A novel wireless light sensing device for planetary and astronomical observations

A novel and versatile wireless light sensing device has been designed and tested for stellar and planetary photometric observations. The device weighing few 10 s of grams finds a number of potential applications in the fields of astronomy and in situ planetary exploration. A Wireless Sensor Network (WSN) using a number of these devices has been deployed to successfully carry out simultaneous photometric observations under different conditions viz. sunlight, twilight, moonlight etc. Observation of a star of known magnitude for flux calibration at low intensity has been carried out by coupling the device to a 1.2 m telescope which demonstrates its sensitivity. A WSN using these devices is further capable of spatio-temporal investigations of sky background intensities. Such a network can also be used to effectively monitor certain astronomical events (lunar eclipse, asteroid occultation etc.) simultaneously from several locations. The capability of the device, level of miniaturization and its versatility makes it a potential tool for many photometric applications.     

Response of the extratropical middle atmosphere to the September 2002 major stratospheric sudden warming

The effects of a major stratospheric sudden warming (SSW) at extratropical latitudes have been investigated with wind and temperature observations over a Brazilian station, Cachoeira Paulista (22.7°S, 45°W) during September–October 2002. In response to the warming at polar latitudes a corresponding cooling at tropical and extratropical latitudes is prominent in the stratosphere. A conspicuous signature of latitudinal propagation of a planetary wave of zonal wavenumbers 1 and 2 from polar to low latitude has been observed during the warming period. The polar vortex which split into two parts of different size is found to travel considerably low latitude. Significant air mass mixing between low and high latitudes is caused by planetary wave breaking. The meridional wind exhibits oscillations of period 2–4 days during the warming period in the stratosphere. No wave feature is evident in the mesosphere during the warming period, although a 12–14 day periodicity is observed after 2 weeks of the warming event, indicating close resemblance to the results of other simultaneous investigations carried out from high latitude Antarctic stations. Convective activity over the present extratropical station diminishes remarkably during the warming period. This behavior is possibly due to destabilization and shift of equatorial convective active regions towards the opposite hemisphere in response to changes in the mean meridional circulation in concert with the SSW.     

Drilling load modeling and validation based on the filling rate of auger flute in planetary sampling

Some type of penetration into a subsurface is required in planetary sampling. Drilling and coring, due to its efficient penetrating and cuttings removal characteristics, has been widely applied in previous sampling missions. Given the complicated mechanical properties of a planetary regolith, suitable drilling parameters should be matched with different drilling formations properly. Otherwise, drilling faults caused by overloads could easily happen. Hence, it is necessary to estab-lish a drilling load model, which is able to reveal the relationships among drilling loads, an auger's structural parameters, soil's mechanical properties, and relevant drilling parameters. A concept for the filling rate of auger flute (FRAF) is proposed to describe drilling conditions. If the FRAF index under one group of drilling parameters is less than 1, this means that the auger flute currently removes cuttings smoothly. Otherwise, the auger will be choked with compressed cuttings. In dril-ling operations, the drilling loads on the auger mainly come from the conveyance action, while the drilling loads on the drill bit primarily come from the cutting action. Experiments in one typical lunar regolith simulant indicate that the estimated drilling loads based on the FRAF coincide with the test results quite well. Based on this drilling load model, drilling parameters have been opti-mized.     

Fast low-energy halo-to-halo transfers between Sun–planet systems

In this paper, the problem of fast low-energy halo-to-halo transfers between Sun–planet systems is discussed under ephemeris constraints. According to the structure of an invariant manifold, employing an invariant manifold and planetary gravity assist to save fuel consumption is analyzed from the view of orbital energy. Then, a pseudo-manifold is introduced to replace the invariant manifold in such a way that more transfer opportunities are allowed. Fast escape and capture can be achieved along the pseudo-manifold. Furthermore, a global searching method that is based on patched-models is proposed to find an appropriate transfer trajectory. In this searching method, the trajectory is divided into several segments that can be designed under simple dynamical models, and an analytical algorithm is developed for connecting the segments. Earth–Mars and Earth–Venus halo-to-halo transfers are designed to demonstrate the proposed approach. Numerical results show that the transfers that combine the pseudo-manifolds and planetary gravity assist can offer significant fuel consumption and flight time savings over traditional transfer schemes.     

Plasma chemical reactions in C2H2/N2, C2H4/N2, and C2H6/N2 gas mixtures of a laboratory dielectric barrier discharge

Plasma chemical reactions in C₂H₂/N₂, C₂H₄/N₂, and C₂H₆/N₂ gas mixtures have been studied by means of mass spectrometry at a medium pressure of 300 mbar in a laboratory dielectric barrier discharge. A major reaction scheme is production of larger hydrocarbons like C_nH_m with n up to 12 including formation of functional CN groups.     

Mechanical behavior of the metal parts welded with extraterrestrial regolith simulant by the solar concentrator in ISRU & ISRF application

The use of in-situ resources plays an important role on future extraterrestrial human activities for the facility repair and habitat construction, especially in sustainable space exploration of Moon and Mars. A method of the metal welded with extraterrestrial regolith simulant using solar processing under ambient conditions is presented. Metal parts are made of Q235B ferroalloy and TA2 titanium alloy into standard tensile members according to the ASTM code. They are disconnected from the middle in advance, and then welded together with lunar and Martian regolith simulant under ambient conditions, respectively. The entire welding process and precautions are detailed. Additionally, the mechanical behavior of weldments is characterized regarding their tensile strength. Furthermore, the fusion zone of weldments is studied by Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) measurements. The results show that it is possible to weld metal parts together with extraterrestrial regolith simulant by the solar concentrator. The average ultimate tensile strength of ferroalloy specimens welded with lunar and Martian regolith simulant is 2.94 MPa and 1.66 MPa; The average ultimate tensile strength of titanium alloy specimens welded with lunar and Martian regolith simulant is 4.95 MPa and 2.59 MPa. Moreover, the failure mode of all weldments was brittle failure. The welding joints strength derives from the phases that the regolith as the solder fusing into ferroalloys in a homogeneous way and titanium alloys in an inhomogeneous way. The presented method may provide a new thought for astronaut assistance associating with repairing and fabricating in subsequent Moon and Mars missions.     

Some comments on the F ring-Prometheus–Pandora environment

The system formed by the F ring and two close satellites, Prometheus and Pandora, has been analysed since the time that Voyager visited the planet Saturn. During the ring plane crossing in 1995 the satellites were found in different positions as predicted by the Voyager data. Besides the mutual effects of Prometheus and Pandora, they are also disturbed by a massive F ring. Showalter et al. [Icarus 100 (1992) 394] proposed that, the core of the ring has a mass which corresponds to a moonlet varying in size from 15 to 70 km in radius which can prevent the ring from spreading due to dissipative forces, such as Poynting–Robertson drag and collisions. We have divided this work into two parts. Firstly we analysed the secular interactions between Prometheus–Pandora and a massive F ring using the secular theory. Our results show the variation in eccentricity and inclination of the satellites and the F ring taking into account a massive ring corresponding to a moonlet of different sizes. There is also a population of dust particles in the ring in the company of moonlets at different sizes [Icarus 109 (1997) 304]. We also analysed the behaviour of these particles under the effects of the Poynting–Robertson drag and radiation pressure. Our results show that the time scale proposed for a dust particle to leave the ring is much shorter than predicted before even in the presence of a coorbital moonlet. This result does not agree with the confinement model proposed by Dermott et al. [Nature 284 (1980) 309]. In 2004, Cassini mission will perform repeated observations of the whole system, including observations of the satellites and the F ring environment. These data will help us to better understand this system.     

Initial design of laboratories for sustainable habitation

An effective and self-sustainable artificial habitat design is essential for human spaceflight and expansion of mankind into orbit or towards other celestial bodies. There are two approaches that need to be implemented in future sustainable habitats: the use of re-cycling technologies in order to gain experience in closed-loop processes and the primary production of resource materials using In Situ Resource Utilisation (ISRU) principles. Various products will be provided and, where applicable, recycled in such a system taking into account basic human factors requirements such as crew work load capacity, safety and well-being, namely:     

Role of sample return and sample science in low cost missions

Sample return is an essential component of solar system exploration. Samples provide a unique data set that is critical for understanding formation and evolution of our solar system. This uniqueness is based on the scale of observations, precision of measurements, the ability to modify experiments as logic and technology dictate, and the ability to use instruments free of the constraints on mass, power, reliability, and data rate of flight instruments. Advances in analytical capabilities in recent years enable fundamental measurements to be made on extremely small samples, greatly reducing mass constraints on robotic sample return spacecraft. Sample studies provide irreplaceable ground truth for remotely-sensed data on planetary surfaces and fit within a variety of architectures for human exploration of the solar system.     

Disks, Extrasolar Planets and Migration

We review results about protoplanetary disk models, protoplanet migration and formation of giant planets with migrating cores. We first model the protoplanetary nebula as an α–accretion disk and present steady state calculations for different values of α and gas accretion rate through the disk. We then review the current theories of protoplanet migration in the context of these models, focusing on the gaseous disk–protoplanet tidal interaction. According to these theories, the migration timescale may be shorter than the planetary formation timescale. Therefore we investigate planet formation in the context of a migrating core, considering both the growth of the core and the build–up of the envelope in the course of the migration. This revised version was published online in June 2006 with corrections to the Cover Date.