Echoes: a new instrumental concept of spectro-imaging for Jovian seismology

Echoes is a project of a space-borne instrument which has been proposed as part of the JUICE mission which is selected in the Cosmic Vision program of the European Space Agency (ESA) to perform seismic and dynamics studies of Jupiter's interior and atmosphere. Based on an original Mach-Zehnder design, the instrument aims to measure Doppler shifts of solar spectral lines, which are reflected by cloud layers of Jupiter's upper troposphere, coupled with imaging capabilities. It is specified to detect global oscillations with degree up to l = 50 and amplitude as low as 1 cm/s at the surface of Jupiter. In order to check the compliance of the instrument, and its capability to operate in representative environment (TRL5), we build a prototype to perform tests. In this paper, we present the prototype implemented at Observatoire de la Côte d'Azur in collaboration with Institut d'Astrophysique Spatiale. We describe the design of the Mach-Zehnder and the procedure of control and adjustment. We present the necessary tests and we show on simulation that the measurements will provide the required precision. In conclusion, we will explain the perspective for such a new instrument.