An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Abstract The aim of this study is to estimate the feasibility of monitoring the surface temperature of an active volcano, using satellite thermal infrared data. For this, the data collected by a radiometer on board the NOAA polar-orbiting satellites over Mt. Etna were processed (geometrical and radiometric corrections) and merged with a Digital Terrain Model in order to correct for the variations of mean ground temperature and atmospheric absorption with altitude. Four pictures, or scenes, subsequent to the eruption of 17th March 1981, have been interpreted; and they display two thermal anomalies: one, near the summit zone; and the other, on the NNW slope where lava flows took place. Some elementary models of thermal evolution are proposed. <s> BIB001 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> For junior/graduate-level courses in Remote Sensing in Geography, Geology, Forestry, and Biology. Introductory Digital Image Processing: A Remote Sensing Perspective focuses on digital image processing of aircraft- and satellite-derived, remotely sensed data for Earth resource management applications. Extensively illustrated, it explains how to extract biophysical information from remote sensor data for almost all multidisciplinary land-based environmental projects. Part of the Pearson Series Geographic Information Science. Now in full color, the Fourth Edition provides up-to-date information on analytical methods used to analyze digital remote sensing data. Each chapter contains a substantive reference list that can be used by students and scientists as a starting place for their digital image processing project or research. A new appendix provides sources of imagery and other geospatial information. <s> BIB002 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Abstract A study of volcanic activity and its effects on the atmosphere is one of 28 interdisciplinary investigations, for the Earth Observing System (EOS), due to be launched in 1997 and 1999. The volcanology investigation will include long- and short-term monitoring of selected volcanoes, the detection of precursory activity associated with unanticipated eruptions, and the detailed study of on-going eruptions. The data collected will allow us to address two aspects of volcanism: volcanic padforms and the atmospheric effects of eruptions. A variety of instruments on the two NASA EOS platforms, together with supplemental data from the Japanese and European platforms, will enable the study of local- to regional-scale thermal and deformational features of volcanoes, and the chemical and structural features of volcanic eruption plumes and aerosols. This investigation fits well within the overall goal of the EOS Project, which is to study the regional and global interrelationships between components of the Earth System, because it specifically investigates the links between volcanism, atmospheric chemistry and short-term (1–3 year) climate change. <s> BIB003 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Between December 1991 and March 1993 a continuous effusive eruption at Mount Etna built a 7.6 km2 lava flow field. Flows extended to within 1 km of the town of Zafferana before a successful artificial diversion was carried out higher up the volcano. During this eruption the spaceborne advanced very high resolution radiometer (AVHRR) acquired 308 images on which the activity could be detected. Since these data can be freely and directly available, such coverage potentially allows regular, real-time monitoring. Ground observations and a flow map that we produced using a SPOT image and electronic distance measurement allowed us to develop and test data extraction techniques. AVHRR radiance maps were consistent with known locations of surface activity. These documented the transition from channel to tube fed phases, the changing threat to Zafferana, and flow diversion. Quantitative analysis of the AVHRR data enabled estimation of active lava area, thermal flux, effusion rates, and total flow field volume. Our estimates for eruption rate and total flow field volume, 5.6 to 7.6 m3/s and 220×106 to 300×106 m3, respectively, are in agreement with published ground-based estimates of 5.8 m3/s and 235×106 m3. These correlations demonstrate the high degree of confidence that can now be placed in interpretations of AVHRR time series for eruptions where ground-based data are scanty. <s> BIB004 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> The free availability of GOES satellite data every 15 minutes makes these data an attractive tool for studying short-term changes on cloud-free volcanoes in the Pacific basin. We use cloud-free GOES-9 data to investigate the chronology of the January 1997, episode 54 eruption of Kilauea Volcano, Hawaii. Seventy-six images for this effusive eruption were collected over a 60-hour period and show the opening and shutdown of active fissures, the draining and refilling of the Pu‘u ‘O‘o lava lake, and the cessation of activity at the ocean entry. <s> BIB005 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Lascar Volcano (22°22'S, 67°44'W) is the most active volcano of the central Andes of northern Chile. Activity since 1984 has been characterised by periods of lava dome growth and decay within the active crater, punctuated by explosive eruptions. We present herein a technique for monitoring the high-temperature activity within the active crater using frequent measurements of emitted shortwave infrared (SWIR) radiation made by the spaceborne along-track scanning radiometer (ATSR). The ATSR is an instrument of low spatial resolution (pixels 1 km across) that shares certain characteristics with the MODIS instrument, planned for use as a volcano monitoring tool in the NASA EOS Volcanology Project. We present a comprehensive time series of over 60 cloud- and plume-free nighttime ATSR observations for 1992–1995, a period during which Lascar experienced its largest historical eruption. Variations in short wavelength infrared flux relate directly to changes in high-temperature surfaces within the active crater. From these data, interpretations can be made that supplement published field reports and that can document the presence and status of the lava dome during periods where direct, ground-based, observations are lacking. Our data agree with less frequent information collected from sensors with high spatial resolution, such as the Landsat thematic mapper (Oppenheimer et al. 1993) and are consistent with field observations and models that relate subsidence of the dome to subsequent explosive eruptions (Matthews et al., 1997). Most obviously, Lascar's major April 1993 eruption follows a period in which the magnitude of emitted shortwave infrared radiation fell by 90%. At this time subsidence of the 1991–1992 lava dome was reported by field observers and this subsidence is believed to have impeded the escape of hot volatiles and ultimately triggered the eruption (Smithsonian Institution 1993a). Extrapolating beyond the period for which field observations of the summit are available, our data show that the vulcanian eruption of 20 July 1995 occurred after a period of gradual increase in short wavelength infrared flux throughout 1994 and a more rapid flux decline during 1995. We attribute this additional, otherwise undocumented, cycle of increasing and decreasing SWIR radiance as most likely representing variations in degassing through fumaroles contained within the summit crater. Alternatively, it may reflect a cycle of dome growth and decay. The explosive eruption of 17 December 1993 appears to have followed a similar, but shorter, variation in SWIR flux, and we conclude that large explosive eruptions are more likely when the 1.6-μm signal has fallen from a high to a low level. The ATSR instrument offers low-cost data at high temporal resolution. Despite the low spatial detail of the measurements, ATSR-type instruments can provide data that relate directly to the status of Lascar's lava dome and other high-temperature surfaces. We suggest that such data can therefore assist with predictions of eruptive behaviour, deduced from application of physical models of lava dome development at this and similar volcanoes. <s> BIB006 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> The National Aeronautic and Space Administration (NASA) plans to launch the moderate resolution imaging spectroradiometer (MODIS) on the polarorbiting Earth Observation System (EOS) providing morning and evening global observations in 1999 and afternoon and night observations in 2000. These four MODIS daily fire observations will advance global fire monitoring with special 1 km resolution fire channels at 4 and 11 μm, with high saturation of about 450 and 400 K, respectively. MODIS data will also be used to monitor burn scars, vegetation type and condition, smoke aerosols, water vapor, and clouds for overall monitoring of the fire process and its effects on ecosystems, the atmosphere, and the climate. The MODIS fire science team is preparing algorithms that use the thermal signature to separate the fire signal from the background signal. A database of active fire products will be generated and archived at a 1 km resolution and summarized on a grid of 10 km and 0.5°, daily, 8 days, and monthly. It includes the fire occurrence and location, the rate of emission of thermal energy from the fire, and a rough estimate of the smoldering/flaming ratio. This information will be used in monitoring the spatial and temporal distribution of fires in different ecosystems, detecting changes in fire distribution and identifying new fire frontiers, wildfires, and changes in the frequency of the fires or their relative strength. We plan to combine the MODIS fire measurements with a detailed diurnal cycle of the fires from geostationary satellites. Sensitivity studies and analyses of aircraft and satellite data from the Yellowstone wildfire of 1988 and prescribed fires in the Smoke, Clouds, and Radiation (SCAR) aircraft field experiments are used to evaluate and validate the fire algorithms and to establish the relationship between the fire thermal properties, the rate of biomass consumption, and the emissions of aerosol and trace gases from fires. <s> BIB007 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Data from the Moderate Resolution Imaging Spectrometer (MODIS) may be used for the thermal monitoring of volcanoes from the NASA Earth Observing System. MODIS uses a wide scan angle to provide a high temporal frequency but this geometry means that zenith angle and pixel size vary greatly across the swath. Similar variations are inherent in radiometric data obtained from the forward- and nadir-views of the Along Track Scanning Radiometer (ATSR) and here we use dual-view ATSR data of volcanic lava domes to investigate how these geometric effects influence the retrieved thermal anomalies. The effect of increasing pixel size with zenith angle is shown to be counteracted by increasing pixel overlap, thus providing comparable thermal anomalies from the two ATSR views in cases where off-nadir obscuration by crater walls is not significant. In such instances data from the majority of the MODIS swath could be combined in a single time-series in order to maximise temporal coverage for volcano monitoring purposes. <s> BIB008 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Long-term thermal modeling of volcanoes using satellite imagery provides an effective tool for monitoring remote yet dangerous volcanoes in the North Pacific. This region includes volcanoes in Alaska, the Aleutian Islands, and the Kamchatkan Peninsula. Thermal infrared data collected multiple times per day from weather satellites show distinct signatures for three different types of volcanic activity at different volcanic centers. Near real-time automated techniques are being developed to monitor relative changes in radiant temperature at volcanoes in this region. Radiant temperature values as a function of time are extracted and compared to background values for a series of active volcanoes. By establishing a long-term thermal record for these volcanoes, significant deviations indicative of an impending eruption can be detected. This tool is used to search for precursors to explosive eruptions in order to increase warning times and hazard mitigation for these potentially catastrophic events. A six year archive of satellite imagery has been compiled for this active region, and is available for study. <s> BIB009 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a high spatial resolution, multispectral imager with along-track stereo capabilities scheduled for launch on the first NASA spacecraft of the Earth Observing System (Terra) in 1999. Data will be obtained in 14 spectral bands covering the visible through the thermal infrared wavelength region. A number of standard data products will be available to requesters through an on-line archival and processing system. Particular, user-specified data acquisitions will be possible through a Data Acquisition Request system. <s> BIB010 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Abstract The paper describes the DLR small satellite mission “BIRD” (Bi-spectral Infrared Detection). The BIRD mission is dedicated to hot spot detection and investigation from space by means of new developed infrared array sensors. They are suitable for Earth remote sensing with small satellites. A dedicated two-channel cooled infrared sensor system is developed for hot spot detection and investigation from space. It is combined with a two-channel VIS/NIR sensor system for special questions of the remote sensing of vegetation. The sensor system and data processing algorithms are tested by airborne experiments. Results of the airborne experiments are pointed out in the paper. A speciality of this mission consists in the constraint to implement this payload on a micro satellite suitable for a piggyback launch. So the launch is not a main cost driver as for other small satellite missions with dedicated launchers. The mass of the complete satellite including payload and launch adapter has to be less than 100kg. To meet the particular requirements of the payload on the spacecraft bus a lot of new developments on component level are done. The paper describes the 3-axis stabilized satellite, the basic spacecraft modes, the mission architecture and the model philosophy within strict design-to-cost constraints. The BIRD mission is now in the Phase C D and will be ready for launch in the summer of the year 2000. <s> BIB011 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Volcanic eruptions can present unpredictable hazards to populations living within regions containing potentially active volcanoes and for people traveling in jet aircraft that intersect with ash-laden eruption clouds. Methods of monitoring volcanic activity include searching for variations in the thermal signal from active fumaroles, lava domes, lava lakes, flows, and other features. Over many active volcanoes in the Western Hemisphere, low spatial resolution (4 km/pixel) weather satellite data acquired every 15 min are used to identify changes in eruptive activity, but are of insufficient spatial resolution to map active volcanic features. The Enhanced Thematic Mapper Plus (ETM+) on Landsat 7 can be used to monitor active volcanoes at a higher spatial resolution (15- to 60-m pixels). ETM+ also offers improvements over its predecessor, the Thematic Mapper of Landsats 4 and 5, by way of a 15-m panchromatic band and higher spatial resolution (60 m/pixel) thermal infrared (IR) band. With higher spatial resolution panchromatic data, we are able to map lava flow fields, trace very high temperature lava channels, and, at Lascar volcano, identify an arcuate feature associated with a collapsed crater floor, a phenomenon that may precede explosive activity. With improved spatial resolution in the thermal IR, we are able to map the bifurcation and braiding of underground lava tubes at Kilauea. Identifying tube locations and tracking their extension are important because, for a given volumetric lava production (effusion) rate, tube-fed flows can extend a much greater distance than surface flows. At both Kilauea and Etna, we are able to use the thermal data to estimate effusion rates, an important parameter for assessing how far a flow is likely to extend and therefore the hazard it poses. An improved ETM+ data collection and distribution system includes a well-formulated and -executed Long-Term Acquisition Plan and less expensive data that is available much faster than previously possible. <s> BIB012 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Thermal data are directly available from the Geostationary Operational Environmental Satellites (GOES) every 15 minutes at existing or inexpensively installed receiving stations. This data stream is ideal for monitoring high temperature features such as active lava flows and fires. To provide a near-real-time hot spot monitoring tool, we have developed, tested and installed software to analyse GOES data on-reception and then make results available in a timely fashion via the web. Our software automatically: (1) produces hot spot images and movies; (2) uses a thresholding procedure to generate a hot spot map; (3) updates hot spot radiance and cloud index time series; and (4) issues a threshold-based e-mail alert. Results are added to http://volcano1.pgd.hawaii.edu/goes/ within ∼12 minutes of image acquisition and are updated every 15 minutes. Analysis of GOES data acquired for effusive activity at Kilauea volcano (Hawai'i) during 1997-98 show that short (<1 hour long) events producing 100m long (102 to 103... <s> BIB013 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Analysis of thermally generated night-time volcanic radiances recorded with a 1-km pixel size at 1.6 and 11 µm during 1991–1993 and 1996–1999 for Mount Etna shows that lava flows extending beyond the summit craters can be distinguished from vent activity. The two phenomena plot in different regions of feature space when the mean volcanic radiance (per anomalous pixel) at 11 µm is plotted against the mean volcanic radiance at 1.6 µm. The distinct feature space characteristics of lava flow fields are apparent within 1–2 days of the onset of each effusive event. Such a plot also enables lava flow fields being fed by open channels to be distinguished from tube-fed flow fields. Rank order analysis of the total 1.6-µm volcanic radiance series shows that vent activity and lava flows belong to different populations, and offers further scope for remotely identifying changes in eruptive state. <s> BIB014 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Fire products are now available from the Moderate Resolution Imaging Spectroradiometer (MODIS) including the only current global daily active fire product. This paper describes the algorithm, the products and the associated validation activities. High-resolution ASTER data, which are acquired simultaneously with MODIS, provide a unique opportunity for MODIS validation. Results are presented from a preliminary active fire validation study in Africa. The prototype MODIS burned area product is described, and an example is given for southern Africa of how this product can be used in modeling pyrogenic emissions. The MODIS Fire Rapid Response System and a web-based mapping system for enhanced distribution are described and the next steps for the MODIS fire products are outlined. <s> BIB015 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Abstract The simultaneous solution of the Planck equation (the so-called “dual-band” technique) for two shortwave infrared Landsat Thematic Mapper (TM) bands allows an estimate of the fractional area of the hottest part of an active flow and the temperature of the cooler crust. Here, the dual-band method has been applied to a time series of Mount Etna eruptions. The frequency distribution of the fractional area of the hottest component reveals specific differences between summit and flank lava flows. The shape of the density function shows a trend consistent with a Gaussian distribution and suggests a relationship between the moments of the distribution and the emplacement environment. Because flow composition of Etnean lavas generally remains constant during the duration of their emplacement, it appears that the shape of any particular frequency distribution is probably related to fluid mechanical aspects of flow emplacement that affect flow velocity and flow heat loss and thus the rate of formation of the surface crust. These factors include the influence of topographical features such as changes in slope gradient, changes in volume effusion rate, and progressive downflow increases in bulk or effective viscosity. A form of the general theoretical solution for the ‘dual-band’ system, which illustrates the relationship between radiance in TM bands 5 and 7, corresponding to hot fractional area and crust temperature, is presented. Generally speaking, it appears that for a given flow at any point in time, larger fractional areas of exposed hot material are correlated with higher temperatures and that, while the overall shape of that distribution is common for the flows studied, its amplitude and slope reflect individual flow rheological regimes. <s> BIB016 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Wildfires have a range of significant environmental effects with respect to both Earth's surface and atmosphere. Spaceborne remote sensing of active fires has been undertaken for more than two decades, but the bi-spectral Infrared Detection (BIRD) Experimental Small Satellite (2001–04) is the first mission dedicated to this task. This paper summarizes the experience gained during the BIRD mission, which has focused both on active fire detection and active fire characterization, in terms of quantifying effective fire temperature (TF), effective fire area (AF) and fire radiative power (FRP). A detailed error analysis for each parameter is undertaken, and the accuracy of FRP retrieval is shown to be significantly better than that of TF or AF. For key fire-affected forest, bush and savanna environments (Australia, Benin, Borneo, Brazil, Canada-US, Portugal and Siberia) BIRD data allows FRP estimation to within 30% in 75% of fires examined, and for the first time from space BIRD is able to allow estimation of fireline length, effective fireline depth and radiative fireline intensity for the more pronounced fire fronts. Some indication of the predominant combustion regime (smoldering or flaming), which has implications for the relative concentrations of emitted pollutant products, is possible through use of the TF parameter. This experience demonstrates the advantages of the new infrared sensor technologies employed in BIRD, and offers suggestions for future fire monitoring sensors based on similar technologies. <s> BIB017 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> A new class of remote sensing and scientific distributed space missions is emerging that requires hundreds to thousands of satellites for simultaneous multipoint sensing. These missions, stymied by the lack of a low-cost mass-producible sensor node, can become reality by merging the concepts of distributed satellite systems and terrestrial wireless sensor networks. A novel, subkilogram, very-small-satellite design can potentially enable these missions. Existing technologies are first investigated, such as standardized picosatellites and microengineered aerospace systems. Two new alternatives are then presented that focus on a low-cost approach by leveraging existing commercial mass-production capabilities: a satellite on a chip (SpaceChip) and a satellite on a printed circuit board. Preliminary results indicate that SpaceChip and a satellite on a printed circuit board offer an order of magnitude of cost savings over existing approaches. <s> BIB018 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> The Landsat Data Continuity Mission (LDCM) is the follow-on mission to Landsat 7 and will be the eighth mission in ::: the Landsat series. The mission is in development via an interagency partnership between the National Aeronautics and ::: Space Administration (NASA) and the Department of Interior (DOI) / United States Geological Survey (USGS). The ::: LDCM satellite will carry two earth-observing sensors, the Operational Land Imager (OLI) to collect image data for nine ::: spectral bands in the reflective portion of the spectrum and the Thermal Infrared Sensor (TIRS) to collect coincident ::: image data for two thermal spectral bands. The LDCM ground segment will control the satellite and will receive, ::: process, archive, and distribute the science data collected by the OLI and TIRS instruments. The USGS Earth Resources ::: Observation & Science Center (EROS) will distribute LDCM data products at no cost to requestors. The mission ::: objective is to continues the Landsat program's collection, archive, and distribution of multispectral imagery affording ::: global, synoptic, and repetitive coverage of the Earth's land surfaces at a scale where natural and human-induced changes ::: can be detected, differentiated, characterized, and monitored over time. The LDCM launch readiness date is currently ::: December, 2012. <s> BIB019 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Shiveluch (Kamchatka, Russia) is the most active andesitic volcano of the Kuril-Kamchatka arc, typically exhibiting near-continual high-temperature fumarolic activity and periods of exogenous lava dome emplacement punctuated by discrete large explosive eruptions. These eruptions can produce large pyroclastic flow (PF) deposits, which are common on the southern flank of the volcano. Since 2000, six explosive eruptions have occurred that generated ash fall and PF deposits. Over this same time period, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument has been acquiring image-based visible/near infrared (VNIR), short wave infrared (SWIR) and thermal infrared (TIR) data globally, with a particular emphasis on active volcanoes. Shiveluch was selected as an ASTER target of interest early in the mission because of its frequent activity and potential impact to northern Pacific air transportation. The north Pacific ASTER archive was queried for Shiveluch data and we present results from 2000 to 2009 that documents three large PF deposits emplaced on 19 May 2001, 9 May 2004, and 28 February 2005. The long-term archive of infrared data provides an excellent record on the changing activity and eruption state of the volcano. <s> BIB020 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Spaceborne remote sensing of high-temperature volcanic features offers an excellent opportunity to monitor the onset and development of new eruptive activity. To provide a basis for real-time response during eruptive events, we designed and developed the volcano monitoring system that we call HOTSAT. This multiplatform system can elaborate both Moderate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) data, and it is here applied to the monitoring of the Etna volcano. The main advantage of this approach is that the different features of both of these sensors can be used. It can be refreshed every 15 min due to the high frequency of the SEVIRI acquisition, and it can detect smaller and/or less intense thermal anomalies through the MODIS data. The system consists of data preprocessing, detection of volcano hotspots, and radiative power estimation. To locate thermal anomalies, a new contextual algorithm is introduced that takes advantage of both the spectral and spatial comparison methods. The derivation of the radiative power is carried out at all ‘hot’ pixels using the middle infrared radiance technique. The whole processing chain was tested during the 2008 Etna eruption. The results show the robustness of the system after it detected the lava fountain that occurred on May 10 through the SEVIRI data, and the very beginning of the eruption on May 13 through the MODIS data analysis. <s> BIB021 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Analysis of thermally emissive volcanic features using satellite infrared remote sensing has been conducted over recent decades, primarily using shortwave and thermal infrared (SWIR; TIR) radiance data. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), mounted on the Earth Observation System (EOS) Terra satellite, offers an advance on earlier instruments, having more bands covering the SWIR atmospheric window and offering a wider dynamic range. This paper compares methods used to analyse ASTER SWIR imagery of active volcanoes, using both simulated cases and actual ASTER imagery of Lascar Volcano, and focuses on radiative power estimates. Those based on the Oppenheimer approach are found to be most reliable for simulated surfaces, with the Lombardo and Buongiorno and Dozier retrievals having larger uncertainties in most cases. However, the Dozier Method results in the highest proportion of successful retrievals, the reliability of which is influenced by factors including band comb... <s> BIB022 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Abstract The intensity is important for comparing eruptions. Remote-sensing data allow investigators to quickly estimate Volcanic Explosivity Index (VEI), an indicator for the intensity of an eruption. The volume of volcanic products and plume height, which can be determined by satellite data, are two major variables used to estimate VEI. Sarychev Peak has been one of the most active volcanoes on Kuril Islands. Most recently it repeated its violent eruptions in June 2009. The volume of volcanic products in Matua Island discharged from Sarychev Peak was estimated, and there was a 0.08 km 3 difference between ASTER and PRISM DEM Data. The plume height was estimated as high as 10 km using ASTER images. The 2009 Sarychev Peak eruptions is rated as VEI “3” based on the measured ejecta volume and the plume height calculated in our analysis, but this did not take into account the volcanic products deposited in the sea. If this volume was considered, the VEI should have been “4”. Satellite remote-sensing is a powerful tool to estimate VEI quickly, even for a volcano on an inaccessible remote island. <s> BIB023 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Direct satellite data reception at high temporal frequencies and automated processing enable near-real-time, near-continuous thermal monitoring of volcanoes. We review what has been achieved in terms of turning this capability into real-time tools of use to volcano monitoring agencies. Current capabilities focus on 2 instruments: the advanced very high resolution radiometer (AVHRR) and the Geostationary Operational Environmental Satellite (GOES) imager. Collection of 10 AVHRR images per day covering Alaska, the Aleutians, and Kamchatka allows routine, on-reception analysis of volcanic hot spots across this region. Data collected between 1996 and 1998 detected 302 hot spots due to lava flows, lava domes, pyroclastic flows, fumaroles, and geothermally heated lakes at 12 different volcanoes. <s> BIB024 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> After the initial observation in 1987 that high spatial resolution data could be used to acquire thermal information for active volcanoes, satellite technology and its applications have leapt forward in possibilities and complexity. Since 1972, the Landsat series of satellites has provided the longest continuous high spatial resolution (<120 m) data set of the Earth recorded by any satellite system. In particular, Landsat 4 and 5 (launched in 1982 and 1984, respectively) featuring the Thematic Mapper system have made it possible to detect, map, and model high temperature features such as lava bodies and fires. Landsat 7 was launched in April, 1999, carrying an enhanced instrument package that includes a higher spatial resolution thermal band and a 15-m panchromatic band that will greatly aid detailed mapping of volcanic features. Current planning for the future Landsat 8 instrument includes a fundamental shift towards a lighter, more energy efficient instrument having a greater number of spectral bands. Hyperspectral sensors, such as that of Earth Orbiter-1, that have been planned for launch as part of the New Millennium Program, are being considered as Landsat 8 prototypes. Initial studies of lava flows and lava lakes using field spectrometers afford a glimpse of the capabilities offered by the next generation of satellites to model lava flow temperatures. Hyperspectral measurements of lava flows allow for the solution of numerous thermal components, which can then be used for much more detailed modeling than can be supported by broad band radiometry. <s> BIB025 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> The Landsat-8 satellite of the Landsat Data Continuity Mission was launched by the National Aeronautics and Space Administration (NASA) in April 2013. Just weeks after it entered active service, its sensors observed activity at Paluweh Volcano, Indonesia. Given that the image acquired was in the daytime, its shortwave infrared observations were contaminated with reflected solar radiation; however, those of the satellite’s Thermal Infrared Sensor (TIRS) show thermal emission from the volcano’s summit and flanks. These emissions detected in sensor’s band 10 (10.60–11.19 µm) have here been quantified in terms of radiant power, to confirm reports of the actual volcanic processes operating at the time of image acquisition, and to form an initial assessment of the TIRS in its volcanic observation capabilities. Data from band 11 have been neglected as its data have been shown to be unreliable at the time of writing. At the instant of image acquisition, the thermal emission of the volcano was found to be 345 MW. This value is shown to be on the same order of magnitude as similarly timed NASA Earth Observing System (EOS) Moderate Resolution Imaging Spectroradiometer thermal observations. Given its unique characteristics, the TIRS shows much potential for providing useful, detailed and accurate volcanic observations in the future. <s> BIB026 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on the Suomi National Polar-orbiting Partnership (S-NPP) satellite incorporates fire-sensitive channels, including a dual-gain high-saturation temperature 4 µm channel, enabling active fire detection and characterization. The active fire product, based on the 750 m moderate resolution “M” bands of VIIRS, is one of the standard operational products generated by the Interface Data Processing Segment of the S-NPP ground system. The product builds on an earlier “Collection 4” version of the algorithm used for processing Moderate Resolution Imaging Spectroradiometer (MODIS) data. Following postlaunch quality assessments and corrections in the input VIIRS Sensor Data Record data processing, an initial low detection bias was removed and the product achieved Beta quality in April 2012. Daily spurious detections along-scan lines were also significantly reduced as a result of further processing improvements in October 2012. Direct product comparison with MODIS over 4 months of data in 2013 has shown that VIIRS produces approximately 26% more detections than MODIS within the central 3 pixel VIIRS aggregation zone of approximately ±31° scan angle range and 70% more detections outside of that zone, mainly as a result of the superior VIIRS scanning and sampling characteristics. Further development is in progress to ensure high-quality VIIRS fire products that continue the MODIS data record and better serve the user community by delivering a full image classification product and fire radiative power retrievals. Research is also underway to take advantage of the radiometric signal from the 375 m VIIRS imager “I” bands. <s> BIB027 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Abstract The Suomi National Polar-orbiting Partnership satellite was launched in 2011. On-board this satellite is the Visible Infrared Imaging Radiometer Suite (VIIRS) with thermal infrared detection capabilities similar to those of the earlier Moderate-Resolution Imaging Spectroradiometer (MODIS) sensors of the National Aeronautics and Space Administration Earth Observation System. Fire detection products have been developed using the thermal infrared data for both VIIRS and MODIS and, although having the observation of fire as their main objective, such products are also sensitive to the radiant emissions of active volcanic surfaces, but a comparison of their capabilities in this regard remains outstanding. Here, this comparison is conducted, with a focus on the volcanoes of Indonesia, and findings are initially promising, suggesting that the VIIRS fire detection capability is an improvement over that of its predecessor. For example, between 3 April 2012 and 14 July 2014, volcanic activity was detected on 519 days by the VIIRS product, as compared with 308 days for the MODIS-Aqua product (MYD14). Causes of this apparent enhanced sensitivity are explored and, with the examination of additional data from the MODIS-Terra product and the MODVOLC system, are shown to be the combined influence of spatial resolution, data processing steps, imaging scan width and the fire product algorithm used. As greater quantities of data become available, a more comprehensive comparison of these observations will be possible and will be undertaken at a global scale. <s> BIB028 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> Current space-borne thermal infrared satellite systems aimed at land surface remote sensing retain some significant deficiencies, in particular in terms of spatial resolution, spectral coverage, number of imaging bands and temperature-emissivity separation. The proposed VISible-to-thermal IR micro-SATellite (VISIR-SAT) mission addresses many of these limitations, providing multi-spectral imaging data with medium-to-high spatial resolution (80m GSD from 800 km altitude) in the thermal infrared (up to 6 TIR bands, between 8 and 11μm) and in the mid infrared (1 or 2 MIR bands, at 4μm). These MIR/TIR bands will be co-registered with simultaneously acquired high spatial resolution (less than 30 m GSP) visible and near infrared multi-spectral imaging data. To enhance the spatial resolution of the MIR/TIR multi-spectral imagery during daytime, data fusion methods will be applied, such as the Multi-sensor Multi-resolution Technique (MMT), already successfully tested over agricultural terrain. This image processing technique will make generation of Land Surface Temperature (LST) EO products with a spatial resolution of 30 x 30 m 2 possible. For high temperature phenomena such as vegetation- and peat-fires, the Fire Disturbance Essential Climate Variables (ECV) “Active fire location” and “Fire Radiative Power” will be retrieved with less than 100 m spatial resolution. Together with the effective fire temperature and the spatial extent even for small fire events the innovative system characteristics of VISIR-SAT go beyond existing and planned IR missions. The comprehensive and physically high-accuracy products from VISIR-SAT (e.g. for fire monitoring) may synergistically complement the high temperature observations of Sentinel-3 SLSTR in a unique way. Additionally, VISIR-SAT offers a very agile sensor system, which will be able to conduct intelligent and flexible pointing of the sensor’s line-of-sight with the aim to provide global coverage of cloud free imagery every 5–10 days with only one satellite (using near real time cloud cover information). VISIRSAT may be flown in convoy with Sentinel-3 and/or Sentinel-2. <s> BIB029 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Historical Perspective on Sensors Used for Volcanic Observation <s> As specifically designed platforms are still unavailable at this point in time, lava flows are usually monitored remotely with the use of meteorological satellites. Generally, meteorological satellites have a low spatial resolution, which leads to uncertain results. This paper presents the first long term satellite monitoring of active lava flows on Stromboli volcano (August–November 2014) at high spatial resolution (160 m) and relatively high temporal resolution (~3 days). These data were retrieved by the small satellite Technology Experiment Carrier-1 (TET-1), which was developed and built by the German Aerospace Center (DLR). The satellite instrument is dedicated to high temperature event monitoring. The satellite observations were accompanied by field observations conducted by thermal cameras. These provided short time lava flow dynamics and validation for satellite data. TET-1 retrieved 27 datasets over Stromboli during its effusive activity. Using the radiant density approach, TET-1 data were used to calibrate the MODVOLC data and estimate the time averaged lava discharge rate. With a mean output rate of 0.87 m3/s during the three-month-long eruption, we estimate the total erupted volume to be 7.4 × 106 m3. <s> BIB030
Infrared remote sensing imagers have been relatively common on orbiting satellites since the early 1960s, with the NOAA TIROS constituting the first operational infrared radiometers in orbit  . As technology progressed, so too did the number of platforms launched with infrared imaging capabilities, but it was not until 1968 that many American infrared remote sensing systems were declassified, with data from the TIROS range being the first BIB002 . Since this period, there has been continuous infrared monitoring of Earth from space  , with sensors gaining in both spectral and spatial resolution and with data becoming more widely available. The next section will provide a chronology of the discipline, while here, the main satellites and sensors will be presented. The AVHRR instruments on-board the satellites of the National Oceanic and Atmospheric Administration (NOAA) series were key to the infrared remote sensing of volcanism becoming mainstream. The first AVHRR instrument was launched in 1978, and soon after, their use in volcanic studies began (e.g.,  BIB001 ). The AVHRR instruments have various characteristics useful for the monitoring of volcanic activity, including of most relevance, two infrared bands with a spatial resolution of 1000 m × 1000 m and, hence, the potential to detect a wide range of thermally-anomalous volcanic phenomena  . Each AVHRR orbits the Earth 14 times a day and, with an altitude of 833 km and a swath width of 2399 km, and provides for repeat imagery of the same surface roughly every 12 hours (of clear utility in monitoring rapidly changing volcanic events (e.g., BIB004 BIB024 BIB009 )). Although used less widely today given the availability of newer sensors, AVHRR monitoring of volcanic activity continues (for example,  ) because of the availability of a long time series of data  and NOAA's policy of retaining two AVHRR satellites in orbit at the same time, effectively enhancing the temporal resolution  ). In the 1970s, the NASA Landsat programme commenced, although it was not until the 1984 launch of Landsat-5 that functioning SWIR and TIR bands of the Thematic Mapper sensor (TM) were  Infrared remote sensing imagers have been relatively common on orbiting satellites since the early 1960s, with the NOAA TIROS constituting the first operational infrared radiometers in orbit  . As technology progressed, so too did the number of platforms launched with infrared imaging capabilities, but it was not until 1968 that many American infrared remote sensing systems were declassified, with data from the TIROS range being the first BIB002 . Since this period, there has been continuous infrared monitoring of Earth from space  , with sensors gaining in both spectral and spatial resolution and with data becoming more widely available. The next section will provide a chronology of the discipline, while here, the main satellites and sensors will be presented. The AVHRR instruments on-board the satellites of the National Oceanic and Atmospheric Administration (NOAA) series were key to the infrared remote sensing of volcanism becoming mainstream. The first AVHRR instrument was launched in 1978, and soon after, their use in volcanic studies began (e.g.,  BIB001 ). The AVHRR instruments have various characteristics useful for the monitoring of volcanic activity, including of most relevance, two infrared bands with a spatial resolution of 1000 m × 1000 m and, hence, the potential to detect a wide range of thermally-anomalous volcanic phenomena  . Each AVHRR orbits the Earth 14 times a day and, with an altitude of 833 km and a swath width of 2399 km, and provides for repeat imagery of the same surface roughly every 12 h (of clear utility in monitoring rapidly changing volcanic events (e.g., BIB004 BIB024 BIB009 )). Although used less widely today given the availability of newer sensors, AVHRR monitoring of volcanic activity continues (for example,  ) because of the availability of a long time series of data  and NOAA's policy of retaining two AVHRR satellites in orbit at the same time, effectively enhancing the temporal resolution  ). In the 1970s, the NASA Landsat programme commenced, although it was not until the 1984 launch of Landsat-5 that functioning SWIR and TIR bands of the Thematic Mapper sensor (TM) were available for thermal studies, possessing spatial resolutions of 30 and 120 m, respectively. The superior spatial resolution of this sensor was achieved with a smaller swath width as compared with AVHRR (185 km versus 2399 km), although this came at the expense of its temporal resolution, which was 16 days. The next successful sensor of the series, on-board Landsat-7, was the Enhanced Thematic Mapper (ETM+), enhanced in terms of its TIR observation capability and superior TIR spatial resolution (60 m). With their higher infrared spatial resolution, the Landsat sensors rapidly became utilized for making more detailed volcanic observations than was possible with AVHRR  BIB025 BIB012 BIB016 , although the reduced temporal resolution meant that the Landsat satellites were less suitable for observing short-lived events. In 2013, the latest in the Landsat series was launched, Landsat-8, as part of the Landsat Data Continuity Mission (LDCM) BIB019  . This satellite was equipped with the Thermal Infrared Sensor (TIRS), possessing two bands with a spatial resolution of 100 m. This reduced spatial resolution, as compared with Landsat-7, was a result of a limited development time BIB019 , but despite this, the TIRS has been shown to acquire accurate volcanic observations, which will, for the foreseeable future, ensure that infrared observations of volcanoes will remain available when MODIS expires BIB026 . Several geostationary satellites were launched in the 1970s with infrared observing capabilities for meteorological purposes. Of these, the NASA GOES series has been most prolifically used for volcanic observations. The chief advantage of sensors on such systems is that they have an extremely regular image acquisition (four times per hour for GOES and Meteosat), but being geostationary, they are at higher altitude meaning, they have a poorer spatial resolution (4 km for the GOES Imager and 5 km for Meteosat's Visible and Infra-Red Imager (MVIRI)). Since 1998, an automated system at the Hawai'i Institute of Geophysics and Planetology has been operational, with the task of processing GOES data for monitoring global volcanic activity, and since this time, various studies have confirmed its utility for extracting volcanic activity chronologies (e.g., BIB005 BIB013 ). SEVERI, the infrared-capable instrument on-board the most recent Meteosat satellites (the Meteosat Second Generation), has similarly been used for such purposes and, indeed, has formed part of an automated volcano monitoring system called HOTSAT, which is implemented, along with MODIS data, when rapid activity detection and monitoring is required BIB021  . In 1986, NASA announced plans for an Earth Observation System (EOS) that would acquire low-Earth orbit observations  . Infrared observations fell within the plans, and even prior to its commencement, scientists were optimistic about the role this system could have in the observation of volcanic activity BIB003 . The EOS satellites were launched from 1999 onwards, and as the data came online, scientists rapidly harnessed them for volcanological applications. The four EOS sensors with infrared observing capabilities were ASTER (on-board the Terra satellite) and MODIS (on-board the Terra and Aqua satellites), as well as the ALI and Hyperion sensors (on-board the EO-1 satellite). Each sensor displayed different characteristics that made them suitable for volcanic observational purposes. ASTER was met with particular optimism within the volcanological community, given that it provided observations in the SWIR (six bands of 30-m resolution) and the TIR (five bands of 90 m), and with a swath width of 60 km and revisit frequency of 16 days, it constituted a follow on to Landsat TM  BIB010  . As of 2008, imagery acquired from ASTER's SWIR bands became unusable; the TIR bands remain functioning at the time of writing. Of the other EOS sensors, ALI possessed ten bands from the VNIR to the SWIR, with a spatial resolution of 30 m, while Hyperion shared the 30-m resolution, but possessed a ground-breaking 172 SWIR bands. Early on, the relatively fine spatial resolution of ASTER's infrared bands was shown to be useful in detecting eruption-precursory thermal anomalies at Chikurachki Volcano, Russia  , while BIB022 BIB020 demonstrated that despite its sub-optimal revisit frequency of 16 days, long-term analysis of its data could be used to characterise the behaviour of Shiveluch and Lascar volcanoes, respectively, with its SWIR and TIR bands showing utility for detecting different thermal components at each volcanic surface. Urai and Ishizuka BIB023 also demonstrated that within several hours of acquisition, ASTER imagery could be used to estimate the volcanic explosivity index (a scale used to quantify eruption explosiveness) of an eruption, although this relied on ASTER viewing the surface at an appropriate time. The two identical NASA MODIS instruments were launched three years apart on-board the Terra (1999) and Aqua (2002) platforms, each possessing 16 infrared bands with a spatial resolution of 1000 m and, given a larger pixel size, a larger swath and shorter revisit period (12 h); they had an envisaged design-life of five years  . The MODIS sensors have become the most commonly-used sensors for regular and reliable observations of thermally-anomalous volcanic activity. Although their spatial resolution is not ideal, their regular overpasses (up to four times daily when both sensors are considered) have contributed to their widespread use. Various products have been developed that extract and process MODIS thermal data. One such group of products with utility for volcanologists is the MODIS Fire Products, which provide a table of all thermally-anomalous pixels identified within each MODIS scene BIB007 BIB015 . The MODIS instruments have now been functioning for over 15 years, and this long time series of regular data has allowed scientists to automatically monitor volcanic activity and to determine baseline activity for every active volcano on Earth (e.g.,    ). The latest NASA satellite to have been launched (in 2011) that possesses infrared imaging capabilities is the S-NPP satellite, which features the VIIRS sensor. The S-NPP was launched as an experimental satellite of the Joint Polar Satellite System (JPSS), coordinated by both NASA and NOAA. This system is envisaged as continuing the satellite record of environmental observations, which commenced with AVHRR in the 1970s and continues with MODIS. The VIIRS possesses two sets of bands with infrared detection capabilities: five high resolution imaging (I) bands (375 m) and sixteen moderate (M) resolution bands (750 m), each covering the MIR and TIR portions of the spectrum. To date, there has only been one attempt at using VIIRS data for monitoring volcanic activity, with BIB028 showing that its detection capabilities are similar, if not superior, to those of MODIS, while a number of studies have similarly confirmed the utility of its infrared bands for monitoring wildfires (e.g.,  BIB027 ). One final set of satellites that has been used for volcanic observations is what are termed 'small satellites'. Varying definitions exist, but in general, a small satellite is one weighing under 1000 kg, with the small size making them more affordable and potentially commercially mass-producible BIB018  . The first small satellite mission for hot-spot monitoring was the Bi-spectral Infrared Detection (BIRD) mission of the German Aerospace Center (DLR). The BIRD satellite was launched in 2001 and possessed two infrared bands (one MIR and TIR) for identifying hotspots BIB011 . The satellite entered a relatively low Earth orbit (570 km), with a swath width of 190 km and a pixel size of 370 m × 185 m. Data collected by the sensor (which itself possessed adjustable gain settings) were examined using a customised hotspot detection algorithm. The chief advantages of BIRD were a higher spatial resolution, as compared with sensors, such as MODIS, and the availability of both MIR and TIR detection capabilities (an advantage over ASTER), although these advantages were at the expense of temporal resolution, given its relatively narrow swath BIB017 . In 2012, a new DLR mission, FireBIRD, commenced, with the micro-Technologieerprobungsträger 1 (TET-1) satellite being launched, possessing two infrared sensors BIB029 . Although fire observation was the objective of FireBIRD, in late 2014, it imaged the effusion of lava at Stromboli Volcano, Italy, and in this case, its adaptive gain settings meant that while a coincident MODIS image experienced saturation, its data remained unsaturated; and its higher MIR spatial resolution (320 m) provided a relatively more detailed image BIB030 . Thermal remote sensors utilised for volcanic remote sensing have also been launched by non-U.S. entities. In 1991 and 1995, the ESA launched the European Remote Sensing (ERS) 1 and 2 satellites, each possessing the Along Track Scanning Radiometer (ATSR), which was equipped with MIR and TIR bands and also one SWIR band. In 2002, a third ATSR, the Advanced ATSR (AATSR), was launched following the success of the two earlier versions. The spatial resolution of the ATSR bands was 1000 m × 1000 m, making them less useful for detailed studies than their American counterparts at the time (those of Landsat TM), but providing an enhanced temporal resolution in the period before MODIS BIB006 . Given the temporal superiority of ATSR compared to Landsat TM, use of the sensor became common place for several years, and it was used to examine temporal variations in volcanic activity at various locations, including Lascar, Chile BIB006 , Fernandina, Ecuador  and Etna, Italy BIB014 , with its surveillance capabilities reviewed in  . Findings from the use of ATSR were also used to assess the potential volcanic-utility of the then, not-launched MODIS sensor BIB008 . Japan also entered the field in 1991 with the launch of the OPtical Sensor (OPS) on-board the Japanese Earth Resources Satellite (JERS-1), possessing, for the first time, four high spatial resolution (18 m × 24 m) SWIR bands; it is arguably data from this sensor that highlighted the potential of the shorter-infrared wavelength part of the spectrum for high-temperature surface monitoring BIB006  .