Doran J. Baker

Rocket measurements of the altitude distributions of the hydroxyl airglow

Measured profiles of the vertical distributions of the volume emission rates of the OH infrared airglow are presented. These measurements by various investigators constitute a total of 34 rocket flights and were obtained at both mid and high latitudes, at various solar depression angles, and at various times of the year using rockets which flew into the middle atmosphere. Some 55 profiles are summarized. Quantitative altitude comparisons are made at various locations. Included in the comparisons are volume emission rate profiles at IR as well as at visible wavelengths. From all of the profiles reported, the value of the mean altitude of the peak OH volume emission rate is 87.4 km, and the mean half-power thickness is 12.4 km. However, we recommend as working numbers to be used: 86.8 ? 2.6 km for the altitude of the peak and 8.6 ? 3.1 for the thickness of the OH emission layer [taken from the selected profiles of Table III].

Simultaneous intensity, temperature and imaging measurements of short period wave structure in the OH nightglow emission

Abstract A low light TV camera co-aligned with a narrow field Michelson interferometer have been used to investigate how variations in the intensity and temperature of the near infrared hydroxyl nightglow emission are related to the passage of short period mesospheric gravity waves. The observations were made from Sacramento Peak, NM (32.8°N, 105.8°W) on the night of 14/15 June 1983, during a spectacular nightglow display that also exhibited wave structure visible to the dark adapted eye. A coherent wave-like pattern of horizontal wavelength 23 ± 1 km moving uniformly with a velocity of 28 ± 2 m s −1 (apparent period 13.7 ± 1.2 min), was measured at several azimuths over an interval of 2.5 h. The induced intensity and temperature perturbations were wave-like in nature and exhibited a high degree of correlation. The intensity variations were large, up to 30%, yet the brightest wave forms were ⩽ 10 K hotter than the adjacent dark forms. The amplitude of the intensity fluctuation was found to be ∼ 8 times larger than the temperature variation. In all cases the intensity wave led the thermal wave, but only by a small amount. High contrast wave patterns of this type are uncommon and are a principal feature of “bright night” displays.

Canopy Reflectance Estimation of Wheat Nitrogen Content for Grain Protein Management

The objective of this study is to evaluate remote sensing as a tool for measuring wheat nitrogen (N) content and then demonstrate how that information may be used by crop managers to improve grain protein content. Remote sensing data from aerial and satellite platforms were collected and compared with flag leaf N concentrations. Flag leaf N was significantly correlated with reflectance (r 2 = 0.52-0.80) during 2002 and 2003. A mid-season application of N increased grain protein in every treatment, but most significantly in the N-stressed treatments. Using remote sensing as a tool, wheat growers can estimate N stress and make decisions about protein management.

Mesospheric minor species determinations from rocket and ground-based i.r. measurements

Abstract As part of the MAP/WINE campaign the infrared hydroxyl airglow layer was investigated at Kiruna, Sweden, by simultaneous measurements with rocket probes of OH≠ and O2(a1Δg) infrared emissions and concentrations of odd oxygen species (O and O3). Coordinated measurements of OH≠ and O2(a1Δg) zenith radiance and emission spectra and their time histories were made from the ground. The rocket-borne Λ = 1.55 μm radiometer ( ΔΛ ≊ 0.23 μm ) provided volume emission rates for OH for both rocket ascent and descent, showing a peak near 87 km with a maximum of nearly 106 photons sec−1 cm−3. The atomic oxygen distribution showed a concentration of about 1011 cm−3 between 88 and 100 km, dropping off sharply below 85 km. The ground-based radiometer at Λ = 1.56 μm, which had a similar filter bandpass to the rocket-borne instrument, yielded an equivalent of 130 kR for the total OH Δv = 2 sequence, which is consistent with the zenith-corrected rocket-based sequence radiance value of ≌ 110 kR. The rotational temperature of the OH night airglow obtained from the rotational structure of the OH M (3,1) band observed by the ground-based interferometer was about 195K at the time of the rocket measurement. Atomic oxygen concentrations were calculated from the OH profile and show agreement with the directly measured values. Atomic hydrogen concentrations of a few times 107 cm−3 near 85 km were inferred from the data set.

The rayleigh: interpretation of the unit in terms of column emission rate or apparent radiance expressed in SI units.

The rayleigh, originally defined as a unit to express the total column light emission rate [10(10) photons sec(-1) (m(2)column) (-1)] can equivalently be defined as a unit for apparent photon radiance ((1/4)pi 10(10) photons sec(-1) m(-2) sr(-1)). The selection of the appropriate definition will depend upon the physical situation and the interests of the user. The applicability of the unit for expressing the quantitative measurement of all extended light sources, including optically thick media, is both handy and valid.

Rocketborne Observations of Atmospheric Infrared Emissions in the Auroral Region

This paper briefly reviews the preliminary results of spectral measurements of IR atmospheric emissions in the wavelength region from 1.6 to 23 μm. These measurements were achieved using cryogenic spectrometers on six recent rocket flights conducted under the Air Force Cambridge/DNA ICECAP program for coordinated auroral measurements from Poker Flat, Alaska.

Rayleigh, the Unit for Light Radiance

A 0.7% accurate formula is derived for the easy conversion of power spectral radiance L(lambda) in W cm(-2) sr(-1) microm(-1)to rayleigh spectral radiance R(lambda) in rayleigh/microm, R(lambda) = 2pilambdaL(lambda) x 10(13), where the wavelength lambda is in microm. The rationale for the rayleigh unit is discussed in terms of a photon rate factor and a solid angle factor. The latter is developed in terms of an equivalence theorem about optical receivers and extended sources, and the concept is extended to the computation of photon volume emission rates from altitude profiles of zenith radiance.

Equatorial enhancement of the nighttime OH mesospheric infrared airglow

Global measurements of the hydroxyl mesospheric airglow over an extended period of time have been made possible by the NASA SABER infrared sensor aboard the TIMED satellite which has been functioning since December of 2001. The orbital mission has continued over a significant portion of a solar cycle. Experimental data from SABER for several years have exhibited equatorial enhancements of the nighttime mesospheric OH (Δv=2) airglow layer consistent with the high average diurnal solar flux. The brightening of the OH airglow typically means more H+O3 is being reacted. At both the spring and autumn seasonal equinoxes when the equatorial solar UV irradiance mean is greatest, the peak volume emission rate (VER) of the nighttime Meinel infrared airglow typically appears to be both significantly brighter plus lower in altitude by several kilometres at low latitudes compared with midlatitude findings.

Decay of O2(a¹Δg) in the evening twilight airglow: Implications for the radiative lifetime

Time-resolved spectra of the decay of the O2 infrared atmospheric ( a¹Δg → X³Σg−) ( 0,0) band emission in the evening twilight at 41.7°N have been obtained using the Fourier transform infrared (FTIR) technique. The measurements were made during a two-month summer-fall period which included the autumnal equinox. The late twilight variations were well described by single exponentials with decay time constants which ranged from (44.4±1.6) min in early August to (61.1±2.1) min near the equinox. In this connection, a strong positive trend in the time constant was observed during late August and early September. When combined with available data for collisional quenching and for fall-winter, upper-mesospheric altitude distributions of O2 (a¹Δg, ν=0) in the late twilight, these observations support a radiative lifetime of about one hour.

Extended-Field Large-Aperture Interferometer–Spectrometer for Airglow Surveys

The design of a field-of-view-widened interferometer for airglow survey work is discussed, and some preliminary airglow results are presented. The 4.5-cm aperture optics of the interferometer give a very large throughput gain compared with a conventional slit spectrometer. In addition, by using optical wedge compensators, the field of view is widened to over 5 degrees full angle, resulting in a field-widened throughput gain of approximately 100 compared with a standard Michelson interferometer of the same aperture size. Digital recording is used to achieve sufficient dynamic range and to aid in computation of the fast fourier transforms. A series of airglow spectra of the midlatitude sky in the spectral region from 0.6 micro to 0.9 micro down to a resolution of about 2 A are given for a sunset transition and also at night. Bright features are the vibration-rotation hydroxyl emission bands and the oxygen red lines. Particularly interesting are enhancement of these emissions during twilight and the observation of what may be vibrationally excited O(2) in the lower atmosphere.