Conceptual design and specification of a microsatellite forest fire detection system

The burning of our forests and other forms of biomass are increasingly harming the local, regional and global environment. As evidenced by studies of the earth\u27s atmosphere, biomass burning is a significant global source of greenhouse gases and particulate matter that impact the chemistry of the troposphere and stratosphere. Current remote sensing methods used for monitoring forest fires and other forms of biomass burning rely on sensors primarily designed for measurement of temperatures near 300 degrees Kelvin or the average surface temperatures of the earth’s surface. Fires radiate intensely against a low-temperature background, therefore it is possible to detect fires occupying only a fraction of a pixel. However, sensors used in present remote sensing satellites saturate at temperatures well below the peak temperatures of fires, or have revisit times unsuitable for monitoring the diurnal activity of fires. The purpose of this study is to review past and present space-based sensors used to monitor fire on a global scale and propose a design intended specifically for fire detection and geo-location. Early detection of forest fires can save lives, prevent losses of property and help reduce the impact on our environment

Performance assessment of low-cost thermal cameras for medical applications

Thermal imaging is a promising technology in the medical field. Recent developments in low-cost infrared (IR) sensors, compatible with smartphones, provide competitive advantages for home-monitoring applications. However, these sensors present reduced capabilities compared to more expensive high-end devices. In this work, the characterization of thermal cameras is described and carried out. This characterization includes non-uniformity (NU) effects and correction as well as the thermal cameras´ dependence on room temperature, noise-equivalent temperature difference (NETD), and response curve stability with temperature. Results show that low-cost thermal cameras offer good performance, especially when used in temperature-controlled environments, providing evidence of the suitability of such sensors for medical applications, particularly in the assessment of diabetic foot ulcers on which we focused this study.This research was funded by the IACTEC Technological Training program, grant number TF INNOVA 2016-2021, and by the European Union Interreg-Mac funding program, grant number MAC/1.1.b/098 (MACbioIDi project)

Comparing properties of different infrared cameras

Infrared (IR) camera enables to measure the temperature of an object without contact. As a result, a thermal image is created, and it is usually visualized by colours/contrast representing different temperature values. Originally, IR cameras were developed for military and surveillance purposes. As the features of IR cameras evolved and cost decreased, the application field expanded also to other areas such as industry and medicine. This thesis work is conducted on requirements and desires of medical technology company Imaqen Ltd. The aim was to acquire a better understanding of different IR camera technologies, compare those to each other on paper and carry out measurements, where the ability of the IR cameras to detect fast effects is tested and the noise levels of the cameras are determined. On this ground, one could find the most suitable IR camera to a future application of the company. Among other things, spectral range, sensitivity and response time of IR cameras depend on the material and technology of the detector. These properties influence e.g. in which temperature range the camera is working, how small temperature differences can be distinguished and how fast effects can be detected. The real functionality of an IR camera is revealed only in practical testing, so in addition to theoretical study, five different IR cameras were tested. Three cameras were cooled photovoltaic (PV) detectors, which measure the temperature of an object by counting incident photons. Two cameras were microbolometers (MB), which operation is based on variation in temperature of sensing elements of the detector. The aim was to measure how well the cameras are detecting heat effects lasting only a couple of milliseconds. A tech-nical phantom was built for the measurement, where a rotating plate with a small hole was adjusting the time a warm object behind it was visible. By increasing the angular velocity of the plate, the time of the heat effect was reduced to 2.7 ms. Noise level of the camera affects how small temperature differences the camera can distinguish. Therefore, the characteristic noise level of every camera was calculated, and this was compared to the NETD (noise-equivalent temperature difference) value provided by the manufacturer. MBs are not suitable for detecting heat effects that last only a couple of milliseconds due to their long response time i.e. the thermal time constant of the sensing element. The PV detectors on the other hand are very suitable for fast recognition tasks as their response time is short. However, an aliasing effect was discovered because of a too low frame rate. This can be a limiting factor when the effect time decreases and if the frame rate of the camera cannot be increased. All the noise levels were higher than values provided by the manufacturers, especially with MBs. This difference of noise levels between MB and PV detectors makes the latter more suitable for detecting small temperature differences on a scene. Based on the results and theory, one can conclude that PV detectors have better fast recognition and noise features than MBs. However, cost and size of MBs are considerably reduced compared to PV detectors. This can turn out to be a selection criterion if the minimum requirements are fulfilled. There are still other detectors used in IR cameras e.g. quantum well infrared photodetector, which were not tested in this work. Thus it would be beneficial to reproduce these tests with a larger variety of different IR detector technologies; only then more precise conclusions about the best detector could be made. Sometimes a trade-off between some features must be made, for example, it has to be decided if a fast response time is more important than high sensitivity with a large resolution. The application will set the requirements for optimal features of the IR camera. Therefore, different cameras cannot be put in order without knowing what the target application is.Lämpökamera mahdollistaa kohteen lämpötilan mittaamisen ilman kontaktia. Sillä saadaan kohteesta lämpökuva, jossa värit/sävyt edustavat eri lämpötiloja. Alun perin lämpökameroita käytettiin ja kehitettiin sotilas- ja valvontakäyttöön. Kameroiden hintojen laskiessa ja ilmaisimien ominaisuuksien parantuessa sovellusalue on laajentunut myös muun muassa teollisuuteen ja lääketieteeseen. Tämä diplomityö on toteutettu terveysteknologia-alan yrityksen, Imaqen Oy:n tarpeita ja toiveita varten. Tavoitteena oli parantaa ymmärrystä eri lämpökamerateknologioiden ominaisuuksista sekä vertailla näitä keskenään niin teoriassa kuin käytännössä. Lähtökohtana oli toteuttaa mittaus, jossa vertaillaan eri kameroiden kykyä havaita nopeita ilmiöitä sekä määrittää kameroiden kohinatasot. Työn tavoitteena oli edesauttaa yrityksen päätöksentekoa tulevaisuuden laitehankintoja ajatellen. Käytetystä ilmaisinmateriaalista ja –teknologiasta riippuen muun muassa lämpökameroiden spektrivaste, herkkyys sekä vasteaika vaihtelevat. Nämä ominaisuudet vaikuttavat esimerkiksi siihen, millä lämpötila-alueella kameralla pystytään kuvaamaan, kuinka pieniä lämpötilaeroja pystytään erottamaan ja kuinka nopeita ilmiöitä havaitsemaan. Todellinen toiminta paljastuu kuitenkin vasta käytännön testeissä. Teoreettisen tarkastelun lisäksi työssä suoritettiin testit viidelle eri lämpökameralle. Kolme kameroista oli jäähdytettyjä fotojännitekameroita, joiden kohteen lämpötilan mittaus perustuu kohteesta saapuvien fotonien laskemiseen. Lisäksi testattiin kaksi jäähdyttämätöntä mikrobolometria, joiden toiminta perustuu ilmaisinmateriaalin lämpötilan vaihteluun. Tavoitteena oli testata, kuinka hyvin eri kamerat havaitsevat lämpöilmiöitä, jotka ovat nopeimmillaan muutaman millisekunnin mittaisia. Tätä varten rakennettiin testijärjestelmä, jossa lämpölähteen näkymisaikaa kameralle säädettiin pyörivän reikälevyn avulla. Pyörimisnopeutta kasvattamalla saatiin lämpöilmiötä lyhennettyä aina 2,7 millisekuntiin asti. Kameran kohinataso vaikuttaa siihen, kuinka pieniä lämpötilaeroja kameralla pystytään havaitsemaan. Tämän vuoksi jokaiselle kameralle määritettiin sen ominainen kohinataso, jota verrattiin kameravalmistajan ilmoittamaan NETD-arvoon (noise-equivalent temperature difference). Mikrobolometrit eivät sovellu millisekunnin luokkaa olevien lämpöilmiöiden havaitsemiseen niiden pitkän vasteajan vuoksi, joka riippuu materiaalin termisestä aikavakiosta. Fotojännitekameroissa vasteaika on lyhyt, joten ne soveltuvat nopeiden ilmiöiden havaitsemiseen. Tuloksissa havaittiin kuitenkin taajuuksien laskostumista liian matalan kuvanottotaajuuden vuoksi. Tämä voi muodostua rajoittavaksi tekijäksi ilmiönopeuden kasvaessa, jos kameran kuvanottotaajuutta ei pystytä nostamaan. Kohinatasot olivat kaikilla kameroilla valmistajien ilmoittamia arvoja korkeammalla, erityisesti mikrobolometreilla. Ero mikrobolometri- ja fotojännitekameroiden kohinatasojen välillä tekee fotojännitekameroista soveltuvampia pienten lämpötilaerojen havaitsemiseen. Tulosten ja teorian perusteella voidaan todeta, että fotojännitekamerat ovat sekä nopeus- että kohinaominaisuuksiltaan mikrobolometreja parempia. Mikrobolometrien koko sekä kustannukset ovat kuitenkin fotojännitekameroita huomattavasti pienemmät. Tämä voi osoittautua valintakriteeriksi, jos kuvattavan kohteen asettamat vaatimukset täyttyvät. On kuitenkin olemassa myös muita lämpökameroissa käytettyjä ilmaisimia, kuten kvanttikaivoilmaisin, joita ei tämän työn aikana päästy testaamaan. Vaaditaan siis testien toistamista laajemmalla otannalla eri ilmaisinteknologioita, jotta tarkempia johtopäätöksiä parhaasta lämpökamerasta pystytään tekemään. Osa kameran ominaisuuksista vaatii myös kompromissien tekemistä. Täytyy esimerkiksi päättää, onko tärkeämpää kuvausnopeus vai pienten lämpötilaerojen havaitseminen suurella resoluutiolla. Käyttökohde asettaa vaatimukset optimaaliselle kameralle, eikä lämpökameroita voida siis asettaa paremmuusjärjestykseen tietämättä ensin, mitä ollaan kuvaamassa

Calibration of microbolometer infrared cameras for measuring volcanic ash mass loading

Thesis (M.S.) University of Alaska Fairbanks, 2014.Small spacecraft with thermal infrared (TIR) imaging capabilities are needed to detect dangerous levels of volcanic ash that can severely damage jet aircraft engines and must be avoided. Grounding aircraft after a volcanic eruption may cost the airlines millions of dollars per day, while accurate knowledge of volcanic ash density might allow for safely routing aircraft around dangerous levels of volcanic ash. There are currently limited numbers of satellites with TIR imaging capabilities so the elapsed time between revisits can be large, and these instruments can only resolve total mass loading along the line-of-sight. Multiple small satellites could allow for decreased revisit times as well as multiple viewing angles to reveal the three-dimensional structure of the ash cloud through stereoscopic techniques. This paper presents the design and laboratory evaluation of a TIR imaging system that is designed to fit within the resource constraints of a multi-unit CubeSat to detect volcanic ash mass loading. The laboratory prototype of this TIR imaging system uses a commercial off-theshelf (COTS) camera with an uncooled microbolometer sensor, two narrowband filters, a black body source and a custom filter wheel. The infrared imaging system detects the difference in attenuation of volcanic ash at 11 μm and 12 μm by measuring the brightness temperature at each band. The brightness temperature difference method is used to measure the column mass loading. Multi-aspect images and stereoscopic techniques are needed to estimate the mass density from the mass loading, which is the measured mass per unit area. Laboratory measurements are used to characterize the noise level and thermal stability of the sensor. A calibration technique is developed to compensate for sensor temperature drift. The detection threshold of volcanic ash density of this TIR imaging system is found to be from 0.35 mg/m3 to 26 mg/m3 for ash clouds that have thickness of 1 km, while ash cloud densities greater than 2.0 mg/m3 are considered dangerous to aircraft. This analysis demonstrates that a TIR imaging system for determining whether the volcanic ash density is dangerous for aircraft is feasible for multi-unit Cubesat platforms

High-resolution debris cover mapping using UAV-derived thermal imagery: limits and opportunities

Debris-covered glaciers are widespread in high mountain ranges on Earth. However, the dynamic evolution of debris-covered glacier surfaces is not well understood, in part due to difficulties of mapping debris cover thickness in high spatiotemporal resolution. In this study we present land surface temperatures (LST) and its diurnal variability measured from an unpiloted aerial vehicle (UAV) at high spatial resolution. We test two common approaches to derive debris thickness maps by (1) solving a surface energy balance model (SEBM) in conjunction with meteorological reanalysis data and (2) least squares regression of a rational curve using debris thickness field measurements. In addition, we take advantage of the measured diurnal temperature cycle and estimate the rate of change of heat storage within the debris cover. Both approaches resulted in debris thickness estimates with a RMSE of 6 to 8 cm between observed and modelled debris thicknesses, depending on the time of the day. The diurnal variability of the LST controls the relationship between LST and debris thickness and the non-linearity increases with increasing LST. During the warming phase of the debris cover, the LST depends strongly on the terrain aspect, rendering clear-sky morning flights that do not account for aspect-effects problematic. Our sensitivity analysis of various parameters in the SEBM highlights the relevance of the effective thermal conductivity when LST is high. Residual and variable bias of UAV-derived LSTs during a flight require calibration, which we achieve with bare ice surfaces. The model performance would benefit from more accurate LST measurements, which are difficult to achieve with uncooled sensors.</p

Uncooled Microbolometer Imaging Systems for Machine Vision

Over the last 20 years, the cost of uncooled microbolometer-based imaging systems has drastically decreased while performance has increased. In the simplest terms, the figure of merit for these types of thermal detectors is given in terms of the τ-NETD product, the combination of the thermal time constant and the noise equivalent temperature difference. Considering these factors, optimal system design parameters are investigated to maximize visual information content. This dissertation focuses on improving scene information in the longwave infrared (LWIR) spectrum that has had its validity and quality degraded by noise, blur, and reflected radiance. Taken together, noise and blur degrade image quality, directly affecting system performance for object detectors trained with deep learning. Representing noise with NETD and blur in terms of equivalent angular resolution, this research provides a systematic method for relating design parameters to specific machine vision tasks that are difficult to define in a traditional imaging sense. This method provides for a system design approach based on information requirements rather than improvements to machine vision algorithms. As a machine vision function, automated target recognition (ATR) has improved with new technologies and the wide proliferation of infrared staring focal planes. Infrared search and track (IRST), which is target detection and localization at long ranges of unresolved targets, can be performed by both photon counting and microbolometer systems. The transition from broadband system design to one that involves spectral characterizations of components provides a better understanding of the performance and capabilities of new technologies. Unlike reflective bands such as visible and shortwave infrared (SWIR), reflected radiance reduces contrast in the LWIR, resulting in lost information. This research considers the sky path radiance contribution to the radiant exitance of a scene that reduces contrast, and consequently, information. Results show that reduced contrast can be overcome by utilizing multiband spectral imaging systems to remove the reflected component, thus increasing the scene information available. In addition, better scene consistency can be achieved between day and night when reflected radiance is removed. The multiband LWIR system designs presented take advantage of the low τ-NETD of modern microbolometers and demonstrate feasibility in future multiband applications

Multi-wavelength infrared imaging computer systems and applications

This dissertation presents the development of three computer systems for multi-wavelength thermal imaging. Two computer systems were developed for the multi-wavelength imaging pyrometers (M-WIPs) that yield non-contact temperature measurements by remotely sensing the surface of objects with unknown wavelength-dependent emissivity. These M-WIP computer systems represent the state-of-art development in remote temperature measurement system based on the multi-wavelength approach. The dissertation research includes M-WIP computer system integration, software development, performance evaluation, and also applications in monitoring and control of temperature distribution of silicon wafers in a rapid thermal process system. The two M-WIPs are capable of data acquisition, signal processing, system calibration, radiometric measurement, parallel processing and process control. Temperature measurement experiments demonstrated the accuracy of ±1°C against blackbody and ±4°C for colorbody objects. Various algorithms were developed and implemented, including real-time two-point non-uniformity correction, thermal image pseudocoloring, PC to SUN workstation data transfer, automatic IR camera integration time control, and radiometric measurement parallel processing. A third computer system was developed for the demonstration of a 3-color InGaAs FPA which can provide images with information in three different IR wavelength range simultaneously. Numbers of functions were developed to demonstrate and characterize 3-color FPAs, and the system was delivered to be used by the 3-color FPA manufacturer

Application of Thermal and Ultraviolet Sensors in Remote Sensing of Upland Ducks

Detection, mapping, and monitoring of wildlife populations can provide significant insight into the health and trajectory of the ecosystems they rely on. In fact, it was not until recently that the benefits of wetland ecosystems were fully understood. Unfortunately, by that point, the United States had removed more than 50% of its native wetlands. The Prairie Pothole Region in North America is the premier breeding location for ducks; responsible for producing more than 50% of the North American ducks annually. The current survey methods for obtaining duck population counts are accomplished primarily using manned flights with observers manually identifying and counting the ducks below with coordinated ground surveys at a subset of these areas to obtain breeding pair estimates. The current industry standard for in situ assessment of nest locations for reproductive effort estimates is known as the “chain drag method”, a manually intensive ground survey technique. However, recent improvements to small unmanned aerial systems (sUAS), coupled with the increased performance of lightweight sensors provide the potential for an alternative survey method. Our objective for this study was to assess the feasibility of utilizing sUAS based thermal longwave infrared (LWIR) imagery for detecting duck nests and ultraviolet (UV) imagery to classify breeding pairs in the Prairie Pothole Region. Our team deployed a DRS Tamarisk 640 LWIR sensor aboard a DJI Matrice 600 hexa-copter at Ducks Unlimited’s Coteau Ranch in Sheridan County, North Dakota, to obtain the thermal imagery. At the ranch, 24 nests were imaged at two altitudes (40m and 80m) during the early morning (04h00-06h00), morning (06h00-08h00), and midday (11h00-13h00). Three main parameters, namely altitude, time of day, and terrain, were varied between flights and the impact that each had on detection accuracy was examined. Each nest image was min-max normalized and contrast enhanced using a high-pass filter, prior to input into the detection algorithm. We determined that the variable with the highest impact on detection accuracies was altitude. We were able to achieve detection accuracies of 58% and 69% for the 80m and 40m flights, respectively. We also determined that flights in the early morning yielded the highest detection accuracies, which was attributed to the increased contrast between the landscape and the nests after the prairie cooled overnight. Additionally, the detection accuracies were lowest during morning flights when the hens might be off the nests on a recess break from incubation. Therefore, we determined that with increases in spatial resolution, the use of sUAS based thermal imagery is feasible for detecting nests across the prairie and that flights should occur early in the morning while the hens are on the nest, in order to maximize detection potential. To assess the feasibility of classifying breeding duck pairs using UV imagery, our team took a preliminary step in simulating UAS reflectance imagery by collecting 260 scans across nine species of upland ducks with a fixed measurement geometry using an OceanOptic’s spectroradiometer. We established baseline accuracies of 83%, 83%, and 76% for classifying age, sex, and species, respectively, by using a random forest (RF) classifier with simulated panchromatic (250-850nm) image sets. When using imagery at narrow UV bands with the same RF classifier, we were able to increase classification accuracies for age and species by 7%. Therefore, we demonstrated the potential for the use of sUAS based imagery as an alternate method for surveying nesting ducks, as well as potential improvements in age and species classification using UV imagery during breeding pair aerial surveys. Next steps should include efforts to extend these findings to airborne sensing systems, toward eventual operational implementation. Such an approach could alleviate environmental impacts associated with in situ surveys, while increasing the scale (scope and exhaustiveness) of surveys