Virtis: An Imaging Spectrometer for the Rosetta Mission

The VIRTIS (Visual IR Thermal Imaging Spectrometer) experiment has been one of the most successful experiments built in Europe for Planetary Exploration. VIRTIS, developed in cooperation among Italy, France and Germany, has been already selected as a key experiment for 3 planetary missions: the ESA-Rosetta and Venus Express and NASA-Dawn. VIRTIS on board Rosetta and Venus Express are already producing high quality data: as far as Rosetta is concerned, the Earth-Moon system has been successfully observed during the Earth Swing-By manouver (March 2005) and furthermore, VIRTIS will collect data when Rosetta flies by Mars in February 2007 at a distance of about 200 kilometres from the planet. Data from the Rosetta mission will result in a comparison – using the same combination of sophisticated experiments – of targets that are poorly differentiated and are representative of the composition of different environment of the primordial solar system. Comets and asteroids, in fact, are in close relationship with the planetesimals, which formed from the solar nebula 4.6 billion years ago. The Rosetta mission payload is designed to obtain this information combining in situ analysis of comet material, obtained by the small lander Philae, and by a long lasting and detailed remote sensing of the comet, obtained by instrument on board the orbiting Spacecraft. The combination of remote sensing and in situ measurements will increase the scientific return of the mission. In fact, the “in situ” measurements will provide “ground-truth” for the remote sensing information, and, in turn, the locally collected data will be interpreted in the appropriate context provided by the remote sensing investigation. VIRTIS is part of the scientific payload of the Rosetta Orbiter and will detect and characterise the evolution of specific signatures – such as the typical spectral bands of minerals and molecules – arising from surface components and from materials dispersed in the coma. The identification of spectral features is a primary goal of the Rosetta mission as it will allow identification of the nature of the main constituent of the comets. Moreover, the surface thermal evolution during comet approach to sun will be also studied.     

Plasma Sheaths of Models in Hot-Shot Wind Tunnels

The nitrogen flow characteristics around models is studied with a view to obtaining data which determine the physical state of the plasma. Among all possible techniques, the most adaptable to the special hot-shot conditions?electrostatic probes and VHF microwave reflectometry?is chosen. The experimental apparatus and results in nitrogen are described. The ionization is not homogenous during the shot; this result seems to confirm the assumption that the plasma flow is utilizable only after a delay of more than ten milliseconds following the shock formation period. The hot-shot utilization range is examined for this type of experiment.     

A Six-Component Balance

A six-component force-measuring balance for impulse wind tunnels is described. The application of semiconductors for force and acceleration measurement, and their mechanical and electronic coupling for the desired operational outputs are given. The dynamic calibration procedures are explained and verified for the conditions encountered in hot-shot-type wind tunnels.     

A brief history of Baikonur

The Baikonur launch site was the world's first and remains its most important in terms of the historic missions that have taken off from it. This article describes the background to the construction of Baikonur, the steps taken to keep it secret from the West, and its chief facilities. It enumerates the major space missions that took place there, as well as acknowledging its failures, e.g. the lunar programmes, before speculating on its future. An increasing emphasis on commercial launches seems likely.