The GPR experiment on NETLANDER

With the regular access of landers to the surface at each launch window during the next decade, one of the major objectives of the exploration of Mars will be to unravel the many unknown in the geological and hydrological history of the planet. Among the presently planned missions, the NETLANDER project offers a unique opportunity to explore simultaneously the deep interior of the planet and the first layers of the subsurface in 4 landing sites displaying different geophysical morphologies. To take advantage of this opportunity we have proposed to fly on the 4 landers a ground-penetrating radar (GPR); this experiment aims at characterizing the geological structures in the vicinity of the landers and at detecting possible water reservoirs under the form of ground ice or even, at some depth, of liquid water. The GPR will operate at a frequency of ∼2 MHz and will include an original assembly of 3 electric and 3 magnetic antennas as receivers. This design will enable to determine not only the distance at which the signal has been reflected but also its direction and thus will provide a 3D imaging of the uppermost layers of the subsurface down to a depth of ∼2.5 km . A model of the electromagnetic properties of the anticipated layering of the Martian megaregolith including a ground ice layer was built and used to predict through a 3D electromagnetic numerical simulation the performances of the GPR. After a review of the scientific objectives of the experiment, this paper presents a technical description of the instrument and display some of the results of the numerical simulation. The GPR will provide as a by-product a sounding of the ionosphere at the fixed operating frequency and will also be used to measure the radioelectric background expected from possible electrical discharges in the atmosphere during dust storms.