An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> Abstract The Advanced Baseline Imager (ABI), designated to be one of the instruments on a future Geo-stationary Operational Environmental Satellite (GOES) series, will introduce a new era for U.S. geostationary environmental remote sensing. ABI is slated to be launched on GOES-R in 2012 and will be used for a wide range of weather, oceanographic, climate, and environmental applications. ABI will have more spectral bands (16), faster imaging (enabling more geographical areas to be scanned), and higher spatial resolution (2 km in the infrared and 1–0.5 km in the visible) than the current GOES Imager. The purposes of the selected spectral bands are summarized in this paper. There will also be improved performance with regard to radiometrics and image navigation/registration. ABI will improve all current GOES Imager products and introduce a host of new products. New capabilities will include detecting upper-level SO2 plumes, monitoring plant health on a diurnal time scale, inferring cloud-top phase and partic... <s> BIB001 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> Future operational geosynchronous remote sensors will respond to a broad range of environmental and ::: military/intelligence mission needs. This paper describes initial system engineering design studies for 4th ::: generation operational geosynchronous remote sensors that address notional future mission requirements. ::: Two hyperspectral sensor architectures were considered: an imaging Fourier transform spectrometer and an ::: imaging prism spectrometer. While both imaging FTS and dispersive approaches are viable over a broad ::: trade space, each requires new technology that must be demonstrated low risk by 2017 to enable a mission ::: pathfinder by 2025. To reach this important objective requires that technology risk reduction start now. <s> BIB002 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> The small satellite renaissance began in the 1980s and is changing the economics of space. Technological trends have supported the advancement of small satellites in the 1-500 kg range. The number of countries actively participating has grown substantially during the past years. Satellite constellations (groups of satellites working in concert) are emerging as a powerful and effective application. In this paper, we focus on the small satellites than can perform remote sensing or Earth observation tasks. An overview is presented of the small satellite literature on Earth observation. The aim of the survey is threefold: an introduction for those new to the field, an overview for those working in the field and a reference for those searching for literature on a specific application for Earth observation. Small satellite programmes are classified according to the geographic regions. The small satellite industry and small satellite systems are addressed. In terms of applications, small satellite constellations are discussed in more detail. Finally, future developments are put forward. Telegeoprocessing combined with grid computing will provide the infrastructure and technologies for the development of Processing on Demand for Small Satellite Constellation systems. <s> BIB003 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> Autonomous onboard processing of data allows rapid response to detections of dynamic, changing processes. Software that can detect volcanic eruptions from thermal emission has been used to retask the Earth Observing 1 spacecraft to obtain additional data of the eruption. Rapid transmission of these data to the ground, and the automatic processing of the data to generated images, estimates of eruption parameters and maps of thermal structure, has allowed these products to be delivered rapidly to volcanologists to aid them in assessing eruption risk and hazard. Such applications will enhance science return from future Earth-orbiting spacecraft and also from spacecraft exploring the Solar System, or beyond, which hope to image dynamic processes. Especially in the latter case, long communication times between the spacecraft and Earth exclude a rapid response to what may be a transient process — only using onboard autonomy can the spacecraft react quickly to such an event. <s> BIB004 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> Thermal infrared (TIR) remote sensing is recognized as a powerful tool for collecting, analyzing and modeling of energy fluxes and temperature variations. Traditional aircraft, satellite or ground TIR platforms can provide valuable regional-scale environmental information. However, these platforms have limitations, such as expensive cost, complicated manipulation, etc. In comparison, small unmanned aircraft systems (UAS) have many advantages in TIR remote sensing applications over traditional platforms. In this paper, a low-cost UAV-based TIR remote sensing platform: AggieAir-TIR is introduced. AggieAir-TIR is a small, low-cost, flexible TIR remote sensing platform, which was accomplished at the Center for Self Organizing and Intelligent Systems (CSOIS) in Utah State University (USU). The detailed introduction of AggieAir-TIR remote sensing platform is provided in the paper. Furthermore, a low-cost TIR imaging camera calibration experiment is designed, and the calibration results are provided. Based on this AggieAir-TIR remote sensing platform, many remote TIR image data collection and analysis projects can be effectively implemented. <s> BIB005 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> Abstract The Sentinel-3 Sea and Land Surface Temperature Radiometer (SLSTR) is a dual-view Earth observing instrument that builds on the heritage of the Along Track Scanning Radiometer (ATSR) series. SLSTR is planned for launch in 2013 on Sentinel-3, with two concurrently operating satellites planned for daily global coverage. Here we review the aspects of the SLSTR instrument design specifically targeted at biomass burning events, including operation of the SWIR channels at night and the inclusion of low-gain middle infrared and thermal IR channels that will minimise saturation over even high intensity fires. We detail the active fire detection and fire radiative power dataset to be provided from these SLSTR observations, which will be part of the SLSTR land product suite aimed at supporting both Global Monitoring for Environment and Security (GMES) operational services and scientific applications. We describe in detail the pre-launch active fire product algorithm, which uses data from the SLSTR near-nadir scan. The algorithm detects pixels containing actively burning fires, and uses the MIR radiance method to estimate their fire radiative power (FRP). We test the algorithm using a series of EOS MODIS scenes covering a range of fire-affected forest and savannah environments, comparing performance to that of the existing MODIS MOD14 ‘Fire and Thermal Anomaly’ products. Across 385 scenes covering Africa, South America and Australia, we find that the SLSTR algorithm applied to MODIS data detects in total 20% more fire pixels than does the MOD14 algorithm applied to the same data. Some scenes show very large differences, while others showed no differences, and some of the extra detections made by SLSTR maybe false alarms. For a better evaluation, we use the simultaneous high spatial resolution active fire detections made from ASTER to provide an independent accuracy assessment. Across 45 separate geographical regions covered simultaneously by ASTER and MODIS, we find that the SLSTR algorithm in fact detects 13% more correctly identified clusters of active fire pixels than the MOD14 algorithm, and that these contain 36% more active fire pixels. In particular, the SLSTR algorithm shows increased detection probabilities at small/low FRP fires, mainly due to the more liberal characteristics of its potential fire pixel detection stage. This performance enhancement comes, however, at the expense of a small ( <s> BIB006 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> One of the main goals of the Hyperspectral and Infrared Imager (HyspIRI) mission is to provide global observations of surface attributes at local and landscape spatial scales (tens of meters to hundreds of kilometers) to map volcanic gases and surface temperatures, which are identified as indicators of impending volcanic hazards, as well as plume ejecta which pose risks to aircraft and people and property downwind. Our project has created precursor HyspIRI data sets for volcanological analyses, using existing data over Mt. Etna, Italy. We have identified 28 EO-1 Hyperion data acquisitions, and 12 near-coincident ASTER data acquisitions, covering six eruptive periods between 2001 and 2010. These data sets provide us with 30 m hyperspectral VSWIR data and 90 m multispectral TIR data (satellite). They allowed us to examine temporal sequences of several Etnaean eruptions. We addressed the following critical questions, directly related to understanding eruption hazards: 1) What do changes in SO2 emissions tell us about a volcano's activity? How well do these measurements compare with ground-based COSPEC measurements? 2) How do we use measurements of lava flow temperature and volume to predict advances of the flow front? 3) What do changes in lava lake temperatures and energy emissions tell us about possible eruptive behavior? <s> BIB007 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> The Small Satellite Constellation for Environment and Disaster Monitoring and Forecasting (SSCEDMF) is an important component of Chinese satellites earth observation system. The first stage of SSCEDMF is composed by “2+1” satellites. The 2 optical satellites (HJ-1-A and HJ-1-B) and 1 S band microwave satellite (HJ-1-C) were successful launched on September 6, 2008 and November 19, 2012 respectively. This article introduced SSCEDMF characteristic and the disaster reduction application system and satellites on-orbit test works, and also analyzed the application capacity in natural disasters included flood, ice flooding, wild fire, severely drought, snow disasters, large area landslide and debris flow, sea ice, earthquake recovering, desertification and plant diseases and insect pests. Furthermore, we show some cases of China’s and other countries’ new natural disasters forecasting, monitoring, assessment and recovery construction. <s> BIB008 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <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> BIB009 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <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> BIB010 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> Abstract In 2007, the NASA Hyperspectral InfraRed Imager (HyspIRI) mission was recommended in Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond (Decadal Survey) to address critical science questions in multiple areas, in particular ecosystems and natural hazards. HyspIRI is comprised of two instruments, a visible to short-wavelength infrared (VSWIR) imaging spectrometer and a thermal infrared (TIR) multispectral imager, together with an Intelligent Payload Module (IPM) for onboard processing and rapid downlink of selected data. The VSWIR instrument will have 10 nm contiguous bands and cover the 380–2500 nm spectral range with 30 m spatial resolution and a revisit of 16 days. The TIR instrument will have 8 discrete bands in the 4–13 μm range with 60 m spatial resolution and a revisit of 5 days. With these two instruments in low Earth orbit, HyspIRI will be able to address key science and applications questions in a wide array of fields, ranging from ecosystem function and diversity to human health and urbanization. <s> BIB011 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> article i nfo The investigation of high-temperature natural phenomena, such as wildland fires and active lava flows, is a primary science objective for the proposed Hyperspectral Infrared Imager (HyspIRI) mission. Current planning for HyspIRI includes a mid-infrared (MIR) channel centered at 4 μm that will allow measurement of radiance emitted from high-temperature targets. In this paper we present the results of a study to specify the saturation temperature for the MIR channel. This study was based on reviews of the literature, together with case studies of airborne and satellite-based data acquired over high-temperature targets. The spatial resolution of MIR radiance measurements is an important consideration in the remote sensing of high-temperature phenomena, due to thepresence ofmaterialsatdifferent temperatures withinthe areacoveredbyanimage pixel.The HyspIRI MIR channel will provide a spatial resolution of 60 m, which is ~40 times finer (in terms of area) than the finest spatial resolution provided by heritage instruments (370 m). This fine spatial resolution will increase the prob- ability that high-temperature targets fill an image pixel and, therefore, the HyspIRI MIR channel will require a saturation temperature 2 to 4 times higher than the saturation limits of heritage instruments. Based on our study, we recommend a saturation temperature of 1200 K (927 °C). This recommendation accounts for the high temperatures expected for natural phenomena, expected performance of the MIR channel, and overlap in sensitivity between the MIR and thermal infrared (7.5-12 μm) HyspIRI channels. <s> BIB012 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <s> Abstract The Hyperspectral Infrared Imager (HyspIRI) mission is proposed to be the first satellite system with the capability to provide global, repeat coverage across the visible and shortwave infrared spectrum, as well as eight channels in the midwave and thermal infrared. HyspIRI has stated objectives to address a host of pressing earth science questions, from radiation budgets to ecosystem functions. A sizable science community has grown to support the mission, and their ongoing research demonstrates HyspIRI's potential to greatly expand our knowledge of the earth system. This special issue features a collection of papers, some reviews and others novel science, that cover the wide array of topics relevant to HyspIRI's mission and reaffirm the necessity for HyspIRI. <s> BIB013 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <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> BIB014 </s> An Overview of Infrared Remote Sensing of Volcanic Activity <s> Prospects for the Future <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> BIB015
Sensors used for the infrared monitoring of volcanic activity have immense utility and indeed, have become essential for the monitoring of volcanoes globally. However, there remains a number of shortcomings dictated by the temporal-spatial-spectral resolution trade-off (see Figure 4) . These trade-offs have significance when it comes to the remote monitoring of volcanic activity, which, itself, is greatly variable in space, time and intensity. In the case of prolonged eruptive behaviour, such as the incessant effusion of fresh lava from Kilauea, Hawaii, the relatively poor spatial resolution of MODIS, for example, is optimal for accurate and quantifiable observations as it reduces the possibility of image saturation, while its relatively high temporal resolution means that variations in the effusive activity can be well monitored through time. For an unexpected explosive eruption, however, even relatively high temporal resolution imagery (e.g., sub-daily) may be inadequate, resulting in such events often going undetected. Consequently, despite its advantages, infrared remote sensing alone cannot be relied upon for volcanic monitoring, although it constitutes an essential tool for geologists to better understand volcanic processes and for hazard managers to monitor and mitigate associated risks. Ramsey and Harris  argued that 2000-2010 had shown greater progress in the field of volcanic remote sensing than they envisaged for the following decade (up to 2020). Indeed, they discussed the debate that was required to ensure that the subsequent generation of Landsat sensors possessed any infrared sensing capabilities at all   ; the apparent dearth of research over recent years might be explained by several factors, such as that the NASA sensors launched in the late 1990s and early 2000s are coming to the end of their operational lives, while those that remain functional (e.g., Landsat-7 and MODIS) have less than optimal spatial or temporal resolutions. New satellites have been launched with infrared imaging capabilities, such as Landsat-8 and VIIRS on-board S-NPP, but volcanic use of these has been limited, despite showing comparability BIB009 , or indeed improved performance BIB010 ; some retrograde steps, such as the reduction in Landsat-8's infrared spatial resolution, have also been taken. The limited utilisation of these sensors for volcanological studies is by no means a reflection of their potential, and it remains to be seen what new and innovative volcanic observational uses will be derived. At the same time, the body of data from all sensors in orbit continues to grow, providing a repository from which more accurate and representative estimations of volcanic activity might be drawn (e.g.,  ). In the near future, the provision of infrared volcanic observations will continue, with the successor to the S-NPP, the NASA Joint Polar Satellite System (JPSS 1), due for launch in 2017 and possessing the already proven VIIRS, and with the launch of the ground-breaking Hyspiri sensor, currently planned for 2020 at the earliest BIB007 . This latter sensor will possess a similar contingent of VNIR and SWIR bands as its predecessor, Hyperion (212 bands between 380 and 2500 nm, although at a reduced spatial resolution of 60 m); additionally, it will have spatially-aligned and higher resolution MIR/TIR imagers (imaging at 60 m in eight bands between 4 µm and 13 µm). Crucially for Hyspiri, for which one second of operation will produce up to 1 GB of data, the capacity for on-board data processing via an 'Intelligent Payload Module' (IMP) and direct broadcast of a subset of the data  BIB011 BIB007 are useful innovations. On-board automated analyses will have the capacity to identify specific features, for example a volcanic eruption, and once identified, this might trigger further observations of the rapidly changing surface and/or re-task other sensors to make such observations  BIB011 . Abrams et al. BIB007 simulated Hyspiri data with regard to its observation of volcanic activity and showed promising results as compared with ASTER TIR data, given a smaller pixel size (60 m) and higher saturation temperature (700-900 K); its TIR bands will also have an improved temporal resolution (five days at the equator) BIB011 BIB012 . Hochberg BIB013 sums up the optimism regarding Hyspiri: "There is no current thermal infrared sensor that combines multiple bands needed for temperature-emissivity separation, a sub-100 m spatial resolution, and a frequent repeat interval with global coverage, which are necessary to answer a wide range of Earth science studies related to surface composition, hydrology, and volcanology" (p. 1). Concerns remain however, as to whether the saturation temperature of the Hyspiri MIR bands will be high enough to prevent saturation over the most radiant lava flows BIB012 . Another project that shows potential relates to the European Commission's Earth Observation Programme: Copernicus. As part of this programme, the Sentinel-3 satellite mission is launching two satellites with infrared Earth observation capabilities (Sentinel-3A was launched in early 2016 and Sentinel-3B is due for launch in 2017) to provide continuity to the ATSR and AATSR range. The primary aim of Sentinel-3, and its Sea and Land Surface Temperature Radiometers (SLSTR), is for monitoring ocean and land surface temperatures; however, given their SWIR, MIR and TIR imaging capabilities, they will also provide continuity in volcanic observations. The chief advantages of the SLSTRs are a saturation temperature of 675 K and an equatorial revisit time of half a day (when both satellites are considered); thermal anomaly detection algorithms have been developed and tested for these sensors BIB006  . For the monitoring of volcanic activity, high temporal resolution data, ideally at a sub-daily resolution, such as that provided by geostationary satellites, is particularly useful, and there are prospects that show promise in this regard. The GOES R-Series, for example (the first satellite of which was launched in November 2016), possesses the Advanced Baseline Imager (ABI), which will retain the GOES high temporal resolution while also improving current capabilities, with a superior spatial resolution (0.5-2.0 km) and more bands (including a new SWIR band) BIB001 . Japan's equivalent satellites, Himawari-8 (launched in 2015) and -9 (launched in November 2016), each possess a sensor largely comparable in terms of features to the ABI  . Similarly, the European Meteosat Third Generation Mission, the first spacecraft of which are due for launch from 2020, will possess more bands on its SEVERI replacement, the Flexible Combined Imager (FCI). FCI's short wave and near-infrared bands will have a 1-km spatial resolution and a temporal resolution of 10 min, as compared with 15 min at present  . These geostationary satellites will also have the capability for rapid scans at times of enhanced activity, and in the case of GOES-R, this may be up to every 30 s BIB001  . Additionally, prospects for the more distant future for instantaneous monitoring are equally promising with Meteosat fourth generation satellites envisioned to be active from around 2035 BIB002 . These systems will possess an increasingly hyperspectral range of instruments and an even greater spatial and temporal resolution, ideal for monitoring the rapidly changing surfaces associated with volcanoes. Davies et al. BIB004 argue that in the future, data from surface sensors, in addition to those from satellites, should form part of any automatic system for identifying volcanic activity. They suggest that had this been the case for the 2010 Eyjafjallajökull eruption, attention would have been focused on the eruption sooner, rather than after the eruption was underway. Ramsey and Harris  , in contrast, envisage most development in the coming years to relate to small satellites launched privately and at less expense than their larger counterparts. One of the chief disadvantages of small satellites is that, given their size, and hence narrow swaths, their revisit frequencies are usually sub-optimal for monitoring phenomena that change on short timescales (such as volcanic activity). Small satellites, however, open the possibility that more can be constructed for the same cost as their expensive relatives, resulting in constellations of satellites BIB003 . Should such constellations be equipped with infrared sensing capabilities, then it would provide the potential for high spatial and temporal resolution observations of thermally-anomalous volcanic surfaces. China launched one such system, the Small Satellite Constellation for Environment Protection and Disaster Monitoring in 2008, and with its 30-m resolution infrared imaging capabilities, this system has proven useful in observing wildfires BIB008 . The DLR has also instigated a fire monitoring constellation, FireBIRD, with the first satellite, TET-1, having already shown utility in providing high resolution MIR and TIR imagery of a Strombolian lava flow BIB014 . The second satellite of the FireBIRD constellation, the Bi-spectral InfraRed Optical System (BIROS), was launched in 2016, and it is envisaged that in total, the FireBIRD constellation will have a three-day revisit period for locations at the Equator BIB014 . A constellation of multi-spectral infrared VISible-to-thermal IR micro-SATellites (VISIR-SAT) has also been proposed by the DLR, with a spatial resolution of potentially less than 30 m and with one of its aims being: "To predict . . . volcanic hazards through detection of transient thermal phenomena" (p. 1286) BIB015 . In the last decade, one development in the field of volcanic remote sensing (other than by satellite) has been the use of unmanned aerial vehicles (UAVs) mounted with infrared cameras (e.g., BIB005 ). The chief advantage of such an approach, over that of using satellites, is a higher spatial resolution, given that the UAVs may be a few metres from the surface of interest. However, problems with payload weight, battery power and distance between operator and the hazardous surface have slowed progress in this promising field of study. In the future, an ideal strategy is for a multi-scale approach, combining the use of high temporal resolution, wide swath spectroradiometers (e.g., MODIS or AVHRR) with higher spatial resolution imagers that focus on high-risk areas. If such systems communicate with each other, events noted at high temporal resolution could be used to trigger higher spatial resolution observations; and the precedence of this has been discussed. One significant prospect in this regard is an ESA Sentinel Convoy, whereby BIB015 suggests that the VISIR-SAT could be flown with the Sentinel-3 satellites, thus providing high spatial resolution observations of thermal anomalies detected by the coarser resolution, but more widely-viewing, Sentinel range. Infrared remote sensing of volcanoes has made much progress in little more than half a century. It is essential that this progress is maintained to ensure areas of potential or imminent volcanic hazard are identified for scientists and decision makers. If investment continues in the development of Earth-orbiting infrared remote sensors, then improvements in what scientists can visualize and interpret will continue. Such developments will aid in the understanding of the actual geological phenomena on the ground and in the management of the associated hazards posed to vulnerable communities globally.