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The European Venus Explorer (EVE) mission was proposed to the European Space Agency in 2007, as an M-class mission under the Cosmic Vision Programme. Although it has not been chosen in the 2007 selection round for programmatic reasons, the EVE mission may serve as a useful reference point for future missions, so it is described here. It consists of one balloon platform floating at an altitude of 50-60 km, one descent probe provided by Russia, and an orbiter with a polar orbit which will relay data from the balloon and descent probe, and perform science observations. The balloon type preferred for scientific goals is one which oscillates in altitude through the cloud deck. To achieve this flight profile, the balloon envelope contains a phase change fluid, which results in a flight profile which oscillates in height. The nominal balloon lifetime is 7 days-enough for one full circumnavigation of the planet. The descent probe's fall through the atmosphere takes 60 min, followed by 30 min of operation on the surface. The key measurement objectives of EVE are: (1) in situ measurement from the balloon of noble gas abundances and stable isotope ratios, to study the record of the evolution of Venus; (2) in situ balloon-borne measurement of cloud particle and gas composition, and their spatial variation, to understand the complex cloud-level chemistry; (3) in situ measurements of environmental parameters and winds (from tracking of the balloon) for one rotation around the planet, to understand atmospheric dynamics and radiative balance in this crucial region. The portfolio of key measurements is complemented by the Russian descent probe, which enables the investigation of the deep atmosphere and surface. © Springer Science+Business Media B.V. 2008.

著者人数：156名, Accepted: 2008-05-27, 資料番号: SA1000998000

International audience; In 2005 the then ESA Directorate for Human Spaceflight, Microgravity and Exploration (D-HME) commissioned a study from the European Science Foundation's (ESF) European Space Sciences Committee (ESSC) to examine the science aspects of the Aurora Programme in preparation for the December 2005 Ministerial Conference of ESA Member States, held in Berlin. A first interim report was presented to ESA at the second stakeholders meeting on 30 and 31 May 2005. A second draft report was made available at the time of the final science stakeholders meeting on 16 September 2005 in order for ESA to use its recommendations to prepare the Executive proposal to the Ministerial Conference. The final ESSC report on that activity came a few months after the Ministerial Conference (June 2006) and attempted to capture some elements of the new situation after Berlin, and in the context of the reduction in NASA's budget that was taking place at that time; e. g., the postponement sine die of the Mars Sample Return mission. At the time of this study, ESSC made it clear to ESA that the timeline imposed prior to the Berlin Conference had not allowed for a proper consultation of the relevant science community and that this should be corrected in the near future. In response to that recommendation, ESSC was asked again in the summer of 2006 to initiate a broad consultation to define a science-driven scenario for the Aurora Programme. This exercise ran between October 2006 and May 2007. ESA provided the funding for staff support, publication costs, and costs related to meetings of a Steering Group, two meetings of a larger ad hoc group ( 7 and 8 December 2006 and 8 February 2007), and a final scientific workshop on 15 and 16 May 2007 in Athens. As a result of these meetings a draft report was produced and examined by the Ad Hoc Group. Following their endorsement of the report and its approval by the plenary meeting of the ESSC, the draft report was externally refereed, as is now normal practice with all ESSC-ESF reports, and amended accordingly. The Ad Hoc Group defined overarching scientific goals for Europe's exploration programme, dubbed "Emergence and co-evolution of life with its planetary environments,"focusing on those targets that can ultimately be reached by humans, i.e., Mars, the Moon, and Near Earth Objects. Mars was further recognized as the focus of that programme, with Mars sample return as the recognized primary goal; furthermore the report clearly states that Europe should position itself as a major actor in defining and leading Mars sample return missions. The report is reproduced in this article. On 26 November 2008 the Ministers of ESA Member States decided to give a high strategic priority to the robotic exploration programme of Mars by funding the enhanced ExoMars mission component, in line therefore with the recommendations from this ESSC-ESF report.

Results from one year of test soundings by the French-Russian ALISSA lidar on board the MIR platform since April 1996, are presented in this paper. They indicate that, even with a low power monochromatic lidar, valuable information on the multi-layered cloud structure can be obtained to complement geo-stationary cloud imagery.

A mission to Mars including two Small Stations, two Penetrators and an Orbiter was launched at Baikonur, Kazakhstan, on 16 November 1996. This was called the Mars-96 mission. The Small Stations were expected to land in September 1997 (Ls approximately 178 degrees), nominally to Amazonis-Arcadia region on locations (33 N, 169.4 W) and (37.6 N, 161.9 W). The fourth stage of the Mars-96 launcher malfunctioned and hence the mission was lost. However, the state of the art concept of the Small Station can be applied to future Martian lander missions. Also, from the manufacturing and performance point of view, the Mars-96 Small Station could be built as such at low cost, and be fairly easily accommodated on almost any forthcoming Martian mission. This is primarily due to the very simple interface between the Small Station and the spacecraft. The Small Station is a sophisticated piece of equipment. With the total available power of approximately 400 mW the Station successfully supports an ambitious scientific program. The Station accommodates a panoramic camera, an alpha-proton-x-ray spectrometer, a seismometer, a magnetometer, an oxidant instrument, equipment for meteorological observations, and sensors for atmospheric measurement during the descent phase, including images taken by a descent phase camera. The total mass of the Small Station with payload on the Martian surface, including the airbags, is only 32 kg. Lander observations on the surface of Mars combined with data from Orbiter instruments will shed light on the contemporary Mars and its evolution. As in the Mars-96 mission, specific science goals could be exploration of the interior and surface of Mars, investigation of the structure and dynamics of the atmosphere, the role of water and other materials containing volatiles and in situ studies of the atmospheric boundary layer processes. To achieve the scientific goals of the mission the lander should carry a versatile set of instruments. The Small Station accommodates devices for atmospheric measurements, geophysical and geochemical studies of the Martian surface and interior, and cameras for descent phase and panoramic views. These instruments would be able to contribute remarkably to the process of solving some of the scientific puzzles of Mars.

In the course of 71 days in lunar orbit, from 19 February to 3 May 1994, the Clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths. These data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side. In addition, laser-ranging measurements provided the first view of the global topographic figure of the moon. The topography of many ancient impact basins has been measured, and a global map of the thickness of the lunar crust has been derived from the topography and gravity.

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.

From OGO-4 airglow photometer data and computed lunar spectral irradiances at the subsatellite point, the highest radiance over clouds and lowest radiance over open ocean are examined near 3914 A, 5577 A, 5893 A, 6225 A, and 6300 A in terms of bidirectional reflectance. The results are compared to and are consistent with mathematical models of the atmosphere developed by Plass and Kattawar, and with daytime measurements from OSO-3 by Neel, Griffin, and Millard.

A low-frequency ground penetrating radar, developed for martian subsurface sounding (Mars 96 Mission) is presented. During the preliminary campaigns, its performances have been studied by ice thickness determination on various glaciers. This radar is a pulse-compression system designed in order to limit the necessary peak power. It involves the phase modulation of the transmitted pulse by coded sequences. By moving the radar along a profile on the surface, a continuous section of the reflected energy associated with dielectric permittivity contrasts is obtained. Modulating the transmitted pulse and matched filtering the received signal provide a significant depth penetration while preserving a satisfactory range resolution. This processing is efficient even if the echo is partially shortened or if the signal is modified by differential attenuation. A multichannel filtering based on the spectral properties of the signal is then applied to the section. Experimental results of ice sounding on glaciers show that the ice-bedrock interface can be identified at depths between 30 and 120 m. >

A spectrometer designed at the Space Research Institute, Moscow, for solar occultation measurements of the Martian atmosphere from the Phobos spacecraft has the spectral range 2706–2740 and 5293–5372 cm −1 in the first and second diffraction orders, respectively, with resolving power λ / Δλ = 1200. Data on the water vapor distribution in the Martian atmosphere were derived from nine occultation profiles at low latitudes and give a mean mixing ratio of 150 ppm below 12 km decreasing to 3 ppm at 40 km. The total amount of the water vapor is 10 μm of precipitable water. Mean scale height of water vapor is 3.8 km between 12 and 45 km. Small-scale variations of the water vapor density, though close to the experimental errors, may be caused by tidal waves with an amplitude of 2 K near 20 km and 5 K at 40 km with a further increase to 15 K at 100 km. The volume extinction coefficients and their spectral slopes at 1.9 and 3.7 μm have been measured to study the properties of aerosols in the Martian atmosphere.

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.

International audience; The soviet mission to Phobos and Mars was launched in July 88. It carries some thirty experiments on board, designed on a broad international basis, devoted to studying the planet Mars and its viscinity, its natural satellite Phobos, the Sun and the Interplanetary Medium. France, through its laboratories participating in a number of experiments and the CNES Space Center at Toulouse in the Phobos spacecraft navigation operations, is the main partner of the Soviet Union in the Phobos mission. Different experiments on the spacecraft are discribed (ISM, AUGUSTE, IPHIR, PWS, LILAS and APEX, the active DION and LIMA-D experiments) as well as the French participation in the long-term automated lander: DAS (cameras, STENOPEE). The first scientific results are presented. The CNES contribution to the international cooperation for Phobos navigation are also described (methods and results).

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.

Backscattering data for the nephelometer experiments conducted aboard the Pioneer Venus mission probes, including data up to the highest altitudes measured by the probes, are presented. A few small signals were detected below the main cloud deck. Ambient radiation was measured at near-ultraviolet and visible wavelengths; the variation of extinction of near-ultraviolet with altitude is inferred. Ambient radiance decreased more rapidly at 530 than at 745 nanometers in the lower atmosphere.

The spacecraft Vega 1 and Vega 2 encountered comet Halley on 6 and 9 March 1986. Their scientific payload comprised 14 instruments, which collected data concerning the comet's optical characteristics, dust emission, and neutral gas, plasma and electromagnetic field environment. The main features of the encounters are described and highlights of the first scientific results are presented.

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.

The results obtained by two extreme ultra violet (e.u.v.) spectrophotometers flown near Venus on VENERA 11 and VENERA 12 in December 1978 are presented. Detectors were placed at discrete wavelength positions to measure e.u.v. emissions from the upper atmosphere of Venus while the spacecraft were drifting on their fly-by orbits. The emissions of HI 121.6 nm (Ly- α ), HeI 58.4 nm, and OI 130.4 nm were measured with unprecedented sensitivity and spatial resolution. An OI signal of 500 Rayleigh (R) measured outside the disc suggested the existence of a large bulge of oxygen atoms. The e.u.v. emissions of two ionic species. OII 83.4 nm and HeII 30.4 nm, were measured for the first time in the atmosphere of Venus. The zero order detector of VENERA 12 indicated the presence of a very intense e.u.v. emission (28 kR) lying between the monitored wavelengths. This emission, which was only 3 kR for VENERA 11, is likely to be associated with the solar wind-ionosphere interaction. An attempt to measure ArI and NeI resonance emissions failed. The Lyman alpha (Ly- α ) interplanetary background was 4 to 5 times larger than expected, suggestive of a very intense solar flux or an increase of the interplanetary density. The distribution of hydrogen indicates two populations with temperatures of 400 and 700 K.

Data from solar and stellar occultations of Uranus indicate a temperature of about 750 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane and acetylene in the lower levels. The ultraviolet spectrum of the sunlit hemisphere is dominated by emissions from atomic and molecular hydrogen, which are kmown as electroglow emissions. The energy source for these emissions is unknown, but the spectrum implies excitation by low-energy electrons (modeled with a 3-electron-volt Maxwellian energy distribution). The major energy sink for the electrons is dissociation of molecular hydrogen, producing hydrogen atoms at a rate of 10(29) per second. Approximately half the atoms have energies higher than the escape energy. The high temperature of the atmosphere, the small size of Uranus, and the number density of hydrogen atoms in the thermosphere imply an extensive thermal hydrogen corona that reduces the orbital lifetime of ring particles and biases the size distribution toward larger particles. This corona is augmented by the nonthermal hydrogen atoms associated with the electroglow. An aurora near the magnetic pole in the dark hemisphere arises from excitation of molecular hydrogen at the level where its vertical column abundance is about 10(20) per square centimeter with input power comparable to that of the sunlit electroglow (approximately 2x10(11) watts). An initial estimate of the acetylene volume mixing ratio, as judged from measurements of the far ultraviolet albedo, is about 2 x 10(-7) at a vertical column abundance of molecular hydrogen of 10(23) per square centimeter (pressure, approximately 0.3 millibar). Carbon emissions from the Uranian atmosphere were also detected.

The high atmosphere of Mars (z > 30 km) has been observed from Phobos 2, using the solar occultation technique. Due to a major error in the pointing system, resulting from a wrong orientation of the spacecraft in the pointing software, the lower atmosphere is never observed in ultraviolet (220–330 nm) and high resolution near-infrared (760 nm, 936 nm) channels. Pointing data sometimes provide useful information on the visible opacity below 30 km. showing that the scale height of dust decreases from ≅ 8 km below 20 km to ≅ 4 km above. Among 32 occultations, four show the presence of a water ice cloud high in the atmosphere (z = 50 km), with a maximum tangential optical thickness varying from ≅ 0.05 to ≅ 2 and a vertical extent in the range from 5 to 15 km. Indications on the particles size (r ≫ 0.01 μm) are obtained using spectral information. From a simple cloud model, where eddy diffusion and sedimentation processes are taken into account, an upper limit of 107 cm2 s−1 is derived for the eddy diffusion coefficient. Similarly, the absence of ozone in detectable amounts above 30 km is interpreted as the signature of a rather weak value of K. Using a simple stationary photochemical model, a value of K as low as 106 cm2 s−1 seems to be required.

Simultaneous measurements of the nighttime atmospheric sodium and potassium layer have been performed over a period of one year, using a lidar facility set up at the Haute Provence Observatory. A detailed description of the calibration method is given together with the estimated accuracy of the experiment. The similarity observed in the behaviour of the spatial parameters of both layers indicates that the same processes are responsible for their day-to-day variations. However, the long term behaviour of the sodium and potassium total column abundances is very different: whereas the sodium one shows the usual seasonal variation already observed, no marked increase is seen in the potassium abundance during the year. The abundance ratio of these two elements varies then between a low summer value (∼10) and a high winter value (∼50). Two different origins can then be assumed for the alkalis in the upper atmosphere: a meteoritic one constant over the year and a terrestrial source due to the vertical transport of particles at high latitudes which only works in winter. Confirmation of this hypothesis can be found in the lack of sodium seasonal variation as observed at low latitudes.

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.

International audience; The OGO-6 6300 Å airglow temperature measurements have been used to develop models of the global temperature distributions under solstice and equinox conditions for the altitude region from 240 to 300 km and for times ranging from dawn in this altitude region to shortly after sunset. The distributions are compared with models derived from satellite orbital decay and incoherent scatter sounding. The seasonal variation of the temperature as a function of latitude is shown to be very different from that derived from static diffusion models with constant boundary conditions.

From observations made with a photometer placed on board D2A-Tournesol from April 1971 to June 1973 at ε = ± 90° for all ecliptic latitudes, we had deduced that the intensity of the zodiacal light is not constant, but shows fluctuations, some of which we correlated with cometary debris. The measurements were carried out by scanning the celestial sphere in a plane orthogonal to the Sun-Earth direction with a one minute period (LEVASSEUR et BLAMONT, 1973). BURNETT, SPARROW and NEY (1974) have pointed out that our data could have been contaminated by stray moonlight; we have therefore refined our data analysis and conclude that indeed fluctuations of the intensity of the zodiacal light do exist, even when the Moon is much below the horizon.

International audience; The Nephelometer instrument flown on all four of the probes of the Pioneer Venus mission is described. The instruments functioned well, returning data on the backscattering properties of the Venusian clouds and ambient solar radiation in several wavelength intervals as a function of altitude at four widely separated planetary locations. The design considerations, instrument construction, calibration and performance are discussed.

The evidence for solid mode 3 particles in the clouds of Venus is reexamined. The sampling characteristics of the cloud particle size spectrometer (LCPS) are reviewed, and reasons are pointed out for believing that relatively small differences in interpreting the measurements of this instrument could produce systematic errors. It is shown that all of the Pioneer Venus and Venera measurements can be understood if it is assumed that the large particles observed by the LCPS form the tail of the mode 2, H2SO4 size distribution.

Several photometric measurements of Venus made from the Pioneer Venus orbiter and probes indicate that solar near-ultraviolet radiation is being absorbed throughout much of the main cloud region, but little above the clouds or within the first one or two optical depths. Radiative transfer calculations were carried out to simulate both Pioneer Venus and ground-based data for a number of proposed cloud compositions. This comparison rules out models invoking nitrogen dioxide, meteoritic material, and volatile metals as the source of the ultraviolet absorption. Models involving either small ( approximately 1 micrometer) or large ( approximately 10 micrometers) sulfur particles have some serious difficulties, while ones invoking sulfur dioxide gas appear to be promising.

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.

The global hydrogen Lyman alpha, helium (584 angstroms), and molecular hydrogen band emissions from Saturn are qualitatively similar to those of Jupiter, but the Saturn observations emphasize that the H(2) band excitation mechanism is closely related to the solar flux. Auroras occur near 80 degrees latitude, suggesting Earth-like magnetotail activity, quite different from the dominant Io plasma torus mechanism at Jupiter. No ion emissions have been detected from the magnetosphere of Saturn, but the rings have a hydrogen atmosphere; atomic hydrogen is also present in a torus between 8 and 25 Saturn radii. Nitrogen emission excited by particles has been detected in the Titan dayglow and bright limb scans. Enhancement of the nitrogen emission is observed in the region of interaction between Titan's atmosphere and the corotating plasma in Saturn's plasmasphere. No particle-excited emission has been detected from the dark atmosphere of Titan. The absorption profile of the atmosphere determined by the solar occultation experiment, combined with constraints from the dayglow observations and temperature information, indicate that N(2) is the dominant species. A double layer structure has been detected above Titan's limb. One of the layers may be related to visible layers in the images of Titan.

Observations of the lunar luminescence are reported for a dozen of specific Moon features using the ‘line-depth’ method with a high resolution spectroscopic technique. The data indicate a variation of the Moon proper emission as a function of the phase angle which is interpreted as a proof of the thermoluminescent origin of this emission.

International audience; Because of the motion of the Sun through the surrounding interstellar medium, interstellar dust particles may penetrate deep into the Solar System. In this paper, we investigate the conditions for this penetration and find that the distribution of such particles should peak along the line of gravitational focusing. Two possible consequences are compared with experimental results: the rate at which particles should strike a micrometeoroid detector and the distribution of scattered solar light. We find that the number density of particles penetrating the solar system, derived from this comparison, is much smaller than predicted by a crude model of interstellar matter.

The VEGA balloons made in situ measurements of pressure, temperature, vertical wind velocity, ambient light, frequency of lightning, and cloud particle backscatter. Both balloons encountered highly variable atmospheric conditions, with periods of intense vertical winds occurring sporadically throughout their flights. Downward winds as large as 3.5 meters per second occasionally forced the balloons to descend as much as 2.5 kilometers below their equilibrium float altitudes. Large variations, in pressure, temperature, ambient light level, and cloud particle backscatter (VEGA-1 only) correlated well during these excursions, indicating that these properties were strong functions of altitude in those parts of the middle cloud layer sampled by the balloons.

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.

The dayside hydrogen exosphere was observed in October–November 1975 with a Lymanalpha photometer carried on board Venera-9 and 10. In addition to intensity measurements, the use of a hydrogen cell allowed for the first time linewidth measurements. Both intensity and linewidth measurements below 1500 km of altitude are well fitted by a single exospheric component (Tc = 500 ± 100 K, nc = 1.5 × 104 atom cm−3 at 250 km). Above 3000 km, the measured linewidth increased sharply, to decrease again above 4500 km. This feature is interpreted as the signature of an additional population of “hot” atoms circulating on satellite orbits, created just behind the bow-shock by charge-exchange collisions (with an efficiency of 4%) between the neutral atoms and the solar wind protons, which became turbulent after bow-shock crossing. The density ratio of “hot” to standard population is of the order of 10% around 3500 km of altitude.

International audience; We succeeded in several attempts at measuring the solar limb-darkening in the continuous spectrum between 1800 Å and 2900 Å. Good spectroheliograms were obtained during a rocket flight in November 1964 and during a balloon flight in October 1966 at 2190 Å, 2665 Å, 2885 Å, and 1980 Å, 2235 Å respectively. A rocket flown at the beginning of 1967 provided excellent spectra allowing the measurement of center-to-limb variation in the continuum and lines from 1800 Å to 2800 Å. The first series of pictures yielded absolute values of the central intensity leading to a minimum temperature close to 4700 °K. The continuous opacity of the photosphere layers has been deduced from the two first experiments. It seems that a non-metallic source of continuous absorption must be taken into account between 2500 Å and 3000 Å. Moreover, as the source functions for the shortest wavelengths show a very flat variation near the minimum temperature, it seems that the transition zone between the photosphere and the chromosphere must be very gradual. These results are discussed in the light of the latest results deduced from the new spectra obtained.

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.

A superpressure balloon flying at a constant density level fortuitously encountered (on two consecutive days) an artificial cloud generated by a French nuclear test over the South Pacific. The measurements of temperature and radiation made aboard the balloon show that the two observed encounters had short durations, and that there were rapid divergences between the trajectories of the cloud and the constant density level trajectory of the balloon. The analysis of the meteorological data and the observations made by the balloon allow us to demonstrate the quasi-isentropic nature of the radioactive cloud's trajectory.

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.

Observations with a horizon scanning airglow photometer on OGO-6 have revealed the presence of a dense scattering layer near 80 km over the geographic pole during the local summer. The layer is detected on all satellite passes above 80° latitude beginning 15 days before the solstice. The optical depth of the layer increases by more than a factor of 50 between 70° and 85°. It is suggested that noctilucent clouds are weak sporadic manifestations of these persistent polar layers.

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).