Free Astronomy Magazine May-June 2016

deploy, to be then jettisoned at 1,300 me- tres from the surface, when the probe speed will be of 270 km/h. At that point the reverse rockets will kick in to bring Schia- parelli below 7 km/h at 2 metres from the ground. The landing, not the softest one, will be cushioned by a crushable structure built into the base of the lander. The landing target is Meridiani Planum (the same chosen in early 2004 for the Op- portunity rover), which, as its name sug- gests, is a flat and mostly rock-free plain. However, some modest-sized obstacles can- not be anticipated, and thus its contact with the ground will be a highly critical phase. In any case, Schiaparelli is capable of resting on ground with stones as high as 40 cm and slopes up to 12.5 degrees. Once landed, its mission will be almost con- cluded, given that its only source of energy is the limited amount of power provided by the batteries fitted onboard, sufficient to keep its instruments operating for a period between 2 and 8 Martian days. Much more ambitious is instead the Trace Gas Orbiter (TGO) mission, which will first take the orbiter to follow a long series of different elliptical orbits around Mars, lead- ing it, towards the end of 2017, to its op- erational orbit, from where it will begin its scientific observations. The TGO will be equipped with three groups of instruments ment, and Environment Analyser on the Martian Surface), Schiaparelli will measure the wind speed and direction, the humidity and transparency of the atmosphere (it will be the sandstorms season), the pressure and temperature at various altitudes, and the atmospheric electric fields close to the surface. Other onboard instruments will relay telemetry data and measure the heat- ing rate of various parts of the lander dur- ing its descent. The most critical phases are also the most interesting in view of Exo- Mars 2018: Schiaparelli's entry into the at- mosphere will occur at about 120 km of altitude, at a speed of 21,000 km/h, which due to the deceleration exerted by the at- mosphere will drop to nearly 1,700 km/h at 11 km of altitude, where its parachute will T he arrangement of Schiaparelli’s main devices and internal sen- sors. [ESA/ATG medialab]