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On June 11 and 15, 1985 two packages with balloons have been inserted in the atmosphere of Venus from the Soviet VEGA landing modules. This paper summarizes the pressure, temperature, wind illumination and backscattering data from the balloons.

A new hypothesis is proposed for recycling Martian CO to CO2. The same hypothesis can satisfactorily explain the recently observed depletion in CO in the middle atmosphere of Mars. The mechanism involves oxidation of carbon monoxide through heterogeneous chemistry in the presence of aerosols. It is further suggested that H2O ice aerosols in the atmosphere of Mars are particularly effective in this process. The thrust for suggesting this mechanism came from the extensive presence of aerosols in the Martian atmosphere detected by the Auguste-Spectrophotometer Interferometer experiment on the Phobos spacecraft, combined with similar results from earlier missions, the detection of relatively low CO mixing ratios in the low to middle atmosphere by the Infrared Spectrometer experiment on the Phobos spacecraft, and the fact that earlier proposed mechanisms for recycling CO2 require either unacceptably high values of the eddy diffusion coefficient or a high water vapor abundance in the middle atmosphere of Mars. The mechanism proposed in this paper might have an analog in the Antarctic ozone hole problem, and it points out a need for laboratory measurements of appropriate sticking coefficients and rate constants.

The adsorption of carbon monoxide (CO) on water ice and on the oxides Fe2O3, Fe3O4, Al2O3, SiO2, CaO, MgO, and TiO2 (rutile and anatase) has been investigated in a flow reactor. A mass spectrometer was employed as a detector to monitor the temporal concentrations of CO. Adsorption coefficients as large as 1 x 10 exp -4 were measured for CO on TiO2 solids in helium at 196 K. The fractional surface coverage for CO on TiO2 solids in helium was also determined to be approximately 10 percent at 196 K. The upper limits of the fractional surface coverage for the other oxides (Fe2O3, Fe3O4, Al2O3, SiO2, CaO, and MgO) and water ice were also measured to be less than 1 percent. The implications for the stability of CO2 in the Martian atmosphere and the 'CO hole' observed by the Phobos/ISM experiment are discussed.

Measurements of the polarization and line shape of the Lyman α hydrogen geocoronal emission obtained on board the satellite D2A Tournesol are compared with theoretical predictions using Kockarts-Nicolet (K-N) profiles. From these data the value of the hydrogen density at the exobase ρ500 can be inferred without a large error, whatever the model; the value of the exospheric temperature Tex, however, depends on the value of the gradient δρ/δz at the exobase level. Data obtained over one orbit (April 27, 1971) provide some values and features in agreement with other experimenters' measurements as follows: (1) ρ500 density at noon near the equator (11.5 ± 2.5)104 atoms cm−3, (2) ρ500 density variation consistent with a diurnal variation of 2 between 6 and 17 h LT, and (3) maximum exospheric temperature Tex late in the evening (1140° ± 100°K). However, the present data show two new features: (1) a density increase of 2 between southern latitudes (22°S–46°S) and northern latitudes (46°N to the equator) and (2) an altitude gradient of hydrogen density different from the gradient predicted by K-N theory in a region between 46°N to the equator.

Absolute intensity measurements of the (8, 6) OH band obtained during 10 flights of the December 1969 NASA Auroral Airborne Expedition are presented. Nightglow intensities higher by a factor of 2 than the usual values are recorded during flights 8, 14, and 15. The OH variations are compared with the evolution of the green line and O2(1 Delta g) emissions measured by other experimenters on board the aircraft. Before sunrise the twilight variations of OH down to a solar depression angle of 5 deg show a rapid decrease. A theoretical prediction of the OH, O I 5577 A, and O2(1 Delta g) emissions is evaluated by means of an extensive time-dependent oxygen-hydrogen model of the 25- to 150-km region. Twilight decrease of the OH emission is interpreted in terms of mesospheric ozone photodissociation. Nighttime variations of the emissions may be reproduced if modifications of the dynamic regime are introduced into the model.

A planned experiment to obtain range and Doppler data with the Phobos 2 Lander on the surface of the Martian satellite Phobos is described. With the successful insertion on January 29, 1989 of Phobos 2 into Mars orbit, it is anticipated that the Lander will be placed on the surface of Phobos in April 1989. Depending on the longevity of the Lander, range and Doppler data for a period of from one to several years are expected. Because these data are of value in performing solar-system tests of general relativity, the current accuracy of the relevant relativity tests using Deep Space Network data from the Mariner-9 orbiter of Mars in 1971 and from the Viking Landers in 1976-1982 is reviewed. The expected improvement from data anticipated during the Phobos 2 Lander Mission is also discussed; most important will be an improved sensitivity to any time variation in the gravitational 'constant' as measured in atomic units.

Measurements of polarization and absorption by a hydrogen cell of the Lyman alpha geocoronal emission, performed on board the French spacecraft D2-A Tournesol over the working period of the tape recorder (April 19 to May 2, 1971), are compared with theoretical predictions given by spherical models of transfer using Kockarts-Nicolet and Chamberlain profiles. From polarization measurements the value of the hydrogen density at the exobase ρ500 and its latitudinal-diurnal variation are inferred. From absorption measurements, by using the exospheric temperature Tex of Jacchia, another independent way of deducing ρ500 variations is presented. Owing to calibration problems, an absolute measurement of Tex derived from absorption measurements is no longer available. However, Tex departures from the Jacchia temperatures are deduced from departures between the two values of ρ500 deduced from absorption and polarization measurements. Data obtained over the considered period of time provided ρ500 measurements independent of the solar flux. For example, the ρ500 density at noon near the equator is equal to (10 ± 2) 104 atoms cm−3. Intensity measurements at Ly α and 1304 A are also reported and are compared with the Oso 4 and 5 results. Measurements of the extrageocoronal Ly α emission are first made from the core of the geocorona. The values obtained during a satellite spin vary between 430 and 780 R. These measurements permit a ρ500 midnight density near the equator equal to (11 ± 3)104 atoms cm−3 to be deduced. The measured latitudinal-diurnal variation of ρ500 over 24 hours LT is compared with the previous experimental and theoretical values. The agreement is roughly good over 16 hours between 0900 LT and 0100 LT: the maximum occurs around 0900 LT, the minimum occurs near 1800 LT, and the midnight to midday ratio is around 1.1. However, the maximum to minimum density ratio ρmax/ρmin is higher than the expected one: 2.7 ± 0.8 as deduced from absorption measurements and 3.8 ± 1.2 from polarization measurements. The discrepancy between these two values can be interpreted by a ∼50°K departure from the Jacchia 71 temperature at southern latitudes in the afternoon. In the second part of the night, between 0100 LT and 0900 LT, a steep and large depression is observed; it can be interpreted as a local one around 35°N or a remote one, above the northern geomagnetic pole. This northern depression, the weak values of densities measured at southern latitudes, and the high density ratio ρmax/ρmin suggest the existence of a hydrogen bulge whose axis seems to be located around the sun-earth axis and to be linked to depressions over the poles.

This paper reviews the work performed in the last three years to the optical study of the thermosphere that is, of the region of the atmosphere above 120 km, excluding all phenomena originating at the mesopause and auroral phenomena.

A total of 3600 spectra of Comet Halley in the 275–710 nm were obtained on March, 8, 9, 10 and 11, 1986, from the VEGA 2 spacecraft. The emissions of OH, NH, CN, C 3 , CH, C 2 , NH 2 and H 2 O + are identified. From the OH intensity in the (0,0) band: 1.1 Megarayleigh at 5400 km from the nucleus, it can be inferred that the OH production rate was (1.4 ± 0.5)×10 30 molecules s −1 . The NH, C 3 , CH and NH 2 bands became comparatively more intense at distances from the nucleus shorter than 3000km. At 06:40 U.T. when the instrument field of view was 6000×4500 km, two jets were observed. Spectra from the jets show significant differences with other spectra. Inside a jet NH, C 3 and NH 2 are comparatively more intense and the rotational distributions of OH, CN and C 2 are strongly distorted. This shows that part of the observed emissions probably comes from radicals directly produced in the excited state during the initial process of photolysis of the parent molecules.

International audience; The Haute-Provence Observatory (44° N, 6°E)lidar facility has been extended to study the atmospheric lithium and its isotopic ratio Li7/Li6 in the upper atmosphere. The experimental features have been improved in order to lower the detection limit to 3.105 cm-2 for the total abundance with a resolution of 1.2 km in the altitude profile. The night-time measurements have been carried out from November 1977 to December 1979 and show some characteristic trends. The seasonal variation of the total abundance is similar to the one observed for sodium. The altitude profile is variable during the night. Total abundance fluctuations and peaks with small scale heights (1.5 km) are observed on numerous occasions. The layer is sensitive to high-altitude artificial releases, like CAMEO in November 1978, and to impinging meteor showers. It is concluded that study of the behavior of atmospheric lithium and sodium should further our understanding of the alkali-metals chemistry.

Two rockets have been fired along the magnetic field line L = 5.6 to altitudes above 400 km to measure the fluxes, energy spectrums, and angular distributions of protons and electrons with energies above 150 kev. The objectives of the experiment are stated and the payload operation is described in this paper. In following papers, the electron and proton results are presented and interpreted.

The atomic oxygen emission line at 6300 A, measured in the nadir direction by a photometer on the polar orbiting satellite OGO-4, was plotted between 40 deg N and 40 deg S latitude on a series of maps for the moon-free periods between 30 August 1967 and 10 January 1968 The longitudinal and local time variations which occur during the northern fall-winter season are indicated. The northern tropical arc is more widespread while the southern arc is not present at all longitudes. The conditions under which the observations were made are described, and four airglow maps were selected to show the local time variations.

This paper describes the primary results of a series of balloon-borne measurements of stratospheric temperature at about 100 mb in the southern hemisphere, conducted as a part of the Solar Monitoring Experiment (SOMEX)[Heinsheimer and Pommereau, 1968]. The data presented here were transmitted by two of the superpressure balloons during the period from July 1 to November 30, 1968. These two flights, launched from Pretoria, Republic of South Africa (26.5°S, 28°E), remained within the southern hemisphere during their lifetimes. They resulted in the collection of some 250 measurements of the mean air temperature (at local noon) near the 100-mb level. As the super-pressure balloon follows the horizontal movements of the air, its displacement allows the accumulation of information in geographical locations inaccessible to short-lived radiosonde probes [Lally, 1967]. This is particularly true in the southern hemisphere, where the distribution of radiosonde stations leaves much to be desired. Two meteorological programs using superpressure balloons have been started : Global Horizontal Sounding Technique (GHOST) by the National Center for Atmospheric Research (NCAR) [Lally, 1968] and EOLE, a French project by the Centre National D'Etudes Spatiales (CNES) [Morel, 1966]. To our knowledge no data on stratospheric temperature have been published.

Calculations are presented of the absorption of radiant energy by sodium vapor in a magnetic field. These calculations are related to the observations of sodium dayglow using a ‘Zeeman photometer’ and it is shown that the observations show a systematic error depending on the time of day at which an observation is made. The direction of the systematic error, in the case of the dayglow measurements of Blamont and Donahue, will be such that the deduced abundances of atmospheric sodium will be overestimates in summer and underestimates in winter. Examination of the data confirms the existence of these effects. A method of correcting for them has been developed, and revised abundance values have been obtained. The average daytime abundance is 14×109 atoms/cm2 with little seasonal variation. The ratio of day to twilight abundances is 2/1 in winter and 5/1 in summer.

International audience; Analysis of the dayglow of the sodium D lines since September 1960 and the twilight glow since 1954 at Haute Provence Observatory shows a large seasonal maximum of 30 kR for the dayglow in June. The ratio of daytime to twilight abundance then is about 7 to 1. The ratio becomes 2 to 1 in December. Evidence presented for the reality of this effect includes actual line profiles showing an emission peak above Rayleigh-scattered background, observation of the dayglow from a high-altitude airplane, and observation of the dayglow with a rocket-borne photometer. The seasonal maximum is accompanied by a seasonal decrease of 5 km in twilight layer altitude in midsummer. The effect is interpreted as being caused by a diurnal variation in atomic oxygen and ozone enhanced by turbulent diffusion of the sodium and its compounds. Other possible interpretations such as photochemical excitation are rejected. A seasonal variation is also found in the ratio of morning to evening sodium abundance in twilight. The maximum ratio is 1.4 at the equinoxes. At Tromsø, Norway, the dayglow intensity is about 15 kR and shows no seasonal variation.

OGO D observations of OI (6300A) emissions reveal a global pattern in the equatorial airglow undetected from the ground-based observations. The post sunset emission rate of OI is generally asymmetrical with respect to the geomagnetic equator and shows no apparent correlation with the ultraviolet airglow (OI 1304 and 1356A) and F region electron density measured simultaneously from the same spacecraft. Both the ultraviolet airglow and the ion density measured in the altitude region of 450 km follow similar latitudinal variations and exhibit properties of the equatorial ionospheric anomaly. The asymmetry in OI emission can be attributed to the asymmetry in the height of the F 2 maximum inferred from the height of the maximum emission. From correlative studies of the airglow and the ionospheric measurements, the mechanisms for the ultraviolet and the 6300A emission are discussed in terms of the processes involving radiative and dissociative recombinations. A relationship between molecular oxygen density and the integrated OI emission rate is derived and the feasibility of using this relationship for estimating O2 density is discussed.

The shape of the Lyman α line emitted by the whole solar disk has been measured with an experiment on board the Oso 5 satellite during the year 1969. The intensity of the line in a 100 A bandpass was measured, and the use of two resonance cells, one filled with hydrogen and the other one with deuterium, gave the intensity of the line at the center and on the blue wing with a resolution better than 0.02 A. These measurements showed that the shape of the line changes considerably with solar activity, owing to variations in intensity at the center of the line, which are much greater than on the blue wing or averaged over the whole line.

Lyman α intensity measurements (1216 A) were obtained by a photometer on board the Ogo 5 spacecraft outside the geocorona. The Lyman α emission originating from hydrogen atoms in the upper part of the geocorona was derived from the total measured intensity after subtraction of the extraterrestrial emission. The hydrogen density distribution between 5 and 16 RE was deduced. This distribution is consistent with the evaporative atmospheric model of J. W. Chamberlain on the night side. A depletion of atoms found above a distance of 6 RE on the day side could be accounted for by the action on satellite particles of charge exchange with solar wind protons and by the solar Lyman α radiation pressure, according to numerical computations of both effects. It was also calculated that orbits with a perigee of 2 RE are rapidly distorted by radiation pressure. The mean time spent in the exosphere by satellite particles on such orbits is only 5 × 105 sec, one-half the ionization lifetime.

This note clarifies an important point of the Vidal-Madjar et al. (1973) paper. In fact, some of the results presented in that paper are sensitive to the choice of the exospheric temperature. Because Vidal-Madjar et al. used a rough estimation of that parameter, neglecting the geomagnetic heating, systematic differences appeared in their results. The use of a more precise representation of the exospheric temperature here allows us to present in particular a better evaluation of the atomic hydrogen density evolution at 100-km altitude. This density variation seems to be rather large and at least a factor of 3 between 2 × 107 and 6 × 107 atoms cm−3. Furthermore, all the densities of atomic hydrogen at 500-km altitude, recalculated with the use of a better representation of the exospheric temperature parameter, are listed here for 3 consecutive years (1969, 1970, and 1971).

A spherical Fabry-Perot interferometer on Ogo 6 (launched June 5, 1969) gives the profile of the 6300-A oxygen line in the dayglow at different altitudes between 200 and 320 km. The temperature of the neutral components of the atmosphere is deduced from these measurements with an accuracy of ±65°K. The results presented in this paper correspond to the storm period September 25 to October 5, 1969. During this period a severe geomagnetic storm occurred. The temperature measurements show a very strong effect in the two polar regions, while the equatorial regions present a smooth temperature variation.

International audience; The University of Paris experiment, operating on board the Oso 5 spacecraft since January 22, 1969, observes the solar Lyman α line integrated over the whole solar disk. The hydrogen and deuterium resonance cells yield information about the solar flux at the center of the line and on the blue wing. The center of the solar line as observed from the spacecraft is strongly absorbed by the earth's geocorona. Therefore the hydrogen resonance data contain solar, as well as geocoronal, information. Comparison of the data with sophisticated exospheric models gives the following principal results: (1) A high correlation (0.87 coefficient) exists between the total Lyman α line flux and the center line flux. A 30% variation in the total flux corresponds to a 47% variation in the central flux. The average fluxes over 1969 and 1970 are 3 × 1011 ph cm−2 sec−1 total flux and 5 × 1011 ph cm−2 sec−1 A−1 central flux. (2) The absolute value of the hydrogen density at 500-km altitude (independent of the experiment's calibration) is of the order of 5 × 104 atoms cm−3 on the day side and 9 × 104 atoms cm−3 on the night side. (3) The earth's hydrogen exobase is controlled by the zero net ballistic flux condition (i.e., the outgoing ballistic flux is everywhere equal to the incoming ballistic flux). This is why an average ratio of 1.7 was found between the maximum and minimum densities at the exobase. A discrepancy appeared between the absolute values of the hydrogen density measured by this experiment and the corresponding absolute values predicted by the model of G. Kockarts and M. Nicolet (1963). In order to fit our data, the values of the model should be increased to the following hydrogen densities at an altitude of 100 km: 2.3 × 107 atoms cm−3 for low solar activity (Zurich number Rz ∼ 60); 2.5 × 107 atoms cm−3 for mean solar activity (Rz ∼ 120); and 4 × 107 atoms cm−3 for high solar activity (Rz ∼ 180).

Both VEGA balloons encountered vertical winds with typical velocities of 1 to 2 meters per second. These values are consistent with those estimated from mixing length theory of thermal convection. However, small-scale temperature fluctuations for each balloon were sometimes larger than predicted. The approximate 6.5-kelvin difference in temperature consistently seen between VEGA-1 and VEGA-2 is probably due to synoptic or planetary-scale nonaxisymmetric disturbances that propagate westward with respect to the planet. There is also evidence from Doppler data for the existence of solar-fixed nonaxisymmetric motions that may be thermal tides. Surface topography may influence atmospheric motions experienced by the VEGA-2 balloon.

International audience; Observation of the sodium dayglow in the scattered sunlight observed on the surface of the earth with a magnetic scanning photometer is reported. The intensity (September to November 1960) is unexpectedly strong—30 kilorayleighs toward the zenith—and evidence is that during the period studied the amount of sodium is 4 times as large in the daytime as at twilight. However, a strong correlation is found between the dayglow and twilight intensities. The abundance can be as high as 40×109 atoms/cm2. The possible role of water vapor absorption in the results is discussed.

Balmer alpha emissions of intensity larger than three times the nominal value have been recorded during five different nights at geomagnetic latitudes inferior to plus or minus 22 deg . They are correlated with sudden impulses in magnetograms. (auth)

Stable subauroral red arcs (SAR arcs) were observed in both the northern and southern hemispheres on Sept. 28 to 30, 1967. For each pass the universal time and the longitude of the spacecraft as it crossed the magnetic equator are given. The SAR arc was noted to be worldwide in its extent and located on the same L shell in the northern and southern hemispheres. It appeared near L equals 3, moved equatorward to L equals 2.4, and later moved to, or reformed, near L equals 2.9. Its intensities were variable over the nearly two days of observations and, apparently influenced by the composition of the lower thermosphere, averaged 60 per cent greater in the northern hemisphere.

The nephelometer measurements by the four Pioneer Venus probes reveal an upper haze area in the vertical cloud structure with several less clearly delineated layers in the main cloud bank. Concentrated sulfuric acid is the main component of the majority of the particulate matter in the clouds; the near UV radiation is absorbed by the clouds. The particles ejected from the planet surface are in the 10 to 100 micron range.