completed online at no cost. Distress Beacons save lives – in some cases it’s the law. Most boats travelling more than two nautical miles from land must carry an Emergency Position Indicating Radio Beacon (EPIRB). Aircraft are also required under Civil Aviation Safety Authority (CASA) regulations to carry an Emergency Locator Transmitter (ELT) in flight.
When activated, beacons transmit a signal that can be detected worldwide by the international satellite system, Cospas-Sarsat. The signal is detected by a Rescue Coordination Centre to coordinate a response. The time it takes for search and rescue to reach you depends on a number of factors, including the weather, if it’s day or night, the terrain, available assets and accessibility of your location. In the future, we will see more examples of beacon technology embedded into life rafts, life vests, flight suits, watches and outerwear. With outdoor sports gaining popularity and given the recent incidents mentioned, we will see a rise in the use of these emergency-ready, location-enabling, wearable safety devices.
Search-And-Rescue Algorithm Identifies Hidden “Traps” In Ocean Waters
Now researchers at MIT, the Swiss Federal Institute of Technology (ETH), the Woods Hole Oceanographic Institution (WHOI), and Virginia Tech have developed a technique that they hope will help first responders quickly zero in on regions of the sea where missing objects or people are likely to be.
The technique is a new algorithm that analyzes ocean conditions such as the strength and direction of ocean currents, surface winds, and waves , and identifies in real-time the most attracting regions of the ocean where floating objects are likely to converge. The team demonstrated the technique in several field experiments in which they deployed drifters and human-shaped manikins in various locations in the ocean. They found that over the course of a few hours, the objects migrated to the regions that the algorithm predicted would be strongly attracting, based on the present ocean conditions. The algorithm can be applied to existing models of ocean conditions in a way that allows rescue teams to quickly uncover hidden “traps” where the ocean may be steering missing people at a given time.
“This new tool we’ve provided can be run on various models to see where these traps are predicted to be, and thus the most likely locations for a stranded vessel or missing person,” says Thomas Peacock, professor of mechanical engineering at MIT. “This method uses data in a way that it hasn’t been used before, so it provides first responders with a new perspective.”
Today’s search-and-rescue operations combine weather forecasts with models of both ocean dynamics and the ways in which objects can drift through the ocean, to map out a search plan, or regions where teams should concentrate their search. But the ocean is a complicated space of unsteady, ever-changing flow patterns. Coupled with the fact that a missing person has likely been continuously floating through this unsteady flow field for some time, Peacock and his colleagues say that significant errors can accumulate in predicting where to look first, when using a simple approach that directly predicts the trajectories of a few drifting objects.
Instead, the team developed a method to interpret the ocean’s complex flows using advanced, data-driven ocean modeling and prediction systems. They used a novel “Eulerian” approach, in contrast to more commonly used “Lagrangian” approaches — mathematical techniques that involve integrating snapshots of the ocean velocity due to waves and currents to slowly generate an uncertain trajectory for where a missing person or object may have been carried. The new Eulerian approach uses the most reliable velocity forecast snapshots, close to the point where a missing person or object was last seen, and quickly uncovers the most attracting regions of the ocean at a given time. These Eulerian predictions are then continuously updated when the next batch of updated velocity information becomes available.
The team has named their approach TRAPS, for its goal of identifying TRansient Attracting Profiles, or short-lived regions where water may converge and be likely to pull objects or people. The method is based on a recent mathematical theory, developed by Serra and Haller at ETH Zurich, to uncover hidden attracting structures in highly unsteady flow data. “We were a bit skeptical whether a mathematical theory like this would work out on a ship, in real time,” Haller says. “We were all pleasantly surprised to see how well it repeatedly did.” “We can think of these ‘traps’ as moving magnets, attracting a set of coins thrown on a table. The Lagrangian trajectories of coins are very uncertain, yet the strongest Eulerian magnets predict the coin positions over short times,” Serra says. “The key thing is, the traps may not have any signature in the ocean current field,” Peacock adds. “If you do this processing for the traps, they might pop up in very different places from where you’re seeing the ocean current projecting where you might go. So you have to do this other level of processing to pull out these structures. They’re not immediately visible.”
The researchers are planning to share the TRAPS method with first responders such as the U.S. Coast Guard, as a way to speed up search-and-rescue algorithms, and potentially save many more people lost at sea. “People like Coast Guard are constantly running simulations and models of what the ocean currents are doing at any particular time and they’re updating them with the best data that inform that model,” Peacock says. “Using this method, they can have knowledge right now of where the traps currently are, with the data they have available. So if there’s an accident in the last hour, they can immediately look and see where the sea traps are. That’s important for when there’s a limited time window in which they have to respond, in hopes of a successful outcome.” This research was primarily funded by the National Science Foundation’s Hazards SEES program, with additional support from the Office of Naval Research and the German National Science Foundation.
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