The infrared signature modelling of rocket plumes is a challenging problem involving rocket geometry, propellant composition, combustion modelling, trajectory calculations, fluid mechanics, atmosphere modelling, calculation of gas and particles radiative properties and of radiative transfer through the atmosphere. This paper presents ONERA simulation tools chained together to achieve infrared signature prediction, and the comparison of the estimated and measured signatures of an in-flight rocket plume. We consider the case of a solid rocket motor with aluminized propellant, the Black Brant sounding rocket. The calculation case reproduces the conditions of an experimental rocket launch, performed at White Sands in 1997, for which we obtained high quality infrared signature data sets from DRDC Valcartier. The jet plume is calculated using an in-house CFD software called CEDRE. The plume infrared signature is then computed on the spectral interval 1900-5000 cm-1 with a step of 5 cm-1. The models and their hypotheses are presented and discussed. Then the resulting plume properties, radiance and spectra are detailed. Finally, the estimated infrared signature is compared with the spectral imaging measurements. The discrepancies are analyzed and discussed.

A computationally efficient methodology based on computational fluid dynamics (CFD) has been developed to predict the flow field and infrared signatures of rocket motor plumes. Because of the extreme environment in the plume and the difficulties in taking measurements of motors in flight, it has been partially validated with temporally- and spatially resolved imaging spectrometer data from the static firings of small flight-weight motors using a non-aluminized composite propellant. Axisymmetric simulations were carried out for a variety of motor burn time, flight velocity, altitude, and modeling parameters to establish their effects on the results. By extrapolating the axisymmetric CFD output into three dimensions, images of the rocket plume as seen by an infrared sensor outside the computational domain were also created. The CFD methodology correctly predicted the afterburning zone downstream of the nozzle, and good agreement for its location was obtained with the imaging spectrometer data. It also showed that flight velocity and altitude have substantial effects on the size, shape, and infrared emissions of the plume. Smaller effects on plume properties were predicted for different motor burn times, but indicated that more experimental data of greater temporal and spatial resolution of single static firings are required to better validate the CFD plume prediction methodology.

Complex domain calibration is an efficient method to correct the amplitude and phase of a spectrum obtained from a Fourier transform spectrometer. This method is, however, not directly applicable in the occurrence of a zero path difference (ZPD) shift between a scene interferogram and calibration blackbody interferograms. This situation is likely to happen for a system with thermal instabilities. It is found that a ZPD shift smaller than 1 sampling point can cause a large disagreement between the spectra evaluated from the two interferometer sweep directions. We have developed an algorithm for a complex calibration in the presence of ZPD shifts. The restricting aspect of the real-time capability is taken into account.

Military targets such as aircrafts and flares do not exhibit unique infrared signatures; their emissions are dominated by combustion products (mostly water vapor, carbon dioxide and hydrogen chloride) and hot metal greybody emissions. An algorithm has thus been developed to categorize target signatures based on their emission source components. The signatures are then partitioned, based on their emission components, into groups of similar emission characteristics. Using previous trial data, seven unique flare categories were defined. A second algorithm was finally developed to exploit this signature description and interrogate individual field measurements for target detection and categorization.

The Defence Research and Development Canada Agency has successfully completed a Technology Demonstration Program to assess the military utility of airborne hyperspectral Imagery. This required developing a sensor, the Airborne Infrared Imaging Spectrometer (AIRIS), and collecting in-flight imagery data. AIRIS was designed as a flexible instrument using a Fourier Transform spectrometer with a spectral resolution ranging from 1 to 16 cm−1, wide spectral coverage (2 to 12 microns), and different optical configurations. This paper provides a description of AIRIS and discusses examples of the spectral images collected during one air-trial. Emphasis is put on images of sub-pixel targets. Processing AIRIS data is labor intensive and can only be performed during post-trial analysis. Hardware and software modifications to AIRIS will implement a real-time processing capability over the next three years. These modifications will enable the instrument to output radiometrically calibrated digital spectrograms. These spectrograms will then be processed in real-time to output target detection and identification for selected target types.

In June 2005, a newly develop long wave Focal Pane Array (FPA), based on photo-voltaic technology was delivered to the Defense Research & Development of Canada (DRDC). This development was part of technological Demonstration program that was founded by the DRDC. This paper will describe the FPA configuration along with its performance assessment configured in the Air PIRATE FTIR spectrometer. Air PIRATE is an airborne version of the hyper spectral spectrometer used by the Canadian Defense for target identification, as well as chemical agent identification.

A new experiment has been conducted with a composite propellant rocket motor in order to get two kinds of information: first one is concerning the physical and optical properties of aluminates particles that are emitted in the plume exhaust; second one is concerning the spectral and spatial repartition of radiance in the plume infrared images.The size distribution and the optical properties of particles are used as entry data for flowfield computation, whereas infrared spectra and images are used to evaluate the capacities of the simulation tools to produce infrared signature data.

The Defence Research and Development Canada (DRDC) Agency has successfully completed a Technical Demonstration Program (TDP) to assess the "Military Utility of Airborne Hyperspectral Imagery ". This required developing a sensor, the airborne infrared imaging spectrometer (AIRIS), and collecting in-flight imagery data. The AIRIS instrument was designed with flexibility and modularity in mind, allowing the study of a wide range of applications. AIRIS simultaneously operates two 8times8 element detector arrays to cover the 2.0 to 12 micron region of the electromagnetic spectrum. It also simultaneously collects broadband video imagery from the visible to the long wave IR. AIRIS was mounted in National Research Council's (NRC) Convair 580 aircraft. A series of three data collection flight tests were conducted in the summer of 2005. The first test collected phenomenological data over rural, suburban and urban areas. The second test used several targets of different types. The last flight collected phenomenological data over the Atlantic ocean. Data analysis showed that sub-pixel targets can be detected and identified from their spectral features. Over the next three years, a real-time processing capability will be added to AIRIS, making its data directly exploitable for Canadian Forces applications

Abstract : The Defense Research and Development Canada (DRDC) has embarked on a Technical Demonstration Program (TDP) to develop an airborne Hyperspectral Imaging System (HSI). This instrument is mounted in a Convair 580 turbo propeller driven aircraft and covers the 1.6 to 12 micron region of the electromagnetic spectrum. The spatial sampling of this system is determined by an 8x8 element detector array. Two arrays are operated simultaneously to cover the entire spectral region (InSb technology to cover 1.6 to 5.3 um region and HgCdTe technology to cover 2.5 to 12 um region). The spectral sampling is generated using a Fourier Transform spectrometer with a spectral resolution ranging from 1 to 16 cm- 1. The frame rate of the system is variable (minimum of 16 Hz at 4 cm-1 spectral resolution). The instantaneous field-of-view (IFOV) of the instrument can be changed from 1.1 to 3.3 mrad, by interchanging collection telescopes (9x or 3x). The total field-of-view (TFOV) of this HSI is therefore small (8xIFOV) but may be pointed over a field-of-regard (FOR) 8 time that of the TFOV. In addition, Wide-FOV broadband cameras, operating in the visible, mid-wave and long-wave infrared bands, are used to register the entire FOR. An GPS/INS system is used to guide the pointing of the imaging spectrometer module. This instrument is essentially nadir looking and is based on the Ground-to-Air spectral imaging system (PIRATE) developed at DRDC Valcartier. The PIRATE system has been used to measure the 2-5 micron region with similar spatial and spectral resolutions as the airborne system. This project has completed the three-year system design and construction phase and is in the process of field testing (up to four distinct scenarios) to evaluate its performance and begin assessing the Military Utility of Airborne Hyperspectral Imagery . This paper will describe the instrumentation and present selected preliminary results.

An hyperspectral imager capable of sensing from 1 to 12 micrometers with three (3) possible field-of-views (FOV) steerable within a field-of-regard eight (8) times larger than the FOV is presented. This level of flexibility imposes several constraints on the front-end optics especially when the maximum etendue of the spectrometer must be maintained for all configurations. This paper presents the design approach and trade-offs leading to a high performance optical design. Other constraints such as mass and volume are also considered. An important limiting factor is the size of the window and its minimum distance to the primary mirror of the telescope. The design has been optimized by re-imaging the aperture stop on each component that are critical in size: the interferometer corner cubes, the steering mirror and the primary mirror of the telescope. A set of two (2) telescopes and two (2) afocal relays are interchanged to produce 3 FOVs with optimized etendue and minimum size on critical components.

The Defense Research Establishment Valcartier (DREV) in Canada, has recently embarked on a program to develop an Infrared Imaging Spectrometer system (DIRIS); a device which combines the properties of a radiometer, a thermal imager, and a spectrometer to permit the simultaneous registration of a target's: infrared intensity, the spatial distribution of its radiation, the spectral distribution of this energy, and its temporal behavior.Conceptually, given the present level of technology, the development of an Imaging Spectrometer system can follow one of two routes. Either one starts with a thermal imager thigh spatial resolution and adds spectral discrimination capability, or one starts with a spectrometer thigh spectral resolution and adds spatial discrimination. Both approaches are valid, with the mast appropriate being dictated by the applications' requirements and implementation hardware constraints. For our work we have chosen the latter approach; moderately high spectral resolution maximum 1 cm(-1) combined with relatively low spatial partitioning (8x8 grid).Our instrument couples existing discrete element InSb detector focal plane, and FTS technologies, to produce a novel capability for the measurement of infrared emissions from distant targets. This is a high technology based system incorporating: fast microcomputers to handle the vast quantities of raw data generated, specialized IR detector focal, plane arrays capable of working in conjunction with Fourier Transform modules, and an optical design and graphical user interface optimized for easy in-field operation.

Design considerations and experimental measurements from an imaging Fourier transform spectrometer are presented. The system is based on the Bomem MB-series of Fourier transform interferometer and is capable of more than 8 frames/second at 4 cm(superscript -1 apodized spectral resolution. The interferometer features dual output beams, allowing for example, the coverage of two different spectral ranges using a short-wave array and a long- wave array. The present system uses a set of two 8 X 8 InSb detector arrays to cover the 2 to 5.3 micrometers spectral range on two coaligned fields of view of 4 mrad X 4 mrad and 1 mrad X 1 mrad. Predicted noise equivalent spectral radiance as well as instrument lineshape are compared to measurements on the actual system. Particular emphasis is devoted to the behavior of the instrument lineshape with respect to off-axis position in the focal plane.

The Electro-Optics division at the Defense Research Establishment Valcartier (DREV) has recently embarked on a program to develop an infrared imaging spectrometer system, a device which combines the properties of a radiometer, a thermal imager, and a spectrometer to permit the simultaneous registration of the following attributes of a distant emission source: its infrared intensity, the spatial distribution of its radiation, the spectral distribution of its energy, and its temporal behavior. The DREV instrument couples existing detector and interferometric technologies to produce a novel capability for the measurement of emissions from distant targets. This is a high-technology-based system incorporating: fast microcomputers to handle, in real-time, the vast quantities of raw data generated; specialized IR detector focal plane arrays capable of working in conjunction with spectral measurement modules; and sophisticated algorithms for processing of the spatially resolved spectral information, and for its presentation in a simple and meaningful form.

The structure of 8-oxabicyclo[3.2.1]octane was calculated by abinitio means at the STO-3G level, and the structural data used to assign the microwave spectrum of the title compound in the range of 26.5 to 40 GHz fitting 144 lines up to J = 48 by adjusting the rotational and three centrifugal distortion constants in the Watson A reduction. Structural parameters were deduced from the rotational constants by allowing all bond lengths and angles to vary in a least-squares manner. These parameters were in good agreement with those calculated at the STO-3G and 3-21G levels. Of many satellite lines observed, only the most intense could be utilized for locating the two lowest fundamental vibrations, estimated to occur at 190 and 240 cm−1. The far-infrared spectrum is reported in the region of 80 to 300 cm−1, exhibiting only one distinct sequence of Q branches at 264 cm−1. On the basis of unsealed abinitio force fields at both levels of the theory the corresponding fundamentals are assigned, respectively, to a twisting (A″) and a bending (A′) of the cycloheptane ring. Keywords: 8-oxabicyclo[3.2.1]octane, microwave and far-infrared spectra, abinitio STO-3G and 3-21G geometries.

The microwave spectrum of 3-methylthietan was investigated in the frequency range 26.5–40 GHz. The rotational spectra were measured for the ground state, five puckering states (including the lowest state of the second conformer), and two methyl torsion excited states. The conformer with the methyl group in the equatorial orientation (the ground state, vp = 0) is more stable than the axial counterpart (vp = 1) by 100(17) cm−1 (1.2(2) kJ/mol). The electric dipole moment was determined for both conformers by measuring the Stark effect on several transitions. A V3 barrier of 1470(30) cm−1 (17.6(4) kJ/mol) was obtained for the internal rotation of the axial methyl group from the A-E doubling of several rotational transitions in the first torsional excited state. Earlier far-infrared assignments were revised on the basis of microwave intensity measurements. The flexible model approach was used to reproduce the spacings between puckering levels simultaneously with the variation of the rotational constants with puckering excitation, allowing some structural relaxation accompanying the ring deformation. Comparisons are made with the results obtained when an asymmetric one-dimensional puckering Hamiltonian is used.

Address of Smithson: DREV, 2459 Blvd. Pie XI NORD, C. P. 8800, Courcelette, Quebec, GOA IRO Canada. Address of others: Department of Chemistry, University of Calgary, Calgary, Alberta, T2N IN4 Canada.

A valence force field and the vibrational wavenumbers are determined for bicyclo[2.2.1]- heptane (I), bicyclo[2.2.1]hepta-2,5-diene (II), and 7-oxabicyclo[2.2.1]heptane (III) by ab initio calculations at the STO-3G level. The calculated wavenumbers are compared to ob-served infrared absorptions and Raman emissions. New and in some cases revised assignments are derived.