Deep Space 1 (DS1) is the first interplanetary spacecraft (s/c) using ion propulsion and aims at investigating the compatibility of innovative technology with scientific measurements. DS1 performed a successful flyby at the asteroid Braille on July 29th, 1999. This closest-ever encounter allowed for the first time a direct measurement of an asteroidal magnetic field. The manifold magnetic disturbances caused by the ion propulsion onboard DS1, however, required an elaborate data processing scheme in order to extract the magnetic signature of Braille. Its successful application to the magnetometer data of the asteroid flyby reveals a magnetic moment of 2.1⋅1011 Am2 for Braille. ¿ 2001 American Geophysical Union