Imaging of extrasolar advanced terrestrial planets

The gravitational lens effect of the Sun would allow, by using a detector at one of its foci, to obtain a “telescope” with gigantic amplification and resolution powers opening extraordinary perspectives for the detailed study of extrasolar planets, particularly technologically advanced ones. But, astronautical challenges are raised by the necessity to align precisely and put in an efficient tracking and scanning mode the detector, necessarily modest in size compared to the dimensions of the planet images and ranges of orbital and rotational motions. In the frame of the FOCAL space mission submitted to ESA, we present the dynamical geometry of the images for two typical cases of observational wavelengths: 10 centimeters (radio) and 10 micrometers (infrared), for a solar-type stellar system 10 parsecs away. Plasma thrusters could provide interesting solutions for the control of the detector for tracking and scanning the focal images.