By Thomas Zajkowski, a remote sensing specialist with the U.S. Forest Service Remote Sensing Applications Center (www.fs.fed.us/eng/rsac), Salt Lake City, Utah.
According to the U.S. Global Change Research Program, the frequency of large wildfires and the length of the fire season have increased substantially in recent decades. Fortunately, Earth imagery can be used to help reduce the risk and minimize damage when a fire occurs.
The benefits of remote sensing in all stages of forest management have been well documented, culminating in a recent U.S. Forest Service agreement with NASA (see “Moving Beyond Unmanned Aircraft” below). For example, weather information, such as measurements of precipitation and temperature, allows foresters to calculate risk assessments and isolate the areas most susceptible to fire. Such areas can be closely monitored by satellites, which can detect small fires almost immediately.
Satellite-based remote sensing also contributes to fire-fighting efforts. Data on wind direction and speed, as well as the dryness of surrounding areas, can help predict the directions and speed at which a fire spreads. With this information, firefighters can be dispatched with maximum effectiveness and safety. After a fire, damage can be quickly and inexpensively assessed using satellite imagery data. With accurate information on the area of the burn scar, amount of biomass destroyed, and the amount of smoke and air pollution, forest managers can efficiently proceed with recovery and planning.
Recent technological developments in sensors, image processing, communications and data display make it possible to develop and deploy remote sensing systems that can deliver accurate geospatial information to decision makers and first responders in near real time. Many of these technical innovations are directly related to investment in unmanned aircraft systems (UASs).
UAS Sensors Continue to Improve
The sensor is the basis for any remote sensing system. The sensor type determines the size of the platform, the amount of image processing that’s possible and the type of communication equipment required. In the case of wildland firefighting, fire managers need to know the location of the fire front, fire behavior and resource location. This information then needs to be disseminated quickly to tactical forces and the public.
The thermal imaging systems available on most UASs are single-band, long-wave infrared (LWIR) sensors that are sensitive from 8–14 μm for hot-spot discrimination. The drawback to LWIR systems is that when they encounter extremely hot fire, the sensor becomes “saturated,” which complicates the identification of small hot areas and other features in the data.
Despite their limitations, tactical LWIR UASs are useful for fire support. These commercial, off-the-shelf units can observe a fire through smoke 24 hours a day. This allows crews to identify new fire starts, monitor fast-moving fire fronts and identify smoldering fires during the mop-up phase.
Small LWIR micro-bolometer sensors constantly are improving as the sensors become smaller, the sensor array sizes become bigger, and as spatial resolution increases unit costs decrease. Many LWIR sensors include a bore-sighted high-definition video camera. Although natural-color video is susceptible to smoke, there are many times during fire-support missions when high-resolution color video can be used to identify fuel types and deployed resources, as well as to observe fire behavior.
Several manufacturers are working on more efficient and smaller quantum well infrared photodetector (QWIP) sensors that can be installed in tactical UASs in the near future. Made from semiconductor materials that contain one or more quantum wells, such sensors will have increased detection thresholds, spatial resolution and spatial coverage for each image area, as well as lower costs.
Short-wave infrared (SWIR) systems (0.9–1.7 μm) also are being installed on UASs. The advantage ofSWIRimagery is that it’s easier to interpret than LWIR imagery, especially for individuals who are unfamiliar with LWIR interpretation. As with visible video cameras,SWIRsensors are more susceptible to smoke obscuration than LWIR sensors.
Larger UASs are capable of carrying larger, more capable sensors with multiple channels. Such systems are able to discriminate among hot objects, such as rocks, metal roofs and vehicle windshields, and small fires. One such sensor is the wide-area imager (WAI), which is being developed for NASA by Xiomas Technologies, Ypsilanti, Mich., under a Small Business Innovative Research grant.
The multispectral system incorporates QWIP focal plane arrays for the MWIR (4–5 μm) and LWIR (9–10 μm) channels that provide a spatial resolution of 3 feet (1 meter) from a platform altitude of 10,000 feet (3,048 meters) above ground level. Three additional spectral bands cover the visible and NIR wavelength
region. This addition allows the WAI to be used for natural resource
applications when not supporting firefighters.
Once a sensor has imaged a wildfire, the imagery must be processed, requiring geospatial metadata that allow fire managers to integrate the imagery into a geographic information system (GIS).
Today, fire-line personnel have access to intelligent maps—maps built using databases and powerful modeling capabilities—in the firehouse and in the field. Mobile GIS technology provides responders with detailed information when and where they need it for a faster and safer response. Furthermore, a mobileGISallows responders to return information to incident commanders and emergency managers on fire status, as well as any unexpected fire behavior.
Converting remotely sensed imagery into KML/KMZ files for Google Earth overlays or Esri shapefiles for Esri GISsoftware analysis allows the data files, which are relatively small compared with full-motion video files, to be imported into an incident GISfor dissemination directly to emergency responders. This provides dynamic information exchange, enabling flexible response that adjusts to ever-changing conditions on the ground.
The final and arguably most important element in any remote sensing system is how the data are delivered to the end user. Disaster management applications, such as wildland fire response, are multifaceted efforts that include federal, state and local agencies. Expensive, dedicated military equipment is out of the question in many cases, so inexpensive solutions must be found.
When Internet connectivity is available, data can be delivered through a secure website that allows decision makers and responders to use agency or personal computers and smart phones to access remotely sensed data—whether the imagery is from a satellite or a UAS. Other options include using a UAS or a group of UASs to form a data network that can deliver data to fire responders’ electronic devices directly. To be successful, data delivery must be intuitive and reliable if it’s to be adopted by firefighters and other responders.
NASA’s new partnership with the U.S. Forest Service aims to highlight wildfire awareness.
NASA and the U.S. Forest Service recently signed a Space Act Agreement that unites the two agencies in raising awareness about the importance of fire prevention and fire safety.
The partnership will highlight areas of common interest in wildfires, forest and plant growth research, and materials science. The joint effort will be enhanced by the personal interest of astronaut Joe Acaba, a flight engineer currently aboard the International Space Station. Acaba is an avid outdoorsman who has focused much of his career on the environment. He selected Smokey Bear, the forest service’s mascot, as the zero-gravity indicator and talisman for his Soyuz flight to the orbiting laboratory in May 2012.
“I’ve always enjoyed the outdoors and our natural environment,” says Acaba. “When you view our planet from space, it only makes you appreciate it more. I hope that sharing my experiences aboard the space station will help others understand the importance of protecting our planet and protecting ourselves from Earth’s natural tendencies.”
Throughout the human spaceflight program, Earth imagery has been a valuable asset to researchers on the ground. The dramatic views of smoke plumes and fire damage to communities from 240 miles above bring unparalleled perspectives of the effects of wildfire and the value of careful forestry resource management to people around the world. The images also help firefighters combat fires more effectively and help researchers learn about wildfire behavior and patterns.
Acaba and his station crewmates recorded high-resolution video and photographs June 28, 2012, of recent wildfires in Colorado and Utah. These videos can be viewed on NASA’s website at http://go.nasa.gov/NXyttH.
Crew observations and Earth imagery from space are just some areas that will be emphasized. Space station experiments that focus on improved understanding of plant growth and physiology, as well as combustion and materials science, also will have a prominent role in related outreach opportunities and events. For more information regarding NASA’s partnership with the U.S. Forest Service, visit www.nasa.gov/mission_pages/station/expeditions/expedition31/acaba_usfs.html.