Grille Spectrometer Research Articles

Atmospheric NO from space: the SCIAMACHY capabilities

The SCanning Imaging Absorption spectroMeter for Atmospheric ChartograpHY (SCIAMACHY) has been proposed in 1988 as a payload of the ESA earth observation satellite ENVISAT 1, which is scheduled for launch in 2001 for a four-year mission. SCIAMACHY operates in eight channels covering the UV, the visible and two infrared regions. Recent developments in the testing of the instrument now enable not only the full use of channel 1 (240 nm–314 nm) at a required high level of performance but in some special cases its extension to 220 nm. This instrumental improvement allows new objectives to be addressed in the upper stratoosphere, on top of the already proposed mesospheric and thermospheric investigations of nitric oxide. Simulations show the instrument capabilities for these studies. These NO observations will be performed in solar occultation, lunar occultation and nadir. Previous NO results are reviewed with an emphasis on results obtained by the infrared solar occultation technique as exemplified by the SPACELAB grille spectrometer and other instruments. The capabilities of SCIAMACHY for mapping the total column of upper atmospheric NO is investigated as well as possibilities to infer NO vertical distribution and transfer properties between the different atmospheric regions.

Second flight of the Spacelab Grille Spectrometer during the ATLAS‐1 mission

The SPACELAB grille spectrometer on its second space flight during the ATLAS‐1 mission (March 24 ‐ April 2, 1992) took advantage of the favorable timeline and of the extra day to perform more than 65 successful solar occultation runs. It succeeded in obtaining spectra pertinent to its ten target molecules in the full range of altitudes available to the solar infrared occultation technique. These ten molecules are H2O, CO, CO2, CH4, NO, NO2, N2O, HCl, HF and O3. The preliminary analysis of the sunset observation presented here adds new information to the available database on HCl vertical profiles, for assessing long‐term trends of this important stratospheric species.

Global results of grille spectrometer experiment on board Spacelab 1

Measurements of atmospheric trace gases have been performed during the first Spacelab mission, on board the Space Shuttle, from 28 November to 8 December 1983. The principle of the observations is absorption spectroscopy, in the infrared, using the sun as a light source during sunset or sunrise periods. The instrumental set-up and the flight operations, already described in previous papers, are briefly summarized. The automatic retrieving method for the processing of the spectra is explained. Finally, all the results, in terms of vertical concentration profiles, are given for NO, NO 2, CH 4, N 2O, CO, CO 2 and H 2O. Several results have been published (Laurent et al., 1985, Nature 315, 126; Muller et al., 1985a, J. Optics ( Paris) 16, 155 ; 1985b, Geophys. Res. Lett. 12, 667 ; Vercheval el al., 1986, Ann. Geophys. 4A, 161 ; Laurent et al., 1986, Planet. Space Sci. 34, 1067). This last version may be slightly different, due to recently available and more accurate orbital parameters.

An interim reference model for the middle atmosphere water vapor distribution

The middle atmosphere water vapor distribution has been the subject of intense investigation in recent years. A host of measurements have been made from balloons via remote sensing methods operating in the infrared and by in situ techniques which use the frost point hygrometer and Lyman-α stimulated fluorescence methods. In addition, rocket and satellite experiments based on the solar occultation and thermal emission approaches have been launched in the last several years giving the prospect of obtaining a reasonable global data base in the future. Most of these measurements have been made in the stratosphere. The only global data set released thus far is from the Nimbus 7 LIMS experiment which operated from late October 1978 to late May 1979 and provided H 2O measurements over the 64°S to 84°N range. The most extensive mesospheric H 2O data base currently available has been obtained using ground-based microwave measurements and rocketborne infrared and mass spectrometer results. These data apply mainly to mid and high latitudes. A limited amount of mesospheric data have also been collected from the shuttle Spacelab 1 and 3 missions by the Grille Spectrometer and ATMOS experiments, respectively. The LIMS data have been used to construct monthly and seasonal zonal mean reference stratospheric profiles over selected latitude bands, and the other available data sets have been combined with LIMS to produce an interim reference profile from the tropopause to 80-km for the mid latitude region averaged over the winter and spring time periods. The profiles show the presence of a hygropause near 50-mb pressure in the Tropics, a relatively constant mixing ratio distribution with height of 4.7 ppmv to 5 ppmv in the mid and high latitude stratosphere, and a decrease in the mid-latitude mesosphere to 1 ppmv at ≈ 80-km. This distribution should be carefully evaluated as more data become available.

Middle atmospheric water vapor observed by the Spacelab One grille spectrometer

Two water vapor atmospheric concentration profiles have been obtained, one at 33°N, 59°E and the other at 68°S, 124°W, during the Spacelab One flight respectively on 2 and 1 December 1983. These profiles extend from the middle stratosphere up to mesopause and show significant differences above the altitude of 70 km, the Antarctic profile showing then higher concentrations. This result correlates with Spacelab One carbon monoxide observations and SM E ozone results as far as the hydroxyl radical chemistry is concerned.

Observations of middle atmospheric CH4 and N2O vertical distributions by the Spacelab 1 Grille Spectrometer

Methane and nitrous oxide have been observed by limb absorption spectrometry using the Spacelab One grille spectrometer. The CH4 ν3 band is obsserved with a 0.1 cm−1 resolution up to 80 km while N2O can be seen up to 52 km in strong lines of its ν3 band. The values are compared, where possible, with previous observations and are in agreement with rocket determinations.

Middle atmospheric NO and NO2 observed by the Spacelab grille spectrometer

Almost 20 years after Nicolet1 suggested the presence of nitric oxide in the upper atmosphere as a source of D-region ionization by solar Lyman α-radiation, this trace species was first observed2 by the resonance fluorescence method; almost 10 years later, its vertical distribution was observed in the stratosphere by means of balloon-borne infrared absorption spectrometry3. Since then much emphasis has been placed on odd nitrogen compounds in the stratosphere, partly because of their role in controlling the ozone abundance. Many measurements have been made of NO, NO2, HNO3 and NO3 in the stratosphere with inferences on the N2O5 abundance. Meanwhile, several determinations of NO in the mesosphere and in the lower thermosphere4–10 have used resonance fluorescence and mass spectrometry11. We report here the first observation of NO from the low thermosphere down to the low stratosphere by instrumentation similar to that used previously on board balloon gondolas, but on this occasion the observation platform was Spacelab I, which gave access to higher altitudes. As before12, NO and NO2 were observed simultaneously.

Sample Performance of the Grille Spectrometer

The grille spectrometer observed the setting and rising sun 18 times during the Spacelab 1 mission. In addition to solar absorption lines, many of which had not been observed before, atmospheric spectral absorptions due to carbon monoxide and carbon dioxide were observed at heights tangent to the thermosphere (greater than 85 kilometers), and absorptions due to ozone, water, methane, and nitrous oxide were observed in the mesosphere (greater than 50 kilometers). The strongly coupled molecules NO-NO(2) and HC1-HF were observed as pairs in the stratosphere. Methane is presented as an example of the instrumental operations because of the characteristic aspect of the Q branch of its v(3) band.

Trace constituents measurements deduced from spectrometric observations on-board spacelab

The observation of infrared absorption lines by means of a grille spectrometer on board Spacelab 1 allows the determination of Co 2 and CO in the low thermosphere and in the middle atmosphere. Equal abundances of CO and CO 2 are found at 115 ± 5 km altitude. CO 2 is observed to depart from its homospheric volume mixing ratio near 100 km, dropping by a factor of 10,15 km higher. The CO largest number density is observed near 70 km altitude, close to the H Lyman alpha photoproduction peak. The analysis of one run dedicated to the observation of water vapor shows a middle atmospheric mixing ratio of this species within the limits : 3 to 8 ppmv up to 70 km altitude, with the indication of an increase from 30 to 50 km altitude. The H 2O mixing ratio drops very rapidly above 70 km. The comparison of the results from strong and weak H 2O and CO 2 lines shows the need to refine the line profile model.

Infrared absorption spectroscopy applied to stratospheric profiles of minor constituents

Infrared absorption by O3, NO, NO2, N2O, HNO3, CO, COS, CH4 and H2O have been observed from a balloon platform at 40 km of altitude and 44°N latitude with a grille spectrometer. The resolution is, for the most part, better than 0.1 cm−1. An analysis is made of the causes of uncertainties. Height profiles are deduced for these species down to 20 km. The mixing ratios near 40 km are 8.5±1.5 ppm for ozone, 8. ±1 ppm for water vapor, and 19±5 ppb for carbon monoxide. Nitric acid and carbonyl sulfide exhibit a decreasing profile with altitude. Mixing ratios near 30 km are <10–10 for COS and 8±1 ppb for HNO3. Some common observations are made, related to the particular temperature profile, which emphasize the importance of simultaneous measurements of stratospheric species and meteorological parameters.

O I (7990 Å) Emission and radiative entrapment of auroral EUV

Auroral observations of the O I (7990 Å) multiplet intensity distribution have been performed using a 2‐m grille spectrometer and a Fabry‐Perot interferometer in Alaska during 1977 and 1982, respectively. In addition, an extensive set of 1‐m and ½‐m Ebert‐Fastie spectrometer data obtained at Poker Flat, Alaska, and Longyearbyen, Svalbard, from 1977 to 1980 has been analyzed. The grille spectrometer results for the singlet/doublet ratio of the O I (7990 Å) multiplet indicate a nonstatistical distribution in the excited state, consistent with preferential scattering of the singlet component of the O I (989 Å) EUV emission and in accord with recent radiative transfer calculations (Meier, 1982). The striking departure of the Fabry‐Perot results from the model may be due to blending of the O2 (4, 4) band with the O I (7990 Å). Complete absorption of the EUV doublet by N2 is precluded by the clear presence of the O I (7990 Å) doublet component in the auroral spectrum. A comparison of O I (7990 Å) intensities measured on the nightside with those from dayside magnetospheric cleft aurora shows a cascade contribution to the O I (8446 Å) line and ultimately the O I (1304 Å) transition that depends on the altitude of the aurora. This is attributed to the greater radiative entrapment of O I (989 Å) at low altitude and corresponding enhanced probability for branching from the 3 s′ to the 3 p level in atomic oxygen.

The MAP/GLOBUS project

The MAP/GLOBUS project is part of the Middle Atmosphere Program (MAP) and was described in general in MAP Handbook I. GLOBUS stands for Global Budget of Stratospheric Trace Constituents.The 1983 program for this project was recently planned during a meeting of the steering committee and of more than 40 interested scientists from the USA, Japan, and five European countries at the Belgian Institute for Space Aeronomy, Brussels, Oct. 18–20, 1982. An integrated campaign of balloon‐borne, airplane, and ground‐based experiments was designed for September 1983 in southern France. Primary scientific objectives are (1) accurate measurements of ozone and its short‐term variability; (2) simultaneous determination of NOx species and their short‐term variability, including diurnal variations; (3) measurement of solar flux, scattered flux, and albedo; and (4) measurement of atmospheric dynamics. The program includes launches of eight balloon gondolas of the 300–400 kg class that contain various in situ and remote‐sensing experiments that will also provide information about numerous trace species, ions, and aerosols. Releases of 50–100 ozone sondes from five stations are also envisaged. Airplane experiments will presumably include remote sensing in the infrared by a grille spectrometer. A network of 14 ground‐based experiments shall be operated in Western Europe during the balloon and airplane flights. It includes, among other instruments, four lidars, one ST radar, two IR and one microwave spectrometer.

Controlling the 1ESO13 spectrometer for spacelab and its data retrieval

The Command and Data Management System for Spacelab is described and how it is used to control the Grille Spectrometer, how the experiment data is handled until it finally reaches the Ground Support Equipment in the Payload Operations Control Center for display and storage.

Analysis of the rotational structure of the v5 band of HNO 3 between 891 and 898 cm −1

We present here the analysis of the rotational structure of the v 5 band of HNO 3. Two spectra were used for this study: one recorded with a grille spectrometer by J.P. Chevillard and R. Giraudet and one with a tunable diode laser by P. Brockman, C.H. Bair and F. Allario. This analysis has led to the determination of the band centre and eight rotational constants of the vibrational level υ 5 = 1.

Etude de la bande 2ν4 du méthane

The band 2ν4 of methane has been studied with the aid of a tensor formalism; 9 constants have been determined from 83 observed transitions. The attribution of these transitions has been made from a spectrum recorded, at low temperature (100 K), on the grille spectrometer of the Laboratory of Molecular Spectronomy at Dijon.The root-mean-square deviation obtained is 0.14 cm−1, and the comparison between the spectrum calculated for T = 100 K and that recorded cold is excellent.

Observations of OI 7774 emission excited by conjugate photoelectrons

Observations and computer calculations of OI 7774 airglow emissions excited by conjugate photoelectrons have been carried out. The observations were made at McDonald Observatory, Texas using a 2m grille spectrometer from December 1972 to June 1973. The zenithal emission intensity during conjugate photoelectron precipitation was fairly constant at 2–4 R until conjugate sunset, after which it diminished steadily and ceased near a conjugate solar zenith angle ( χ c ) of 105 ± 3°. A predawn enhancement in both OI 7774 and [OI] 6300 was observed to commence near χ c ∼ 102°. The computations utilize the two-stream technique of Nagy and Banks (1970) to obtain the escaping photoelectron flux and the local excitation rates of the oxygen emissions. Good agreement with the observations is obtained for the dependence of the emission rate on conjugate solar zenith angle. A lack of agreement in absolute intensity may not be due entirely to uncertainties in the excitation cross section. The discrepancy may indicate significant magnetospheric scattering of photoelectrons with energy greater than 15 eV.

Conjugate photoelectron excitation of O I 4368 airglow emission

Conjugate photoelectron fluxes are shown to be mainly responsible for the excitation of O I 4368 radiation observed with a grille spectrometer located at Langmuir Laboratory, New Mexico (L equals 1.7). On the basis of observations of O I 7774 and 4368 tropical emissions at Agulhas, Negras, Brazil (L equals 1.1), the contribution of radiative recombination to the New Mexico intensity is shown to be small. Conjugate photoelectron excitation at the Brazilian site has not been observed.

Observations and computations of twilight helium 10,830-Angstrom emission

Observations of helium 10,830-A radiation with a grille spectrometer at Socorro, New Mexico, from 1967 to 1970 are presented. The data are discussed in light of new computations of the excitation and emission profiles. The observational data show an intensity increase of a factor of 3 during this period that is closely related to a corresponding change in the solar EUV radiation (λ<380 A). A large seasonal variation is discussed that is caused in part by a 5∶1 variation in the neutral helium abundance and that is augmented by seasonal variation in the conjugate photoelectron flux. In addition, a diurnal variation of the helium abundance of about 30% with a maximum in the morning is suggested.

A Grille Spectrometer for Measurements near 14 μ

A new design of the grille spectrometer allows its use for measurements of thermal ir emissions. The grilles are made of self-supporting etched metal foil, and the curved chessboard pattern allows optical chopping of one spectral element at a time by oscillation of the exit grille. Although the effective noise level obtained is as low as 1 erg sec(-1) cm(-2) sr(-1) cm(-1) for an integration time of 448 ms, the specific detectivity of the thermister bolometer appropriate for the large throughput of this instrument is much less than in small throughput versions, and a different detector or detector system will be required to achieve optimum performance.

The Circularly Symmetric Grille Spectrometer

A grille spectrometer, with grilles formed of alternately transparent and nontransparent concentric circular zones, has been constructed. The quantity of light that can be accepted from an extended source with such an instrument is orders of magnitude greater than that of a slit spectrometer with the same resolution, and greater even than that of a scanning Fabry-Perot spectrometer of the same resolution. For extended sources of brightness insufficient to bring the photon shot noise above detector noise, the grille spectrometer offers an advantage over the slit spectrometer and Fabry-Perot in greater signal to noise. In cases where the photon shot noise is greater than the detector noise, the better signal to noise applied for emission-line sources, and also for continuum sources if a large interference filter premonochromator is used. The spectrometer is being used in airglow observation.