The contribution of methanol to the 3.4 micron feature in comets

With the advent of improved detectors and improved moderate resolution spectrometers several interesting features have been seen in the infrared spectra of comets. In particular, an emission excess at 3.52 microns was observed in several comets, and has recently been tentatively assigned to the nu 3 band of methanol (CH3OH). Using a developed model it is possible to calculate the relative strengths of the CH3OH features. The 3.52 microns emission strengths were used in a number of comets to retrieve methanol amounts, and the model was used to predict the fraction of the 3.4 micron flux which is contributed by the species. Implications for cometary formation are discussed

Infrared remote sensing of cometary parent volatiles from the ground, air, and space

A balanced view of the present generation of infrared instruments for cometary compositional studies is presented. Ground-based instruments are compared with airborne and spaceborne capabilities. An attempt to give examples of the unique science achievable with each is made, and particular emphasis is on the unique aspects of a dedicated Cometary Composition Telescope in earth orbit for investigating the chemical and structural heterogeneity of the cometary nucleus

Pseudoslit Spectrometer

The pseudoslit spectrometer is a conceptual optoelectronic instrument that would offer some of the advantages, without the disadvantages, of prior linear-variable etalon (LVE) spectrometers and prior slit spectrometers. The pseudoslit spectrometer is so named because it would not include a slit, but the combined effects of its optical components would include a spatial filtering effect approximately equivalent to that of a slit. Like a prior LVE spectrometer, the pseudoslit spectrometer would include an LVE (essentially, a wedge-like narrowband- pass filter, the pass wavelength of which varies linearly with position in one dimension) in a focal plane covering an imaging planar array of photodetectors. However, the pseudoslit spectrometer would be more efficient because unlike a prior LVE spectrometer, the pseudoslit spectrometer would not have to be scanned across an entire field of view to obtain the spectrum of an object of interest that may occupy only a small portion of the field of view. Like a prior slit spectrometer, the pseudoslit spectrometer could acquire the entire spectrum of such a small object without need for scanning. However, the pseudoslit spectrometer would be optically and mechanically simpler: it would have fewer components and, hence, would pose less of a problem of alignment of components and would be less vulnerable to misalignment

Simulation of Image Performance Characteristics of the Landsat Data Continuity Mission (LDCM) Thermal Infrared Sensor (TIRS)

The next Landsat satellite, which is scheduled for launch in early 2013, will carry two instruments: the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). Significant design changes over previous Landsat instruments have been made to these sensors to potentially enhance the quality of Landsat image data. TIRS, which is the focus of this study, is a dual-band instrument that uses a push-broom style architecture to collect data. To help understand the impact of design trades during instrument build, an effort was initiated to model TIRS imagery. The Digital Imaging and Remote Sensing Image Generation (DIRSIG) tool was used to produce synthetic “on-orbit” TIRS data with detailed radiometric, geometric, and digital image characteristics. This work presents several studies that used DIRSIG simulated TIRS data to test the impact of engineering performance data on image quality in an effort to determine if the image data meet specifications or, in the event that they do not, to determine if the resulting image data are still acceptable

Landsat Data Continuity Mission Expected Instrument Performance

The Landsat Data Continuity Mission (LDCM) is scheduled for a December 2012 launch date. LDCM is being managed by an interagency partnership between NASA and the U.S. Geological Survey (USGS). In order to provide the necessary spectral coverage of the visible through shortwave-infrared (SWIR) and the thermal-infrared (TIR), the satellite will carry two sensors. The Operational Land Imager (OLI) will collect data for nine visible to shortwave spectral bands with a spatial resolution of 30 m (with a 15 m panchromatic band). The Thermal Infrared Sensor (TIRS) will collect coincident image data for two TIR bands with a spatial resolution of 100 m. The OLI is fully assembled and tested and has been shipped by it's manufacturer, Ball Aerospace and Technology Corporation, to the Orbital Sciences Corporation (Orbital) facility where it is being integrated onto the LDCM spacecraft. Pre-launch testing indicates that OLI will meet all performance specification with margin. TIRS is in development at the NASA Goddard Space F!ight Center (GSFC) and is in final testing before shipping to the Orbital facility in January, 2012. The presentation will describe the LDCM satellite instrument systems, present pre-launch performance data for OLI and TIRS, and present simulated images to highlight notable features and expected imaging performance

A Spectral Atlas of the Nu(sub 12) Fundamental of (13)C(12)CH6 in the 12 Micron Region

The recent discovery of the minor isotopomer of ethane, (13)C(12)CH6, in the planetary atmospheres of Jupiter and Neptune, added ethane to the molecules which can be used to determine isotopic (12)C(12)C ratios for the jovian planets. The increased spectral resolution and coverage of the IR and far-IR instruments to be carried on the Cassini mission to Saturn and Titan may enable the detection of the minor isotopomer. Accurate frequency and cross-section measurements of the nu(sub 12) fundamental under controlled laboratory condition are important to interpret current and future planetary spectra. High resolution spectra of the minor isotopomer (13)C(12)CH6 have been recorded in the 12.2 micron region using the Kitt Peak Fourier Transform (FTS) and the Goddard Tunable Diode Laser spectrometer (TDL). In a global fit to 19 molecular constants in a symmetric top Hamiltonian, transition frequencies of the nu(sub 12) fundamental ranging up to J=35 and K=20 have been determined with a standard deviation of less than 0.0005 cm(exp -1). From selected line intensity measurements, a vibrational dipole moment for the nu(sub 12) fundamental has been derived. Observed and calculated spectra covering the region from 740 cm(exp -1) and to 910 cm(exp -1) are presented. A compilation of transition frequencies, line intensities, and lower state energies are included for general use in the astronomical community

Using Terahertz Time-Domain Spectroscopy to Discriminate Among Water Contamination Levels in Diesel Engine Oil

Terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 2.0 THz was evaluated for discriminating among water contamination levels (0%, 0.1%, and 0.2%) in diesel engine oil (SAE 15W-40). The absorption coefficient demonstrated potential to discriminate among the three water contamination levels with significant differences among all three levels across the 1.111 to 1.332 THz and 1.669 to 1.934 THz ranges. At each of these frequency ranges, each water contamination level was significantly different from the other two. The 0% water contamination level had the lowest absorption coefficient, while 0.2% water had the highest absorption coefficient. The refractive index demonstrated greater potential to discriminate among water contamination levels with significant differences among all three water levels across the 0.5 to 1.5 THz range. The refractive index of 0% water was the lowest and 0.2% water was the highest across the THz range. Linear regression analysis of the refractive index as a predictor of water contamination level yielded a highly significant equation (p \u3c 0.0001, R2 = 0.99, RMSE = 0.01) when using the refractive indices at 0.5 THz. The refractive indices of these oil samples were promising for discrimination of water contamination. THz spectroscopy should be evaluated for discriminating other engine oil contaminants

13C-ETHANE IN THE ATMOSPHERES OF JUPITER AND SATURN

High-resolution12C- and13C-ethane spectra of Jupiter and Saturn were acquired with the McMath-Pierce 60 inch (1.5 m) Telescope and Celeste, Goddard Space Flight Center's cryogenic grating spectrometer, in 1995 November and December. A relative abundance ratio12C/13C of 91 +26–13 for Jupiter and 99+43-23 for Saturn was derived from the measurements. These nearly terrestrial values suggest little or no fractionation of carbon isotopes in the atmospheres of Jupiter and Saturn. A weighted average of the available12C/13C ratios for the outer planets yields 88 ± 7, thus presenting no evidence for change in the carbon isotopic ratio between the presolar nebula and the present atmospheres of the outer planets

Ralph: A Visible/Infrared Imager for the New Horizons Pluto/Kuiper Belt Mission

The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA's first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with IR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg), power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.Comment: 18 pages, 15 figures, 4 tables; To appear in a special volume of Space Science Reviews on the New Horizons missio

Spectral Analysis of the Primary Flight Focal Plane Arrays for the Thermal Infrared Sensor

Thermal Infrared Sensor (TIRS) is a (1) New longwave infrared (10 - 12 micron) sensor for the Landsat Data Continuity Mission, (2) 185 km ground swath; 100 meter pixel size on ground, (3) Pushbroom sensor configuration. Issue of Calibration are: (1) Single detector -- only one calibration, (2) Multiple detectors - unique calibration for each detector -- leads to pixel-to-pixel artifacts. Objectives are: (1) Predict extent of residual striping when viewing a uniform blackbody target through various atmospheres, (2) Determine how different spectral shapes affect the derived surface temperature in a realistic synthetic scene