Giacomo Colombatti

In situ measurements of the physical characteristics of Titan's environment

On the basis of previous ground-based and fly-by information, we knew that Titans atmosphere was mainly nitrogen, with some methane, but its temperature and pressure profiles were poorly constrained because of uncertainties in the detailed composition. The extent of atmospheric electricity (‘lightning’) was also hitherto unknown. Here we report the temperature and density profiles, as determined by the Huygens Atmospheric Structure Instrument (HASI), from an altitude of 1,400 km down to the surface. In the upper part of the atmosphere, the temperature and density were both higher than expected. There is a lower ionospheric layer between 140 km and 40 km, with electrical conductivity peaking near 60 km. We may also have seen the signature of lightning. At the surface, the temperature was 93.65 ± 0.25 K, and the pressure was 1,467 ± 1 hPa.

The ExoMars DREAMS scientific data archive

DREAMS (Dust Characterisation, Risk Assessment, and Environment Analyser on the Martian Surface) is a payload accommodated on the Schiaparelli Entry and Descent Module (EDM) of ExoMars 2016, the ESA – Roscosmos mission to Mars successfully launched on 14 March 2016. The DREAMS data will be archived and distributed to the scientific community through the ESA’s Planetary Science Archive (PSA). All data shall be compliant with NASA’s Planetary Data System (PDS4) standards for formatting and labelling files. This paper summarizes the format and content of the DREAMS data products and associated metadata. The pipeline to convert the raw telemetries to the final products for the archive is sketched as well.

Analysis of Passive System to Damp the Libration of Electrodynamic Tethers for Deorbiting

In the last decade, the continuous and alarming growth of space debris prompted many space agencies all over the world to adopt debris mitigation strategies. Present guidelines indicate the need to deorbit new satellites launched into low Earth orbit (LEO) within 25 years from their end of life. At present, a space-proven technology suitable to carry out a complete deorbit utilizes classical chemical propulsion. However, a deorbit maneuver by means of chemical rocket strongly affects the satellite propulsion budget, thus limiting the operational life of the satellite. These issues bring the need to develop innovative deorbiting technologies. One of these consists in using electrodynamic tethers that, through its interaction with the Earth ionosphere and magnetic field, can take advantage of Lorentz forces for deorbiting. Previous studies have shown the effectiveness of such a technology to deorbit LEO satellites from different altitudes and inclinations in a relatively short time. However, the continuous injection of small amount of energy produced by Lorentz forces into the tether system can cause dynamic instabilities. This paper addresses this issue through the analysis of the benefits provided by a damping device installed at the attachment point of the tether to the spacecraft. The damped tether system is modeled with a two-bar model to represent the dynamics of the tether and damping device. A key issue is how to maximize the energy transfer from the electrodynamic tether to the damper and its dissipation. The analysis carried out by means of linearization of dynamics equations and numerical simulations show that a well-tuned damper can effciently damp out the tether kinetic energy thus greatly increasing the system stability.