Integrated VIS-NIR Hyperspectral / Thermal-IR Electro
Contents
1. 550 5 American Institute of Aeronautics and Astronautics aware that the present system includes an additional component the spectrograph ImSpector Also the kind of reference scene must be taken into account 2 Spectral calibration The spectral axis of the detector needs calibration i e determination of the function that maps output image line indexes to frequencies It must determined experimentally and it was done by observing light sources with known emission spectrum Line spectrum mercury argon Hg Ar lamps were adopted Both calibration sources by Oriel and commercial lamps by Philips were used obtaining comparable results When imaging such a kind of light sources single lines in the spectral direction were produced on the focal plane Fig 5 The calibration function Fig 6 was obtained after linear least square fit of experimental data Misow 0 782 ioy 874 3 row where A i ow is the wavelength of the spectral band imaged on the detector line number irow The 576 lines available in the output image determine that the experimental spectral response band of the system is 424 to 873 nm 900 yp 9 Computed spectral calibration function 850b Reference data a al i Q E Experimental wil 800 L gt S Theoretical M 3 7 Loo 4 3 750 A c S el oO x 700 fa i lt 8 5 4 4 5 650 4 2 5 3 E 5 4f 600 4 3 550 gf J 2 a T 500 2r2. it offers great flexibility in managing different kind of data there exist COTS systems which can be adopted without need of customization After a preliminary analysis of typical operating conditions it has resulted that the cameras output flows at high data rate from tens of kB s to tens of MB s Hence to guarantee adequate real time downlink capability attention has been focused on existing COTS systems capable high data rate and compatible with installation on Figure 10 AC 5124 developer kit and transceiver compact mobile platforms The search was carried out among products available on the market during year 2004 Two different solutions were identified radio modem transceivers operating up 880kbps and PC radiolan devices capable of more than 10Mbps The former ones have been preferred because can guarantee link operating ranges in the order of thousand meters whilst compact radiolan mobile units performance is at least one order of magnitude lower The requirement on link operation range has been considered definitely dominant with respect to maximum data rate When full data stream is larger than channel capacity partial download is adopted and data are pre processed on board Solutions can be represented by image resolution degradation or data compression The selected device is the AC5124 transceiver by Aerocomm Fig 10 It operates at 2 4 GHz and adopts the Frequency Hopping Spread Spectrum FHSS transmission tec
3. 11 cycles mrad Fig 4 the EIFOV results to be 4 54 mrad 0 26 while the IFOV is equal to 2 42 mrad 0 14 for the considered sensor configuration The same test facility has been exploited to assess sensor resolution by displaying pairs of 1 pixel thick lines at various separations along the direction of the spatial axis of the sensor This could be done because 1 pixel separation corresponds to about 1 5 of IFOV of the sensor in the arranged test bed Sensor output images have been resampled in along the spatial axis direction and then examined accurately A resolution of 5 3 mrad 0 30 has been estimated being this one the minimum separation between lines in the reference scene that appear distinct in all of the output bands according the criterion of 3 dB drop of the instrument response 15 However closer line pairs can still be distinguished but i only in part of the sensor output spectral bands ii until the separation is not smaller 100 200 300 400 500 600 700 than 2 3 mrad 0 15 Spatial axis pixels X Figure 5 VNIR hyperspectral sensor output image when When considering these results worse than those expected for a classical EO device consisting of observing the Lot Oriel Hg Ar reference source RT superimposed pixel intensity profile diffraction limited optics amp detector one must be Spectral axis pixels A A S wo ie De gt a Q oa Q oa Oo a a Oo O O D O O O O O a Q o
4. S S Wegener First Response Experiment FIRE Using An Uninhabited Aerial Vehicle UAV Proc of Fifth International Airborne Remote Sensing Conference San Francisco 17 20 September 2001 9 pp J A Brass V Ambrosia J D Ricker jr and A C Roberts Forest Firefighting from Real Time Airborne Infrared Remote Sensing Proc of Fifth International Airborne Remote Sensing Conference San Francisco 17 20 September 2001 pp 21 A Barducci D Guzzi P Marcoionni and I Pippi Infrared detection of active fires and burnt areas theory and observations Infrared Physics amp Technology Vol 43 2002 pp 119 125 IG Rufino and A Moccia UAV Remote Sensing Payload for Natural Disasters Monitoring Proc 28 Conference of the Italian Association of Aeronautics and Astronautics Volterra Italy 19 22 September 2005 10 pp Olp Shippert Why Use Hyperspectral Imagery PERS Vol 70 No 4 2004 pp 377 380 Indigo system Corporation Omega Camera User Manual doc no 412 0006 10 v 110 2002 Specim ImSpector user manual v 2 21 2003 G D Boreman Modulation Transfer Function In Optical and Electro Optical Systems SPIE Press Bellingham USA 1 No Gf CI D Accardo F Esposito and A Moccia Low cost Avionics for Autonomous Navigation Software Hardware Testing Proc IEEE Aeroconf 2004 Vol 5 2004 pp 3016 3024 IG C Holst Electro Optical Imaging System Performance
5. SPIE Press Bellingham USA 2000 lSony Corporation XC ST70 70CE User s Guide v 1 0 1999 Aerocomm inc AC5124 2 4 GHz OEM Transceiver User Manual v 4 4 2003 9 American Institute of Aeronautics and Astronautics
6. amp lens 590 g and light weight sealed unit tolerating high Dimensions 44x29x65 176 mm temperature humidity physical shock and including ImSpector amp lens camera body ImSpector amp lens Vibrations 12 It is a passive component that does not require electrical power to operate A standard objective is installed at the ImSpector p P entrance aperture to manage FOV size and focus Main specifications of the adopted components ImSpector and b w camera are in 2 The same table and table 3 report the features resulting for the assembled hyperspectral systems The camera is a COTS b w device with standard PAL analog output and shutter time adjustable by means of dip switches on camera rear panel The only remote control usable is a TTL trigger signal to control single image acquisition Activities related to this instrument have dealt with its characterization i e imaging performance assessment and calibration A specific laboratory facility has been arranged to this purpose in which the sensor is installed on Figure 3 Laboratory facility for calibration of the VNIR hyperspectral sensor 4 American Institute of Aeronautics and Astronautics T T TI T Experimental data an optical bench and test scenes are supplied to it by Theoretical Detector MTF sampling amp footprint displaying them on a LCD computer screen Fig 3 Theoretical Diffraction limited Optics MTF y Speen 8 E 1 ERR x J A
7. the acquisition of the electro optical sensors of Regione Campania that supported the development of the digital communication system for an unmanned platform and of the Ministry of Education University and Research All of the projects are co funded by the Department of Space Science and Engineering of the University of Naples Federico IT References P J Riggan J W Hoffman and J A Brass Estimating Fire Properties by Remote Sensing Proc of IEEE Aerospace Conference 2000 Big Sky USA pp 173 179 D A Roberts and P E Dennison Hyperspectral technologies for wildfire fuel mapping Proc 4th Int Worshop Rem Sens amp GIS to Forest Fire Management 2003 10 pp 3J Verbesselt S Fleck and P Coppin Estimation of fuel moisture content towards Fire Risk Assessment A review in Forest Fire Research amp Wildland Fire Safety edited by Viegas Millpress Rotterdam The Netherlands 2002 11 pp 4N El Sheimy and B Wright Real time Airborne Mapping System for Forest Fire Fighting F3 System PERS Vol 70 2004 pp 381 383 V G Ambrosia S S Wegener D V Sullivan S W Buechel S E Dunagan J A Brass J Stoneburner and S M Schoenung Demonstrating UAV Acquired Real Time Thermal Data over Fires PERS Vol 69 No 4 2004 pp 391 402 J A Brass V G Ambrosia R S Dann R G Higgins E A Hildum J McIntire P J Riggan S M Schoenung R E Slye D V Sullivan S Tolley R Vogler
8. A o Zz 450 4 1 i J 400 J L it L L i L L L L 0 L tA t f ii i L 1 50 100 150 200 250 300 350 400 450 500 55 400 450 500 550 600 650 700 750 800 850 900 Image line Wavelength nm Figure 6 VNIR hyperspectral sensor spectral Figure 7 VNIR hyperspectral sensor calibration function reference data from several lamps radiometric calibration function 3 Radiometric calibration Finally relative radiometric calibration was carried out to produce the function that compensates for non uniform sensitivity at different wavelengths It was generated by observing a light source with known spectral emission and comparing the output spectral profile to the input one The corresponding ratio is the searched function Since neither the absolute radiance emitted by the lamp toward the sensor nor the collected one could be determined only the relative radiometric calibration function F 1 has been computed i e it has been normalized by referring it to the unknown radiance level at the first spectral interval that is observed f L i ow LGrowo g 4 cal rr i Do Vpix G row V pix i rowo where irowo is the line index of the first spectral band L iirow is the reference radiance in the sensor spectral band no irow and Vpix irow is the intensity of pixel no i oy In this case a tungsten filament lamp was used as reference source and it was modeled as a black body radiator Figure 7 plots the computed spectral calibration function com
9. Infotech Aerospace AIAA 2005 7009 26 29 September 2005 Arlington Virginia Integrated VIS NIR Hyperspectral Thermal IR Electro Optical Payload System for a Mini UAV Giancarlo Rufino and Antonio Moccia University of Naples Federico II Napoli I 80125 Italy This paper presents the development of a modern electro optical payload system for remote sensing from a mini UAV It is aimed at applications of natural disasters monitoring in particular forest fires Both the sensor and the mini UAV platform are being developed at the Dept of Space Science and Engineering DISIS of the University of Naples Federico II The core of the system is an integrated multi band sensor that includes a thermal imager and a hyperspectral sensor in VNIR band Instrument characterization laboratory tests and payload architecture are discussed I Introduction Remote Sensing RS for monitoring and management of natural disasters is of great interest currently and increasing attention is being gained by forest fires because of their frequent occurrence and the relevance of the damage they cause There exists several studies dealing with applications of RS to detect forest fires and to monitor them for suppression and damage mitigation 1 2 3 as well as experiments have been carried out for technology demonstration 4 5 Both aeronautical and satellite platforms have been considered showing relevant performance and limitations The latter on
10. ccurate relative positioning of the sensors with respect to the reference scene i e the LCD screen is operated via optical table accessories for translation and rotation The whole facility is based on COTS components 7 1 Imaging Performance To assess imaging performance the sensor Modulation Transfer Function MTF i e the system response to sinusoidal input radiance has been evaluated along the spatial axis It has been J computed experimentally in the laboratory test facility following the procedure described by i i Boreman 13 that is based on the direct 2 pee o1 one oe oes measurement of the system Contrast Transfer Frequency cycles mrad y 4 Figure 4 Experimental MTF of the hyperspectral VNIR Function CTF the response to square wave input radiance The MTF was computed as sensor 0 8 F 0 6 Nyquist Frequency MTF Detector 0 4 1 0 2 Frequency 1 2 EIFOV 0 1 MTO CTF Ta 1n rf where amp is the spatial frequency of the input radiance The input square wave radiance was supplied to the sensor by showing black and white bar patterns with different periods on the LCD display Figure 4 shows the obtained MTF at the imaged maximum emission wavelength 540 nm The Effective IFOV EIFOV was evaluated on the basis of the frequency n at which the MTF drops to 50 of its maximum value as 15 1 EIFOV 2 1 2 Since it is n 0
11. ction update output image freezing output of reference images and reading of camera status camera internal temperature general settings link test B VNIR Hyperspectral Sensor The hyperspectral system configuration envisages coupling a b w camera equipped with a two dimensional detector to an imaging spectrograph the ImSpector by Specim 12 This produces an instrument capable of observing a one dimensional scene and of analysing the spectrum of the collected energy form each resolution element of the scene in a single acquisition Conventional spectrometers measure the spectrum of the radiance acquired Figure 2 Imspector spectrograph functional scheme from 12 from a single scene element Target Objective 3 American Institute of Aeronautics and Astronautics Table 2 Hyperspectral sensor components main spectral specifications scanning the spectrum in Model Specim ImSpector V9 narrow wavelength bands if i E Spectral response Band nm 430 900 based on one detector or 5 b Spectral Resolution nm 2 7 acquiring g spectral D Teror i a Slit size um o dimensional array of Focal plane image size um 9900 x 4350 detectors Then acquisition Model Camera Sony XC ST70 CE of extended scenes requires 5 Detector Sony ICX 423 AL mechanical scanning Spectral response Band nm 400 1000 Differently in this case the gt Pixel size um 11 6 x 11 2 imagi
12. es in particular can be pointed out after considering the main issues of an ideal system for monitoring forest fires to the aim of suppression and damage mitigation 6 ability to detect fire in its early stage and to distinguish the associated degree of danger day and night operation capability detection of fire location extension as well as propagation direction in relation to topography and forest resources vegetation and fuels Additional desirable features are long observation time ability to follow the whole duration of the event and real time transmission of the acquired data to users i e fire management personnel in format that allows for immediate exploitation by disaster management operators rather than RS application specialists Because of these requirements satellite based systems that showed adequate measurement performance in several experiments and that were limited only in resolution in some cases have poor performance in terms of coverage ability 7 8 The latter one in fact is restricted both in space and time because it is constrained by orbit ground track repetitivity typically in the order of days or even weeks for medium high resolution RS systems performing global coverage Hence such systems are often not available for observation at site and time of a fire event and almost certainly they cannot follow fire evolution but just offer a single survey of it neither platform passes over the area of interest can be adju
13. hnique 17 which allows for RF data rate up to 882kbps and line of sight operational range in the order of 3 5 km with 200 mW transmitted power The device can be easily connected to a CPU via standard pc ports thanks to its TTL serial interface The Developer Kit optional unit supplies serial RS 232 RS 422 and USB standard connections Further features of the system are in table 4 Two identical units are used one connected to the on board CPU and one to the ground station computer Also an analog video transmitter 200mW at 2 4 GHz has been envisaged to be used as an alternative to the digital channel It is particularly interesting for its compactness 38x20x5 mm Fig 11 and low power consumption lt 2W Figure 11 Analog video signal transmitter C Ground Station The ground station is being developed with specific reference to the tasks of the digital communication system ground terminal It consists of a transportable high performance personal computer connected to the ground transceiver RS 232 RS 422 485 and USB ports are available The unit is also equipped with interfaces to acquire the output of generic EO sensors i e a Camera Link frame grabber and a four channel analog one making tests of any payload unit possible before flight Also two IEEE 1394 firewire ports are available It is worth noting that the presence of the analog frame grabber allows this system to be used as ground station also for the a
14. nalog transmission system In fact in this case the analog video signal demodulated by the radio receiver can be acquired via the analog frame grabber and then digitalized stored and processed Maintenance free batteries were chosen as power source for use during outdoor test campaigns Two 12 Vdc 40 Ah units are connected in series to supply the CPU with the required 24 Vdc power Lower voltages are derived by means of dc dc converters to power radio receivers and other devices Gel electrolyte based batteries were selected because offering trouble free transportation Considering worst case overall power consumption of 500W 20 8A at 24 Vdc autonomy of nearly 2 hours is guaranteed 8 American Institute of Aeronautics and Astronautics IV Conclusion A modern multi band hyper spectral payload of electro optical sensors has been presented in this paper Its has been conceived to be operated from a UAV in missions aimed at natural disasters monitoring in particular forest fires The core of the payload described in detail in the paper is an integrated sensor including a thermal imager and a VNIR hyperspectral camera Analysis of sensors performance and configuration of the payload have been described including its CPU and communications subsystems Acknowledgments The activities described above are being carried out under the sponsorship of Centro Regionale di Competenza Analisi e Monitoraggio del Rischio Ambientale that supported
15. ng spectrograph roa Number of pixels 752 x 582 captures a line image and Sensing area size um 8720 x 6520 disperses it to its spectrum Spectral response band nm 430 900 in _the direction g Q Spectral resolution nm 2 7 perpendicular to the line 8x amp 5 _Number of bands 174 image Fig 2 Hence it zeoDE Size um pixels 8720 x 4350 752x390 Converts a matrix camera to 5 9 5 o Usable image a one dimensional spectral zm g2 Total pixels eo imaging system The rows T n Number of required Spatial xX spectral 752 x LA of each acquired frame samples Total pixels 1 47x10 contain images of the same line of targets but at Table 3 Hyperspectral system main specifications different wavelengths As a result a high Detector CCD number of close spectral samples is acquired Frame rate Up to 25 Hz producing a hyperspectral sensor The size of Electronic shutter 1 120 1 10000 s the imaged scene is determined by the width of Focal length 4 8 mm the entrance aperture of the spectrograph a FOV IFOV 85 x 0 30 0 14 x 0 30 narrow slit and by the shortest one between the Output Analog standard PAL length of the slit and camera detector row The Operatin conditions 7 patented dispersion technique implemented in ee ee 5 45 C up to 95 Specim Imspector operates axially so that Power consumption 21W aberrations reduce to the utmost It is based on a Mass gelatinous component resulting in a compact including ImSpector
16. ound station A pcl04 unit Figure 8 DISIS mini UAV aircraft Figure 9 Payload dedicated on board computer has been selected and it has _ Table 4 main characteristics of the on board auxiliary subsystems been equipped with a frame DISIS mini UAV mission grabber to acquire the output of the two sensor a power CPU conditioning unit to generate stable electrical voltage for Frame grabber s cameras and transceiver and a Power power relay module to switch Mass payload units on or off as needed for minimum power consumption Fig 9 With reference to communications a digital link has been envisaged because it can be efficiently integrated both on board and at the ground station since at both AMPRO pc 104 format 400MHz Celeron 256MB RAM RS 232 422 485 LAN and USB1 1 ports compact flash 2 5 hhd 4 ch mux analog frame grabber lt 15 W lt 0 2 kg RF communication Frequency Transmission technique Transmitted power RF data rate Sensitivity Operating conditions Power consumption Mass Dimensions Aerocomm AC 5124 transceiver 77 non interfering channels in 2 402 2 478 GHz FHSS 200 mW Up to 882 kbps 90 dBm 40 80 C lt 90 humidity non condensing 0 95 1 4 2 4 W 25 50 100 Tx 0 55 W 100 Rx 0 22 W interface On RF Off lt 20g 42x68x5 mm 7 American Institute of Aeronautics and Astronautics locations digital CPUs are in use
17. pared to the reciprocal of the detector spectral response 16 6 American Institute of Aeronautics and Astronautics HI Platform and Auxiliary Systems A Mini UAV Platform The mini UAV under development at DISIS is based on a RC model a reproduction of the Dornier DO27 by VMAR Fig 8 Its wingspan is 2 75m and its length is 1 7m It is equipped with a 28cc engine It offers wide regular volumes in the front and central part of the fuselage for installing avionics and payload Currently the avionics system installed for navigation experiments consists of an INS GPS integrated system 14 It includes an embedded computer a Pentium based pc104 unit by Ampro running the real time operating system WxWorks that gathers and processes the output of a strapdown inertial measurement unit by Crossbow and a GPS receiver by Trimble The navigation functionalities are of great importance because they allow for spatial referentiation of the observed scene B On Board Auxiliary Sub Systems of the Payload The core of the RS payload is represented by the two EO sensors described in the previous section It also includes a computer for operation management and a radio communication system for data downlink and command uplink Their main characteristics are in table 4 The task of the on board computer is control of sensor operation storage and real time elaboration of remotely sensed data and management of communications with the gr
18. pectral sensor were chosen because they are compatible with the available on board resources and they allow for the desired mission objectives at least at basic level Indeed they offer the ability to identify hot spots and to observe equivalent radiant temperature distribution on the ground along with characterization of surface coverage thanks to the ThIR camera and VNIR hyperspectral camera respectively 2 American Institute of Aeronautics and Astronautics The system has been conceived for pushbroom operation sensor are installed on board to observe downwards along the flight nadir direction and subsequent areas along the ground track are observed thanks to platform movement The ThIR camera is based on a two dimensional arrays of detectors so that various targets along the across track direction are imaged simultaneously and at the same time a number of lines of targets equal to the number of pixel rows of the detector Differently as described in detail in the following the hyperspectral sensor observe only one line of scene per acquisition since the rows of its detector again a two dimensional array of detectors is exploited for spectral analysis of the scene A Thermal Camera Figure 1 Indigo OMEGA thermal The adopted ThIR camera is the Indigo Omega now FLIR A10 camera after acquisition of Indigo by Flir Systems in 2004 Fig 1 Its spectral Table 1 Th l i ificati 11 wspone le da he TAFDINEI able ermal came
19. puters running software logic for autonomous flight and payload operation control are suitable for installation on board of UAVs that typically have limited availability of resources Also Staff scientist Department of Space Science and Engineering Piazzale Tecchio 80 Napoli t Full professor Department of Space Science and Engineering Piazzale Tecchio 80 Napoli AIAA Member 1 American Institute of Aeronautics and Astronautics Copyright 2005 by the American Institute of Aeronautics and Astronautics Inc All rights reserved materials progress allows now for platforms in which significant volume and mass can be devoted to payload and auxiliary subsystems Finally for the specific objective of a fire monitoring RS mission unmanned vehicles offer the important feature of not endangering a human crew during risky missions as flights over areas interested by fires permitting close surveys to achieve detailed observation that could not be attempted with a manned vehicle The Laboratory of Guidance Navigation and Control GNC Lab of the Department of Space Science and Engineering DISIS of the University of Naples Federico IY Italy is carrying out a series of projects dealing with the above research topics First of all DISIS takes part in a project of the Centro Regionale di Competenza Analisi e Monitoraggio del Rischio Ambientale CRdC AMRA a recently founded institution for coordination of regional hi tech laborato
20. ra main specifications 11 wavelength range of the spectrum Detector Un coola ne oll 7 5 13 pm and it is based on an Vanadium Oxide VOx technology advanced detector a microbolometer in Spectral response band 7 5 13 ym Vanadium Oxide VOx technology that Resolution 160x120 pixels does not need focal plane cooling The Noise Equivalent Temperature lt 80 mK latter feature turns into a great advantage difference NedT for power consumption and Frame rate Up to 25 Hz compactness which are definitely Calibration source Internal outstanding for this instrument see 1 Thermal stabilisation Not needed Omega resolution is 160x120 pixels _Cooling Conduction to camera bottom The camera has an internal reference for poy FOV 40 x 30 deg square 0 27 deg compensation of non uniform detector 11mm focal length sensitivity flat field correction without Output Analog standard PAL temperature reference The output signal Operating conditions 0 40 C umidity up to 95 is a standard analog black amp white b w Power consumption lt 15W PAL video generating 25 frames per Mass lt 1208 second Camera remote control is j 35 x 37 x 50 30 mm possible via a dedicated RS 232 I O Dimensions camera body lens channel allowing for command input on off of auto adjust function of brightness and contrast selection of one of two temperature ranges up to 150 C and up to 500 C flat field corre
21. rest in navigation and flight control autonomous functionalities 14 These latter activities have been supported by the Ministry for Education University and Research MIUR and in part they have been carried out in co operation with the Italian Aerospace Research Centre CIRA In this paper the EO payload for the mini UAV platform and the relevant activity are described including instrument characterization on board integration and development of auxiliary on board systems for sensor operation control Preliminary results are presented II Payload System Several studies have been published dealing with the topic of RS for forest fires risk detection and monitoring that describe techniques for fire properties estimation by collecting the upwelling radiance in the optical bands of the spectrum from VIS to Thermal InfraRed ThIR 1 2 3 In fact to carry out forest fires suppression and damage mitigation efficiently besides the capability of fire detection and determination of its size and position on the ground it is desirable to foresee fire evolution Models have been developed that require to distinguish temperature distribution in the active fire areas and in burnt ones as well as to ascertain the kind of vegetation in adjacent areas if present which could represent fuels for fire evolution The latter issue can be effectively exploited also at the stage of prevention by mapping fire risk probability in areas of interest The above req
22. ries carrying out activities in the field of environmental risk monitoring and for technology transfer to practical applications The project objective is the development of a cutting edge RS system for compact aeronautical platforms aimed at monitoring forest fires natural disasters In the framework of this project DISIS is in charge of the development of an integrated multi hyper spectral EO sensor 9 It is based on four Electro Optical EO instruments a thermal camera a 3 band multispectral camera operating in the visible VIS spectrum two hyperspectral sensors operating in the Visible Near InfraRed VNIR and in the Near InfraRed NIR band All of these instruments are COTS devices or they have been realized by assembling COTS components as in he case of the hyperspectral sensors Another activity in progress at DISIS is supported by Regione Campania the local regional administration institution within its plan for sustaining scientific research It is centered on the development of the digital communication system dedicated to the RS EO payload of a compact UAV for environment monitoring applications Also a co operation with the ISAFoM institute of the National Research Council CNR is in progress to fly the above sensors on board a two seat general aviation light aircraft ERA SkyArrow already equipped with instruments to study ground atmosphere interaction phenomena Finally DISIS is developing a mini UAV platform with particular inte
23. sted for the peculiar extension and evolution of the fire under observation On the other hand airborne platforms offer plenty of interesting capabilities for this application timely observation limited only by ground base distance from the area of the event and availability of operational units survey flight trajectory not fixed a priori but adaptable to the case and in particular flight altitude modifiable to satisfy resolution and instantaneous coverage requirements flight duration that can be extended and flights that can be repeated as needed Finally also issues concerning distribution of acquired data is in favor of aeronautical platforms In fact for typical satellite RS systems download of acquired data is not continuous but subdue to ground station links that can operate only during limited fractions of orbits Differently data can be transmitted from an airplane in real time by exploiting high capacity channel radio links to a ground station or satellite communications Then data distribution to users community can be accomplished by means of existing networks even the internet 6 Recent technology progress has made possible to base the above applications on UAV platforms 4 5 First modern electronics also Commercial Off The Shelf COTS components is characterized by high performance in spite of reduced size mass and power consumption so that even complex integrated systems RS sensors on board avionics and MEMS devices com
24. uirements turn into EO sensors specifications With reference to spectral bands in order to evaluate surface and fire temperature and characteristics both of active fire and burnt surface the Thermal InfraRed ThIR band and the NIR one are to be preferred because the feature of interest are dominant in those spectrum region and especially for NIR band slightly affected by fire gaseous emissions 1 In addition VIS and VNIR observation allow for evaluation of indicators of surface vegetation and potential fuels characteristics Vegetation Indexes VIs Fuel Mosture Content FMC Water Index WI etc that are useful to evaluate local fire risk 2 3 To carry out these estimations multiple measures in distinct bands preferably narrow are necessary hence multispectral and hyperspectral sensors and integrated sensor suites represent the most interesting solution 2 10 The payload of integrated EO sensors that DISIS is setting up in the framework of the CRdC AMRA well suits the above objectives in particular thanks to the two hyperspectral sensors A subset of the CRdC AMRA sensors mentioned in the previous section has been selected to be installed in the mini UAV under development at DISIS The objective is the realization of a compact UAV platform capable of autonomous operation in missions for fire risk monitoring The selection was imposed by the limited volume and mass for the payload available on board The thermal camera and the VNIR hypers
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