From Space to the Outback


As 2002 drew to a close and summer approached in the Southern Hemisphere, parts of eastern and southern Australia were in the midst of one of the worst multi-year droughts on record. Precipitation was at an all time low, thanks in part to a strong El Niño. Daily temperatures regularly exceeded 100 degrees Fahrenheit (37.7 degrees Celsius) and 70-mile-per-hour (113-kilometer-per hour) winds ripped across the bush. To the west, central Australia was seeing the end of three years of above-average rainfall. In the wet season, pasture grasses were more luxuriant than they had been in 25 years. In the semi-arid environment, such lushness was destined to fade. During the dry season, the verdant fields of grass became millions of acres of tinder. Ironically, these opposite ends of the climate spectrum produced the same result: both the drought-parched landscapes of the southeast and the well-watered central portion of the country ended up in flames.

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Title graphic: Smoke from bushfires in southeast Australia thickens the air behind an antenna at NASA’s Deep Space Network station in Tidbinbilla. Image courtesy Barry Davis.


Map of Australian Rainfall Anomalies


More than 500,000 square kilometers (123.6 million acres)—70 percent of the arid zone of Australia’s Northern Territory—burned in Central Australia between 2000 and 2002, as did large areas of the arid regions of South Australia and Western Australia. Fires threatened homesteads and devastated pasture, fences, and bores (artesian wells). In southeast Australia, fires exploded at the New South Wales-Victoria border in the Great Dividing Range and Snowy Mountains and grew in all directions. The fires encroached on dozens of communities and blazed through the natural bush corridors of Australia’s capital, Canberra. More than five hundred homes were destroyed, and with regional cotton, wheat and other winter crops at roughly half their typical yield due to drought, farmers suffered another blow: thousands of livestock were lost in the fires, and millions of acres of forest, rangeland, and tree plantations were scorched.


Over the past three years, record rains in central Australia (and the accompanying build up of pasture grass) and record drought in the east have produced widespread and severe bushfires across the country. In the map above, dark blue shows record-high rainfall; dark red shows record-low rainfall.


Photographs of Flames and Fire Aftermath


This year’s devastating fire season is an echo of the 2001-02 season that climaxed in the bush on the outskirts of Sydney and drew international attention once again to the city that had hosted the 2000 Summer Olympics. In the aftermath of that season, Australian scientists and government agencies developed a new fire monitoring system that uses observations from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra and Aqua satellites to identify fires in remote locations in Australia. The system provides a big-picture perspective of fires across the country and helps fire emergency agencies allocate resources to the areas where they are needed most. In remote areas, MODIS data are even being used to map large fire perimeters and monitor fire movement and growth.

Sentinel On Guard for Australian Fires
Called Sentinel Hotspots, the fire mapping system uses a special capability of the MODIS instruments by which they continuously broadcast their observations of the Earth in “real time.” Anyone with the right equipment can capture this radio signal as the spacecraft passes over head, seeing exactly what MODIS sees within seconds of collection. This feature is known as MODIS direct broadcast, and receiving stations have sprung up all over the world to take advantage of this unique capability.


The 2003 fire season around Canberra, Australia burned more than 2 million acres of land, destroyed more than 500 homes, and claimed at least 4 human lives. Flames destroyed the Stromlo Astronomical Observatory (top), and parts of the Canberra suburb of Duffy were almost leveled (lower).(Photographs copyright Simon Bennett.)


Image of Canberra Fires

The Australians harness the MODIS direct broadcast signal at three receiving stations: one near Alice Springs in central Australia, one in Perth, on the southwest coast, and one in Hobart, in southern Tasmania. The advantages of MODIS Direct Broadcast observations captured multi-agency attention. The Alice Springs and Hobart Facilities are operated by the remote-sensing division of Geosciences Australia (the Australian version of the United States Geological Survey); the Perth receiving station is run by Geosciences Australia in conjunction with the Department of Land Administration in Western Australia and the Australian Bureau of Meteorology. Another MODIS receiving station is planned for Darwin, on the north-central coast.


Satellite data from the Moderate Resolution Imaging Spectroradiometer showed both immense plumes of smoke and the location of active fires (red dots). Firefighters used the data to allocate resources and map fire perimeters and burn scars, especially in remote areas. This image was acquired February 4, 2003. (Image courtesy MODIS Land Rapid Response Team at NASA GSFC)


Map of Australia


The direct broadcast signal includes all of MODIS’ observations—all 36 spectral bands (discreet segments of the electromagnetic spectrum ranging from visible to infrared wavelengths of light). Just five minutes of observations create a file that is about 400 megabytes—not something that could be easily sent via the Internet all over the country! For the Sentinel Hotspots project, a dedicated computer at the Alice Springs station analyzes the data stream up to four times in a 24-hour period, scanning for unusually high amounts of thermal and short-wave-infrared radiation detected by MODIS, which indicate possible fires. The computer automatically creates a small file that includes only these “hot spot” locations and in less than an hour of the satellite’s overpass, sends it across the continent to the Land and Water Division of Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) in Canberra. Using this simple latitude and longitude information, the hot spots are incorporated into interactive maps that users can create from any Internet Web browser. The maps show important surface features near the fires, such as roads, rivers, topography, and towns.

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The data used in this study are available in one or more of NASA's Earth Science Data Centers.

  MODIS direct broadcast receiving stations located across Australia provide coverage across the continent. Perth, Alice Springs, and Hobart have operating stations, and a fourth is being planned for Darwin. (Map copyright Stafford Mall)


Sentinel Gets Its Start

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The Sentinel project has a lot in common with a similar project developed in the United States by scientists at Goddard Space Flight Center (GSFC), the University of Maryland, the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Department of Agriculture Forest Service. Known as the MODIS Rapid Response Project, it provides near-real-time fire detection from MODIS to the National Interagency Fire Center in Salt Lake City, Utah, where fire management and resource allocation decisions for the U.S. are made.

The parallels between the two projects aren’t coincidence. Scientist Chris Justice of NASA-GSFC and the University of Maryland leads the Rapid Response Project, which was designed as a prototype system to demonstrate MODIS’ ability to detect active fires all over the world. Through the Global Observations for Forest and Land Cover Dynamics project, the Rapid Response group “had been working to make the international fire science community familiar with the MODIS Rapid Response system and what it could offer to researchers across the world,” says Justice. Australia’s Sentinel Project was just the kind of endeavor they hoped to motivate.



Sentinel Fire Map of Australia

Among those motivated was Alex Held, a principal research scientist with the land and water division at CSIRO. He’s a team leader for a group that specializes in environmental remote sensing. “The idea for our Sentinel Hotspots project started during last year’s devastating fires around Sydney, where we began looking at the NASA Rapid Response Website, which provided us next-day, MODIS-derived imagery for areas of Australia. Rather than relying on day-old data,” explains Held, “we figured that with the right level of automation, we could use the MODIS direct broadcast data to provide the coordinates for the detected hotspots on a publicly-available Website much faster—within an hour of MODIS data download in Alice Springs.”

  At the Sentinel Hotpots Website, anyone can create maps of active fires detected by MODIS. Sentinel integrates fire detections with maps of geographic features. Each feature exists as a separate map layer, and users decide which features to display on their maps. This technique is called Geographic Information Systems (GIS) mapping. Users can get more detail by outlining an area of interest (black box) and refreshing the map.

Sentinal Map New South Wales

Held and his colleagues began discussions with the Rapid Response Project and John Guthrie from the U.S. Geological Survey, whose Web-based Geographic Information Systems (GIS) mapping tool, GEOMAC, had incorporated the MODIS fire detections as Held hoped to do with the Sentinel Project. The MODIS Rapid Response Project provided computer software for analyzing the MODIS direct broadcast signal and identifying hot spots and advised the fledgling project on purchasing and installing commercial software packages that would serve as the foundation of Sentinel’s Web-based GIS interface. From this international collaboration, and with additional funding from Australia’s Defense Imagery and Geospatial Organization, the Sentinel Hotspots project began to materialize.

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The image at left shows the fires detected around Canberra between January 14 and 17, 2003, along with latitude and longitude lines, the boundary of the Australian Capital Territory (larger gray outline), and the urban limits of the city of Canberra (small gray outline filled with cross-hatching). Other GIS layers that users can choose from (not shown) include rivers and lakes, railroads, topography, and highways.


Sentinel Gets Its Start

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To assure Sentinel’s usefulness, especially to fire and emergency services teams across Australia, the group needed to handle a stumbling block that had been discovered not long after the Australians began receiving MODIS direct broadcast data at the Alice Springs location. The Terra and Aqua satellites sometimes passed over Australia as many as four times each day, in theory providing plenty of opportunity for coverage of the area, but there always seemed to be bits and pieces of the data stream missing. These apparently random periods of data loss, or blackouts, marred an otherwise seamless flow of key fire observations to state agencies.

Among the first users to notice the problem was research scientist Grant Allan from Australia’s Northern Territory Bushfires Council. In addition to NOAA hotspot detections that they had been using since 1998, Allan’s group had been using MODIS hotspot data provided by the Western Australia Department of Land Administration (DOLA) from the Perth receiving station throughout 2002. DOLA provided simple image maps, listings of fires by geographic location, or data files that could be imported into users’ GIS-mapping software applications. DOLA did not provide MODIS true-color imagery, however. As a complement to the MODIS and NOAA AVHRR hotspots from DOLA, Allan had been using the MODIS imagery that the Alice Springs facility was providing from its Web site as a precursor to the Sentinel Hotspots project. “The first MODIS images we had acquired, beginning in April 2002, were unaffected by the data drop outs,” Allan says. “At the time, we were able to collect images every second day to delineate the changing perimeters of active fires.”


Photographs of Smoke and Burn Scars in the Outback


According to Allan, the mapping of fire perimeters and burned areas with MODIS imagery provided more information to the Bushfires Council than just the hotspots. “Although we have found that a sequence of hotspots is invaluable to monitor the spread of fires,” says Allan, “it is not always possible to compile an accurate picture of the area burned using that information by itself. By April 2002, we were regularly collecting MODIS direct broadcast images from the Alice Springs receiving station, and they had become a significant component of our program in a short amount of time. As our fire season continued across the southern region of the Northern Territory, the unpredictability both of the timing of the drop outs and what area would be affected became frustrating.”

  Fires are impossible to track from the ground, or even by aircraft, across the wide open spaces of Australia’s Northern Territory. At left a pillar of smoke rises above a fast-moving bushfire. At right, dark red burn scars reveal the complexity of fire patterns across the grassland. In the center and upper left, isolated patches of unburned vegetation remain green.(Photographs courtesy Grant Allan, Northern Territory Bushfires Council)

Image of Burn Scars from Satellite


Help from the States
In September 2002, Allan emailed Justice, asking for an explanation of the MODIS blackouts and suggestions for overcoming the problem. “MODIS on Terra regularly stops its direct broadcast as it passes over central Australia, usually for an area extending from 21 to 25 deegrees [south latitude]. This causes a major problem for us,” he wrote. “We are in the middle of a big fire season and we have come to rely on MODIS images to delineate fire perimeters. If we can’t get around the problem in Australia, can we get around it with your help? Is there an opportunity for your system to provide suitable image products for central Australia?”

Feeding MODIS Rapid Response images produced at Goddard Space Flight Center (GSFC) to Allan’s group and other fire agencies in Australia was possible, but not ideal. Because the MODIS Rapid Response project is a global fire detection effort, it can’t rely on the real-time observations provided by the direct broadcast signal because those can only be collected when the satellite passes over the receiving station. The direct broadcast receiving station at GSFC in Maryland usually picks up real-time observations of the Atlantic Coast of the U.S. and sometimes gets images from as far inland as the Mississippi River. But once the satellite gets out of range, the signal is lost.

The MODIS Rapid Response system instead uses the standard MODIS data feed, in which the satellite stores several hours worth of observations and then passes them off to a nearby geostationary satellite, which relays them to a ground station in the New Mexico desert. This relay yields global coverage, but creates a two- to four-hour lag in posting the images to the web. Justice knew it would be better to find a way to reduce or eliminate the direct broadcast blackout periods when fire-monitoring activities were underway in Australia.

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Timely satellite data allowed Northern Territory Bushfires Council scientist Grant Allan to track and map fires in the wilderness. Burn scars appear as dark reddish smudges against the brown and green grasslands. Faint gray smoke rises above some actively burning fires. This true-color image was acquired on October 16, 2002. (Image courtesy MODIS Land Rapid Response Team at NASA GSFC)


Sentinel Gets Its Start

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For help in solving the problem, MODIS Rapid Response Leader Chris Justice contacted Bob Kozon, the Flight Operations Director for the Terra spacecraft. Kozon had no trouble identifying the problem. “The MODIS direct broadcast signal transmits using what is called X-band,” Kozon explains. “The main radio frequency is about 8.2 gigahertz, but it doesn’t transmit exclusively on that frequency. The signal has side lobes that cause the transmission to spill over into the 8.4-gigahertz range or higher.”

That spill over created a problem: NASA reserves the 8.4-gigahertz frequency for communicating with its deep space missions, such as the Voyager spacecrafts. NASA operates three Deep Space Network stations spaced roughly 120 degrees of longitude apart across the Earth. When Terra flew within radio “earshot” of a Deep Space Network antenna, the MODIS direct broadcast signal had the potential to cause radio frequency interference if NASA were communicating with one of its more far-flung progeny. The problem for Allan and Held and their fire mapping projects was that one of those stations was located just outside Canberra.


Photograph of Deep Space Network Antenna Farm


When NASA first identified the potential conflict between the MODIS direct broadcast and the Deep Space Network, the Terra Flight Operations Team and the Radio Frequency Spectrum Management group at NASA’s Jet Propulsion Laboratory developed a blackout schedule that would prevent interference while maximizing access to direct broadcast observations for the increasing number of users building receiving stations around the world. “The schedule we worked out took into consideration not just where Terra was in relation to the three Deep Space Network stations—in the Mojave Desert in California, near Madrid, Spain, and Canberra—but also where it was with respect to the actual location of the nine crafts presently in deep space,” says Kozon. Using this approach, they had reduced the blackouts to a few minutes, sometimes even seconds, each day.

But even these brief blackouts hampered the near-real-time effectiveness and fire tracking abilities of the Bushfires Council and the emerging Sentinel Program. So in November 2002, when the Sentinel Hotspots Project was set to begin delivering data to fire agencies, Held added his voice to those petitioning NASA for a waiver of the mandatory Deep Space Network blackout. Held was optimistic. “I sent an open letter as a concerned CSIRO team leader involved in a public-good project. I had every confidence of a positive response,” he says, “given the close relationship NASA has shared with Australia going all the way back to the Apollo moon missions.”

On behalf of the Australian direct broadcast users, Kozon asked the Deep Space Network personnel for one last concession. Kozon suggested they leave the MODIS direct broadcast on near the Canberra Deep Space Network so long as there were no scheduled contacts planned between the Canberra station and any spacecrafts. Given the possibility that unscheduled contacts might need to be made, the group was initially a little reluctant. Kozon persuaded them with a promise to immediately return to complete blackout if any suspected interference occurred. The results of the first four-week trial period passed without a single incident, and a second waiver was granted.

International Cooperation Yields Success
Both Allan and Held were thrilled with the arrangement. As the fire season in the southern part of Australia began to pick up late in 2002, it gave every indication of becoming at least as severe as the fire season of 2001-02 that initiated the Sentinel Hotspots project. According to Kozon, “Subsequent waivers were easier to get, since by the time the last one was set to expire, the fires in southeast Australia were getting pretty close to the Deep Space Network station in Canberra. Suddenly we all had an interest in keeping the MODIS direct broadcast feed going. We are into our fourth waiver at this point, and we haven’t had a single radio frequency interference incident, so it’s likely we’ll be able to continue helping out.”

  The antennas of the Canberra Deep Space Communication Complex (part of NASA’s Deep Space Network) track the faint signals from space missions hundreds of millions of miles from Earth. Located in Tidbinbilla, 40 km from Canberra, the sensitive antennas were placed far away from ground-based sources of radio frequency interference.

Unfortuantely, the data broadcast from the MODIS instrument can interfere with signals from more remote probes, so the data stream is turned off as the Terra satellite flies overhead. This prevents complete coverage of Australia, hampering the efforts of firefighters. (Photograph courtesy NASA Jet Propulsion Laboratory)


Photograph of Smoke Rising Above Tidbinbilla Nature Reserve


The waiver ensures that Terra MODIS direct broadcast data can keep Sentinel Hotspots going even as the project expands to include data from other satellite sources. “The response to Sentinel Hotspots has been overwhelming—much larger than anticipated,” says Held. “Over the past few weeks, with the fires around Canberra and the Snowy Mountains, this prototype system has undergone a baptism of fire. We have recorded over 1.6 million [Web] hits on peak days and over 20,000 active users per day creating their own maps. The primary use of the Sentinel information seems to be in the preparation of fire status reports before the 6 a.m. planning meetings that emergency agencies have during such times, but we are also getting some feedback from the public, especially in remote rural areas, who are using our information to help them decide to evacuate their properties or not. The system has filled an important niche in public information, and the media have also been using our information as part of their regular updates on the national fire situation.”


At sunset, smoke from bushfires approaching the Canberra Deep Space Network in Tidbinbilla billows over a ridgeline near Mount Pleasant. Image courtesy Fred Pilcher.


High Resolution Satellite Image of Burn Scars near Canberra, Australia


Held feels that the new system has brought many people in closer touch with their natural surroundings and has increased awareness of potential environmental threats. “This prototype system has ignited the imagination of many Australians. In a sense Sentinel has become a ‘Webcam in the air’ for them.” In the future Held looks forward to using Sentinel to bring information to Australians about not just fires, but all kinds of threats from the natural environment, such as floods, cyclones, or oil slicks.

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Above, burn scars from fires in southeast Australia stand out in red. Fires came close, but did not damage the Deep Space Network receiving station. Fires approached Canberra from the west along a river (top center) and invaded the city’s suburbs. Irrigated parks and lawns are bright green, while wilderness forests and brush are dark green. Naturally bare land is brown. This image combines visible, near-infrared, and shortwave infrared data acquired on February 26, 2003. (Image courtesy USGS EROS Data Center)