Title: Seeing the Invisible: Radar Experiments in Space Missions for the Exploration of the Solar System

Speaker: Prof. Roberto Orosei

Time: 09: 30-10: 00, December 4, 2023

Place: Liangjiang Grand Ballroom

Abstract: Electromagnetic waves in the radio and microwave frequency bands can propagate through media that are opaque to visible and infrared light. The very low natural emission at these frequencies makes it also possible to use active sensors illuminating Solar System bodies hundreds or thousands of kilometers away, and to receive echoes carrying information on their topography, morphology, structure and composition. Radar sensors have thus been flown on deep space missions since the seventies of the last century, first to the Moon, then to Venus, Mars, the Saturnian system and to the nucleus of a comet. On the Moon, radar sounders operating at MHz frequencies penetrated below the surface and mapped the thickness of lunar Maria, while polarized SAR experiments studied the interior of permanently-shadowed craters near the poles searching for ground ice. An imaging radar and altimeter mapped the topography of Venus, shrouded in perennial clouds, and yielded the first views of its surface morphology. On Mars, both orbiting and rover-mounted ground penetrating radars provided unique insight on the thickness and composition of polar caps, on the presence of ground ice at low latitudes, and on the stratigraphy of lava flows and volcanic ash deposits. A multi-mode radar was used to study the surface geology and hydrology of perennially haze-shrouded Titan, Saturn's largest moon and the only satellite in the Solar System possessing an atmosphere. A tomographic radar was landed on the nucleus of comet 67P/Churyumov-Gerasimenko, providing information on its density and composition. Interpretation of data from planetary radars required the development of new analysis methods and the use of electromagnetic propagation simulations, as ground truth for data calibration and validation is not available. As this new methodology is developing, radar sounders are on their way to study the interior of the Galilean moons of Jupiter, and more experiments of this type are envisioned for the continuing study of planets, satellites and asteroids. Radar experiments are thus expected to continue to be part of the scientific payload of future missions for the exploration of Solar System objects in the foreseeable future.

Biography: Roberto Orosei was born in Reggio Emilia, Italy. He studied at the University of Bologna and received a Ph.D. degree from the University of Rome "La Sapienza". After spending two years as a Research Fellow at the European Space Research and Technology Centre in Noordwijk, the Netherlands, he moved to the Institute for Space Astrophysics in Rome, where he participated in the design and realization of instruments for solar system exploration missions. He is a science team member of space experiments for the Rosetta and Jupiter Icy Moons Explorer missions of the European Space Agency, and for NASA's Cassini, Mars Reconnaissance Orbiter, Dawn and Juno probes. He is the principal investigator of the MARSIS radar on board ESA's Mars Express spacecraft, which provided evidence of the presence of liquid water beneath the South polar cap of Mars. He currently works at the Institute for Radioastronomy in Bologna and teaches a course of astrobiology at the University of Bologna.