Observations of limb radiance with Cryogenic Spectral Infrared Rocket Experiment

Abstract

A Spectral Infrared Rocket Experiment was launched from Poker Flat, Alaska, on September 28, 1977, to measure infrared emission spectra from the earth limb atmosphere. Spectrometers measured emission spectra from 1.40 to 16.5 µm during 12 vertical scans of the limb region (tangent heights 0 to 250 km) traversing the night, terminator, and day sectors of the limb atmosphere. The spectrometers were cryogenically cooled and telescoped for out‐of‐field rejection of the more intense radiation from lower altitudes. High‐quality spectra were obtained with clearly identifiable features of CO2, O3, NO, OH, H2O, NO2, HNO3, and O2, as well as Rayleigh scattering. Spectra and tangent height emission profiles of selected species are presented and compared with theoretical emission models including those of Degges and Smith (Limb Model) and LOWTRAN 4. The salient findings are as follows: At a height of 80 km, CO2 daytime emission from fluorescence around 4.3 µm was almost 2 orders of magnitude greater than the nighttime emission. At 15 µm the CO2 radiance profiles showed little day‐night differences but exhibited an unexpected radiance plateau between 95 and 110 km. The ozone peak radiance at 9.6 µm (ν3) showed order of magnitude day‐night differences above 70 km tangent height showing a decrease in concentration of O3 during daytime due to photodissociation. The observed radiance in the 9‐ to 12‐µm wavelength region exhibited evidence of chemiluminescent emission from hot bands of O3. NO (Δυ = 1) peak radiance at 5.3 µm, due to O atom excitation, is a broad maximum at 120 km tangent height. The nighttime OH fundamental (Δυ = 1) and overtone (Δυ = 2) emissions showed extensive radiation from higher vibrational levels. The daytime 2.7‐µm fluorescent radiation was composed of emission from both H2O and CO2. Emission from NO2 at 6.15 µm (ν3) was observed at night only but was clearly identifiable amid the H2O (ν2) spectrum. Measured radiation in the 6.3‐µm vibrational band of water vapor at 60 and 70 km agrees with the Air Force Geophysics Laboratory non‐local thermodynamic equilibrium Limb Model using mixing ratios of 5 and 1.5 parts per million by volume, respectively. The radiance from O2 (a¹Δg) at 1.58 µm was observable from tangent heights of 30 to 80 km in the daytime only and shows a critical dependence upon the solar elevation angle. As expected, Rayleigh scattering was the dominant daytime source of radiation between 1 and 3 µm in the limb atmosphere for tangent heights of up to 40 km.

Near-Infrared Brightness of the Galilean Satellites Eclipsed in Jovian Shadow: A New Technique to Investigate Jovian Upper Atmosphere

“…The column density of OH is estimated to be 10 10 -10 11 cm −2 in the Ganymede atmosphere (Marconi 2007), which is comparable to that of the OH layer in the Earths atmosphere. However, the Ganymede SED, especially the non-detection at 3.6 μm, is difficult to explain by OH airglow because there is an emission band (Δν = 1) at 2.5-3.5 μm (Stair et al 1985) as shown in Figure 3, although the excitation state of OH molecules and chemical environment in the atmosphere Each data point of Ganymede in eclipse was obtained in the different date and impact parameter, thus the geometric relation among Jupiter, Ganymede, and the observer is different. Spectra of Jupiter (Rayner et al 2009) and the Earths atmosphere (Stair et al 1985) are also shown as a reference, scaled to the Ganymede brightness.…”

Non local thermodynamic equilibrium (LTE) atmospheric limb emission at 4.6 μm: 2. An analysis of the daytime wideband radiances as measured by UARS improved stratospheric and mesospheric sounder

“…tion (SISSI)) [e.g., Stair et al, 1975Stair et al, , 1983Stair et al, , 1985Smith et al, 1990;Vollmann and Grossmann, 1998], and also from space by the C!RRIS 1-A experiment on the Space Shuttle [Lee et al, 1991]. Among these data, those analyzed in most detail are the SPIRE measurements [Nebel et al, 1994].…”

Technical Note: On the possibly missing mechanism of 15 μm emission in the mesosphere–lower thermosphere (MLT)

“…Since only 2.4 % of the N 2 molecules participate in the RV energy transfer process, the rate coefficient for deactivation of CO 2 (v 2 ) by N 2 would be k VT (N 2 ) = ((2.32 ± 1.1) × 0.024) × 10 −12 = (5.6 ± 2.6) × 10 −14 . A larger calculated rate coefficient k N 2 would not be a problem, since the v 2 mode of CO 2 at least up to 90 km altitude is in local thermodynamic equilibrium (LTE); i.e., its vibrational temperature is nearly the same as the translational temperature (Feofilov et al, 2012;Stair et al, 1985). Tables 1a-d, using the atmospheres, provided by Feofilov and López-Puertas, give the rate coefficients k VT (N 2 ), the fifth column, and k VR (N 2 ), the last column, required by k x given by these atmospheres.…”

“…In the chemical literature, the rate coefficients of the reactions are given in the exothermic direction (reverse of Reaction 1a), and we will follow that convention. The room temperature value of the rate coefficient k ATM for the exothermic process derived by modeling the 15 µm emission, observed by the Spectral Infrared Rocket Experiment (SPIRE) (Stair et al, 1985) from the MLT region of the atmosphere, is 5×10 −13 cm 3 s −1 (Sharma and Nadile, 1981), 5.2 × 10 −12 cm 3 s −1 (Stair et al, 1985), 3.5 × 10 −12 cm 3 s −1 (Sharma, 1987), and (3 − 9) × 10 −12 cm 3 s −1 (Sharma and Wintersteiner, 1990). These studies gave values of k ATM that are 1-2 orders of magnitude greater than values recommend earlier (Crutzen, 1970;Taylor, 1974).…”