An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <s> Remote sensing in the short wavelength infrared (SWIR) has the potential for providing a great deal of information about activity at volcanoes, by virtue of the radiation emitted by hot surfaces. This can be used to give warning of imminent eruptions, monitor their progress and model volcanic processes. The Landsat TM is the only operational instrument which returns suitable data. This is particularly valuable because it incorporates two SWIR bands enabling constraints to be put on the sub-pixel structure of the image. Current orbital themial infrared imagery (eg AVHRR, TM band 6) cannot resolve most volcanic thermal anomalies because the pixel size is too coarse. Moreover, the gains of operational thermal infrared sensors make them unsuitable for measuring volcanic temperatures. <s> BIB001 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <s> Onboard NASA Terra spacecraft is one of the most sophisticated earth observing instruments ever flown, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), created as part of a joint project between the Japanese Ministry of Economy, Trade, and Industry and NASA. This instrument consists of three independent bore-sighted telescopes with 14 channels in the visible, near-infrared, and thermal infrared regions capable of being pointed up to 22.5° off-nadir. In addition, there is an additional backward-looking visible channel telescope for stereo-photogrammetric observations. The spatial resolutions are 15 m/pixel in the visible, 30 m/pixel in the near-IR, and 90 m/pixel at thermal wavelengths, and the swath width is 60 km. ASTER instrument offers unprecedented opportunities for observing volcanoes and their activity from low earth orbit. It is the purpose of this short paper to introduce ASTER to the volcanological community, highlight its capabilities, advantages and limitations, and to show some examples of ASTER data and related analyses. We will also explain how users can readily access ASTER data. <s> BIB002 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <s> Abstract Satellite remote sensing represents a mature technology for long-term monitoring of volcanic activity at Mount Erebus, either independently or as a complement to field instrumentation. Observations made on 4290 discrete occasions over a six year period by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) indicate that the radiant flux from the volcano's summit crater (and by inference, the lava lake contained therein), while variable on the time scale of days to weeks, has varied little on an inter-annual basis over this period. The average radiant flux from the lake during this time was 15 MW, with a maximum flux of 100 MW. Such heat flux time-series have been shown to act as a reliable proxy for general levels of activity at erupting volcanoes around the world, particularly when these time-series are of a long duration. The apparent stability of Erebus' power output is in marked contrast to fluxes observed at three other terrestrial volcanoes, Erta ‘Ale (Ethiopia), Nyiragongo (Democratic Republic of Congo) and Ambrym (Vanuatu), which, while also hosting active lava lakes, all exhibit much greater variability in radiant flux over the same period of time. The results presented in this paper are confluent with those obtained from geochemical considerations of the Erebus' degassing regime, and confirm that remarkably stable open-system volcanism appears to be characteristic of this long-active volcano. <s> BIB003 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <s> During the past decade an average of 60 volcanoes erupted each year, around 20 of which were erupting on any given day. Some of these, such as Erta Ale in Ethiopia, are persistently active, whereas others, such as Bezymianny in Russia, erupt more sporadically. Satellite remote sensing offers a convenient way to monitor changes in the thermal budgets of these volcanoes from space. Using data acquired by the National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, we show how the amount of heat radiated into the Earth's atmosphere by 65 active volcanoes has varied between 26 February 2000 and 31 December 2006. We find that the radiant volcanic heat flux into the atmosphere occurs at a relatively steady-state baseline level, superimposed on which are large thermal emission 'spikes'. These anomalous emission events are associated with the emplacement of basaltic 'a'a lava flows at volcanoes such as Mount Etna, Italy, and Nyamuragira, in the Democratic Republic of Congo. We also demonstrate how these data can be used to estimate lava effusion rates during effusive eruptions, and magma flux rates at persistently active volcanoes that host active lava lakes. <s> BIB004 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <s> Abstract Bezymianny (Kamchatka Peninsula, Russia) is an active stratovolcano, characterized by a summit lava dome and overlapping pyroclastic flow (PF) deposits to the southeast. Three explosive eruptions (24 December 2006, 11 May 2007, and 14 October 2007) generated PFs that were dominated by juvenile material and were emplaced primarily due to column collapse. Following this, a gravitational lava flow front collapse event generated block and ash flow on 5 November 2007. Moderate spatial resolution data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument were collected between October 2006 and December 2007 to assist in post-eruption monitoring and interpretation of the volcanological processes that produced the PF deposits. Using multitemporal ASTER thermal infrared (TIR) data, three periods of increased activity were observed that coincided with each eruption and subsequent activity. During a field campaign in August 2007, the May 2007 PF deposit was investigated in detail. Eight ASTER TIR pixels (90 m spatial resolution) were selected from the 30 June 2007 ASTER TIR image, seven of which were accessible in the field. Forward-Looking Infrared (FLIR) image and thermocouple data over these areas were collected to observe thermal heterogeneities with distance along the PF deposit. Although synchronous ASTER data were not possible at the time of fieldwork due to cloud cover, a field survey of blocks versus ash in each pixel was carried out to investigate thermal and textural variation with distance from the vent and to provide preliminary field results. Based on the field-derived temperature data and surface block percentages, the May 2007 PF deposit was more block-rich in the medial portion of the flow surface, but more ash-dominated at the PF terminus region, which promoted more rapid cooling. We present multitemporal ASTER data spanning a 14 month period and highlight ground-based observations acquired within the same period of eruptive and dome-growth activity. These data collectively provide thermal radiative and emissivity information on an actively changing explosive volcanic system and specifically documents changes over recently-emplaced and cooling PF deposits. <s> BIB005 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <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> BIB006 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <s> Abstract A combination of satellite and airborne high-resolution visible and thermal infrared (TIR) image data detected and measured changes at Redoubt Volcano during the 2008–2009 unrest and eruption. The TIR sensors detected persistent elevated temperatures at summit ice-melt holes as seismicity and gas emissions increased in late 2008 to March 2009. A phreatic explosion on 15 March was followed by more than 19 magmatic explosive events from 23 March to 4 April that produced high-altitude ash clouds and large lahars. Two (or three) lava domes extruded and were destroyed between 23 March and 4 April. After 4 April, the eruption extruded a large lava dome that continued to grow until at least early July 2009. <s> BIB007 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <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> BIB008 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Sensor Characteristics <s> Abstract Merapi is one of Indonesia's most active and dangerous volcanoes. Prior to the 2010 VEI 4 eruption, activity at Merapi during the 20th century was characterized by the growth and collapse of a series of lava domes. Periods of very slow growth were punctuated by short episodes of increased eruption rates characterized by dome collapse-generated pyroclastic density currents (PDCs). An eruptive event of this type occurred in May–June, 2006. For effusive eruptions such as this, detailed extrusion rate records are important for understanding the processes driving the eruption and the hazards presented by the eruption. We use thermal infrared (TIR) images from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on NASA's Aqua and Terra satellites to estimate extrusion rates at Merapi Volcano during the 2006 eruption using the method of Harris and Ripepe (2007). We compile a set of 75 nighttime MODIS images of the eruptive period to produce a detailed time series of thermal radiance and extrusion rate that reveal multiple phases of the 2006 eruption. These data closely correspond to the published ground-based observational record and improve observation density and detail during the eruption sequence. Furthermore, additional analysis of radiance values for thermal anomalies in Band 21 (λ = 3.959 μm) of MODIS images results in a new framework for detecting different styles of activity. We successfully discriminate among slow dome growth, rapid dome growth, and PDC-producing dome collapse. We also demonstrate a positive correlation between PDC frequency and extrusion rate, and provide evidence that extrusion rate can increase in response to external events such as dome collapses or tectonic earthquakes. This study represents a new method of documenting volcanic activity that can be applied to other similar volcanic systems. <s> BIB009
Advanced Along-Track Scanning Radiometer (AATSR) on-board the European Space Agency (ESA) Envisat satellite Early satellites such as the National Aeronautics and Space Administration's (NASA's) Television Infrared Observation Satellite (TIROS) series, launched throughout the 1960s, possessed TIR Earth-observation capabilities for meteorological observations. Since this period, infrared observations have remained crucial for meteorological purposes while also providing an excellent means of observing terrestrial 'hot phenomena', ranging from wildfires to active volcanoes. Some examples of using orbiting infrared sensors for this purpose include  , in which it was shown that subtle precursory TIR signals could be detected prior to a 2006 eruption of Bezymianny Volcano in Russia and BIB005 , which similarly showed how TIR observations of Bezymianny could be used to monitor the volcano's changing state during a later eruption. More recently, BIB007 used satellite-retrieved TIR observations, augmented with ground-based observations, to isolate precursory signals, and a subsequent eruption, at Redoubt Volcano in Alaska and BIB009 demonstrated the utility of satellite TIR observations for determining lava extrusion rates and discriminating different types of lava dome activity, at Merapi Volcano, Indonesia. Likewise, several satellite sensors have MIR detection capabilities, which have been shown to be useful in monitoring both thermally-anomalous volcanic surfaces and, also, those at a more ambient temperature. Wright and Pilger BIB003 BIB004 , for example, utilised MIR bands to quantify the radiant emissions from a number of volcanoes and used the same data to monitor the variability in heat flux from the lava lake at Mount Erebus in Antarctica, respectively, while  demonstrated a volcanic activity detection system that harnesses detected MIR signals. Some satellite sensors have been equipped with SWIR detection capabilities, in large part because SWIR image data can be used in land surface reflectance studies  ; in fact, the SWIR bands on ASTER were chosen for the absorption features of various minerals and clays BIB001 BIB002 . However, such bands are also useful in monitoring hot surfaces, especially at night BIB006 , and until the malfunction in 2008, ASTER was regularly used for such purposes. Comparable functionality has now passed to the largely under-investigated SWIR bands of Landsat-8 BIB008 . The advantage of SWIR volcanic observations is that, in the absence of sunlight, terrestrial SWIR signals recorded from space will be purely a product of the temperature of a hot emitting surface. In contrast, MIR and TIR detections from space will be the product of emissions from both ambient and hot surface components, the former of which must therefore be removed. The advantage that MIR and TIR observations have over SWIR observations, however, is that they will also detect cooler volcanic surfaces, thereby negating the requirement of incandescent or fresh lava to be present while facilitating the monitoring of a greater range of volcanic activity.