The DREAMS experiment flown on the ExoMars 2016 mission for the study of Martian environment during the dust storm season

The DREAMS(Dust characterization, Risk assessment and Environment Analyser on the Martian Surface) instrument on Schiaparelli lander of ExoMars 2016 mission was an autonomous meteorological station designed to completely characterize the Martianatmosphere on surface, acquiring data not only on temperature, pressure, humidity, wind speed and its direction, but also on solar irradiance, dust opacity and atmospheric electrification; this comprehensive set of parameters would assist the quantification of risks and hazards for future manned exploration missions mainly related to the presence of airborne dust. Schiaparelli landing on Mars was in fact scheduled during the foreseen dust stormseason (October 2016 in Meridiani Planum) allowing DREAMSto directly measure the characteristics of such extremely harsh environment. DREAMSinstrument’s architecture was based on a modular designdeveloping custom boards for analog and digital channel conditioning, power distribution, on board data handling and communication with the lander. The boards, connected through a common backbone, were hosted in a central electronic unit assembly and connected to the external sensors with dedicated harness. Designed with very limited mass and an optimized energy consumption, DREAMSwas successfully tested to operate autonomously, relying on its own power supply, for at least two Martiandays (sols) after landing on the planet. A total of three flight models were fully qualified before launch through an extensive test campaign comprising electrical and functional testing, EMC verification and mechanical and thermal vacuum cycling; furthermore following the requirements for planetary protection, contamination controlactivities and assay sampling were conducted before model delivery for final integration on spacecraft . During the six months cruise to Mars following the successful launch of ExoMars on 14th March 2016, periodic check outs were conducted to verify instrument health check and update mission timelines for operation. Elaboration of housekeepingdata showed that the behaviour of the whole instrument was nominal during the whole cruise. Unfortunately DREAMSwas not able to operate on the surface of Mars, due to the known guidance anomaly during the descent that caused Schiaparelli to crash at landing. The adverse sequence of events at 4 km altitude anyway triggered the transition of the lander in surface operative mode, commanding switch on the DREAMSinstrument, which was therefore able to correctly power on and send back housekeepingdata. This proved the nominal performance of all DREAMShardware before touchdowndemonstrating the highest TRL of the unit for future missions. The spare models of DREAMSare currently in use at university premises for the development of autonomous units to be used in cubesatmission and in probes for stratospheric balloons launches in collaboration with Italian Space Agency.