The The Kannad Integra Smart Pack by McMurdo Group could make it twice as easy to find missing aircraft. Photo: McMurdo Group
McMurdo Group, maker of end-to-end search and rescue solutions, has launched the Kannad Integra Smart Pack, an aviation emergency locator transmitter (ELT) bundle with both GPS and antenna redundancy. The product can result in Integra Smart Pack-equipped aircraft being twice as likely to be found in the event of an emergency compared to standard ELTs.
The Kannad Integra Smart Pack includes:
The Kannad Integra ELT – a small, light ELT with a built-in antenna and embedded GPS receiver.
The new Kannad Integra e-NAV NMEA – an NMEA-standard interface cable that connects the Integra ELT to the aircraft GPS. The latest known aircraft GPS position is continually updated and stored on the interface cable itself to provide an additional level of redundancy over the embedded Integra ELT GPS data.
Traditional ELTs rely on an aircraft’s external antenna and GPS equipment, which is subject to failure in the event of an emergency. The Integra ELT, however, can operate independently of the aircraft to provide key positioning data through its internal antenna and GPS receiver.
With the Integra Smart Pack bundle, in the event that the Integra ELT’s internal GPS antenna is unsuccessful for any reason, the positioning coordinates from the Integra e-NAV NMEA will be used. This additional GPS redundancy will result in better location positioning and higher chance of rescue.
“McMurdo is delighted to continue its long history of aviation search and rescue innovation with the introduction of the Kannad Integra Smart Pack,” said Christian Belleux, head of McMurdo’s Kannad Aviation Business Unit. “The Integra Smart Pack is a must-have SAR [search-and-rescue] solution to help ensure accelerated rescue response in the event of an emergency and to ultimately save more lives.”
The Integra ELT Smart Pack is suitable for all types of aircraft with specific versions to support helicopters, general aviation planes and large commercial jets. Once activated, the Integra ELT transmits a distress signal to alert international rescue services to the emergency location via the global Cospas-Sarsat Search and Rescue satellite system, which has helped to save more than 37,000 lives since 1982.
The McMurdo Group is exhibiting this week at Heli Expo 2015, Booth 5465, in Orlando, Fla.
Europe’s fifth Galileo satellite, one of two delivered into a wrong orbit by VS09 Soyuz-Fregat launcher in August, transmitted its first navigation signal in space on Saturday, November 29. It has reached its new target orbit and its navigation payload has been successfully switched on.
A detailed test campaign is under way now the satellite has reached a more suitable orbit for navigation purposes.
Recovery
The fifth and sixth Galileo satellites, launched together on August 22, ended up in an elongated orbit traveling up to 25,900 km above Earth and back down to 13,713 km.
A total of 11 maneuvers were performed across 17 days, gradually nudging the fifth satellite upwards at the lowest point of its orbit. As a result, it has risen more than 3,500 km and its elliptical orbit has become more circular.
“The maneuvers were all normal, with excellent performance both in terms of thrust and direction,” explained Daniel Navarro-Reyes, ESA Galileo mission analyst. “The final orbit is as we targeted and is a tribute to the great professionalism of all the teams involved.”
The Launch and Early Operations Phase (LEOP) for Galileo satellites is overseen by a joint operations team from ESA and the French space agency CNES, alternately working from ESOC in Darmstadt, Germany, and the CNES LEOP Control Centre in Toulouse, France. Photo: ESA
The commands were issued from the Galileo Control Centre by spaceopal, the Galileo operator, at Oberpfaffenhofen in Germany, guided by calculations from a combined flight dynamics team of ESA’s Space Operations Centre, ESOC, in Darmstadt, Germany and France’s CNES space agency. The commands were uploaded to the satellite via an extended network of ground stations, made up of Galileo stations and additional sites coordinated by France’s CNES space agency. Satellite manufacturer OHB also provided expertise throughout the recovery, helping to adapt the flight procedures.
Until the maneuvers started, the combined ESA–CNES team maintained the satellites pointing at the Sun using their gyroscopes and solar sensors. This kept the satellites steady in space but their navigation payloads could not be used reliably.
In the new orbit, the satellite’s radiation exposure has also been greatly reduced, ensuring reliable performance for the long term.
A Galileo Full Operational Capability (FOC) satellite, following on from the first four Galileo satellites already in orbit. A total of 22 FOC satellites are on the way, built by OHB in Germany with navigation payloads from Surrey Satellite Technology Ltd. in the UK. Photo: ESA
A suitable orbit
The revised, more circular orbit means the fifth satellite’s Earth sensor can be used continuously, keeping its main antenna oriented towards Earth and allowing its navigation payload to be switched on.
Significantly, the orbit means that it will now overfly the same location on the ground every 20 days. This compares to a normal Galileo repeat pattern of every 10 days, effectively synchronizing its ground track with the rest of the Galileo constellation.
The navigation test campaign
The satellite’s navigation payload was activated on November 29, to begin the full In-Orbit Test campaign. This is being performed from ESA’s Redu centre in Belgium, where a 20-meter-diameter antenna can study the strength and shape of the navigation signals at high resolution.
“First, the various payload elements, especially the Passive Hydrogen Maser atomic clock, were warmed up, then the payload’s first ‘signal in space’ was transmitted,” said David Sanchez-Cabezudo, managing the test campaign.
“The satellite-broadcast L-band navigation signal is monitored using the large antenna at Redu, with experts from OHB and Surrey Satellite Technology Ltd — the payload manufacturer, based in Guildford, UK — also on hand to analyze how it performs over time.”
The first Galileo FOC navigation signal-in-space transmitting in the three Galileo frequency bands (E5/E6/L1) was tracked by Galileo Test User Receivers deployed at various locations in Europe, namely at Redu (B), ESTEC (NL), Weilheim (D) and Rome (I). The quality of the signal is good and in line with expectations.
The Search And Rescue (SAR) payload will be switched on in few days in order to complement the in-orbit test campaign.
John All takes an ice sample from a glacier in the Ishinca Valley, Peru.
A climate scientist relies on a GPS satellite communicator to get him out of tight spots.
By Tracy Cozzens Photos by Clinton Lewis, Western Kentucky University
Please call Global Rescue.
John broken arm, ribs, internal bleeding.
Fell 70 ft crevasse.
Climbed out.
Himlung camp 2.
Please hurry.
That simple text message, sent May 19 via the DeLorme inReach communicator, alerted search-and-rescue monitors that the leader of a Himalayan research team was in dire straits.
Dr. John All, director of the American Climber Science Program (ACSP), was leading a team collecting snow samples in the highest mountain range in the world to study the impacts of climate change when he tumbled into a crevasse. “After crawling back for hours to my tent, I sent texts via my sat messenger for help,” All told the local Kathmandu newspaper.
Friends and family of the expedition followed the rescue efforts every step of the way as text messages were sent via the InReach to the ACSP’s Facebook page.
The climate scientist was rescued via a helicopter and admitted to Norvic International Hospital in Kathmandu with five broken ribs, a dislocated shoulder, and internal bleeding. After a day in the ICU, he was discharged for a week of rest before returning for further care in the United States.
The DeLorme inReach Explorer.
In an emergency such as All experienced, the interactive SOS capability of the inReach automatically triggers remote tracking and allows users to communicate via text with responders at GEOS, DeLorme’s partner for international 24/7 search-and-rescue monitoring.
Going Out Again. All and his ACSP team departed for Huascaran National Park in Peru on June 23, just a month after his harrowing rescue in the Himalayas, for a two-month research expedition. All and several of his team members will be carrying the inReach devices.
Just like in the Himalayas, the inReach will give the team the ability to send and receive 160-character text messages from the remotest locations, provide location updates with GPS tracking, and keep them within reach of rescue with its SOS capabilities.
Besides providing peace of mind, the latest version of the inReach — the Explorer — allows the team to plan a route, mark waypoints, and create detailed track logs of their expedition.
“Knowing we would consistently be out of cell-phone range, we researched all satellite communication options to keep us connected,” All said. “A satellite phone was more than we really needed, and as a volunteer-driven non-profit program, it wasn’t very cost effective. We needed to be able to communicate back and forth in the event of an emergency, but we also wanted to keep everyone updated on the day-to-day status of the mission.”
Checking on the team’s status is as easy as visiting their Facebook page. Team members regularly post messages from anywhere in the world they might travel.
In Peru, the team of 20 students and scientists will examine changing climate conditions and the impact of human land use in the mountainous Cordillera Blanca region of the Andes, where Huascaran National Park is located. The park, a magnet for American climbers, has more than 33 peaks higher than 6,000 meters and hundreds of 5,000+ meter peaks. ACSP has been sampling snow in the region for the past three years in an effort to quantify the glacial contamination levels.
“Our work in Peru will be much more comprehensive than our high-elevation work in the Himalayas and will cover whole gamut of environmental parameters, from vegetation to water quality. The region is very remote and we will be collecting some samples from the walls of a crevasse to assess the seasonality of pollutants and their impact over time, so having an inReach with us is critical — both to communicate with each other and our team back home,” All said. Plus, he added, the students on his team will be able to communicate with their parents, providing their parents with peace of mind as their children travel to remote regions.
“Now that we’ve seen how well inReach works, we are looking forward to having more of them on this next trip — especially the newest Explorer model, which will allow us to mark waypoints during data collection,” All said.
In addition to the messaging, tracking and SOS capabilities, users of the company’s latest product inReach Explorer can view, create or navigate routes and waypoints. A map view displays routes, waypoints, tracks, and messages geo-located onscreen for backtracking or self-rescue. The built-in digital compass, barometric altimeter, and accelerometer sensors ensure accuracy and provide heading and bearing information, elevation readings, speed, and other useful trip statistics.
inReach communicates over the Iridium satellite network, providing global two-way satellite connections, high network reliability and low-latency data links (less than 60-second delivery of messages end-to-end) anywhere on Earth, with no gaps, fringe or weak signal areas. inReach has the ability to maintain a satellite signal lock even in difficult GPS environments, such as in a steep canyon or under a heavy forest canopy, DeLorme said.
The ACSP has visited Peru for climate research for three years, including in 2013 the Quillcayhuanca Valley (left) and the Ishinca Valley, places so remote that staying in touch can be a challenge. (Photos: Clinton Lewis/WKU)
A new emergency locator transmitter for aviation has received Cospas-Sarsat and FAA approvals and is now available for sale. The ELT 1000 by ACR Electronics, Inc., is designed with multiple installation configurations to reduce overall installation cost, the company said.
The electronics maximize frequency stability and power while incorporating a new, built-in GPS navigational interface, the company said. Including GPS data in the emergency transmission allows search-and-rescue personnel to know the location within 100 meters in less than a minute. Designed to accommodate multiple installation configurations, the new ELT 1000 is a quick retrofit for obsolete 121.5 MHz ELTs.
“We are very excited to announce this new ELT to the general aviation market. This is the first new ELT from the Artex family in many years and the first we have designed and certified at ACR. We feel we are bringing an ELT that offers excellent value, along with the highest quality workmanship available to the market,” said Gerald Angeli, president and general manager.
Built under the exacting standards of AS9100C quality certification, the ELT 1000 exceeds all government and regulatory standards including the latest FAA guidelines with its new robust stainless steel mounting strap.
ELT 1000 features and specifications:
Quick and easy retrofit for general aviation aircraft
Single antenna output for emergency transmission on both 406 MHz (Cospas-Sarsat) and 121.5 MHz frequencies (local Search & Rescue)
Enhanced positional accuracy with a built-in GPS interface that does not require aircraft power
Encoded digital message broadcasts aircraft identification/registration and owner/emergency contact details
New stainless steel mounting strap for increased stability that complies with the most current FAA guidelines
Simple self-testing from the cockpit. When combined with 406Test.com, the self-test will provide SMS/e-mail confirmation within seconds that the ELT signal reached the satellites successfully
New hermetically sealed G-Switch for increased reliability.
McMurdo Group, an end-to-end search and rescue (SAR) and maritime domain awareness (MDA) company, has acquired Techno-Sciences, Inc. (TSi), a provider of SAR satellite ground stations, integrated emergency response center systems and coastal surveillance solutions. Terms of the acquisition were not disclosed. TSi’s Beltsville, Maryland, location becomes the U.S. headquarters for McMurdo Group, a division of Orolia, global specialist in critical GNSS solutions.
TSi has been instrumental in the development of the COSPAS-SARSAT international satellite-based SAR program, which has helped to save more than 35,000 lives worldwide since 1982. TSi is also actively involved in the next-generation COSPAS-SARSAT system, MEOSAR (Medium Earth Orbit Search and Rescue), which will greatly improve the existing SAR process with near-instantaneous detection, identification and location of emergency distress beacons.
MEOSAR, currently in its demonstration and evaluation phase, is expected to have initial operational capability in 2016 and full operational capability by 2018. MEOSAR will use SAR-enhanced Galileo (Europe), GPS (U.S.) and GLONASS (Russia) satellite constellations for greater global coverage and includes innovative end-user beacon functionality such as a return-link service on Galileo satellites to acknowledge distress signal receipt and provide ongoing rescue effort status.
“The acquisition of TSi firmly establishes McMurdo Group as the global leader in satellite-based search and rescue solutions. We are the only provider capable of supplying a single-vendor, end-to-end COSPAS-SARSAT emergency solution with a seamless ecosystem of products, technologies and processes that will streamline and expedite search and rescue efforts,” said Jean-Yves Courtois, CEO, McMurdo Group and its holding company Orolia Group. “TSi expands our global sales, support and customer footprint and adds to our already extensive expertise in SAR and MDA. We look forward to developing a U.S. SAR Center of Excellence to include manufacturing, distribution and support of McMurdo Group’s broad solution offering of distress beacons, AIS equipment, satellite communications units and emergency control centers equipped with search and rescue management software.”
TSi solutions are installed in more than 20 countries worldwide and include satellite ground stations or local user terminals (LUTs), rescue and mission control centers, and coastal surveillance/instruction detection systems. TSi installed the world’s first operationally ready six-channel MEOSAR LUT (MEOLUT) in 2011 for the U.S. National Oceanic and Atmospheric Administration (NOAA) and has recently completed a second NOAA installation (March 2014). With a team of 40 employees, TSi has a prominent list of government, military and commercial customers in Asia, Europe, Africa and the U.S. (including NOAA, NASA and the U.S. Navy).
SPOT LLC, a wholly owned subsidiary of Globalstar, Inc., says its SPOT products have been used to initiate 3,000 rescues around the world since the technology’s launch in 2007. With more than 200,000 SPOT units in service, that averages to one rescue a day. SPOT delivers affordable and reliable satellite-based connectivity and real-time GPS tracking, completely independent of cellular coverage.
“Lifesaving rescues around the globe are now a daily occurrence for our SPOT products. SPOT is an absolute must for the outdoor recreation market and aviation, as well as an essential government and enterprise solution,” said Jay Monroe, CEO and Chairman of Globalstar. “With 3,000 confirmed rescues, saving lives continuously drives us to innovate, creating affordable satellite communications solutions that reach a market well beyond traditional mobile satellite users, including millions of people globally.”
SPOT products allow users to track their assets, use location-based messaging and emergency notification services, and make calls beyond the boundaries of cellular. SPOT products work around the world, including virtually all of the continental United States, Canada, Mexico, Europe and Australia, portions of South America, Northern Africa, North-Eastern Asia and thousands of miles offshore of these areas. Over the past seven years, boaters, hunters, recreational pilots, hikers, off-road travelers and outdoor enthusiasts have come to depend on the lifesaving capabilities of SPOT.
The 3,000th rescue occurred in the Hayman Fire area of Central Colorado. Two dirt bikers were outside of cell range when an accident occurred. One of the riders, Kevin, activated the SOS button on his SPOT Satellite GPS Messenger. The GEOS International Emergency Response Coordination Center was alerted and coordinated the rescue with local law enforcement. “SPOT worked really well. Without it, getting out would have been more difficult and time consuming and who knows what could have happened in that time. There were a lot of different variables involved,” Kevin said.
SPOT products and services include:
SPOT Gen3, a device that provides off-the-grid messaging, emergency alerts, extended battery life, and extreme GPS tracking at 2½-minute intervals.
SPOT Trace, a GPS tracking device that uses satellite technology to track anything, anytime, anywhere.
SPOT Global Phone, a satellite phone that allows users to make calls virtually anywhere beyond the boundaries of cellular.
The SPOT App, a web-based interface allowing users to view their SPOT messages, show their track points, and monitor their assets via smartphone or tablet.
Boatracs, Kannad, McMurdo and TSi have combined to form McMurdo Group, a single-vendor provider of end-to-end search and rescue, maritime domain awareness solutions.
McMurdo Group has announced a suite of Automatic Identification System (AIS) survival solutions for enhanced collision avoidance and man overboard (MOB) response in the U.S. recreational boating market. The offerings include AIS beacons, transponders, receivers and software.
AIS is an automatic tracking system used on boats and ships that identifies and tracks nearby AIS-equipped vessels and devices to help avoid collisions. AIS transponders send and receive critical navigation information – such as vessel identification numbers, vessel type, position, course and speed – and graphically display a map of the surrounding vessels and area. AIS receivers are often used in conjunction with AIS-capable computer software for similar tracking and monitoring purposes.
In the event a person with an AIS MOB beacon falls overboard, an AIS signal from the beacon is activated. This signal is then sent to AIS receiving devices where the location of the individual in the water can be pinpointed using GPS positioning and presented on graphical chart maps.
The Smartfind M5 has an on-screen beacon location indicator and audible alarm that is triggered to accelerate rescue efforts. It also has a “buddy list” feature that can identify the specific individual needing MOB assistance. For larger fleets, the McMurdo Group AIS Alarm Notification System extends graphical mapping, alarm notification and messaging capabilities to shoreside fleet management operators.
The McMurdo Group AIS product suite includes the following:
AIS Search and Rescue Transponders (SART) or Beacons
Smartfind S5 – a compact, lightweight, waterproof (to 10 meters) AIS SART with high-visibility buoyant carry-off bag ideal for use on life rafts or survival crafts.
Smartfind S10 – a personal, waterproof (to 60 meters) AIS Man Overboard (MOB) device with built-in flashing light and used by individuals or as an additional device to complement a yacht’s on-board flare pack.
Smartfind S20 – a compact AIS MOB device with integrated light for use in a lifejacket.
AIS Transponders and Receivers
Smartfind M5 AIS Class A Transponder – the industry’s first AIS Class A transponder with color display and AIS MOB and AIS SART alarm with crew list functionality to aid in MOB recovery.
Smartfind M10 AIS Class B Transponder – typically used for smaller vessels, charter boat operators or where the additional features of an AIS Class A transponder are not required (includes an a 30 day data logger).
Smartfind M15 AIS Receiver – economical AIS receiver for all recreational vessels.
AIS Software
PC Viewer – Graphical software package ideal for individual vessel operators (included with the Smartfind M5, M10 and Smartfind M15 products).
AIS Alarm Notification System – Vessel Monitoring System with integrated AIS MOB Alerts and Messaging typically used for ship-to-shore communications.
Svalbard station on Spitsbergen in the Norwegian Arctic.
The European Space Agency’s completion of a pair of dedicated ground stations at opposite ends of Europe has enabled Galileo satellites in orbit to participate in global testing of the Cospas–Sarsat search and rescue system.The Maspalomas station, at the southern end of the largest island of the Canary Islands, at the southern fringe of European waters, was activated in June. And this last month has seen the Svalbard site on Spitsbergen in the Norwegian Arctic come on line — the two sites can already communicate and will soon be performing joint tests.
This speedy progress has enabled the participation of the latest two Galileo satellites in an international demonstration and evaluation program — a worldwide test campaign for a new expansion of the world’s oldest and largest satellite-based rescue system, Cospas–Sarsat.
The Maspalomas station in the Canary Island has an ESA-built Maspalomas Medium-Earth Orbit Local User Terminal (MEOLUT).
Founded by Canada, France, Russia and the U.S., Cospas–Sarsat has assisted in the rescue of tens of thousands of souls in its three decades of service. Distress signals from across the globe are detected by satellites, then swiftly relayed to the nearest search and rescue (SAR) authorities.
Now the program is introducing a new medium-orbit SAR system to improve coverage and response times, with the Galileo satellites in the vanguard of this major expansion.
Supporting search and rescue is a separate function to Galileo’s main task of providing global navigation and timing services, but no less important.
The second pair of Europe’s Galileo satellites — launched together on 12 October last year — are the first of the constellation to host SAR payloads. These can pick up UHF signals from emergency beacons aboard ships, aircraft or carried by individuals, which are then relayed to ground stations. There, the source is pinpointed and automatically passed on to a control center, which then routes it to local authorities for rescue.
“The Galileo satellites, tested in combination with the same SAR payloads on Russian Glonass satellites as well as compatible repeaters on a pair of US GPS satellites, showed an ability to pinpoint simulated emergency beacons down to an accuracy of 2-5 km in a matter of minutes,” explained ESA’s Galileo SAR engineer, Igor Stojkovic.
“Our in-orbit validation tests so far have been in line with expectation and beyond, giving us a lot of confidence in the performance of the final system, once completed.
“And using a combination of satellites is just how the upgraded system will operate in practice, in order to localise distress signals.”
Localization test performed from the Maspalomas MEOLUT on 29-30 July 2013 as part of Galileo’s search and rescue in-orbit validation. Beacon locations obtained with four satellites are shown in black, while those using three satellites are shown in grey. More than 93% of all beacon locations, after only a single beacon burst has been received, are within the required 5 km from the actual beacon position.
DeLorme has announced the launch of its newest product, the inReach SE (Screen Edition) satellite communication device. With 90 percent of the world’s surface lacking cell phone coverage, inReach SE is designed for the traveler or outdoor adventurer to keep them connected and safe anywhere in the world. The expanded standalone capabilities of inReach SE include a color screen, virtual keyboard, slim design and long-lasting internal lithium battery. In standalone mode, inReach SE provides free-form texting capabilities of up to 160 characters to any cell phone number, email address or social media page.
Using DeLorme’s Earthmate App, inReach SE pairs wirelessly with iPhone, iPad and iPod touch to access topographic maps and NOAA charts and to make text messaging more convenient. inReach SE is also compatible with Android devices.
With the ability to maintain satellite signal lock even in difficult GPS environments, inReach SE also offers global SOS capabilities, adjustable tracking intervals from 10 minutes to four hours, and remote real-time follow-me/find-me tracking and ping-me locating. In the event of an emergency, the interactive SOS capability of inReach automatically triggers remote tracking and allows users to describe and update their situation so proper resources can be deployed, DeLorme said.
“Whether you’re deep in the backwoods, floating on a remote lake, or simply traveling abroad, anyone can benefit from the comprehensive functionality of inReach SE,” said Michael
Heffron, DeLorme CEO. “Over the last two years we have been listening to customer feedback, so the next generation of inReach includes many new features based on their input. The internal rechargeable battery and the on-screen, free-form texting are especially beneficial, making on-the-go communications more convenient and delivering peace of mind to family and friends easier than ever before.”
inReach operates over the Iridium satellite network, providing global two-way satellite communications, high network reliability and low-latency data links (less than 60 second delivery of messages end-to-end) anywhere on Earth, with no gaps, fringe or weak signal areas, DeLorme said.
The follow me / find me tracking feature of inReach provides GPS position updates allowing family and friends to follow the user’s trip as it happens. Family and friends can log into a dedicated MapShare page to follow a detailed breadcrumb trail, ping a location, and send messages to the inReach owner. In the event of an emergency, the built-in SOS button can be activated to trigger a distress alert with delivery confirmation and it automatically activates the remote GPS tracking feature. GPS tracking assists search-and-rescue personnel with homing in on the user’s location, whether stationary or on the move.
Pairing the inReach SE via Bluetooth with the Earthmate App turns a mobile device into a global satellite communicator and navigation tool. Real-time GPS location, tracking and text messages are overlaid on the digital maps for easy navigation and position location. inReach owners get exclusive, unlimited access to DeLorme’s topographic maps and North American NOAA charts, which can be downloaded via an Internet connection prior to departure and remain available in the Earthmate App even when outside cellular coverage.
The first switch-on of a Galileo search and rescue package shows it to be working well, according to the European Space Agency. Its activation begins a major expansion of the space-based Cospas–Sarsat network, which brings help to air and sea vessels in distress.
The second pair of Europe’s Galileo navigation satellites — launched together on October 12 last year — are the first of the constellation to host SAR search and rescue repeaters. These can pick up UHF signals from emergency beacons aboard ships and aircraft or carried by individuals, then pass them on to local authorities for rescue.
Galileo search and rescue repeater signal.
Once the satellites reached their 23,222 km-altitude orbits, a rigorous test campaign began. The turn of the SAR repeater aboard the third Galileo satellite came on January 17.
“At this stage, our main objective is to check the repeater has not been damaged by launch,” explained ESA’s Galileo SAR engineer Igor Stojkovic. “The first day was a matter of turning the repeater on and checking its temperature and power profiles were as predicted. The following day involved sending a signal to the repeater using the UHF antenna at ESA’s Redu Centre in Belgium, then picking up the reply from our L-band antenna.”
Redu’s antenna is 20 meters in diameter, so the shape of the relayed signal was captured in great detail, out of all proportion to surrounding noise.
“We can precisely measure its power, the time the relay took and so on,” added Igor.
More detailed system testing will follow, to completely prove this new type of SAR payload in orbit.
Cospas–Sarsat system.
The international system has been in use for more than three decades, saving some 31,000 lives. Cospas is a Russian acronym for “Space System for the Search of Vessels in Distress,” with Cospas standing for “Search and Rescue Satellite-Aided Tracking.” Ground stations — known as Local User Terminals — pinpoint the source of distress calls using signals relayed by participating satellites, then alert local authorities.
The GPS satellites will also provide a medium-Earth-orbit Sarsat capability and testing is underway. All nine Block IIR satellites carry experimental payloads and all IIF satellites are scheduled to. See “The Distress Alerting Satellite System” for more details.
The alarm operations center for the state of Bavaria receives this message from the accident location, and swiftly moves into coordinating activity, gathering and distributing real-time geospatial data and other key information to all emergency teams and medical facilities in the area. A demonstration of large-scale rescue operations showed how Galileo-based positioning signals in the Galileo test-bed in Berchtesgaden, Germany can more efficiently organize complex and costly rescue work through use of GNSS-supported mobile navigation devices.
Current decision-making aids in the field of search-and-rescue offer only a limited IT-supported common operational picture (COP). Many components for a full solution are still lacking. Heterogeneity in sensor networks and proprietary system designs limit interoperability and flexibility, hampering the creation of a full COP across collaborating organizations.
“E mergency Alert: Bus collision in Berchtesgaden, parking area Salzbergwerk. Many injured. Bus overturned, some thrown from vehicle, some trapped inside. Local temperature below freezing, snow falling. All crews respond immediately.”
An extensive training exercise (photo above) performed by the Fire Brigade, Bavarian Red Cross, and German Federal Agency for Technical Relief focused on challenges and advantages in this framework. The ERA-Star Project G2Real integrates real-time Earth-observation data and onsite measurements, leveraging existing and emerging open geospatial consortia. Spanish, Austrian, and Bavarian research institutes and enterprises collaborated to prepare and upgrade a COP based on integrated live information, satellite-navigation, and remote sensing. The overall aim is utilization of GNSS-enabled tools and Global Monitoring for Environment and Security (GMES) services to support search-and-rescue operations. The specific goal is a common, real-time COP that can be used by the local primary control unit/service command vehicle and by higher ranking administrations.
The common operational picture (COP).
Mission control, decision, and guidance was coordinated from a remote control room, where the mission leader, through the COP, knew everything about the position of accident vehicles, victims, rescue vehicles, and rescue team personnel, and could track their status and locations in real time. Local team chiefs on the ground also had access to this data through their mobile devices.
The mission leader could plan resources for the ensuing phases of transport and treatment, and teams on the ground could communicate with each other via a simple mobile phone application, which replaced existing calls and radio voice signals and facilitated operations and coordination.
GNSS receivers were installed in a fire engine using Galileo, GPS, and GLONASS signals to achieve best practice across all phases of emergency management. The Galileo signals were furnished by the Galileo Test and Development Environment (GATE), provided by eight transmitters atop the Alpine ridges surrounding Berchtesgaden.
Lars Holstein is project manager for Initiative Satellite Navigation Berchtesgadener Land.
By David W. Affens, Roy Dreibelbis, James E. Mentall, and George Theodorakos
In 1997, a Canadian government study determined that an improved search and rescue system would be one based on medium-Earth orbit satellites, which can provide full global coverage, can determine beacon location, and would need fewer ground stations. This month’s column examines the architecture of the GPS-based Distress Alerting Satellite System and takes a look at early test results.
INNOVATION INSIGHTS by Richard Langley
IT IS NOT COMMONLY KNOWN that the GPS satellites carry more than just navigation payloads. Beginning with the launch of the sixth Block I satellite in 1980, GPS satellites have carried sensors for the detection of nuclear weapons detonations to help monitor compliance with the Non-Proliferation Treaty. The payload is known as the Nuclear Detonation (NUDET) Detection System (NDS) and is jointly supported by the U.S. Air Force and the Department of Energy.
And now a third task is being assigned to the GPS satellites — that of search and rescue. Since the mid-1980s, a combination of low Earth orbit (LEO) and geostationary orbit (GEO) satellites have been used to detect and locate radio beacons activated by mariners, aviators, and others in distress virtually anywhere in the world and at any time. Some 28,000 lives have been saved worldwide since the search and rescue satellite-aided tracking, or SARSAT, system was implemented.
But the current system has some drawbacks. LEO satellites can determine a beacon’s position using the Doppler effect but their field-of-view is limited and one of them may not be in range when a beacon is activated. Furthermore, a large number of ground stations is needed to relay data from these satellites to search and rescue authorities. GEO satellites, on the other hand, have a large field of view (although missing parts of the Arctic and Antarctic), but they cannot position a beacon unless its signal contains location information provided by an integral satellite navigation receiver.
In 1997, a Canadian government study determined that a better SARSAT system would be one based on medium Earth orbit (MEO) satellites. A MEO system can provide full global coverage, determine beacon location, and do this with fewer ground stations. GPS was identified as the ideal MEO constellation.
And so was born the Distress Alerting Satellite System (DASS) that will become fully operational on Block III satellites. But already nine GPS satellites are hosting prototype hardware that is being used for proof-of-concept testing.
In this month’s column, we examine the architecture of DASS (including its relationship with the NDS), and take a look at some of the very positive test results already obtained — results that support the claim that DASS will take the search out of search and rescue.
NASA, which pioneered the technology used for the satellite-aided search and rescue capability that has saved thousands of lives worldwide since its inception nearly three decades ago, has developed new technology that will more quickly identify the locations of people in distress and reduce the risk to rescuers.
The Search and Rescue (SAR) Mission Office at the NASA Goddard Space Flight Center, in collaboration with several government agencies, has developed a next-generation satellite-aided search and rescue system, called the Distress Alerting Satellite System (DASS). NASA, the National Oceanic and Atmospheric Administration (NOAA), the U.S. Air Force, the U.S. Coast Guard, and other agencies are now completing the development and testing of the new system and expect to make it operational in the coming years after a complete constellation of DASS-equipped satellites is launched.
When completed, DASS will be able to almost instantaneously detect and locate distress signals generated by emergency beacons installed on aircraft and maritime vessels or carried by individuals, greatly enhancing the international community’s ability to rescue people in distress, This improved capability is made possible because the satellite-based instruments used to relay the emergency signals will be installed on the GPS satellites.
A recent satellite-aided rescue started on June 10, 2010, when 16-year-old Abby Sunderland on her 40-foot (12.2-meter) sailboat “Wild Eyes” encountered heavy seas approximately 2,000 miles (3,200 kilometers) west of Australia in the Indian Ocean. Her sailboat was dismasted and an emergency situation resulted. Ms. Sunderland activated her two emergency beacons whose signals were picked up by orbiting satellites. Using coordinates derived from the signals, a search plane spotted Ms. Sunderland the next day, and a day later she was rescued by a fishing boat directed to the scene. This highly publicized event is one of thousands of successful rescues made possible by years of NASA research and development.
Background
The beginnings of satellite-aided search and rescue date back to 1970, when a plane carrying two U.S congressmen crashed in a remote region of Alaska. A massive search and rescue effort was mounted, but to this day, no trace of them or their aircraft has ever been found. At the time, search for missing aircraft was conducted by search aircraft flying over thousands of square kilometers hoping to sight the missing aircraft. As a result of this tragedy, Congress recognized this inefficient search method and passed an amendment to the Occupational Safety and Health Act of 1970 requiring most aircraft flying in the United States to carry emergency locator beacons (ELTs) to provide a local homing capability. NASA then developed the technology to detect and locate an ELT from ground stations using the beacon signal relayed by satellites to provide more global coverage. This concept evolved into a highly successful international search and rescue system called COSPAS-SARSAT (COSPAS is an acronym for the Russian words “Cosmicheskaya Sistema Poiska Avariynyh Sudov,” which translates to “Space System for the Search of Vessels in Distress;” SARSAT is an acronym for Search and Rescue Satellite-Aided Tracking). Established by Canada, France, the United States, and the former Soviet Union in 1979, the system has 43 participating countries and has been instrumental in saving more than 28,000 lives worldwide, including 6,400 in the U.S. — all as a result of NASA’s innovations.
Since this auspicious beginning, NASA has continued to perform SAR research and development as a member of the National Search and Rescue Committee, and supports the National Search and Rescue Plan through an interagency memorandum of understanding with the Coast Guard, the Air Force, and NOAA. NOAA is responsible for operation of the U.S. portion of current COSPAS-SARSAT system that relies on SAR payloads on weather satellites in low-earth and geostationary orbits. As shown in Figure 1, the satellites relay distress signals from emergency beacons to a network of ground stations and ultimately to the U.S. Mission Control Center (USMCC) operated by NOAA. The USMCC distributes the alerts to the appropriate search and rescue authorities: the U.S. Air Force or the Coast Guard. The Air Force coordinates search and rescue for the mainland U.S. SAR region and operates the Air Force Rescue Coordination Center. The Coast Guard performs maritime search and rescue and oversees the U.S. national SAR policy.
FIGURE 1. Overall concept of search and rescue system. (Image: Cospas-Sarsat)
Beacons
Three types of distress emergency locator beacons are in use that are compatible with the COSPAS-SARSAT system:
EPIRBs (emergency position-indicating radio beacons) designed for maritime use.
ELTs (emergency locator transmitters) for use on aircraft.
PLBs (personal locator beacons) for personal use. These can be used by persons engaged in high-risk activities such as mountain climbing and backcountry skiing.
Originally, emergency locator beacons transmitted an analog signal on two frequencies: 121.5 MHz and 243 MHz in the civil and military aeronautical communications bands, respectively, so that they would be audible over aircraft radios. Later, a signal that was encoded with a digital message and transmitted at 406 MHz was added. Since February 1, 2009, only the 406-MHz-encoded signals are relayed by satellites supporting the international COSPAS-SARSAT system. Therefore, older beacons that only transmit the 121.5/243-MHz signals are now only detectable by ground-based receivers and aircraft overflying a crash site.
The 406-MHz beacons transmit an approximately half-second message, or burst, approximately every 50 seconds, beginning 50 seconds after being activated. The actual time of burst transmission is dithered in time so that no two beacons will have all of their bursts coincident. A 406-MHz beacon may also have an integral global navigation satellite system (GNSS) receiver. Such a beacon uses the GNSS receiver to attempt to determine its location for inclusion in the transmitted digital message. In this way, the beacon will be located once it is detected by a low-Earth-orbit (LEO) or geostationary orbit (GEO) satellite.
Distress messages contain information such as:
The beacon’s country of origin.
A unique 15-digit hexadecimal beacon ID.
Location, when equipped with an integrated GNSS receiver.
Whether or not the beacon contains a 121.5-MHz homing signal.
Room for Improvement
SARSAT first became operational in the mid-1980s. The current system uses instruments placed on LEO and GEO weather satellites to detect and locate mariners, aviators, and recreational enthusiasts in distress almost anywhere in the world at anytime and in almost any condition. Previously, dedicated Russian LEO satellites were also implemented but the use of these satellites was discontinued in 2007.
Although it has proven its effectiveness, as evidenced by the number of persons rescued over the system’s lifetime, the current capability does have limitations. LEO spacecraft orbit the Earth 14 times a day and use the Doppler effect with satellite orbital ephemeris data to calculate the position of a beacon. However, a satellite may not be in a position to pick up a distress signal the moment a user activates the beacon. Time is critical in responding to an emergency situation. Unfortunately, delays of two hours or longer are possible, especially near the equator.
LEO spacecraft carry two instruments: a Search and Rescue Repeater (SARR) supplied by the Canadian Department of National Defence, and a Search and Rescue Processor (SARP) provided by the French Centre National d’Etudes Spatiales (CNES). The SARR is a pure repeater, which relays the beacon signal to a local ground station where the data is analyzed to obtain a location. The SARP processes the received beacon signal by measuring the Doppler shift as a function of time, and decoding the digital message included in the 406-MHz signal. This information is stored until it can be transmitted to a ground station using the SARR’s downlink transmitter. Under most conditions beacon locations can be determined to within a radius of 5 kilometers.
Geostationary weather satellites, on the other hand, orbit above the Earth in a fixed location over the equator. Although they do provide continuous visibility of much of the Earth, they cannot independently locate a beacon unless it contains a GNSS receiver that determines its position and includes it in the beacon’s digital message. Currently, not all beacons contain integral GNSS receivers. Furthermore, even if a beacon contains a GNSS receiver, the navigation signal may be obstructed by terrain or thick foliage.
The next-generation system, DASS, overcomes these limitations and will improve accuracy and response time to provide an even more capable life-saving system.
Distress Alerting Satellite System
A 1997 Canadian government study of possible alternative satellite systems for SARSAT, including commercial sources, determined that the ideal system is based on medium Earth orbit (MEO) satellites. A MEO system will be able to provide superior global detection and location data with fewer ground stations than the existing COSPAS-SARSAT system. The GPS constellation was identified as an ideal MEO platform.
The concept of the DASS system is straightforward. Three or more antennas track different GPS satellites equipped with search and rescue repeaters that receive the distress signal and retransmit the signal to the ground. Since each satellite is in a different orbit, each received signal has a different Doppler-shifted arrival frequency and time of arrival. Knowing the position and orbit of each satellite, it is possible to determine the position of the distress beacon.
Future improvement in location accuracy is made possible by one of the strengths of the DASS space segment. That is, the DASS location algorithm optimizes location accuracy utilizing time and frequency measurements of beacon signals that were not designed for that purpose. The DASS space segment allows for the beacon signal to be modified in the future, enhancing the performance of this type of location process.
Other advantages of DASS over the existing system are fairly obvious. Reception of the emergency signal is immediate. Locations can be determined after receiving a single beacon burst since it does not rely on measuring the Doppler shift over time to determine position, as in the current LEO system. A full constellation of DASS-equipped GPS satellites in orbit will ensure that four or more satellites are in view of the transmitting emergency beacon anywhere in the world while requiring fewer ground stations.
Another key strength of the DASS system is the promise of SARSAT transponders on each satellite in the large and well-managed GPS constellation. There are at least 24 GPS active satellites in orbit at any given time (currently, 31 are active). When the GPS constellation is fully populated by satellites with DASS transponders, it will provide global coverage for satellite-supported search and rescue and provide capabilities for rapid detection and location of distress beacons.
Efforts are ongoing to integrate a satellite beacon repeater instrument, to be provided by the Canadian government, onto the GPS Block III B and C satellites to provide the DASS space segment for operational use.
DASS Development
DASS development will proceed in phases referred to as the definition and development, proof of concept, demonstration and evaluation, initial operating capability, and final operating capability. The proof of concept (POC) phase was completed in January 2009. The POC testing and results are summarized in this article. At the time of this writing, preparations are ongoing to initiate the demonstration and evaluation phase.
Definition and Development. In 2000, as part of the definition and development phase, the NASA GSFC SAR Mission Office began discussions with the Department of Energy’s Sandia National Laboratories (SNL) to determine if it would be feasible to add a SAR repeater function to a Department of Energy (DOE) instrument on GPS satellites. Sandia representatives thought it possible, and NASA agreed to fund a study to determine if, with minor modification, one could include a search and rescue repeater function to their instrument. The SNL feasibility study concluded that the GPS DOE package could, with minor modifications, perform the SAR mission. The study also determined that accurate locations could be calculated after a single beacon transmission and improved with each subsequent beacon transmission. Based on this information, NASA, with the cooperation of the U.S. Air Force Space Command and SNL, proceeded with the development of the new space-based search and rescue system, which was named the Distress Alerting Satellite System.
Proof of Concept. In 2003, a memorandum of agreement (MOA) between NASA, NOAA, the Air Force, the Coast Guard, and the Department of Energy tasked NASA to perform a POC program for DASS. The MOA included the development of a POC space segment and a prototype ground station to perform post-launch checkout, performance testing, and implementation planning of an operational DASS system. It stressed the need for DASS, gave authority to each participating agency to participate in the POC demonstration, and defined the roles of each.
The Air Force Space Command approved the addition of modified equipment on GPS satellites. The DASS POC space segment operates as a subcomponent of GPS Block IIR and IIF satellites. Nine GPS Block IIR satellites carry experimental DASS payloads, and all 12 IIF satellites are scheduled to. Therefore, the final POC space segment will consist of 21 DASS-equipped GPS satellites. Each payload receives 406-MHz SAR signals on an extant GPS UHF antenna and relays the signals at a GPS S-band frequency on a second extant antenna.
It is important to note that the performance of the DASS POC space segment will be exceeded by the performance of the operational space segment being designed specifically for DASS and planned for launch on GPS Block III satellites.
A prototype DASS ground station (Figure 2) was funded by NASA and installed at GSFC. The DASS prototype ground system consists of four antennas, four receivers, and the workstations and servers necessary to process the received data, command and control the operation of the ground station, and display and analyze the results. The antennas are located on the corners of the roof of a building connected by fiber-optic cable to signal processing equipment located in another building two kilometers away.
FIGURE 2. Prototype ground station at NASA GSFC. (Images: NASA)
Proof of Concept Testing
The overall objectives of the POC tests were to demonstrate the effectiveness of the DASS concept and to define its technical and operational characteristics. The primary technical objective was to demonstrate the system’s ability to detect and locate 406-MHz emergency beacons under various controlled conditions. This is the most important measure of the system’s ability to perform as expected.
The specific objectives of the DASS POC demonstration were to
Confirm the expected performance of the DASS concept.
Determine if new or enhanced requirements needed to be established.
Define preliminary performance levels that will be used to establish the scope and content of the next phase of development, referred to as the demonstration and evaluation phase.
Therefore, during POC testing, performance measurements were taken for the probability of detection, probability of location, and location accuracy, defined as follows.
Probability of detection is the probability of detecting the transmission of a 406-MHz beacon and recovering a valid beacon message from any available satellite.
Probability of location is the probability of obtaining a location solution within a given time after beacon activation, independently of any encoded position data in the 406-MHz beacon message.
Location accuracy is the distance from the location solution obtained within 5 minutes after beacon activation, to the actual beacon location. The required performance is specified as the probability that a given solution is within a given distance of the actual location.
It is important to note that the predicted performance of DASS assumes a full constellation of DASS-equipped GPS satellites. In fact, one of the key strengths of DASS is the promise of DASS transponders on each satellite in the GPS constellation. When a full constellation is equipped with DASS transponders, there will typically be between seven and 13 GPS satellites visible at the NASA ground station. Thus, it will be possible to schedule the ground-station antennas to receive data from the best satellites in terms of geometry, signal strength, processing capability, and other factors.
However, at the time of the POC testing, there were only eight GPS satellites equipped with DASS transponders. A maximum of three DASS-equipped GPS satellites were visible at the same time at the NASA ground station (above a 15-degree elevation angle), and there were times when only one DASS-equipped GPS satellite was visible. Thus, it was impossible to optimize satellite selection since there was never an opportunity to select from an excess of satellites that a full constellation would provide.
In particular, satellite geometry and its effect on performance is never as optimal as what would be obtained from a full constellation of GPS satellites. To predict the results of a full constellation using the results from a severely reduced constellation, a calculation based on “dilution of precision” was used.
Dilution of precision (DOP) or geometric dilution of precision, to be specific, is used to describe the geometric strength of satellite configuration on GPS accuracy. When visible satellites are close together in the sky, the geometry is said to be weak and the DOP value is high; when far apart, the geometry is strong and the DOP value is low. Thus a low DOP value gives rise to a better GPS positional accuracy due to the wider angular separation between the satellites used to calculate a beacon’s position.
Location accuracy results can be scaled to reflect the true DOP that would be obtained by a satellite constellation of 24 GPS satellites. The DOP error caused by uncertainty in time and frequency measurements is used for scaling. The DOP of the satellites actually used to calculate a location solution, denoted by ftDOPACT, is always bigger than the DOP that would have been available from a constellation of 24 GPS satellites, ftDOP24. The raw location errors need to be multiplied by the ratio ftDOP24 / ftDOPACT to reflect the results that would have been obtained if all 24 satellites were present.
The raw average location error, erravg, is given by the following:
err(b) = err(lat(b),lon(b))= distance from the known location to (lat(b),lon(b))
erravg(b0) = err(latavg(b0),lonavg(b0))
where Ω(b0) is the set of seven or fewer consecutive burst locations within 5 minutes, starting with burst b0.
The scaled location error is the location error scaled by the DOP ratio:
Since DOP changes little over 5 minutes, the error of the average is approximately
where ftDOPACT(b) is the time-frequency DOP of burst b calculated with either three or four satellite geometries depending on
the number of measurements used in the location calculation.
Test Source
A custom-designed beacon simulator was used to generate the transmissions of multiple COSPAS-SARSAT 406-MHz beacons over an extended period of time. To represent expected operational realism in the tests, the beacon simulator was used to transmit beacons at the limits of the five major beacon parameters specified by COSPAS-SARSAT as well as the nominal values. The five major beacon parameters are transmit power, modulation index, bit rate, un-modulated carrier duration, and modulation rise and fall times (see TABLE 1).
During POC testing, five beacons were transmitted using three scenarios: maximum beacon parameter values, minimum beacon parameter values, and variable power. The parameter values changed in each test scenario and are highlighted in TABLE 2. Beacon detection and location performance is measured for periods when there are three or more satellites visible at the same time, and for durations sufficient to collect a statistically significant amount of data.
Table 2. Beacon parameter values for each test scenario. (Data: Authors)
Two characteristics of the test source that affect system performance are the beacon antenna pattern and ground mask. To simulate beacons, the beacon simulator has a monopole antenna with the gain pattern shown in Figure 3. There is a substantial reduction in the transmitted signal at high-elevation angles (above 60°). DASS-equipped GPS satellites are often at high-elevation angles during a typical day. As expected, the effect of the pattern on test results can clearly be seen upon close inspection of the data. However, the beacon antenna pattern is an unavoidable reality and is, therefore, fully represented in the data used to generate the results presented here. Additionally, there were significant ground obstructions of the beacon signal in certain directions. The effect of beacon antenna pattern is fully included in the results presented in this article, but ground mask is taken into account by limiting satellite visibility to an elevation cut-off angle of 15 degrees.
FIGURE 3. Beacon simulator transmit antenna gain pattern.
POC Test Results
In this section, we discuss the POC test results in terms of probability of detection, probability of location, and location accuracy.
Probability of Detection. As previously mentioned, probability of detection is the probability of detecting the transmission of a 406-MHz beacon and recovering a valid beacon message from any available satellite. The requirement is that 95 percent of individual transmitted messages are detected.
Test results are given in TABLE 3 and show that the probability of detection is approximately 99 percent for all scenarios, even though only three satellites were in view at a time. Obviously, the probability of detection is dependent on the number of available satellites and performance would improve with continuous coverage by four or more satellites.
Table 3. Probability of detection test results. (Data: Authors)
Probability of Location. Again, the probability of location is the probability of obtaining a location solution within a given time after beacon activation, independently of any encoded position data in the 406-MHz beacon message. The requirement is that the probability of calculating a beacon location is 98 percent within 5 minutes.
Since the probability of location is dependent on the number of visible satellites, our performance was limited by the reduced constellation of DASS-equipped satellites. Results from periods of three-satellite coverage were 85 percent within 5 minutes, 92 percent within 10 minutes, and 94 percent within 15 minutes.
Again, the probability of location is dependent on the number of visible satellites, and performance would improve with continuous coverage by four or more satellites. To investigate the possible improvement with enhanced satellite coverage, we reduced the minimum satellite elevation angle from 15 to 10 degrees. This allowed a fourth satellite to become visible for a limited time at very low elevation angles. Even though the signal quality from such a satellite was poor, the probability of location during this period of four-satellite coverage improved as follows: 91 percent within 5 minutes, 96 percent within 10 minutes, and 97 percent within 15 minutes.
As can be seen from these results, even adding a satellite with a very low elevation-angle pass significantly improves performance. The expectation is that having a full constellation of satellites available would improve performance even more. Furthermore, the increase in satellite performance expected in the operational system will also improve probabilities of detection and location.
Location Accuracy. Recall that location accuracy is measured as the percentage of location solutions obtained within five minutes after beacon activation that are within five kilometers of the actual beacon location.
The requirement is to obtain 95 percent of the locations to within 5 kilometers of the actual location and 98 percent within 10 kilometers within five minutes after beacon activation.
As mentioned earlier, the requirements included in the performance specification assume a constellation of 24 DASS-equipped GPS satellites. POC testing was done with a system that had only eight DASS-equipped GPS satellites available. However, location errors can be scaled to reflect what the DOP would be if the satellite constellation contained all 24 GPS satellites. Therefore, it is the scaled results that can be used to determine whether performance will meet the requirement.
TABLE 4, therefore, presents the location accuracy results as measured, and after being scaled by DOP.
Table 4. Location accuracy for 5-minute periods. (Data: Authors)
Another important performance metric for DASS is location accuracy obtained after a single beacon burst is received. Even though there is not currently a requirement for single burst location accuracy, it is a very desirable feature of DASS since an emergency situation does not guarantee that more than a single burst will be received. Single burst location accuracy was, therefore, measured with the results shown in TABLE 5. Once again, the results are scaled by DOP values to remove the effect of non-optimal satellite geometry.
Table 5. Single burst location accuracy. (Data: Authors)
More insight into this performance can be gained by examining the single burst location accuracy distribution as a function of distance error, as shown in TABLE 6. It can be seen that, for these beacons, computed locations are within 9 kilometers of the actual location 95 percent of the time. Again, the expectation is that having a full constellation of satellites available would improve this performance. For instance, having more satellites to choose from might allow the system to select data from satellites with stronger or less noisy links.
Table 6. Single burst location accuracy by distance error. (Data authors)
Conclusion
The promise of search and rescue instruments on each satellite in the large and well-managed GPS constellation will provide a significant advancement in the capabilities of the already highly successful COSPAS-SARSAT system. The new system will provide global coverage for satellite-supported search and rescue and provide capabilities for rapid detection and location of distress beacons while requiring fewer ground stations.
The DASS POC system has validated, by test, the predictions made by analysis during the definition and development phase. The DASS POC testing has demonstrated reliable detection and accurate location of beacons within five minutes of activation. Accurate locations are also produced after even a single burst of a newly activated beacon, which is a desirable feature of DASS, since an emergency situation does not guarantee that more than a single burst will be received.
The performance obtained using a reduced constellation of satellites equipped with a modified, existing instrument not only demonstrates the existing capability, but also confirms the improvements to come with the operational system. In fact, the success of DASS is being emulated by the European Union in the design of their future Galileo GNSS constellation and the Russians in an upgraded GLONASS GNSS constellation, all of which will be interoperable by international agreement.
DASS will contribute to NASA’s goal of taking the search out of search and rescue. Achieving this goal will not only improve the chances of rescuing people in distress quickly, which is critical to their survival; it will also reduce the risk to rescuers who often put themselves in dangerous situations to affect a rescue. That is why the motto of the Search and Rescue Office is “Saving more lives, reducing risks to search personnel, and saving resources.”
David W. Affens is the manager of the NASA Search and Rescue (SAR) Mission Office at the Goddard Space Flight Center (GSFC) in Greenbelt, Maryland, where he began working in 1990. He holds a degree in electronic engineering. Before joining NASA, he worked in various aspects of submarine warfare and intelligence gathering for the U.S. Navy over a span of 21 years.
Roy Dreibelbis is a consultant who has worked in rescue-related jobs since 1957, including helicopter rescue missions in Vietnam. As an officer in the U.S. Air Force, he was the director of Inland SAR at rescue headquarters for the coterminous 48 states, was commander of the 33rd Air Rescue Squadron, and served as deputy chief of staff for rescue operations at rescue headquarters from 1979 until 1981. Upon retirement from the Air Force, he was employed by the State of Louisiana as flight operations director and chief pilot. In 1987, he accepted employment with contractors in the District of Columbia area that supported NASA and NOAA SARSAT activities.
James E. Mentall is the NASA/GSFC Search and Rescue Instrument Manager. He has a Ph.D. in physics and has spent more than 42 years of his professional life at GSFC. For 15 of those years, he has been responsible for the integration and test of the Search and Rescue Repeater and the Search and Rescue Processor on the NOAA Polar-orbiting Operational Weather Satellites. He has also served as the deputy mission manager for the Search and Rescue Mission Office and played a significant role in the procurement of the DASS antenna system and ground station.
George Theodorakos is the chief staff engineer for MEI Technologies, Inc. He received his B.S. summa cum laude and M.S. degrees in electrical engineering from the University of Maryland, College Park, Maryland, in 1978 and 1987, respectively. Since 2002, in his role as chief staff engineer at MEI, he has provided technical management support to the Search and Rescue Mission Office at GSFC.
FURTHER READING
• Distress Alerting Satellite System (DASS)
“Distress Alerting Satellite System (DASS)” on the NASA Search and Rescue Mission Office website, Goddard Space Flight Center, Greenbelt, Maryland.
• Search and Rescue Satellite-Aided Tracking (SARSAT)
“Search and Rescue,” Chapter 6 in Review of the Space Communications Program of NASA’s Space Operations Mission Directorate by the Committee to Review NASA’s Space Communications Program, Aeronautics and Space Engineering Board, Division on Engineering and Physical Sciences, National Research Council, published by the National Academies Press, Washington, D.C., 2007.
“Overview of MEOSAR System Status” by J. King, a presentation at BMW-2009, Beacon Manufacturers Workshop, St. Pete Beach, May 8, 2009.
“MEOSAR to the Rescue” by J. King in Channels, the EMS SATCOM Quarterly, published by EMS Technologies, Inc., January 31, 2007.
• Nuclear Detonation (NUDET) Detection System
“Detecting Nuclear Detonations with GPS” by P.R. Higbie and N.K. Blocker in GPS World, Vol. 5, No. 2, February 1994, pp. 48–50.
