Engineering topics

Chance, K. V.

Publications and source records attributed to Chance, K. V..

30 records · Page 2

NASA NTRS1989

Measurement of stratospheric HOCl - Concentration profiles, including diurnal variation

Determinations have been made of concentration profiles of HOCl in the earth's stratosphere, including the diurnal variation. Measurements of the rotational Q2 branch at 99.5/cm and of five RR(J3) transitions between 143 and 159/cm were made using far-infrared thermal emission spectroscopy. The spectra were obtained during a balloon flight of the FIRS 2 far-infrared Fourier-transform spectrometer and telescope from Palestine, Texas on May 12-13, 1988. From these measurements, altitude profiles of HOCl from 23 to 42 km are obtained. Daytime and nighttime average profiles of HOCl, as well as measurements on a 30-min time scale through the sunset transition at a single (35 km) altitude are presented. The measured profiles are lower than the current predictions from several modeling groups by a factor of approximately 0.6.

Chance, K. V.↗

NASA NTRS1987

Evidence for stratospheric hydrogen peroxide

A statistically significant measurement of H2O2 in the stratosphere has been obtained. The results were obtained from the 112.19/cm RQ5 branch of the torsional-rotational spectrum with a remote-sensing far-infrared Fourier transform spectrometer during the Balloon Intercomparison Campaign (BIC-2), on June 20, 1983. The concentration above the balloon gondola is unexpectedly large, corresponding to 0.68 + or - 0.21 parts per billion by volume (ppbv) at an effective altitude of 38.3 km. Below the gondola altitude the concentration of H2O2 is slightly less than expected from the model predictions at 33.2 km (0.19 + or - 0.05 ppbv) and significantly less than expected at 29.3 km (0.08 + or - 0.03 ppbv).

Chance, K. V.↗

NASA NTRS1986

Measurement of H2O and other trace gases in the stratosphere using a high resolution far-infrared spectrometer at 28 KM

The highlights of the stratospheric program were reviewed for the past 2.5 years. The major efforts were analysis of the data from the BIC-2 campaign, and the building or new instrumentation to replace that lost at the end of BIC-2. For clarity, the review will be done by topic, rather than chronologically: construction of the initial far-infrared spectrometer, balloon slight program, laboratory measurement, data analysis, and duplicate stabilized platform.

Traub, W. A.↗

NASA NTRS1986

Performance of a single-axis platform for balloon-borne remote sensing

The balloon flight performance of the Mark I single-axis platform and telescope is presented. Three performance indicators are examined: inclinometer output, gyro output, and infrared detector signal. The gondola itself experiences periodic angular disturbances with maximum amplitudes in the 0.1-2.0 deg range, with peaks occurring at periods of about 1, 2, 7, 20, and 250 s. The 2- and 20-s oscillations are identified with simple and compound pendulum motions, while the 250-s oscillations are speculated to be caused by atmospheric waves. The system meets the basic goal of providing a stable pointing direction within an uncertainty which is much less than the 0.3 deg telescope beam diameter.

Traub, W. A.↗

NASA NTRS1985

Far-infrared spectroscopy of the earth's stratosphere

This paper discusses the spectrum of the earth's stratosphere in the far-infrared, from 5 to 250/cm. Many of the trace gases that are important in stratospheric photochemistry have been measured, or are potentially measurable in the far-infrared. The spectral features of these gases are discussed with application to spacecraft measurements. In particular, the suitability of the spectrum for measurements of the HO(x) and ClO(x) families and of O3 are compared for different classes of instruments: Fourier transform spectrometers, filter radiometers, and scanning high-resolution Fabry-Perot instruments. It is found that these types of instruments have complementary capabilities that would best be used in combination in a comprehensive multispecies measurement scheme.

Chance, K. V.↗

NASA NTRS1985

Far-infrared radiometer to map OH in the middle atmosphere

A baseline design is evaluated for a far-infrared radiometer to map global concentration profiles of OH from a satellite platform. The instrument performance is modeled using the spectral database and radiative transfer models developed from recent balloon-based studies of the upper atmosphere. The results indicate that the OH concentration can be measured by limb sounding with 10-percent accuracy in the region of its peak concentration near 40 km, but with useful data for the altitude range between 25 and 120 km. The resolution is 3.5 km in the vertical and 500 km in the horizontal direction. The same technique in principle can be expanded in a multichannel mode to address other related species, e.g. H2O, O3, and HO2, which have accessible rotational emission features in the far-infrared spectral region.

Nolt, I. G.↗

NASA NTRS1984

An upper limit for stratospheric hydrogen peroxide

It has been postulated that hydrogen peroxide is important in stratospheric chemistry as a reservoir and sink for odd hydrogen species, and for its ability to interconvert them. The present investigation is concerned with an altitude dependent upper limit curve for stratospheric hydrogen peroxide, taking into account an altitude range from 21.5 to 38.0 km for January 23, 1983. The data employed are from balloon flight No. 1316-P, launched from the National Scientific Balloon Facility (NSBF) in Palestine, Texas. The obtained upper limit curve lies substantially below the data reported by Waters et al. (1981), even though the results are from the same latitude and are both wintertime measurements.

Chance, K. V.↗

NASA NTRS1984

Measurement of H2O and other trace gases in the stratosphere using a high resolution far-infrared spectrometer at 28 km

Data analysis results from the 1983 BIC 1 and 2 balloon flights are presented, with emphasis on H2O2, OH, HCL, O3, O2, and H2O. A 2 sigma limit on H2O2 abundance was set, as a function of altitude. This is comparable to or less than the theoretically predicted winter abundances from the 2-D models of Dupont, with a large enough summer maximum to facilitate concentration profile measurements. There is a definite drop in OH concentration from day to night following two model profiles. There was general agreement between HF measurements. The dominant role of the far wings of H2O lines in low altitude spectra was recognized. The strength of these wings exceeds that of many molecular line cores, including O3 and O2, especially near the long wavelength end of the spectra (100 cm (-1)). Newly measured positions for O3 and H2O were obtained.

Traub, W. A.↗

NASA NTRS1983

Q branches in the rotational spectrum of HOCl

The far IR rotational spectrum of HOCl from 70-263/cm have been obtained. The most prominent features of the rotational spectrum are the Q branches, for which positions have been measured. Statistical strengths for the Q branches have been calculated and mu sub b, the component of the dipole moment that allows Q branch transitions, has been determined from P and R branch line intensities. It is found that mu sub b = 1.4 + or - 0.2 D. Q branch strengths and shifts at stratospheric temperature are calculated.

Chance, K. V.↗

NASA NTRS1982

Use of a Fourier transform spectrometer on a balloon-borne telescope and at the multiple mirror telescope (MMT)

The design and use of an infrared Fourier transform spectrometer which has been used for observations of laboratory, stratospheric, and astronomical spectra are described. The spectrometer has a spectral resolution of 0.032/cm and has operated in the mid-infrared (12 to 13 microns) as well as the far-infrared (40 to 140 microns), using both bolometer and photoconductor cryogenic detectors. The spectrometer is optically sized to accept an f/9 beam from the multi-mirror telescope (MMT). The optical and electronic design are discussed, including remote operation of the spectrometer on a balloon-borne 102-cm telescope. The performance of the laser-controlled, screw-driven moving cat's-eye mirror is discussed. Segments of typical far-infrared balloon flight spectra, lab spectra, and mid-infrared MMT spectra are presented. Data reduction, interferogram processing, artifact removal, wavelength calibration, and intensity calibration methods are discussed. Future use of the spectrometer is outlined.

Traub, W. A.↗

NASA NTRS1981

Stratospheric HF and HCl observations /15 June 1981/

Balloon measurements of the stratospheric HF/HCl ratio are reported. Seven far-infrared rotational lines of HF and HCl were observed at elevation angles of 25, 18 and 8 deg by a far-infrared Fourier-transform spectrometer on board a balloon platform at 28.5 km. Analysis of line intensities yields an average HF/HCl ratio of 0.18 + or - 0.02 at an effective altitude of 33 km, with a water vapor mixing ratio of about 4 ppmv. Results are noted to be in reasonable agreement with the calculated profile of Sze and Ko (1981) with 4.5 ppmv H2O.

Traub, W. A.↗

NASA NTRS1980

Far infrared measurement of stratospheric HCl

Thermal emission from three rotational lines of H(Cl-35) and H(Cl-37) was observed with a Fourier transform spectrometer from a balloon platform at 28.9 km. The measured HCl line-of-sight density at 1.9 deg elevation above 28.9 km is 4.7 + or - 1.3 x 10 to the 15th/sq cm, implying an average volume mixing ratio of 0.8 + or - 0.2 x 10 to the -9th at the mean sampling altitude of 32.5 km. For a uniform mixing ratio model, this corresponds to a vertical column density of 2.4 + or - 0.6 x 10 to the 14th/sq cm. This result is in reasonable agreement with near infrared spectroscopic determinations and an abundance from a chemical sampling technique of HCl at this altitude; a pressure modulator radiometer measurement yields a significantly higher amount of HCl.

Chance, K. V.↗