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Bertaux, J. L.

Publications and source records attributed to Bertaux, J. L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Mars Solar Balloon Landed Gas Chromatograph Mass Spectrometer

A Mars surface lander Gas Chromatograph Mass Spectrometer (GCMS) is described to measure the chemical composition of abundant and trace volatile species and isotope ratios for noble gases and other elements. These measurements are relevant to the study of atmospheric evolution and past climatic conditions. A Micromission plan is under study where a surface package including a miniaturized GCMS would be delivered to the surface by a solar heated hot air balloon based system. The balloon system would be deployed about 8 km above the surface of Mars, wherein it would rapidly fill with Martian atmosphere and be heated quickly by the sun. The combined buoyancy and parachuting effects of the solar balloon result in a surface package impact of about 5 m/sec. After delivery of the package to the surface, the balloon would ascend to about 4 km altitude, with imaging and magnetometry data being taken for the remainder of the daylight hours as the balloon is blown with the Martian winds. Total atmospheric entry mass of this mission is estimated to be approximately 50 kg, and it can fit as an Ariane 5 piggyback payload. The GCMS would obtain samples directly from the atmosphere at the surface and also from gases evolved from solid phase material collected from well below the surface with a Sample Acquisition and Transport Mechanism (SATM). The experiment envisioned in the Mars Micromission described would obtain samples from a much greater depth of up to one meter below the surface, and would search for organic molecules trapped in ancient stratified layers well below the oxidized surface. Insitu instruments on upcoming NASA missions working in concert with remote sensing measurement techniques have the potential to provide a more detailed investigation of mineralogy and the extent of simple volatiles such as CO2 and H2O in surface and subsurface solid phase materials. Within the context of subsequent mission opportunities such as those provided by the Ariane 5 piggyback payload based Micromissions, it is essential to implement an even broader chemical analysis and to enable a significant extension of previous isotope measurements. Such a development would enhance the presently very active study of questions of atmospheric evolution and loss and past climatic conditions. The method selected to implement this program can be based on well-established mass spectrometry techniques. Sampled gas is chemically and physically processed to separate the gas mixture into components using gas chromatograph and related enrichment techniques. This allows trace species to be identified and reveals isotopic distributions in many cases with improved precision. Samples of interest, such as organic molecules, may lie deep below the highly oxidized surface layer and the suggested program includes enhanced sampling techniques to measure volatiles preserved in solid phase material deep below the surface as well as gas from the well mixed atmosphere.

Mahaffy, P.↗
NASA NTRS1995

Observations of a groove in the interplanetary Lyman alpha pattern as the signature of enhanced ionisation in the neutral sheet

We report several observations of the Lyman alpha interplanetary emission recorded by a photometer flown in 1976-1977 on board the Soviet spacecraft Prognoz-5 and Prognoz-6. Several scans made in a plane perpendicular to the sun were cutting through the maximum emission region. where the interstellar hydrogen is approaching nearest to the sun (upwind region). On each of these scans is observed a dip in the intensity curve near the ecliptic plane. about 30 deg wide and approximately equals 10% deep. They reveal the presence of a new feature of the interplanetary emission. a 'groove' aligned approximately with the ecliptic plane. This groove is present only near the upwind direction, and is interpreted as the result of enhanced ionisation of interstellar H by charge-exchange with the solar wind in a sheet of approximately 30 deg around the average position of the neutral sheet at this time of solar this Lyman alpha groove is a prime target for future observations with SWAN experiment on SOHO.

Bertaux, J. L.↗
NASA NTRS1995

Comparison between solar wind latitude distribution derived from Lyman-alpha observations and Ulysses measurements

The all-sky interplanetary Lyman-alpha pattern is sensitive to the latitude distribution of the solar wind because of destruction of neutral H by charge-exchange with solar wind protons. Lyman-alpha intensities recorded by Prognoz 5 and 6 in 1976 in a few parts of the sky were demonstrating a decrease of solar wind mass flux by about 30 % from equator to pole, when assuming a sinusoidal variation of this mass flux (harmonic distribution). A new analysis with a discrete variation with latitude has shown a decrease from 0 to 30 deg and then a plateau of constant mass flux up to the pole. This distribution bears a striking resemblance with Ulysses in-situ measurements, showing a clear similarity at 19 years interval. The Ulysses measurements were then used as a model input to calculate an all-sky Lyman-alpha pattern, either with a discrete model or with a harmonic solar wind variation with the same Ulysses equator-to-pole variation. There are conspicuous differences between the two Lyman-alpha patterns, in particular in the downwind region which are discussed in the context of future all-sky measurements with SWAN experiment on SOHO.

Quemarais, E.↗
NASA NTRS1995

Lyman alpha emissions in the outer heliosphere

Since 1993, the Ultraviolet Spectrometers aboard both Voyager 1 and 2, were used to study the Ly-alpha glow pattern backscattered by neutral hydrogen atoms at great distance from the sun. When compared to a radiative transfer calculation for an unperturbed interstellar hydrogen flow into the solar system, the data present an excess of intensity seen in the direction of the incoming interstellar wind. An absolute estimate of this Lyman alpha intensity yields 10 to 15 Rayleighs for each spacecraft. We discuss the possibility that this excess is caused by a gradient of hydrogen at large distance from the Sun due to the filtration of interstellar hydrogen when crossing the heliopause. Comparisons with results from the Baranov-Malama model of neutral-plasma coupling at the heliopause are presented. The data yield a range of possible values for the hydrogen gradient which may be used to infer the location of the heliopause.

Quemerais, E.↗
NASA NTRS1994

GOMOS: Gobal Ozone Monitoring by Occultation of Stars

In this paper we report on the progress and status of the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument, and imaging spectrometer under development for flight on the European Space Agency's Polar Orbiting Earth Mission (POEM-1) mission in 1998. Employing occultation of stars as a light probe of the Earth's atmosphere from a sun-sychronous polar orbit, the instrument will monitor ozone and other atmospheric trace gases over the entire globe. Atmospheric transmission resolution of approximately 1.7 km. When data are combined regionally, it will be possible to detect ozone concentration trends as small as 0.05 percent/year, depending on the degree of combination.

Leppelmeier, G. W.↗
NASA NTRS1991

Interplanetary Lyman-alpha observations with UVS on Voyager - Data, first analysis, implications for the ionization lifetime

A fraction of the measurements of the interplanetary Lyman-alpha background collected by the Ultraviolet Spectrometer during the cruise of Voyager 1 and 2 between 1977 and 1983 is presented and compared with results from current models of the interaction between the sun and the neutral interstellar gas. An analysis of two sets of data indicates that the same H atom lifetime cannot fit all the data. The actual ionization rate is inferred from the intensity gradient in the maximum emissivity region observed from a sidewind Voyager position at 6 AU, yielding a lifetime of about 1 exp 6 s at 1 AU, whereas the upwind/downwind intensity ratio in the inner solar system favors 2 x 10 exp 6 s, as measured by Voyager, Prognoz, and Pioneer Venus instruments. It is proposed that there is an excess of Ly-alpha emission in the downwind region which forces the model toward excessively high values of the lifetime. Possible explanations are discussed, like incorrect modeling or an additional source of H atoms.

Lallement, R.↗
NASA NTRS1989

Ultraviolet spectrometer observations of Neptune and Triton

Results from the occultation of the sun by Neptune imply a temperature of 750 + or - 150 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane, acetylene, and ethane at lower levels. The ultraviolet spectrum of the sunlit atmosphere of Neptune resembles the spectra of the Jupiter, Saturn, and Uranus atmospheres in that it is dominated by the emissions of H Lyman alpha (340 + or - 20 rayleighs) and molecular hydrogen. The extreme ultraviolet emission in the range from 800 to 1100 angstroms at the four planets visited by Voyager scale approximately as the inverse square of their heliocentric distances. Weak auroral emissions have been tentatively identified on the night side of Neptune. Airglow and occultation observations of Triton's atmosphere show that it is composed mainly of molecular nitrogen, with a trace of methane near the surface. The temperature of Triton's upper atmosphere is 95 + or - 5 kelvins, and the surface pressure is roughly 14 microbars.

Broadfoot, A. L.↗
NASA NTRS1988

Atmospheric Lyman-Alpha Emissions (ALAE)

The Atmospheric Lyman-Alpha Emissions (ALAE) experiment which is designed to measure atomic hydrogen and deuterium in the terrestrial atmosphere is described. The development of the instrument is a joint effort of the Service d'Aeronomie du CNRS in France and the Institut d'Aeronomie Spatiale in Belgium. This experiment will be part of the atmospheric science research payload flown on the Atmospheric Laboratory for Applications and Science (ATLAS 1) NASA mission planned for late 1990.

Bertaux, J. L.↗
NASA NTRS1986

Optical probing of comet Halley from the Giotto spacecraft

The Halley optical probe experiment (HOPE) aboard the Giotto spacecraft has provided the first measurements of the optical properties of the dust and of some gaseous species (CN, C2, CO/+/ and OH) from inside the coma of comet Halley. The dust spatial distribution, inferred from sunlight scattering, obeys an r exp -2 law for distances from the nucleus r greater than about 2,000 km. The more rapid increase of dust density with distance observed in the innermost coma probably reflects the presence of a jet, or a surge of activity within a few hours before closest approach. The CN and OH signals increase more slowly than the dust signals, but faster than predicted by a simple model (of solar-excited resonance fluorescence) for the distribution of these species. This effect is probably caused in part by the dust contribution, as well as by the production from parent molecules of OH and CN in an excited state.

Levasseur-Regourd, A. C.↗
NASA NTRS1985

Models of Venus neutral upper atmosphere - Structure and composition

Models of the Venus neutral upper atmosphere, based on both in situ and remote sensing measurements, are provided for the height interval from 100 to 3500 km. The general approach in model formulation was to divide the atmosphere into three regions: 100-150 km, 150-250 km, and 250-3500 km. Boundary conditions at 150 km are consistent with both drag and mass spectrometer measurements. A paramount consideration was to keep the models simple enough to be used conveniently. Available observations are reviewed.

Keating, G. M.↗
NASA NTRS1984

Helium and Hydrogen of the Local Interstellar Mdium Observed in the Vicinity of the Sun

The Sun illuminates the hydrogen and helium atoms of the interstellar medium through which it travels. As a result, the Sun and the whole solar system are imbedded in a glow of the resonance lines of hydrogen (H Lyman alpha; 121.6nm) and helium (58.4nm). From the intensity distribution of the glow in the solar system, the density of H and He in the local interstellar medium (LISM) and the direction of the relative motion between the Sun and the LISM in the vicinity of the Sun are derived. The velocity module and the LISM temperature are more adequately found from a measurement of the Lyman alpha line shape, which is an image of the velocity distribution of H atoms. The result is summarized and together the methods of interpretation and difficulties are dicusssed.

Bertaux, J. L.↗
NASA NTRS1984

A spectral photopolarimeter for Giotto - Halley Optical Probe Experiment

The Halley Optical Probe Experiment (HOPE) will furnish in situ photopolarimetric data on Comet Halley's coma dust cloud and atmosphere. The optical probe concept involves measurements of the polarized spectral radiance in the direction of motion at two points on the spacecraft trajectory, parallel to the direction of motion; their difference is the spatial derivative of the radiance along the line-of-sight, as well as of the light scattered by dust or emitted by gas in a tube along the trajectory. HOPE is proposed for the Giotto spacecraft's flyby of Comet Halley.

Levasseur-Regourd, A. C.↗
NASA NTRS1982

Copernicus measurement of the Jovian Lyman-alpha emission and its aeronomical significance

It is pointed out that the intensity of the Lyman-alpha emission is a good indicator of the principal aeronomical processes on the major planets. The high-resolution ultraviolet spectrometer aboard the Orbiting Astronomical Observatory Copernicus was used in 1980 April and May to detect the Jovian Lyman-alpha emission by spectroscopically discriminating it from other Doppler shifted Lyman-alpha emissions such as those of the geocorona, and the interplanetary medium. Taking into consideration the reported emission data, it appears that an unusually large energy input due to the particle precipitation in the auroral region must have been responsible for the large observed Lyman-alpha intensity during the Voyager encounter. At most other times, the observed Jovian Lyman-alpha intensity can be explained, within the range of statistical uncertainty, by a model that takes into consideration the solar EUV flux, the solar Lyman-alpha flux, the high exospheric temperature, and the eddy diffusion coefficient without energy input from the auroral sources.

Atreya, S. K.↗
NASA NTRS1981

Overview of the Voyager ultraviolet spectrometry results through Jupiter encounter

The observations of a number of objects by the Voyager EUV instruments are summarized. The summary is considered to demonstrate the wide ranging application of the EUV spectroscopy. It also marks an important step forward in spectrography and emphasizes the continuing importance of the search and discovery nature of spectroscopic techniques.

Broadfoot, A. L.↗
NASA NTRS1979

Extreme ultraviolet observations from Voyager 2 encounter with Jupiter

The extensive Voyager 2 EUV spectral observations of the Jovian planetary system have produced a number of significant results. The positions of the auroral zones have been defined with the aid of support imaging to the extent that the aurora is now known to correspond to the location of the planetary magnetic field lines intersecting the Io plasma torus. The observations do not preclude the possibility of a simultaneous magnetotail aurora, but if present it must not be a dominant component. Emission in molecular hydrogen has been detected from the equatorial regions of Jupiter, which indicates planetwide electron precipitation. Hydrogen Lyman alpha from the dark side of the planet has been measured at an intensity of about 1 kilorayleigh. Occultation of Alpha Leonis by Jupiter has been observed, and the data are being analyzed in detail.

Sandel, B. R.↗
NASA NTRS1977

Ultraviolet spectrometer experiment for the Voyager mission

An objective grating spectrometer covering the wavelength range of 500 to 1700 A with a 10-A resolution is employed for the Voyager ultraviolet spectrometer experiment. In determining the composition and structure of the atmospheres of Saturn, Jupiter and several satellites, the ultraviolet spectrometer will rely on airglow mode observations to measure radiation from the atmospheres due to resonant scattering of solar flux, and the occultation mode for assessments of the atmospheric extinction of solar or stellar radiation as the spacecraft enters shadow zones. Since it is capable of prolonged stellar observations in the 500 to 1000 A wavelength range, the spectrometer is expected to make important contributions to exploratory studies of UV sources.

Broadfoot, A. L.↗
NASA NTRS1976

Lyman-alpha observations of Comet Kohoutek 1973 XII with Copernicus

Comet Kohoutek 1973 XII was observed with a telescope-spectrometer on the Copernicus satellite on six occasions over a 1-month period starting on January 29, 1974. Positive detection of the cometary Ly-alpha emission profile was obtained on January 29 and February 2. Earlier observations of the geocoronal Ly-alpha emission profile allowed an instrumental intensity calibration and confirmation of the computed instrumental profile for an extended source at the Ly-alpha wavelength. After allowing for broadening by the instrument, a hydrogen-outflow velocity of about 10.6 km/s is derived from the width of the Ly-alpha emission on January 29. The intensity calibration combined with an appropriate cometary model led to cometary water-production rates for January 29 and February 2. Only upper limits were obtained for Ly-alpha on and after February 14. Searches for OH and D led to negative results.

Drake, J. F.↗