C. Lippens

The study of the martian atmosphere from top to bottom with SPICAM light on mars express

Abstract SPICAM Light is a small UV-IR instrument selected for Mars Express to recover most of the science that was lost with the demise of Mars 96, where the SPICAM set of sensors was dedicated to the study of the atmosphere of Mars (Spectroscopy for the investigation of the characteristics of the atmosphere of mars). The new configuration of SPICAM Light includes optical sensors and an electronics block. A UV spectrometer (118–320 nm, resolution 0.8 nm) is dedicated to Nadir viewing, limb viewing and vertical profiling by stellar occultation (3.8 kg). It addresses key issues about ozone, its coupling with H2O, aerosols, atmospheric vertical temperature structure and ionospheric studies. An IR spectrometer (1.2– 4.8 μm , resolution 0.4–1 nm) is dedicated to vertical profiling during solar occultation of H2O, CO2, CO, aerosols and exploration of carbon compounds (3.5 kg). A nadir looking sensor for H2O abundances (1.0– 1.7 μm , resolution 0.8 nm) is recently included in the package (0.8 kg). A simple data processing unit (DPU, 0.9 kg) provides the interface of these sensors with the spacecraft. In nadir orientation, SPICAM UV is essentially an ozone detector, measuring the strongest O3 absorption band at 250 nm in the spectrum of the solar light scattered back from the ground. In the stellar occultation mode the UV Sensor will measure the vertical profiles of CO2, temperature, O3, clouds and aerosols. The density/temperature profiles obtained with SPICAM Light will constrain and aid in the development of the meteorological and dynamical atmospheric models, from the surface to 160 km in the atmosphere. This is essential for future missions that will rely on aerocapture and aerobraking. UV observations of the upper atmosphere will allow study of the ionosphere through the emissions of CO, CO+, and CO2+, and its direct interaction with the solar wind. Also, it will allow a better understanding of escape mechanisms and estimates of their magnitude, crucial for insight into the long-term evolution of the atmosphere. The SPICAM Light IR sensor is inherited from the IR solar part of the SPICAM solar occultation instrument of Mars 96. Its main scientific objective is the global mapping of the vertical structure of H2O, CO2, CO, HDO, aerosols, atmospheric density, and temperature by the solar occultation. The wide spectral range of the IR spectrometer and its high spectral resolution allow an exploratory investigation addressing fundamental question of the possible presence of carbon compounds in the Martian atmosphere. Because of severe mass constraints this channel is still optional. An additional nadir near IR channel that employs a pioneering technology acousto-optical tuneable filter (AOTF) is dedicated to the measurement of water vapour column abundance in the IR simultaneously with ozone measured in the UV. It will be done at much lower telemetry budget compared to the other instrument of the mission, planetary fourier spectrometer (PFS).

Spaceborne measurements of the upper stratospheric HCL vertical distribution in early 1992 and the trend in total stratospheric chlorine since 1985

The GRILLE infrared spectrometer was part of the shuttle pay load during the first ATLAS mission in March-April 1992. This experiment measured the vertical distribution of several important minor constituents in the middle to high atmosphere by solar occultation mid-infrared absorption spectroscopy. Among the molecules observed is the stratospheric chlorine reservoir species HCl. This paper discusses the vertical profiles measured, including their validation with respect to correlative measurements from ATMOS on board the same mission and from HALOE on board UARS. The most important conclusion drawn from the measured HCl volume mixing ratio of (3.6±0.2) ppbv above 50 km presently measured by GRILLE in comparison with published ATMOS data from 1985 is that the actual GRILLE data confirm the increase of the upper stratospheric total chlorine loading by about 40% with respect to 1985, as reported and/or predicted earlier.

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 H[sub 2]O, CO, CO[sub 2], CH[sub 4], NO, NO[sub 2] N[sub 2]O, HCl, HF and O[sub 3]. 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. 11 refs., 4 figs., 1 tab.

Material from the El Chichon volcano above spain on 3 may 1982—one month after the eruption

Abstract Stratospheric dust layers photographically observed in the altitude range 16–28 km from a balloon gondola floating at 36.6 km altitude on 3 May 1982 over southern France are identified as originating from the 4 April eruption of the Mexican El Chichon volcano. The identification is compatible with the zonal air motions leading to lidar detections over Japan, United States and Italy. The observations confirm the eastward motion of part of the injected material below 20 km altitude and the westward motion above this altitude. They imply a northward component of the meridional motion of the order of 20° (from 17°N to 37°N) in one turn around the Earth. The observation of scattered sunlight in blue and red light allows to deduce some optical properties of the aerosol, mainly those implied by the wavelength dependence of the scattering efficiency being highly variable, particularly above the Junge layer.

Stratospheric ozone concentration profiles from Spacelab-1 solar occultation infrared absorption spectra

A Grille Spectrometer was operated on board Spacelab-1, launched on 28 November 1983 for a nine-day mission. Solar occultation absorption spectra that show ozone-specific absorption features have been taken in the infrared range between 1039.6 and 1081.3 cm-1, with a spectral resolution of about 0.055 cm-1. Northern as well as southern hemisphere locations have been covered. The determination of ozone vertical-concentration profiles from these spectra has required the development of an improved inversion program based on Mills algorithm. The most important ameliorations are the more accurate treatment of the molecular-line parameters and the introduction of Fourier-filter techniques for minimizing the influence of noise that severely affects the ozone spectra. The resulting ozone vertical profiles, between about 25 and 65 km altitude, are discussed and compared with data taken at the same time and location by other instruments (e.g., SME). In the future, these results will be compared with data taken with the same instrument during the ATLAS-1 mission and with a slightly adapted version of the spectrometer onboard the Soviet space station MIR is order to detect global changes.