https://elib.dlr.de/59672/1/scientdir.pdf

Transport impacts on atmosphere and climate: Aviation

Infrared signature studies of aerospace vehicles

We present a high-temperature version, CDSD-1000, of the carbon dioxide spectroscopic databank. The databank contains the line parameters (positions, intensities, air- and self-broadened half-widths and coefficients of temperature dependence of air-broadened half-widths) of the four most abundant isotopic species of the carbon dioxide molecule. The reference temperature is T ref =1000 K and the intensity cutoff is I cut =10 −27 cm −1 / molecule cm −2 . More than 3 million lines covering the 260–8310, 418–2454, 394–4662, and 429– 2846 cm −1 spectral ranges for 12 C 16 O 2 , 13 C 16 O 2 , 12 C 16 O 18 O , and 12 C 16 O 17 O , respectively, are included in CDSD-1000. The databank has been generated within the framework of the method of effective operators and based on the global fittings of spectroscopic parameters (parameters of the effective Hamiltonians and effective dipole moment operators) to observed data collected from the literature. Line-by-line simulations of several low- and medium-resolution high-temperature (T=800– 3000 K ) spectra have been performed in order to validate the databank. Comparisons of CDSD-1000 with other high-temperature databanks HITEMP, HITELOR, and EM2C are also given. CDSD-1000 is able to reproduce observed spectra in a more satisfactory way than the high-resolution databank HITEMP for temperatures higher than 1000 K . The databank is useful for studying high-temperature radiative properties of CO2. CDSD-1000 is freely accessible via the Internet.

CDSD-1000, the high-temperature carbon dioxide spectroscopic databank

The impact of NOx, CO and VOC emissions on the air quality of Zurich airport

In August 2001, the Aerodyne Mobile Laboratory simultaneously measured NO, NO2, and CO2 within 350 m of a taxiway and 550 m of a runway at John F. Kennedy Airport. The meteorological conditions were such that taxi and takeoff plumes from individual aircraft were clearly resolved against background levels. NO and NO2 concentrations were measured with 1 s time resolution using a dual tunable infrared laser differential absorption spectroscopy instrument, utilizing an astigmatic multipass Herriott cell. The CO2 measurements were also obtained at 1 s time resolution using a commercial non-dispersive infrared absorption instrument. Plumes were measured from over 30 individual planes, ranging from turbo props to jumbo jets. NOx emission indices were determined by examining the correlation between NOx (NO + NO2) and CO2 during the plume measurements. Several aircraft tail numbers were unambiguously identified, allowing those specific airframe/engine combinations to be determined. The resulting NOx emission indic...

NO and NO2 emission ratios measured from in-use commercial aircraft during taxi and takeoff.

Nonintrusive systems for the measurement on test rigs of aeroengine exhaust emissions required for engine certification (CO, NOx, total unburned hydrocarbon, and smoke), together with CO2 and temperature have been developed. These results have been compared with current certified intrusive measurements on an engine test. A spectroscopic database and data-analysis software has been developed to enable Fourier-transform Infrared measurement of concentrations of molecular species. CO2, CO, and NO data showed agreement with intrusive techniques of approximately ±30%. A narrow-band spectroscopic device was used to measure CO2 (with deviations of less than ±10% from the intrusive measurement), whereas laser-induced incandescence was used to measure particles. Future improvements to allow for the commercial use of the nonintrusive systems have been identified and the methods are applicable to any measurement of combustion emissions.

Nonintrusive optical measurements of aircraft engine exhaust emissions and comparison with standard intrusive techniques.

The Advanced Technology Centre (ATC) is responsible for developing IR signature prediction capabilities for its parent body, BAE SYSTEMS To achieve this, the SIRUS code has been developed and used on a variety of projects for well over a decade SIRUS is capable of providing accurate IR predictions for air breathing and rocket motor propelled vehicles SIRUS models various physical components to derive its predictions A key component is the radiance reflected from the surface of the modeled vehicle This is modeled by fitting parameters to the measured Bi-Directional Reflectance Function (BDRF) of the surface material(s) The ATC have successfully implemented a parameterization scheme based on the published OPTASM model, and this is described However, inconsistencies between reflectance measurements and values calculated from the parameterized fit have led to an elliptical parameter enhancement The implementation of this is also described Finally, an end-to-end measurement-parameterization capability is described, based on measurements taken with SOC600 instrumentation

SIRUS spectral signature analysis code

A method for the non-intrusive determination of temperature and concentrations of the exhaust gases of aeroengines will be presented. A MIROR-type FTIR spectrometer is used to measure spectra of the IR radiation emitted by the hot gases in the exhaust. New evaluation software, specially developed for this application, is described. The software permits line-by-line radiative transfer modeling of the radiance emitted by the exhaust of these engines. Least squares fitting routines are then used to match the measured with the modeled spectrum, thereby determining the unknown quantities, i.e., temperature and species concentrations. Results of measurements aboard aircraft are presented. The achieved accuracy in temperature is estimated to be better than 1 percent. Comparison of the values determined for the NOx emission index with results from correlation models show deviations of 15 to 20 percent and are thus within the accuracy limits claimed for both methods.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Evaluation procedure for nonintrusive exhaust gas analysis of jet engines using FTIR spectroscopy

The requirement for realistic simulation of military scenarios arises from a dearth of suitable and accessible measured data. Furthermore, measurement campaigns are restricted by the trial locality and availability of appropriate targets. Targets located in and around tree-lines are of particular interest, as they present scenarios that conventional broadband sensor systems find problematic. Utilising the spectral component of scenes, through the use multi- or hyperspectral technologies, can be beneficial in detecting these difficult targets. 
In this paper we describe the use of a Monte Carlo ray-tracing model (FLIGHT) to simulate forest scenes. This model is capable of calculating the interesting BRDF properties specific to forests. Targets are also incorporated in these simulations, and we describe contrast discrimination of the target from the background. This technique has application for targets in deep hide as well as at the forest edge (i.e., in a tree-line).
Assessment methods that can be applied to simulated hyperspectral imagery are investigated, to determine how realistic these scenes are in comparison to measurement. This is of key importance in ensuring that simulated imagery, as well as measured data, can be used to assess algorithmic techniques to detect and discriminate targets. Statistical assessment measures are discussed that utilise the spatial and spectral properties of the image.

Rachel Mary Geatches

Papers

Nonintrusive optical measurements of aircraft engine exhaust emissions and comparison with standard intrusive techniques.

SIRUS spectral signature analysis code

Evaluation procedure for nonintrusive exhaust gas analysis of jet engines using FTIR spectroscopy

Simulation and assessment of hyperspectral imagery