The H Lyman-α emission line from the upper atmosphere of Jupiter: Parametric radiative transfer study and comparison with data

This study uses the adding-doubling radiative transfer method in which we take into account the curvature effect of the planetary atmosphere in order to test the sensitivity of the jovian Ly-α emission line in relation to H column density, eddy diffusion coefficient, frequency redistribution function for photon scattering, temperature vertical profile, and an added hot atomic H layer on the top of the atmosphere. We also focus here on developing new diagnostic tools that will help us to obtain more confidently the underlying thermospheric structure of Jupiter. First, using the brightness distribution for specific wavelength bands as proposed by Ben Jaffel et al. [Ben Jaffel, L., Magnan, C., Vidal-Madjar, A., 1988. Astron. Astrophys. 204, 319-326], we show that the spatial thickness of the atomic H layer above the homopause level can be measured directly as the separation between the vertical positions of respectively the line core and line wing optical limbs. This thickness also constrains the [H] column and the value KH of the eddy diffusion coefficient at the homopause level at the disc location under consideration. We also propose to refine the value of KH and [H], respectively, at a specific planetary latitude, using the Q ratio of the limb peak brightness to the intensity from other regions over the planetary disc. Finally, the relationship between the disc brightness distribution from specific wavelength bands of the emission line and the temperature gradient in the thermosphere is demonstrated, thus providing an accurate tool to access this key information from high resolution observations. Quick, preliminary comparisons with some existing HTS/STIS data show the H layer thickness at auroral latitudes (∼1700 km) is much smaller than at equatorial latitudes (∼3900 km). These results strongly support the existence of a gradient in both H density and KH versus latitude, with higher values of KH at high latitudes and higher values of the H density at the equatorial regions. Such a small H layer thickness at auroral latitudes is consistent with a high mixing in the atmosphere that brings the hydrocarbons upwards, reducing consequently the column of hydrogen that scatters photons. These preliminary results show the strength of the proposed approach and open new horizons to use strong resonant emission lines at high resolution as a diagnostic for the state and structure of planetary upper atmospheres.     

空间飞行器远尾区内等离子体与场的相互作用

从理论上得到一组在考虑非静态极限下描述空间飞行器远尾区内等离子体与场之间的非稳态非线性相互作用耦合方程，并对其进行数值解，通过来用数值模拟计算方法，表明由于高频包络场的调制不稳定性，会产生密度空腔和电磁孤波，这对探测隐身飞行器有很重要的意义．     

Radiometer effect in the μSCOPE space mission

Space experiments to test the Equivalence Principle (EP) are affected by a systematic radiometer effect having the same signature as the target signal. In [PhRvD 63 (2001) 101101(R)] we have investigated this effect for the three proposed experiments currently under study by space agencies: μSCOPE, STEP and GG, setting the requirements to be met—on temperature gradients at the level of the test masses—for each experiment to reach its goal. We have now re-examined the radiometer effect in the case of μSCOPE and carried out a quantitative comparative analysis, on this issue, with the proposed heliocentric LISA mission for the detection of gravity waves. We find that, even assuming that the μSCOPE spacecraft and payload be built to meet all the challenging requirements of LISA, temperature gradients along its test masses would still make the radiometer effect larger than the target signal of an EP violation because of flying in the low geocentric orbit required for EP testing. We find no way to separate with certainty the radiometer systematic disturbance from the signal. μSCOPE is designed to fly a second accelerometer whose test masses have the same composition, in order to separate out systematic effects which—not being composition dependent like the signal—must be detected by both accelerometers. We point out that this accelerometer is in fact insensitive to the radiometer effect, just as it is to an EP violation signal, and therefore even having it onboard will not allow this disturbance to be separated out. μSCOPE is under construction and it is scheduled to fly in 2004. If it will detect a signal to the expected level, it will be impossible to establish with certainty whether it is due to the well known classical radiometer effect or else to a violation of the equivalence principle—which would invalidate General Relativity. The option to increase the rotation speed of the spacecraft (now set at about 10⁻³ Hz) so as to average out the temperature gradients which generate the radiometer effect, is allowed in the GG design, not in that of STEP and μSCOPE.     

VISPO project: visible image-spectrometer for planetary observations

Satellite instrumentations designed for planetary studies are often open to other interesting applications from ground: not only one can efficiently carry out detailed calibrations before space data become available, but also the prototypes of the satellite instruments can be successfully employed in different fields ranging from astrophysics to cosmology. Both possibilities are opened by coupling these instruments with ground based telescopes having short focal ratios, like those designed for far infrared studies. These possibilities are particularly amazing in view of the long delay usually present between the launch and the collection of the first scientific data (months in case of Mars Express, years in case of Rosetta).

We propose in this article to employ immediately this technology, by coupling the developing model of the Image-Spectrometer VIRTIS-M with the ground telescope MITO.

This project will allow us to perform a better calibration of the space qualified instrument and observational campaigns, including some important cosmological investigations.     

The effect of the prompt particle environment at L2 on optical CCDs for astronomy and astrophysics

The increasing number of probes carrying large focal planes consisting of many charge-coupled devices (CCDs), planned to be sent to the L2 Lagrangian point, 1.5 million kilometres from Earth in the next 15 years, implies that a detailed study of the effects of the prompt particle environment at L2 on CCDs is required. The focus of this study will be on CCDs for optical astronomy, astrometry and photometric applications. This study will be of particular interest to GAIA the European Space Agency's (ESA) cornerstone optical astronomy mission to further explore and map sections of our galaxy in greater detail. The results will also have implications for future X-ray astronomy missions like the X-ray Evolving Universe Spectroscopy Mission (XEUS). Both the above missions will require large area focal planes incorporating many CCD detectors.The sources of the instrument background are both solar and galactic and if a probe is launched around the peak in the next solar cycle (2010), the possible false detection rate or the amount of data that could be lost during a mission must be determined. This paper presents measured data for a spacecraft in a geostationary orbit, specifically Geosynchronous Operational Environmental Satellites (GOES) data, and makes predictions of the flux and energy of the particle environment at L2. The solar and galactic cosmic ray background was determined by using the Cosmic Ray Effects on Micro-Electronics or CREME96 code. A comparison was then made between the GOES data and the output from the CREME96 code in order to make predictions about the L2 environment.     

Using SNAP for Galactic &; extragalactic astronomy

SNAP, the SuperNova Acceleration Probe, is planned as a space-based telescope designed specifically to search for and monitor cosmological supernovae and weak lensing. In this paper we propose some other mission objectives which are of great importance in the fields of Galactic and extragalactic astronomy and which can be done as by-products with the same instrumentation and survey strategy as currently proposed for the main SNAP mission.     

On target for Venus – set oriented computation of energy efficient low thrust trajectories

Recently new techniques for the design of energy efficient trajectories for space missions have been proposed that are based on the circular restricted three body problem as the underlying mathematical model. These techniques exploit the structure and geometry of certain invariant sets and associated invariant manifolds in phase space to systematically construct energy efficient flight paths. In this paper, we extend this model in order to account for a continuously applied control force on the spacecraft as realized by certain low thrust propulsion systems. We show how the techniques for the trajectory design can be suitably augmented and compute approximations to trajectories for a mission to Venus.     

Advances in determining asteroid chemistries and mineralogies

Considerable progress has been made in the last few years in determining asteroid chemistries and mineralogies. Dedicated spacecraft missions have allowed mineralogical predictions based on ground-based data to be confirmed or refuted. These missions include NEAR-Shoemaker to (253) Mathilde and (433) Eros, Hayabusa to (25143) Itokawa, and Dawn to (4) Vesta and (1) Ceres, the upcoming Hayabusa2 to (162173) Ryugu, and the upcoming OSIRIS-Rex to (101955) Bennu. All of these missions have or will make significant advances that could not have been made through just Earth-based observations. The recovery of Almahata Sitta from 2008 TC₃ was a rare opportunity to recover meteorite samples from a spectrally observed body from a naturally occurring event. This review will discuss the importance of spacecraft missions to asteroids.     

Contested claims over space and identity between fishers and the oil industry in Mexico

This essay examines neoliberal forms of resource governance and emerging struggles over control of sea space between coastal fishers, the para-statal oil industry and government authorities in the State of Tabasco, Mexico. The analysis focuses on the changing mechanisms of resource governance and networking related to contested claims over rights to offshore space. The study is based on material collected during ethnographic field research in Tabasco in 2011–2014. By linking a post-Foucauldian approach to governmentality with a Deleuzian perspective on networks, our research examines resource governance as a socio-political arena, constructed in negotiation between multiple governmental, private and civil society actors, including heterogeneous groups from local populations. The study demonstrates how hybrid techniques of resource governance lead to fishers’ socio-spatial displacement, marginalization in the fields of political representation and subjection to ideas of aquaculture entrepreneurship. The ensemble of private regulation and governmental control provides a venue for drawing fishers into clientelist practices of governing while it diffuses questions of responsibility. These modes of governance fragment the fishers’ efforts to mobilize politically, making them rely on less visible networks of contestation shaped by heterogeneous fishing groups, with varying access to resources and political representation. Recent transformations in environmental legislation and the fishers’ mobile tactics of networking may offer opportunities for them to reclaim their resource rights.     

兴都库什及邻近区域空间应力场特征及其构造意义

兴都库什及邻近区域地处印度洋板块和欧亚板块碰撞带的西缘,是大陆内部中源地震最为活跃的区域,各种数据均显示出该区域有着十分特殊的现象.本文从地质构造、地震分布特征、震源机制解、应力场等方面进行初步分析.结果表明,不同的深度应力场方向表现各不相同,不同的区域震源机制特征各异,尤其是正断层性质地震在北东向表现出了线性展布.通过构造模拟认为该区域可能是在地壳的碰撞、推挤、俯冲作用下出现的褶皱,由于地层倒转嵌入,从而形成了多层位地震密集现象.同时在推挤、拖曳的过程中形成了一条深度约100 km以下的北东向的拉张性破裂.