Gale A. Harvey

Measurements of the HCN ν3 band broadened by N2

Abstract N 2 -broadened halfwidths have been measured for 51 absorption lines belonging to the ν 3 fundamental band of hydrogen cyanide ( 1 H 12 C 14 N) near 3311 cm −1 . The data were recorded at room temperature using a Fourier transform spectrometer with a nominal resolution of 0.06 cm −1 . A nonlinear least-squares spectral-fitting procedure was used to obtain both line intensities and collision-broadened halfwidths from scans recorded at several different pressures. The N 2 -broadened halfwidths, determined for all lines with J ≤ 25 in both the P and R branches of the band, show the expected distribution with J for broadening by a nonpolar gas. The halfwidth values range from approximately 0.17 cm −1 atm −1 near the band center to 0.11 cm −1 atm −1 for high- J lines. The band intensity for the ν 3 fundamental derived from these measurements is 236.2 ± 9.5 cm −2 atm −1 at 296 K, and empirical coefficients for the vibration-rotation interaction F -factor were also determined.

Q branches of the ν 7 fundamental of ethane (C 2 H 6 ): integrated intensity measurements for atmospheric measurement applications

Laboratory spectra covering the nu7 band of ethane (C2H6) have been recorded, and measurements of integrated intensities of selected Q branches from these spectra are reported. The method by which the spectra were obtained is described, and a typical spectrum covering the PQ3 branch at 2976.8/cm is shown along with a plot of equivalent width vs. optical density for this branch. The values of the integrated intensities reported for each branch are the means of five different optical densities.

Cleanliness and damage measurements of optics in atmospheric sensing high energy lasers

Langley Research Center has several atmospheric remote sensing programs which utilize high energy pulsed lasers. These lasers typically have many damaged optics after several million shots. Damage is defined herein as color changes and/or optical flaws seen in microscopic inspection, and does not necessarily relate to measured performance degradation of the optic. Inspections and measurements of some of these optics indicate that energy thresholds for several million shots damage is about an order of magnitude lower than that for single shot damage. Damage initiation is often at micron size areas at the coating interface, which grows and sometimes develops as erosion of the top of the coating. There is a wide range in polish and coating quality of new optics, even on different faces of the same optic. Military Standard 1246C can be used to provide overall particulate, and molecular film, or nonvolatile residue cleanliness scales. Microscopic inspections and photography at 10X to 500X with brightfield (perpendicular) and darkfield (oblique) illumination are useful in assigning cleanliness levels of new and in-service optics. Microextraction (effecting concentration of molecular films to small areas) provides for enhanced optical detection and surface film chemical analysis by electron-microscope energy-dispersive-spectroscopy. Similar measurement techniques can be used to characterize and document optical damage initiation and optical damage growth. Surface contamination interferes with and complicated measurements of polish and coating quality, and of optical damage. Our work indicates ultrasonic cleaning, and packaging of optics in Teflon sleeves or cups is advantageous over conventional cleaning and packaging for characterization of new optics.

Nitrogen-broadened halfwidths of HF lines in the 1-0 band

Abstract Nitrogen-broadened halfwidths for seven lines in the fundamental infrared band of HF have been determined from laboratory measurements at room temperature. The spectra were recorded using a Fourier transform spectrometer with a nominal resolution of 0.0603 cm −1 . A nonlinear least-squares spectral-fitting technique was used in the data analysis to obtain halfwidth values for the P 3 through R 3 lines, with an average uncertainty of approximately 15%.

Shuttle and MIR Special Environmental Effects and Hardware Cleanliness

The Evaluation of Space Environment and Effects on Materials (ESEM) experiments were developed, flown in-space on the STS-85 mission (August 1997), returned to Earth and analysed as one element of a collaboration between the National Space Development Agency (NASDA) of Japan and the National Aeronautics and Space Agency (NASA) of the United States. The primary objectives of the ESEM experiments were to investigate atomic oxygen effects on materials, cosmic dust and man-made debris, and Shuttle-induced contamination. In particular, the change in scattering of light from the 1/4 mil aluminized Kapton film due to atomic oxygen erosion and Shuttle-induced molecular contamination are discussed. The MIR environmental effects payload (MEEP) was attached to the docking module of the MIR space station for 18 months during calendar years 1996 and 1997 (March 1996, STS 76 to October 1997, STS 86). A solar panel array with more than 10 years space exposure was removed from the MIR core module in November 1997 and returned to Earth in January 1998, STS 89. MEEP and the returned solar array are part of the International Space Station (ISS) Risk Mitigation Program. This space flight hardware has been inspected and studied by teams of space environmental effects (SEE) investigators for micrometeoroid and space debris effects, space exposure effects on materials and electrical performance. This paper reports changes in cleanliness of parts of MEEP and the solar array due to the space exposures. Special attention is given to the extensive water soluble residues deposited on some of the flight hardware surfaces. Directionality of deposition and chemistry of these residues are discussed.

MISSE 5 Thin Films Space Exposure Experiment

Abstract The Materials International Space Station Experiment (MISSE) is a set of space exposure experiments using the International Space Station (ISS) as the flight platform. MISSE 5 is a co-operative endeavor by NASA-LaRC, United Stated Naval Academy, Naval Center for Space Technology (NCST), NASA-GRC, NASA-MSFC, Boeing, AZ Technology, MURE, and Team Cooperative. The primary experiment is performance measurement and monitoring of high performance solar cells for U. S. Navy research and development. A secondary experiment is the telemetry of this data to ground stations. A third experiment is the measurement of low-Earth-orbit (LEO) low-Sun-exposure space effects on thin film materials. Thin films can provide extremely efficacious thermal control, designation, and propulsion functions in space to name a few applications. Solar ultraviolet radiation and atomic oxygen are major degradation mechanisms in LEO. This paper is an engineering report of the MISSE 5 thin films 13 months space exposure experiment.

Particle generation by silicone potting compound of returned Mir solar cells

A solar panel with more than ten years space exposure was returned to Earth in January 1998. Methy-phenyl silicone was used for both the adhesive between the coverglasses and silicon wafer, and for the potting compound between individual solar cells. Glass fiber scrim was used for structural integrity of the panel. Atomic oxygen in low-Earth-orbit interacted with the exposed silicone and converted the outermost layer (several microns thick) to oxidized silicon, i.e. SiOx, where x~2. This brittle SiOx served to protect underlying silicone from oxidation, unless the film was removed by some means. There is much evidence of microeruptions within the potting compound and spewing of silicone and SiOx film debris across the solar cell coverglasses. Ten of 409 solar cells of a returned panel have been scanned with a 50x brightfield microscope. This paper presents measurements of millimeter size SiOx particles and, glass fibers on the returned solar cell coverglasses. Erosion of the potting compound is also discussed.