Ultraviolet spectrometer experiment for the Voyager mission

The Voyager Ultraviolet Spectrometer (UVS) is an objective grating spectrometer covering the wavelength range of 500–1700 Å with 10 Å resolution. Its primary goal is the determination of the composition and structure of the atmospheres of Jupiter, Saturn, Uranus and several of their satellites. The capability for two very different observational modes have been combined in a single instrument. Observations in the airglow mode measure radiation from the atmosphere due to resonant scattering of the solar flux or energetic particle bombardment, and the occultation mode provides measurements of the atmospheric extinction of solar or stellar radiation as the spacecraft enters the shadow zone behind the target. In addition to the primary goal of the solar system atmospheric measurements, the UVS is expected to make valuable contributions to stellar astronomy at wavelengths below 1000 Å.     

Venus Express: Scientific goals, instrumentation, and scenario of the mission

The first European mission to Venus (Venus Express) is described. It is based on a repeated use of the Mars Express design with minor modifications dictated in the main by more severe thermal environment at Venus. The main scientific task of the mission is global exploration of the Venusian atmosphere, circumplanetary plasma, and the planet surface from an orbiting spacecraft. The Venus Express payload includes seven instruments, five of which are inherited from the missions Mars Express and Rosetta. Two instruments were specially designed for Venus Express. The advantages of Venus Express in comparison with previous missions are in using advanced instrumentation and methods of remote sounding, as well as a spacecraft with a broad spectrum of capabilities of orbital observations.     

Comet Halley: Nucleus and jets (results of the VEGA mission)

The VEGA-1 and VEGA-2 spacecraft made their closest approach to Comet Halley on 6 and 9 March, respectively. In this paper those results of the onboard imaging experiment which were obtained around closest approach are discussed. The nucleus of the comet was clearly identifiable as an irregularly shaped object, with overall dimensions of (16±1)×(8±1)×(8±1) km. The nucleus rotates in the prograde sense about an axis nearly perpendicular to the orbital plane with a period of 53±2 hours. Its albedo is only $\text{0.04±}\text{0.02}\text{0.01}$ Many of the jet features observed during the second fly-by have been spatially reconstructed. Their sources form a quasi-linear structure on the surface. The dust above the surface is shown to be generally optically thin with the exception of certain specific dust jets. Brightness features on the surface are clearly seen. Correlating our data with other measurements, we conclude that the dirty snow-ball model will probably need to be revised.     

Alice: The rosetta Ultraviolet Imaging Spectrograph

We describe the design, performance and scientific objectives of the NASA-funded ALICE instrument aboard the ESA Rosetta asteroid flyby/comet rendezvous mission. ALICE is a lightweight, low-power, and low-cost imaging spectrograph optimized for cometary far-ultraviolet (FUV) spectroscopy. It will be the first UV spectrograph to study a comet at close range. It is designed to obtain spatially-resolved spectra of Rosetta mission targets in the 700–2050 Å spectral band with a spectral resolution between 8 Å and 12 Å for extended sources that fill its ～0.05^ × 6.0^ field-of-view. ALICE employs an off-axis telescope feeding a 0.15-m normal incidence Rowland circle spectrograph with a toroidal concave holographic reflection grating. The microchannel plate detector utilizes dual solar-blind opaque photocathodes (KBr and CsI) and employs a two-dimensional delay-line readout array. The instrument is controlled by an internal microprocessor. During the prime Rosetta mission, ALICE will characterize comet 67P/Churyumov-Gerasimenko's coma, its nucleus, and nucleus/coma coupling; during cruise to the comet, ALICE will make observations of the mission's two asteroid flyby targets and of Mars, its moons, and of Earth's moon. ALICE has already successfully completed the in-flight commissioning phase and is operating well in flight. It has been characterized in flight with stellar flux calibrations, observations of the Moon during the first Earth fly-by, and observations of comet C/2002 T7 (LINEAR) in 2004 and comet 9P/Tempel 1 during the 2005 Deep Impact comet-collision observing campaign.     

Rosina – Rosetta Orbiter Spectrometer for Ion and Neutral Analysis

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer important questions posed by the mission’s main objectives. After Giotto, this will be the first time the volatile part of a comet will be analyzed in situ. This is a very important investigation, as comets, in contrast to meteorites, have maintained most of the volatiles of the solar nebula. To accomplish the very demanding objectives through all the different phases of the comet’s activity, ROSINA has unprecedented capabilities including very wide mass range (1 to >300 amu), very high mass resolution (m/Δ m > 3000, i.e. the ability to resolve CO from N₂ and ¹³C from ¹²CH), very wide dynamic range and high sensitivity, as well as the ability to determine cometary gas velocities, and temperature. ROSINA consists of two mass spectrometers for neutrals and primary ions with complementary capabilities and a pressure sensor. To ensure that absolute gas densities can be determined, each mass spectrometer carries a reservoir of a calibrated gas mixture allowing in-flight calibration. Furthermore, identical flight-spares of all three sensors will serve for detailed analysis of all relevant parameters, in particular the sensitivities for complex organic molecules and their fragmentation patterns in our electron bombardment ion sources.     

UV studies and the solar wind

The solar wind carves a cavity in the flow of interstellar H atoms through the solar system by charge-exchange ionization. The resulting Ly- sky pattern depends on the latitude distribution of the solar wind flux and velocity. We review how the solar wind characteristics (mass flux latitude distribution) can be retrieved from Ly- observations, yielding a new remote sensing method of solar wind studies, through UV optical measurements.     

Impact of Solar Activity on Stratospheric Ozone and NO2 Observed by Gomos/Envisat

Energetic proton precipitation occurring during solar events can increase the production of odd nitrogen in the upper stratosphere and mesosphere. A very intense solar proton event (SPE) occurred on 28 October 2003. Its impact on the composition of the middle atmosphere was observed in details due to the availability of several space instruments. Here we present GOMOS observations of a strong NO₂increase and a related ozone decrease in the upper stratosphere at north polar latitude. The perturbation of the chemical composition of the stratosphere was observed until the middle of December 2003. A strong NO₂ increase was also observed in the south polar vortex in June-July 2003. It is tentatively attributed to the effect of an SPE with protons of moderate energy occurring on 29 May 2003. If this hypothesis is confirmed, it will imply that the global effect of SPEs on the composition of the stratosphere is underestimated when only strong energy SPEs are considered.     

MEP (Mars Environment Package): toward a package for studying environmental conditions at the surface of Mars from future lander/rover missions.

In view to prepare Mars human exploration, it is necessary to promote and lead, at the international level, a highly interdisciplinary program, involving specialists of geochemistry, geophysics, atmospheric science, space weather, and biology. The goal of this program will be to elaborate concepts of individual instruments, then of integrated instrumental packages, able to collect exhaustive data sets of environmental parameters from future landers and rovers of Mars, and to favour the conditions of their implementation. Such a program is one of the most urgent need for preparing human exploration, in order to develop mitigation strategies aimed at ensuring the safety of human explorers, and minimizing risk for surface operations. A few main areas of investigation may be listed: particle and radiation environment, chemical composition of atmosphere, meteorology, chemical composition of dust, surface and subsurface material, water in the subsurface, physical properties of the soil, search for an hypothesized microbial activity, characterization of radio-electric properties of the Martian ionosphere. Scientists at the origin of the present paper, already involved at a high degree of responsibility in several Mars missions, and actively preparing in situ instrumentation for future landed platforms (Netlander--now cancelled, MSL-09), express their readiness to participate in both ESA/AURORA and NASA programs of Mars human exploration. They think that the formation of a Mars Environment working group at ESA, in the course of the AURORA definition phase, could act positively in favour of the program, by increasing its scientific cross-section and making it still more focused on human exploration.     

Conversations on the Habitability of Worlds: The Importance of Volatiles

Our scientific forefathers discuss the interrelationships between water, climate, the atmosphere, and life on Earth and other terrestrial planets at a workshop in Nichtchatel, Switzerland.