ar X iv : a st ro - p h / 05 09 86 4 v 1 2 9 Se p 20 05 ELVIS – ELectromagnetic Vector Information Sensor

The ELVIS instrument was recently proposed by the authors for the Indian Chandra-yaan-1 mission to the Moon and is presently under consideration by the Indian Space Research Organisation (ISRO). The scientific objective of ELVIS is to explore the electromagnetic environment of the moon. ELVIS samples the full three-dimensional (3D) electric field vector, E(x,t), up to 18 MHz, with selective Nyqvist frequency bandwidths down to 5 kHz, and one component of the magnetic field vector , B(x,t), from a few Hz up to 100 kHz. As a transient detector, ELVIS is capable of detecting pulses with a minimum pulse width of 5 ns. The instrument comprises three orthogonal electric dipole antennas, one magnetic search coil antenna and a four-channel digital sampling system, utilising flexible digital down conversion and filtering together with state-of-the-art onboard digital signal processing. Vector measurements are critical for an unambiguous characterisation of electromagnetic fields and their polarisation [1], including wave direction finding. Therefore , ELVIS comprises three, 5 m long, electric dipole antennas, mounted on the satellite body in an as close as possible orthogonal configuration. Each dipole is