Composite Infrared Spectrometer

Fig. 5.8.11 Optical layout of the Composite Infrared Spectrometer, flown on the Cassini mission to Saturn (Kunde et al, 1996).

At this point, it is also appropriate to mention the Composite Infrared Spectrometer (CIRS) on the Cassini spacecraft, that flew past Jupiter in December 2000 and will arrive at Saturn in July 2004, and the Planetary Fourier Spectrometer (PFS) on the Mars Express spacecraft, to arrive at Mars in December 2003. Both spectrometers are dual channel instruments consisting of short- and long-wave interferometers. First, we discuss CIRS. 

Fig. 6.3.2 Spectrum of Jupiter recorded with the Composite Infrared Spectrometer (CIRS) on Cassini.

The Composite Infrared Spectrometer (CIRS) on-board Cassini had an improved sensitivity and better resolution in the far IR than the ISO spectrometer. The measurements were in good agreement (Nixon et al., 2006 [249], Bjoraker et al., 2008 [33]). 

The Composite Infrared Spectrometer (CIRS) consists of dutil interferometers that measure infrared emission from atmospheres, rings, tmd surfaces over wavelengths from 7 to 1000 micrometers (1400 to 10 cm ) to determine their composition and temperatures. It consists of a 50-cm telescope. 

Because the cast films are relatively thin, the optical density of the light absorbing species can he low and can vary with time of exposure. Additionally, the depth penetration of the absorbed light can be inhomogeneous in some systems. However, thin films can be mounted directly in UV/visible or infrared spectrometers, and so the course of the photopolymerization (and the rate) can be monitored directly in some systems. The most common observation made is the disappearance of monomer (e.g., loss of double bond absorption in the IR) as a function of irradiation time. It must be emphasized that in most thin film compositions important industrially, the monomers used are multifunctional. The polymer which results is then highly cross-linked and simple kinetic arguments are usually not valid. 

Johnson et al. (2001) employed the Smithsonian astrophysical far-infrared spectrometer on seven balloon flights to measure stratospheric ozone isotopic compositions. There are two important aspects to these observations. First, they confirm and are consistent with the mass spectrometric and laboratory observations. Second,... 

The crystal structure of as prepared samples was identified by using a powder X-ray diffractometer equipped with CuKa radiation (30kV, 20mA) and a monochromator. An infrared spectrometer was used for the chemical structure analysis. Chemical composition of samples was determined by EDX analysis. To determine the content of organic species in the composites, thermal gravimetric (TG) analysis was carried out at a heating rate of 10 °C/min in air. The BET surface area was determined by measuring N2 adsorption isotherms at 77 K. The microstructure of samples was observed by FE-SEM. Diffuse reflectance spectra were recorded with a UV-vis spectrometer. 

Other space-based observatories have been designed and built to study radiation at the opposite end of the EM spectrum, the infrared region. The first infrared spectrometer sent into space to study the chemical properties of another planet was the Mars Infrared Spectrometer (IRS), carried by the Mariner Mars 7 spacecraft into orbit in 1969. The IRS instrument swept the surface of Mars, collecting and analyzing radiation in the 1,800-14,400 nm range. More than 30 years after that initial flight, space scientists are still examining the IRS data to see what information it can provide about the chemical composition of the Red Planet s surface. 

The most attractive sensors now being developed are the Fourier transform infrared spectrometer (FTIR) and the near-infrared (NIR) spectrometer for the on-line measurement of composition changes in complex media during cultivation. The FTIR measurements are based on the type and quantities of infrared radiation that a molecule absorbs. The NIR measurements are based on the absorption spectra following the multi-regression analyses. These sensors are not yet available for fermentation processes. 

Two types of infrared spectroscopic analysis have been applied. The first is to follow the changes in the evolved gas product infrared spectra during heating. The precursor polymer is heated in a thermal gravimetric analyzer (TGA) and the evolved gases are directed into a gas cell in the infrared spectrometer. This TGA-IR method enables us to characterize the composition of the species evolved during the thermal elimination reaction. 

A chemical ionization mass spectrometer (MS), from V F named Air-sense 500, an electron pulse ionization mass spectrometer, fi-om V F named H-sense, and Fourier-transformed infrared spectrometer (FTIR), from MKS named MultiGas 2030 Model, are used simultaneously to analyze the product composition. FI2O is calculated via the oxygen mass balance. 

Usually, a composite sample of raw milk is analyzed once or twiee per month for each dairy farmer with the Milko Sean (Foss-Electrie A/S, Hillerod, Denmark), a mid-infrared spectrometer designed specifically for this job (1). Farmers are paid according to the results from the Milko Scan. Milko Scan measurements are made on samples brought from the dairy farm into the lab, quite often several hours after the sample is collected. Unless handled properly, the samples ean increase in SCC during the interval between the time the sample is collected and the analysis is performed. It should be obvious that a method for making more timely measurements would be in order. 

A tetrahydrofuran or acetone solution of the sample is run on an infrared spectrometer and the true absorbance of the 700 cm absorption calculated. The method is calibrated against styrenated alkyl resins of known composition. 

The Philae lander carries ten scientific instruments panoramic, stereoscopic and descent camera a-p-x-ray spectrometer evolved gas analyser for elemental, molecular and isotopic composition infrared microscope comet acoustic surface and sounding experiment permittivity probe dust impact monitor multi-purpose sensor for surface and sub-surface science magnetometer plasma monitor comet nucleus sounding experiment drill and sample distribution system. 

Many aspects of surface science and surface spec troscopy are concerned with the geometrical structure of surfaces, the composition of the surface and the identification of adatoms that may be present. Vibrational spectroscopy is a method for direct measurement of specific chemical bonds of adsorbed atoms and molecules, both between the adsorbate and the surface and the adatoms themselves. In the early days of HREELS, the 1970s, an added attraction for this type of spectroscopy was the ability to observe adsorbate surface bonding modes (often <125 meV = 1000 cm ), because the infrared spectrometers of the day used grating spectrometers, and IR detectors that were useful only above 1600 cm . The low cost and versatile Fourier transform infrared spectrometer (FTIR) and improved detector technology have eclipsed HREELS for routine surface chemical bond analysis. There are, however, some surface processes that can only be observed with electrons. Some diagnostic benefits that are related to the scattering mechanisms operative in HREELS continue to be useful for surface science. It should be noted that HREELS is usually performed on a known adsorbate, with a focus on the details of a specific adsorption system. HREELS is seldom used for the identification of unknown adsorbate species. 

Physical and chemical characterization methods are essential to assess aspects such as material and processing quality. Raman microprobe is an analytical tool coupled to an optical microscope. Elemental analysis using the x-rays emitted from the specimens in the electronic microscopy techniques can be used for local composition determination or to obtain a map of the distribution of a certain element in a wider area wavelength and energy-dispersive x-ray spectrometers are used for these purposes. Fourier transform infrared spectrometer is widely used for the qualitative and quantitative analysis of adhesives, the identification of unknown chemical compounds, and the characterization of chemical reactions. Thermal methods such as thermomechanical analysis and differential scanning calorimetry are discussed as valuable tools for obtaining information during postfracture analysis of adhesively bonded joints. 

In most cases in which line profiles are completely resolved by the infrared spectrometer both collision and Doppler broadening contribute to the line shape. The function that describes the composite line profile is a convolution of a Gaussian and a Lorentzian function,... 

BARNEY CONRATH was affiliated to the Goddard Space Flight Center from 1960 until 1995 and is currently a visiting faculty member in the Cornell University Center for Radiophysics and Space Research. His research interests include the study of the thermal structure, composition, and d5mamics of planetary atmospheres. He has participated in spacecraft missions to the Earth, Mars, and the outer planets, and is currently a member of the infrared spectrometer teams on the Mars Global Surveyor and Cassini missions. 

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